|In this page descriptions of various animals and plants not included to basic chapters are gathered. The wanishing of the description from this part means that you just must search for new chapter in English version of "The incredible world tour to Neocene".|
big-tongued lamprey (Glossolampetra heliciphaga)
Order: Lampreys (Petromyzodontiformes)
Family: Northern lampreys (Petromyzontidae)
Habitat: Florida, coast of Gulf of Mexico, Cuba and Great Antigua.
During the ice age at the boundary of the Holocene and Neocene the habitats of many representatives of cold-water flora and fauna extended further from the poles into the lower latitudes. At the end of the ice age the fates of species distributed during glaciation have developed indifferent ways: some retreated to the poles and became extinct in warmer climates, while others remained in the separate “refuges” of mountain ranges, while others have adapted to the warming and have become one of the components of the new subtropical or even tropical flora and fauna. One species of a small group of lampreys represents this kind of polar component in the tropical fauna of central and southern North America. This species, the Floridian big-tongued lamprey, flourishes thanks to an unusual feeding specialization.
The Floridian big-tongued lamprey is a small animal: the body length of an adult is about 15 cm. The mouth of the lamprey is a soft, round sucker ring with rows of small teeth. Also at this species there is a powerful tongue with large hooked corneous teeth, capable of extending far ahead of his mouth. This is due to the nature of the animal’s food: the Floridian big-tongued lamprey feeds on snails. It sticks its mouth to the snail, expands its mouth over the mouth of the shell, and deeply thrusts its tongue into the shell, and in one motion hooks and pulls the body of the mollusk out of its shell. After this the snail is swallowed whole and the shell is left intact. This species does not stick to living fish and only occasionally scrapes the meat of dead animals.
Unlike many lampreys, the Floridian big-tongued lamprey is colored quite vividly: on a pale yellow background brown spots of irregular shape merge into traverse bands separated by areas without spots. On fins small black specks are scattered.
Usually this animal burrows among plants or sunken leaves. The Floridian big-tongued lamprey shows the most activity at dusk. This species inhabits fresh and marine waters, easily withstanding considerable desalination. In the mangroves there are large individuals up to 20 cm long. With the ability to live in seawater this species is widely spread throughout the tropical waters of southern North America and the Caribbean.
Reproduction of the Floridian big-tongued lamprey occurs in fresh water. Because of this small islands, where there are only few rivers productive enough, represent a barrier to the expansion of this species into South America. Before spawning the coloration of lampreys greatly changes: spots on the body merge into distinct transverse bands, the back darkens and a distinct black border appears on the fins. The lampreys stop feeding and their bowels begin to degenerate. Adults ascend the rivers and spawn in areas with soft ground and slow flow. The larval stage lasts up to 5 years. The ammocoetes eat mud and the rotting remains of small animals.
Translated by FanboyPhilosopher
ghost shark (Caecorectolobus cirrhosissimus)
Order: Wobbegongs (Orectolobiformes)
Family: Carpet sharks (Orectolobidae)
Habitat: Pacific Ocean, depth about 1500 – 2000 meters.
Picture by Timothy Morris, colorization by Alexander Smyslov
Initial image by Timothy Morris
Sharks are highly adaptive creatures: this group of fishes
is known from Devonian, having proved thus the abilities to adapt to various
changes of environment. Opinion that sharks do not evolve till their history
is deeply wrong. Various species, families and orders of these fishes replaced
each other as regularly, as groups of sea mammals, for example. From most ancient
times sharks aspired to take a place of supreme predators of ecosystems. It
was possible to them for many times, but sharks had reached especial success
in Cenozoic when requiem and mackerel sharks, the top of evolution of sharks,
had appeared. The place at top of food pyramid is honourable, but too risky
– at ecological crisis predators die out at first. At the boundary of Holocene
and Neocene “charismatic” pelagic sharks dwelt at ocean had disappeared – schools
of pelagic fishes served as food to them and their catch had died out. Their
populations undermined by chasing of people gradually degraded. To early Neocene
at the planet mainly medium-sized bottom-dwelling sharks survived. And they
had given in Neocene a new wave of speciation. The majority of Neocene sharks
are descendants of these species.
After ecological crisis and extinction of pelagic organisms sharks descending from shallow-water species developed the oceans anew. Among them there were species had mastered polar waters of Arctic Ocean and Subantarctic. And some sharks had started to storm ocean depths. Deep-water fauna depended on efficiency of ecosystems of top layers of water had suffered huge damage till the time of “plankton accident” at the boundary of epochs, therefore at early Neocene deep-water ecosystems had started to form practically from zero.
Among sharks occupied depths of ocean there is one descendant of carpet sharks, whose ancestors lived in shallow waters earlier. Obviously, ancestors of this fish had “moved down” to depths of ocean along the continental slope (obviously, somewhere in area of Australia or Indonesia). Therefrom this fish had passed to pelagic habit to life already as deep-water animal. Hence of fantastical appearance this fish named ghost shark. The length of this fish is about 2 meters; tail fin with much lengthened top blade located almost horizontally makes about one third of general length.
This fish lives in depths where change of day and night is not felt at all – at the depth over thousand meters. Colouring of skin of ghost shark is unicolor light grey; that’s why fish looks “belongig to the beyond”. As against overwhelming majority of Neocene sharks it is completely blind fish – even a sign of eyes is not remained from outside. Eyes are functionally replaced with another “secret weapon” especially advanced at sharks – instead of them organs of lateral line are used for orientation in water. Ghost shark has flat head, lengthened body and rather short fins. At this fish there are two back fins, on each back fin there is hollow corneous spike connected with poisonous gland. This is the main protective adaptation against deepwater predators: sometimes these sharks are attacked by squids and their own larger congeners.
Similarly to all carpet sharks the ghost shark has many skin outgrowths at the edge of muzzle. This inheritance from carpet sharks of shallow water habitats earlier serving for masking had got other function in gloom of depths, much more important for survival: very much advanced outgrowths on head contain branches of lateral line, and fish orientates with their help. Outgrowths on muzzle reach the length equal to fish’s head. It has determined the specific name of fish: “cirrhosissimus” means “the most whiskered”. Organs of lateral line located on outgrowths of fish’s head permit to trace the slightest changes of electric field surrounding fish, meaning presence of other live creatures.
Besides long-wattled ghost shark there is very keen sense of smell: it has large chinky nostrils.
This shark is slow: the most part of time it passively floats in thickness of water, tracking down other fishes and various pelagic invertebrates – squids and octopuses. Its catch not always differs in speed; therefore it may be easily caught even by such blind and slowly moving predator. Long-wattled ghost shark is able to catch fast catch, making short sharp throws. This fish eats basically fishes and squids having soft and flabby body consistence. Therefore its teeth have not cutting or crushing, but thrusting type – they are rather thin, awl-like and slightly bent. With the help of such teeth it is easy to catch slippery and soft-bodied prey. Having an opportunity, long-wattled ghost shark sometimes eats carrion – corpses of fishes and large sea animals immersed to the bottom. Eating carrion, the fish seizes sticking up parts of carcass and sharply turns, trying to tear off a piece. But more often this shark is interested not in carcass, but in animals coming to feed at it.
In typical case sharks lay large eggs from which the posterity hatches after rather long time. For the pelagic species living above the big depths, such vital strategy is unacceptable: females should make migrations to the continental slope to hatch posterity or to lay eggs right in water where they will fall to depth and can not develop there. The smaller number of sharks is live-bearing species, and long-wattled ghost shark belongs to their number. Pairing at this species occurs at any time of year – in ocean depths seasonal change are not expressed. Male is a little bit smaller than female (its length is about 170 cm), and has advanced copulating organs on abdominal fins. It has keen sense of smell and searches for the female ready to pairing by smell. Having found it, male catches it up and slightly compresses by jaws her back fin, stopping the female and showing to it readiness to copulation. As a rule, deep-water animals differ in small intensity of metabolism processes. For this reason pregnancy at this shark lasts for very long time: about 15 months. Fertility of long-wattled ghost shark is very small: the female gives rise only to two young fishes. But the newborn shark of this species is about 60 cm long at once is able to eat independently and due to the size avoids the fate to be eaten. After birth of posterity the female picks up and eats egg shells. In some days after birth of posterity the female is ready to reproduction again. The young fish reaches length of 1.5 m at the age of 10 – 13 years. In same time it becomes able to breeding. Survival rate at young long-wattled ghost sharks is very high. It partly compensates the low reproduction rate: for all life the female gives birth to no more than two tens of young ones.
shark (Esocisqualus rivularis)
Order: Dog sharks (Squaliformes)
Family: Dog sharks (Squalidae)
Habitat: Asian rivers of Pacific and Arctic Ocean basins.
Picture by Alexander Smyslov
Shark in the river is more exception, rather than rule. Usually these cartilaginous
fishes live in sea, though some species of fossil sharks of Paleozoic era
were found in river deposits, and in Holocene some species of sharks were
able to live and breed normally in rivers. Basically such phenomenon was
typical in tropical zone of Earth. However in this case occurrence of freshwater
species of sharks in northern rivers was quite natural: approach of glacier
from the north forced some sea polar species to recede to rivers. This way
in the rivers of Eurasia burbot (Lota lota), the freshwater descendant of
cod fishes, has appeared.
Ancestor of the pike shark is one of sea dog species of Pacific Ocean. Receding to rivers during ice age, they adapted to long existence in fresh water, and then had made very important step: began to breed in rivers, having torn thus connection with salt water of ocean. At floods of rivers these sharks had settled over far inside of continent - in headstreams of rivers of Arctic Ocean basin. Being isolated from ocean, small sea dogs evolved to separate species – pike shark.
Pike shark is rather large fish: its length is up to 2 meters. Though for sea species it is rather mediocre size (frankly speaking), in fresh water of cool rivers of Northeast Asia only few species, capable to be compared to this shark in size, may be found. Body of this fish is very long and thin: the maximal height of it does not exceed 15 cm. Pike shark crowns feeding chain of northern rivers, being in them the original ecological analogue of crocodile.
The shape of pike shark is characteristic for the majority of sharks: pointed snout, inferior mouth, triangular fins and crescent tail. Colouring of body of this fish is striped: on olive-brown background cross light strips pass, breaking to separate spots on head. Head of pike shark is narrow and flat. Teeth are triangular and sharp: the basic food of this shark is medium-sized fishes and crayfishes. Sometimes pike shark eats small mammals got in water, and waterfowl.
This shark has kept a heritage of ancestors – sharp sense of smell and well advanced circuit of bodies of lateral line on head. These adaptations are especially useful at life in the river when water frequently happens muddy. However sight at pike shark also is well advanced: at it there are large yellow eyes with narrow vertical pupils.
By the habits this fish is typical bottom-dwelling predator. This shark spends the most part of time in thickets of plants, having directed by head against current. So it is easier to it to ventilate gills, and fishes and swimming animals, carrying by current, are visible. Colouring helps pike shark to mask.
In case of necessity this shark can swim from one place to another, bending eel-like by all body. But at attack it develops significant speed: up to 60 km per hour during several tens seconds. However in general it is nevertheless rather bad and lazy swimmer. This fish spends winter in deep holes in river channel, having stopped feeding completely. In winter time pike shark lives due to fat had been accumulated in long liver, stretching along all abdominal cavity.
Appetite at the pike shark awakes in spring when day becomes longer, and water gets warm. During floods of rivers when in river many bodies of drown animals float, pike sharks almost completely pass to feeding by carrion. In summertime when river water strongly gets warm, and the contents of oxygen in it decreases, sharks leave shallow tributaries and keep in places with cooler water: at the bottom of river and near underwater springs. In summer this shark hunts at night.
The basic problem of many sea fishes at transition to life in fresh water is the egg development: their eggs may develop only in salt water. Pike shark had avoided this problem by simple way: it is live-bearing fish. Pairing occurs in the beginning of summer, when fishes grow fat and restore forces after winter catalepsy. Males start to chase females, from time to time cautiously biting them to back edge of back fin. Pairing lasts not for long, and takes place in thickness of water.
In oviducts of the female within 10 months simultaneously 2 youngs develop, growing up to 30 cm. They are born in late spring and at once live quite independently, eating small fishes and crustaceans. Colouring of young fishes is more sated and contrast, than at adults. At the sixth – seventh year of life, when the length of young fishes reaches one and half meters, they become able to breeding.
Pike shark yields to pike in longevity: the age limit of this fish can exceed 100 years.
shark (Platysqualus cephalodiscus)
Order: Dogfishes (Squaliformes)
Family: Flat-headed sharks (Platysqualidae)
Habitat: coastal waters of the tropical zone of Indian and Pacific oceans.
Picture by fanboyphilosopher
Significant changes took place between Holocene and Neocene
among the sharks. Because of the “planktonic catastrophe” in the oceans, following
the numerous fish of the open ocean, the pelagic sharks disappeared as well.
Near the coasts, the mass extinction first of all affected all the animals that
dwelled on the coral reefs. The inhabitants of coastal waters, including sharks,
began to evolve actively after the stabilization of the conditions in the ocean,
occupying places in the new ecosystems. Sharks, in spite of the changes in the
natural conditions, did not yield their place of supreme predators, and among
them appeared forms, that obtain their food by the most diverse methods.
One of the strange sharks of Neocene is the whimsical-looking disk-headed shark, species no more than one-and-a-half meters in length. This fish is to some degree an analog of the hammerhead shark from the human epoch, but its appearance is somewhat different. The head of the disk-headed shark is very wide, flattened vertically and rounded on top. This form of head is caused mainly by the outgrown maxillary bones. The gills are located on the upper side of head disk, at its rear edge. The head partly provides lift during the movement of the fish; therefore the thoracic fins of this form have grown in length and are comparatively narrow. There are two dorsal fins, both bearing on their front edge tough and poisonous spines, inherited from their ancestor – one of the species of squalid shark. The tail fin has a very long and pointed upper portion. This species of sharks lives near the sea-floor at the depths from 1 to 50 meters. The disk-headed shark does not avoid fresh water and frequently hunts in the mangroves, remaining in puddles during the ebbing tides. In river mouths this shark lives in places with strong undertow and water is brackish.
The body of this species is beige with numerous dark spots, small on the head and the fins, and large on the body. On the back of the shark the spots merge into an uneven strip that goes along the length of the backbone.
The eyes of the disk-headed shark are small, located on the front edge of the head disk. The snout characteristic for the sharks in this species is quite short and almost does not disrupt the disk-shaped form of the head – it only slightly protrudes forward between the eyes of the fish. The narrow vertical slit-shaped nostrils are located next to the internal edges of the eyes. The eyes of this shark shine in the darkness with greenish color – a layer of the cells, rich in guanine, underlines the retina. The sight of this species is good, but it plays only a secondary role in hunting of this species.
The specific form of the head of the disk-headed shark is caused by the presence of special adaptation for the search of prey. The lower side of the head and edges of the jaws of this shark are supplied with a large number of electro-receptors, which make it possible to track down the minimum electrical activity at the small distance from the skin of the fish. When hunting, the disk-headed shark swims above the sea bottom, holding the lower part of its head parallel to the flat sea-floor. In this case, the electro-receptors indicate the presence of the animals that are burying into the sand, which this fish eats – cephalopods, crustaceans and small fishes. The mouth of this fish is relatively small, but because of the mobile joints between the maxillary bones, it can be extended downwards in the form of a tube. The teeth are numerous, thin, designed for splitting – they are designed to catch middle-sized, but slippery prey. Swimming above the sea-floor, the fish literally “scans” sand in search of hidden animals. After determining the location of prey, it with one strike puts the prey under its head disk. After sensing the attack, the prey, most frequently, attempts to bury itself even deeper, but the shark extends its jaws downwards, overtaking the prey. With this method of hunting, the shark gets plenty of sand in its mouth, but this is not a problem for the predator: the sand is forcefully ejected through the gills, while the jaws reach for the prey.
The disk-headed shark is viviparous. Once per year a female gives birth to twenty young sharks, completely ready for independent life. The young sharks mostly feed on free-swimming prey and their heads are less disk-like. At the age of approximately one year heads of the young sharks begin to widen. At the age of five years the shark reaches length of approximately 120 cm and can breed.
Translated by Bhut, the forum member.
Arrow-headed shark (Sagittoselache diplocauloides)
Order: Dogfishes (Squaliformes)
Family: Flat-headed sharks (Platysqualidae)
Habitat: coastal waters from the tropical to the warm-moderate zone of Pacific Ocean: Indonesia, the coast of Asia to the north of Japan Islands.
In Neocene, the sharks proved again the success of their evolutionary branch. Many species of these fishes disappeared after “planktonic catastrophe”, but those who survived, rapidly evolved, occupying the freed ecological niches. During evolution many species succeeded to survive, and many bizarre types appeared among them. Several species of sharks with very wide heads became the original analogues of the hammerhead sharks of the Holocene epoch.
A large representative of flat-headed shark family is the arrow-headed shark, a predatory fish up to 3 meters in length. This species of fish possesses a very characteristic appearance, and it cannot be confused with other fishes. The head of this fish has a form of a stylized arrow tip – it is flattened, extended at the edges, triangular in shape, with large lateral lobes turned backwards and to the sides. The lobes form the kind of wings and by function they supplement the pectoral fins. The eyes are located on the front edge of the lobes, approximately between the snout and the tips of lobes. They are large, and the pupils are capable to enlarge strongly: this is an adaptation for living in habitats with low illumination. The nostrils, positioned widely to the sides, are located next to the eyes.
The pectoral fins of this species are shortened and extended. When swimming quickly, this shark thrusts its pectoral fins against its body and their function is taken over by the head of the fish. In search of the prey, the arrow-headed shark slowly swims above the sea-floor. At this time, its head fulfills another important function – the receptors on its bottom side help to determine the presence of prey. Pectoral fins have also another very important function. The tips of pectoral fins of this shark are armed with a kind of claws – the part of the edge of fins is covered with several rows of increased skin “teeth”. They are larger in males – with their aid, the male retain the female during mating. Furthermore, these “claws” help the shark to escape from the storm. The arrow-headed shark dwells along shallow coasts, and it lies down into deep holes on the sea-floor and attaches itself before the beginning of storm, butting its fins against the walls.
The skin of the arrow-headed shark is dark grey in color, with dark strip located on the front edge of the head lobes. Another dark strip outlines the rear edge of the tail fin. The belly and the lower part of the head are brighter than background coloration. The upper fluke of the tail is approximately twice as long as the lower. The back fin is tall with a dark tip. At the front edge of the fins there is a small spine, which lacks a poisonous gland.
This shark lives only in water of oceanic salinity, and avoids fresh water, not entering the mouths of rivers. Because of this special feature, it does not compete with its close relative, the disk-headed shark. Also it feeds at a greater depth: from 3 to 100 meters and even deeper. This species is a bottom-dwelling shark, which feeds mostly on octopi and crustaceans. In contrast to its smaller relative, it does not dig in sand and patrols over rocky areas of the sea-floor. When hunting, the arrow-headed shark slowly swims above a reef. It senses the electrical activity of the nervous systems of the hidden animals. With sharp thrusts the shark flushes them out and catches them in its jaws.
The arrow-headed shark is viviparous. Once per year, the female gives birth to two large young up to 60 cm in length, already prepared for independent life. Soon after the birth, the female is again ready to bear young. The male of this species is smaller and slimmer than the female, with larger back fin. It finds the female by smell and begins to pursue it. If there are several males, they swim after the female as one. Usually, in several hours, the female chooses one male that chases away the rest ones. The mating occurs in a stomach to stomach position. The male grabs the female by the pectoral fins during the entire mating. During it, the fishes swim slowly in the deep, open water; the female usually swims with its back upwards and the leading role in this undertaking belongs to it. After the mating, the male leaves the female.
The young arrow-headed sharks differ from the adults by their darker colours with brighter spots in upper part of the body. They have narrower heads with the smaller lateral lobes, which do not prevent its birth. As they grow, the lobes of the head grow, and it takes the form that characteristic for this species. At the age of five years, the young shark becomes capable of mating. The lifespan of this species reaches 30 years and more.
Translated by Bhut, the forum member.
Zeus's shark (Electroselache zeusii)
Order: Dog sharks (Squaliformes)
Family: Electric sharks (Electroselachidae)
Habitat: Atlantic, depths from 50 up to 300 meters in tropical and subtropical area; at night emerges to water surface.
During the evolution process organs and tissues may considerably change the functions in comparison with their initial applicability. So, at fishes belonging to various systematic groups muscles had changed to electric organs becoming the effective adaptation for orientation and hunting weapon. In Neocene new groups of fishes had got electric organs. Zeus's shark living in Atlantic Ocean is an electric species of sharks. It is an example of parallelism with rays of order Torpediniformes, known even in human epoch as owners of strong electric weapon – hunting and protective adaptation. Zeus's shark has received the name by analogy to skill of antique god Zeus to fulminate, but, as against the mythical person, it makes it in real life.
This species is a pelagic fish of about 2 meters long weighting up to 150 kgs and living in top layers of water in temperate and subtropical zone of Northern hemisphere. Appearance of Zeus's shark is typical for the majority of sharks – it has streamlined body, pointed fins, unequally-lobed tail with the increased top lobe. Pectoral fins of this shark are rather short: it is able to swim quickly only at short distances. Colouring of body of a Zeus's shark is light blue with black spots on tips of pectoral fins. The top lobe of tail from the tip up to middle is colored white.
The anatomy of head of this shark is remarkable. It has wide short snout, and skull is expanded in top part, forming two big crests directed sideways and a little bit upwards. These crests serve as original stabilizers of position of body at swimming. Eyes are shifted downwards under stabilizer crests. The distant relative of this species, huge cachalot shark (Physelache planicephala), has a similar structure of head. Mouth of Zeus's shark is small; jaws are attached to skull and to each other by elastic ligaments. Teeth of this species of sharks are peaked, needle-like, small and weak; they grow on jaws forming six – eight lines. It is impossible to cut half-and-half even the soft body of squid by them; they serve only for keeping of prey. Jaw muscles of this shark are also very weak. It is connected to the fact that the significant part of strong muscle closing the mouth at ancestors had turned to electric organ and had lost the ability of contracting. Besides crests on skull of this fish were also formed for increase of size of electric organs which are attached to their basis. The voltage creating by Zeus's shark may reach 250 volt at force of current up to 2 amperes.
Zeus's shark hunts schooling fishes, pelagic crustaceans and cephalopods. Usually it slowly swims in thickness of water, but, having felt approach of school of prey, makes a throw. Wedging in school of sea animals, shark produces some strong electric pulses one by one. It happens enough to kill or to paralyze several fishes or squids. Usually the most part of school escapes, but this shark always gets some prey animals. It simply swims across the “battlefield” and gathers shocked fishes. This shark swallows prey entirely: jaws can opened widely due to extensible and elastic ligaments. Due to the ability to produce strong electric impulses the present species of sharks does not have any satellite animals of various kinds usually accompanying sharks.
Zeus's shark is a solitary species; only during the pairing some males may court for one female. During the courtship ritual males produce the short weak electric impulses having signal function. Female also replies them with electric impulses. If it is not ready to pairing, it banishes male by stronger electric pulse.
This species is viviparous: after the pregnancy lasting about 7 months the female gives rise to up to 6 large (about 30 cm long) and independent young sharks. Young ones the first days of life can not produce electric impulses – it protects the female at delivery process, but makes young sharks very vulnerable. During the first days of life the electric organ starts to develop, and at young fishes grown up a little electric impulses are already strong enough to frighten off the predators really dangerous to fishes of their size. Sexual maturity at young Zeus's sharks comes at the age of 4 years, and life expectancy reaches 25 years.
In northern part of Pacific Ocean Zeus's shark is substituted by close species – Taranis’s shark (Electroselache taranisii), named after Taranis, the god of lightning of ancient gauls. This species differs from Zeus's shark in larger size – up to 3 meters at weight more than 200 kg. Because in the top layers of water in Pacific Ocean sharkodile (Carcharosuchus deinodontus), ecologically replacing large sharks and being an active predator dominates, in day time this shark keeps at the depths of about 100 – 200 meters. Possible, the settling of an ancestor of these fishes had proceeded through Panama Passage. Taranis’s shark also has electric weapon. Fertility of females of this species reaches to 10 – 15 young fishes.
Meganesian sawfish (Pristis meganesianus)
Order: Sawfishes (Pristiformes)
Family: Sawfishes (Pristidae)
Habitat: rivers of Meganesia.
During Holocene sea ecosystems had suffered not less than land ones, because people polluted ocean and caught many species of food fishes and invertebrates, not reflecting about the future. Besides “planktonic accident” had caused destruction of great number of species of pelagic animals. Species had not died out during the reorganization of ecosystems, should adapt to existing is sharply changed conditions of Neocene. Bentic communities of coastal waters had suffered lesser; more kinds inhabited such areas had kept. Dwarf sawfish (Pristis clavata) was among ones managed to survive in epoch of anthropogenous pressure and biological crisis. Having managed to go through threat from the side of people in Holocene, in Neocene it was compelled to adapt to new neighbours: Neocene saw-nosed crocodile (Pristisuchus serratorostris) had occupied the ecological niche of sawfishees in brackish reservoirs of Meganesia, and other crocodile species, giant sharkodile (Carcharosuchus deinodontus), has risen on top of food pyramid in tropical waters of Pacific Ocean. In such conditions the way of life of sawfish could not remain former. It had adapted to new neighbours and conditions of life by the same way, as well as some other species of cartilaginous fishes. Like pike shark (Esocisqualus rivularis) of Asian rivers and river shark (Neocarcharinus flumineus) of East Africa, dwarf sawfish had passed to life in fresh water. This species lives in Meganesia where there is enough forage and there are no large competitors. Meganesian sawfish inhabits rivers flowing to Eyre Gulf. In Arafura Lake this species of fishes is superseded by saw-nosed crocodile, and submitted by only separate individuals.
Meganesian sawfish is not so large kind of rays: its maximal length is 60 – 80 cm. The largest individuals, sometimes up to one meter long, live in coastal freshened zone and mangrove thickets of Eyre Gulf. Colouring of flattened body is concealing: greenish-brown (at females there is a prevalence of yellow shade). The snout has kept the characteristic sawtooth shape, but became much shorter, than at ancestor – less than one third of total length of fish. On it 9 – 11 pairs of teeth grow; they are sharp enough and quite capable to deliver dangerous laceration to predator or prey. But by its habits Meganesian sawfish is sluggish and inactive fish, preferring to attack from an ambush instead of prey chasing. This ray eats small river fishes and invertebrates, dexterously digging them from silt by snout. The mouth of this fish is located on the bottom side of body, and fish swallows prey, preliminary having pressed it to the bottom by body. At threat of predator attack this fish gets deeper into thickets of aquatic plants, or is simply dug in silt. However the seized fish strikes wounds to the enemy by snout. Male has longer snout, than female; also it is more graceful and smaller a little, than female.
Meganesian sawfish has very small eyes shifted to the basis of snout. Bad sight is quite compensated by a circuit of electroreceptors on skin, especially on bottom part of body. With their help fish easily finds out the prey hidden in sand, in total darkness. This adaptation allows Meganesian sawfish to hunt successfully even during high water, when rivers carry a plenty of dregs.
This is live-bearing species of fishes similarly to its ancestor. The female bears posterity within approximately eight months and gives rise up to four young fishes completely ready to independent life. At newborn sawfishes snout is protected with dense cover of jelly-like mass, which falls down right after birth. To one-year-old age approximately half of young growth stays alive, but further death rate reduces. Female becomes sexually mature at the seventh year of life. Total life expectancy of Meganesian sawfish reaches 40 – 50 years.
This species of fishes was discovered by Bhut, the forum member.
Bunyip (Teratoceratodus bunyip)
Order: Australian lungfishes (Ceratodiformes)
Family: Barramundas (Ceratodidae)
Habitat: rivers of Eastern Australia to the north up to Carpentaria Lake.
Picture by Alexey Tatarinov
Colorization by Carlos Pizcueta
The bunyip is a mythical predatory aquatic monster from Australian
rivers. In Neocene the legend about this creature had been unexpectedly embodied
Crocodiles had died out in an ice age, but to change them in their ecological
niche the new predator had come, quite suitable by its habits to the image
of legendary monster.
Ancestor of this creature is not a reptile, but fish, the amazing Australian barramunda (Neoceratodus forsteri). As it is paradoxical, this creature had got advantage in survival because of human activity: in XX century of human epoch this fish had been widely settled by people at the continent for the purpose of preservation of this species. It was successful act, and the small population of barramunda had survived in lakes at bottom of Great Dividing Ridge. To survive, these fishes had starting to master other food sources, than were at their ancestors. Rather large animals, mainly vertebrates, are including to ration of Neocenic bunyip. This fish had replaced the extinct crocodiles at top of food pyramid.
It is strictly freshwater fish. Bunyip does not come to Carpentaria Lake far from coast because of residual salinity of depths (this lake represents a former sea gulf), moving only along coast and is settling in swamps surrounding this lake. Bunyip does not live in Arafura Lake at all: it is even more salt, and here one of relic species of crocodiles replaces it. But bunyips live in the rivers running into these lakes, and in circuit of channels and bogs of tropical rainforest.
Bunyip not so strongly differs from the ancestor: it had kept features of structure characteristic for the barramunda – flipper-like fins, large scale and one lung. But it had appreciably increased its size: it is a huge predatory fish up to 4 meters long and weighting over 400 kg. The female is larger and paler than male, but at the male head is larger. The tail of bunyip is short, rounded and expanded in comparison with the lengthened peaked tail of barramunda. It is used only for sharp throws for catch, and not hunting fish swims with the help of movements of wide flipper-like paired fins.
The head of bunyip had turned to true ram: the cartilaginous skull is considerably strengthened by shell scutes. Corneous plates, with which help fish grasps and dismembers catch, have peaked cutting outgrowths. They can split half-and-half seized catch: fish, lizard, bird or mammal. Bunyip avoids only attacks on the adult turtles protected by firm carapace, but this fish swallows the young growth of turtles entirely and exterminates it in plenty.
At the bunyip there are small eyes and bad sense of sight, but sharp sense of smell and sensitive lateral line. Even in darkness this fish can easily find and seize small frog swimming several meters far from predator.
Bunyip is bad swimmer, but it is the master of camouflage: its colouring – brown with dark speckles – makes it badly seen among river dust: driftwood, trunks of trees and layer of fallen leaves. Having masked, the fish passively expects catch, attacking it by fast throw. About two - three times at hour bunyip emerges for air, though in case of necessity and in fresh water, rich in oxygen, it can make it only once per hour, and even less often. At breath the fish utters loud groaning sound especially far heard in silent night. Each fish protects territory from neighbours, and this sound distributing under water, warns neighbours of territorial claims of bunyip.
The bunyip tolerantly concerns to life in pond with muddy stinky slush to which water turns during a drought: it respires by air, and the zero contents of oxygen in such water is indifferent to it. However this fish does not live in completely drying up reservoirs, because it has no special mechanisms promoting preservation of water in body. When the drought begins, bunyips leave inundated reservoirs and migrate to the central channel of river, or stay in deepest ponds. When in river channel many fishes of this species swim together at once, between them there are fights and many borders of territories are reconsidered. Though in inundated reservoirs there are young and weaker fishes, and in the main channel the strongest individuals live, some young applicants had “grown up” till the rain season, more often succeed to win at older individuals a place to themselves. Fight is accompanied by demonstration of forces, pushes by sides and impacts by head. When forces are equal and any contender does not concede, jaws are used for fight. Some old individuals have characteristic traces of stings on back and sides – four deep V-shaped small holes placed in corners of rectangular, staying from the pointed ends of cutting plates.
The spawning of bunyips occurs once a year in rain season: at this time many fishes leave the basic channel, and the competition is reduced. The unitary fast spawning is a consequence of very short period favorable for spawning at ancestors of bunyip during the ice age (at the barramunda spawning is portional and dragged out to some months). For spawning the male chooses underwater small-leaved plants, clears them of silt by movements of fins, carries off stones and dust, and starts to invite the female to the prepared breeding bottom. It pushes the female by head, swims around of chosen bush of water plants, emerges and specially “sings”, exhaling air with all its might.
In clutch of bunyips there is up to thousand of very large grains of roe (their diameter is about 2 cm). Fishes spawn eggs in plants prepared by male, and he stays to protect territory around of clutch, not caring special way about eggs.
Egg incubation lasts about 2 weeks, and then approximately equal time the larva passively lives at the bottom, hiding from enemies, not eating and digesting the rests of contents of yolk sac. Later it passes to feeding by small water invertebrates and fry of fishes. At one-year-old age the bunyip reaches length about 10 cm. Further, having transited to feeding by fish, fish strongly accelerates the growth rate, and at ten years' age, at length about two meters, the fish already can take part in spawning. The maximal life expectancy of bunyips may exceed 150 years.
boltergiller (Potamocetus balaenognathus)
Order: Osteoglossoids (Osteoglossiformes)
Family: Aravanas (Osteoglossidae)
Habitat: rivers of South America, central part of channel.
Picture by Amplion
After the ice age had marked border of Holocene and Neocene,
climate began considerably more humid: seas have filled coastal sites of land,
of water evaporation had increased. Rains had returned again to equatorial
areas of Earth, having filled with water great rivers. Amazon and Hyppolite,
flowing in parallel to it, are two rivers gathering water from significant
part of South-American continent. Each of these rivers differs in large width,
overflowing at tens kilometers and flooding riverbank woods.
Waters of these rivers gather organic substances from huge woody area, and current of the rivers is slow enough. Due to it in central part of river channel in upper layer of water plankton (algae, small crustaceans and worms) plentifully develops. Shoals of fishes serving as food to some predatory reptiles, mastered channels of big rivers, eat river plankton. But these predators respectfully make way for one of inhabitants of channel – huge four-meter fish slowly swimming near the surface. This fish inspires respect in size, but it is not furious predator. It is the river boltergiller, the descendant of aravana (Osteoglossum). This fish does not represent danger for animals longer than 3 – 4 centimeters: it eats plankton, tiny schooling fishes and fry.
Due to abundance of food this river giant easily increases weight up to about 300 kgs. Body of the boltergiller is compressed from sides, especially in tail part, right after abdominal fins. Back, head and top part of tail make practically straight line: it is an attribute of top-skimmer fish spending the most part of time at water surface. Boltergiller swims rather slowly, bending by all body like eel. The tail fin at it is small and narrow, grown together with anal. Wide band-like anal fin stretching from middle of body up to the end, is the main organ of movement of fish. The back fin is reduced up to the several fin rays not connected by membrane.
The head of boltergiller is high, and mouth can open widely. Thus jaws draw downwards and in sides, forming wide funnel. Gills of fish had changed to effective filter device: branchial stamens have turned to similarity of dense grid, detaining even smallest zooplankton. Eyes of boltergiller are rather large, orange-colored. In spawning season eyes of males get ruby-red color. On chin pair of characteristic wattles directed forward stick.
The body of fish is covered with large rounded scale. Colouring of body is silvery with blue shine and grey back. The anal fin is bordered by black strip.
The boltergiller spends all adult life far from river coast. It is solitary fish, only at “pastures” rich in river plankton it is possible to meet at once several fishes. They do not pay attention against each other.
The spawning season at these fishes lasts within all year, but fishes show especial activity after rain season when water in the rivers is rich in plankton. Male ready to spawning declares itself by high jumps from water. At times fish takes off from water vertically at three - four meters upwards, and plops down on side, splashing a cloud of splashes. The booming sound lets females know, that the male is ready to take part in courtship. This fish is monodin. Spawning proceeds in thickness of water. Female spawns large egg in portions, male fertilizes them, and then female picks them up by mouth. Such acts repeat, while all eggs will be spawned.
At this species not only the female, but also the male, shows care of posterity: when all eggs are spawned, female delivers a part of clutch to the male from mouth in mouth. Term of egg incubating is about one week. All this time fish, bearing posterity, does not eat. But it does not harm to its organism: fishes are able to fast for very long time. Fry spend first days in mouth of the parent, but starting to swim, they leave it and further live independently. When the fish bearing posterity, feels, that fry are ready to leave the refuge, it approaches to riverbank and comes into small rivers. Here parent opens mouth, and fry swim out in searches of food.
Larvae of river boltergillers feed in coastal waters, occasionally remaining in lakes after river floods. Here, far from the majority of predators, fishes grow fat, and at the following floods leave temporary refuge and swim to the basic channel of river. They become sexual matured at the fifth year of life at length about two meters.
The boltergiller differs in significant longevity: this fish can live up to 60 - 70 years.
In shallow rivers of Amazon and Hyppolite basins there are close species: green boltergiller (Potamocetus viridis) smaller fish reaching only two-meter length. It differs in richer branchial stamens allowing filtering from water phytoplankton – the main food of this species. The body of this fish is higher and also has greenish colouring.
phyllomormyrus (Phyllomormyrus lethalis)
Order: Elephantfishes (Mormyriformes)
Family: Elephantfishes (Mormyridae)
Habitat: Zinj Land, steady flowing rivers and lakes.
Picture by fanboyphilosopher
Till the evolution process the role of adaptations produced
by ancestors of any species of live organisms can vary strongly. For example,
leaves of plants may turn to spikes, and stalk fulfills the function of leaves.
When any plant loses petals, but later comes back to pollination with the help
of insects again, floral bracts become bright like petals. Such phenomenon of
function change is not a rarity in nature.
At African elephant fishes till the evolution the adaptation was developed for orientation in space in conditions of bad visibility – fishes had got ability to develop faint electric field, and began to define the presence of other objects near to themselves by its changes. Such attribute during the evolution process appeared repeatedly at various species of fishes, therefore the development of electric bodies at elephantfishes does not look something oustanding. When the East African subcontinent (Zinj Land) had separated from the continent, these fishes began to evolve independently of continental species. In reservoirs of Zinj Land the special ecosystem had formed, where the original species of elephantfishes became one of top predators. It has developed special hunting tactics getting food – small schooling fishes and tadpoles.
These species of elephantfishes is named phyllomormyrus (“leaf-like Mormyrus”) for the special body shape and coloring. This fish has cryptic coloring and shape which simulates rotting leaves very precisely. High rhomb-like body of fish is compressed from sides; it is about 20 cm long and colored brown with yellowish spots. Along the side rough light strip stretches. On back and anal fins there are rough dark brown borders similar to rotten edges of leaves of any tree. The edge of back fin, pectoral fins and tail of fish are completely transparent. Eyes of phyllomormyrus are also disguised – iris of eyes is brown with grey “marble” pattern masking the eye at the background of body colouring. The snout of phyllomormyrus has the lengthened shape characteristic for these fishes, and simulates a leaf petiole. It is very long, and also makes about one third of general length of fish. On the tip of snout there is small mouth with short appendage on lower lip. The male of this species does not differ from the female in colouring; it is only smaller a little than the female.
The hunting tactics of phyllomormyrus combines tactics of South-American fishes of Holocene epoch known to people: leaf fish (Monocirrhus polyacanthus) and electric eel (Electrophorus electricus). This species of elephantfishes eats small animals, preferring tiny schooling vertebrates. This predator creeps to fry or tadpole school using cryptic colouring. The shape of fish simulates leaves of a tree beginning to rot so well that it misleads even the most cautious fishes. Hunting phyllomormyrus is slowly swimming to planned prey, moving by transparent fins. For most persuasiveness fish can swim in any position, keeping body obliquely or even laying on the side. Appearing among fry or tadpole school the fish suddenly strikes them by electric impulse. Stunning prey, fish can emit one by one up to four electric impulses in succession. After that fish simply gathers paralysed catch by proboscis from the bottom. If necessary the phyllomormyrus gives additional electric impulses, paralyzing animals trying to escape from it. Phyllomormyrus also eats larvae of insects, searching for them in thickets of underwater plants.
This fish is a single predator. Each individual occupies the certain site in shallow waters overgrown with plants. Large driftwood and bushes of water plants serve as marks of territory borders. When two fishes meet at the border of territory, they exchange series of faint electric pulses, distinguishing each other and estimating physical condition of the contender. Usually young fishes live at boundaries of sites of adult fishes, avoiding an opportunity of meeting the adult individuals. These fishes can not injure each other by stings - mouth at them is too small for it. But the adult fish can paralyze and even kill young individual of this species by electric impulse.
The spawning of phyllomormyruses begins with approach of rainseason. Pairs at this species are formed of adult individuals living at next sites. Before the spawning male and female exchange electric pulses in special rhythm which is analogue of courtship dance. For this purpose partners rise under floating plants in parallel to each other, and emit a series of electric impulses. First male and female do it alternately, and then pulses become simultaneous. Such feature of behavior synchronizes processes of roe ripening. Prespawning games proceed till approximately day and night. For spawning fishes build a nest of floating long-steme plants. They weave plants to dense tangle among thickets, and get into it together to spawn large eggs.
In clutch of phyllomormyruses it may be totally more than three hundred large eggs. The male protects nest against possible predators with the help of electric impulses. At this time it eats almost nothing, and only occasionally catches prey had casually appeared near the nest. The egg incubating lasts about three days, and two more weeks larvae not able to swim sit in nest. When fry starts to swim and leaves the nest, male ceases to protect the posterity. Young fishes usually keep in rich thickets of plants where adult fishes of this species can not make the way. To the end of first year of life young fishes reach the length 4 – 5 cm, and at the third year of life at length about 15 cm they already start to breed.
Ice galaxia (Antarctogalaxia cryoresista)
Order: Galaxiiforms (Galaxiiformes)
Family: Galaxias (Galaxiidae)
Habitat: fresh waters of Antarctica.
Antarctica is a continent which nature had gone through catastrophic changes in late Cenozoic. The severe congelation had held down continent for millions years by ice layer of more, than one kilometers thick, having completely deprived this ground of vegetation and fresh water. In Holocene the nature of this continent was presented only by sea animals dependent on efficiency of ocean, and several species of tiny terrestrial invertebrates.
In Neocene, due to climate warming, glaciers of Antarctica had started to thaw. The significant part of continent had exempted from ice, but in polar area still there is a glacial cover. But the edges of continent directed to Indian Ocean and Australia, are covered with meadows of graminoids and sedges. In spring, when snow thaws, meadows become covered by circuit of lakes and bogs. Besides on central glacier short rivers spring. In them an interesting ecosystem had formed – the primal freshwater fauna of fishes was destroyed by a congelation, and various larvae of dragonflies have partly replaced small fishes live in the majority of temporary and constant reservoirs. Sea fishes come into lower reaches of Antarctic rivers, but they do not live in fresh water constantly. However some descendants of sea fishes passed to life in fresh water. It is rather difficult step – in Antarctica extreme conditions of an inhabiting dominate. In frosty winter rivers of Antarctica become covered by thick layer of ice, and shallow standing reservoirs may freeze up to the bottom. But all the same, as soon as ice thaws, in the rivers of Antarctica it is possible to see fishes.
Long-bodied fishes about 20 – 30 cm long slide in ice-cold water among stones. At them there is rounded in section eel-like body supplied with short fins. The skin of fish is lack of scales, covered with layer of slippery slime due to what fish freely rummages in stones, not being afraid, that it may be pressed down. Colouring of this fish is brown with numerous green speckles. This inhabitant of Antarctica is named ice galaxia, and it belongs to group of fishes very characteristic for southern hemisphere. In prehistoric times galaxias, obviously, lived in Antarctica before the continent was buried under ice cover. In Neocene descendants of one species of these fishes (possible, South-American or Tasmanian one) had conquered the continent “fishless” earlier.
Ice galaxia almost constantly lives in fresh waters of Antarctica - in rivers, lakes and bogs. It eats larvae of numerous Antarctic species of dragonflies. This fish can catch swimming larvae in thickness of water, but prefers to dig ground by flattened head in searches of sluggish creeping larvae of large species of dragonflies.
For Antarctica the seasonal climate with sharp difference between winter and summer temperatures is characteristic. Though Neocene is rather warm epoch, Antarctica still is near South Pole, and it is only slightly warmed with sea currents from equator. Therefore in winter ice galaxias put on trail on durability – they should resist to all-permeating rigorous cold. These fishes do not try to escape in warmer places (for example, in sea). They continue to live in the same place where they lived before colds. When frosts lock the surface of reservoir, fishes dig in silt, plaiting in tangle of several tens individuals and plentifully secreting slime. Such tangle of fishes is surrounded with viscous mucous mass which has two important qualities – antifreeze and antiseptic. It interferes the freezing of integuments of fishes, and does not enable parasites to attack hibernating fishes. In winter at weakened fishes in collective hibernation wounds heal easier, and individuals struck by ectoparazites recover. In deep whirlpools fishes do not dig in ground, but also surround itself with slime. This way fishes hibernate more successfully – even if ice is formed on the surface of common mucous cover, fishes will not be injured. And even if the tangle of fishes will freeze in thickness of ice, inside it all the same semi-liquid slime remains.
Ice galaxia spawns in lower reaches of rivers and at the sea shallows. In spring till the high water time fishes had survived in wintering, migrate to lower reaches of rivers by large shoals. If fishes hibernated in standing reservoir, they all the same aspire to reach the sea. While night replaces day, fish creeps out of water and creeps by ground to the nearest river, being guided by smell of river water. Males arrive to breeding bottoms the first. Having felt brackish water, they get courtship dress. In breeding-dress at the male green speckles in forward part of body turn golden, and iris of eyes brightens. Males begin courtship demonstrations in places well protected from local fish-eating birds – yellow-headed divesparrow and large penguigulls: among brown algae where birds do not swim. They gather schools, and while there are no fish-eating birds around, demonstrate themselves in shallow water. At the slightest sign of danger they hide among seaweed and turn dull.
When females come, males change. Any care is lost, and rough spawning begins. Schools of males and females join, and leave a trace of pale soft roe and small translucent eggs. At this time they are not afraid neither birds, nor predatory fishes, absorbed by the purpose of breeding. Fishes scatter eggs at the bottom, and it is the limit of their care of posterity. After spawning schools of ice galaxias remain in lower reaches of rivers till some days, restoring forces. Strongest individuals spawn once again, though a repeated spawning is not as active, as main one.
Young fishes spend first two years in river estuaries which do not freeze – they are too small to resist to cold. It is easier to hibernate to large fishes, and small fishes often freeze in ice and freeze through, that results in their death. Having reached approximately 2/3 of the size of adult individual, ice galaxias rise upstream and settled from river mouth to fresh waters of continent. Young fishes rise against the current in common with adult individuals coming back from spawning. It will pass about 2 – 3 years, and they will mature and can take part in spawning.
Long growth of ice galaxia is compensated by enviable longevity – cold winters as if brake ageing of fish organism, “preserving” it approximately for half-year. For this small species of fishes the age of 40 years is usual term of life, and occasionally even 50 – 60-years old “patriarchs” are found.
Ichthyophyseter, cachalote fish (Ichthyophyseter theutiphagus)
Order: Tarpons (Elopiformes)
Family: Cachalote fishes (Ichthyophyseteridae)
Habitat: temperate and cold waters of all oceans, depths from 100 up to 2000 meters. At night individuals from the populations living in the top layers of ocean may rise almost to water surface.
Picture by Alexander Smyslov
Overhunting and pollution of ocean had resulted in sharp decrease of number
of cetacean population, including odontocetes feeding at the great depths
– sperm and bottlenosed whales. Populations of these animals appeared too
in order to restore the species of these mammals in former number. This event
had resulted in growth of number of cephalopods – the basic prey of these
whales. In early Neocene squids had made serious attempt to press fishes
of open ocean. They had occupied ecological niches of medium-sized
and some of them became very large animals.
To reply to the burst of number and variety of squids among fishes the species
capable to compete to them,
and even to attack squids began to evolve. Among them false
to catch up even the fastest squids, had appeared. And other species had
staked on strenght and had turned to specialists in large squid hunting.
shark (Physelache planicephala) from Northern Atlantic and also cosmopolitic
mesopelagic cachalote fish, or ichthyophyseter, belong to such species. It
descends from one species of tarpons (Megalops) – representative of low-specialized
group of osseous fishes. Due to unpretentiousness and ability to live in
water of various degrees of salinity tarpons managed to survive in epoch
pressure, and after human disappearance had made a number of successful attempts
to manage pelagic habit of life.
The body length of this species is up to 6 – 7 meters; it is one of the largest osseous fishes of Neocene. The body of ichthyophyseter has a shape typical for tarpon fishes – fish resembles huge herring with disproportionately large head reaching the one fifth of a body length of fish.
Ichthyophyseter is bad swimmer. This fish is able to do short fast throws but swimming to long distances is an excessive task for this predator. Unpaired fins of this fish are shifted back. Back fin is pointed, and tail fin is wide and forked. Body is covered with tiny scales deeply immersed in skin. Because of it the skin of fish seems rough to the touch. Skin has dark grey color; fins are transparent. Peritoneum is also transparent, and swallowed prey is visible through walls of stomach.
Muscles of ichthyophyseter are rather flabby and soft. The most part of time fish passively floats in water due to fat with which its muscles and skeleton are impregnated. Eyes of ichthyophyseter are completely reduced. Even traces do not remain from them; the optic nerve is also reduced. In life of fish sight is functionally replaced with seismosensoric feeling: at ichthyophyseter bodies of lateral line are well advanced. They form dense circuit on head and the dual lateral line along the body. Sense of smell of ichthyophyseter is also very keen. Large nostrils have the unusual shape – they are extended to long grooves, are arch-like bent upwards and stretch from tip of muzzle up to the place of former eye-sockets.
Teeth of ichthyophyseter are numerous and similar to nails – they are very thin and long. Some hundreds teeth grow not only at the edges of jaws, but also on the palatal bones and on edges of tongue. Small peaked teeth also cover a surface of tongue. The main task of such teeth is not to cut flesh, but to keep slippery and flabby body of squid – the basic prey of ichthyophyseter.
This species lives mainly in depths of ocean. In Atlantic ichthyophyseter competes to cachalote shark and consequently keeps in depths. In other parts of area this fish frequently rises to the top layers of water, and it happens, that the heavy gale casts such fishes ashore.
As a meeting of such fishes in depths is rather rare event, in breeding physiology of ichthyophyseter the essential changes take place. This species is hermaphroditic; each individual is capable to produce simultaneously male and female sexual products. Fertilization is carried out with the help of cloaca capable to turn outside. Self-fertilization is possible only in extreme cases, and usually two sexually mature individuals mutually fertilize each other. Sperm is kept viable for a long time in distal part of ovoduct. At the moment of egg spawning spermatozoids leave in water, turn more active and fertilize eggs. Eggs are spawned as a long slimy cord that facilitates care of posterity: fish at once takes the fertilized eggs in mouth and bears clutch within several days. Spawning takes place repeatedly within one year.
The characteristic for tarpons leptocephalus larva of prolonged leaf-like shape hatches from egg. It leads pelagic way of life and has well advanced eyes and wide mouth with pointed teeth. Leptocephali of ichthyophyseter live in top layer of water and eat young ones of other species of fishes and pelagic invertebrates. Cannibalism is also characteristic for them. At the length of about 4 – 5 cm metamorphosis begins: the reduction of eyes and increase of mouth take place, body turns narrower and shorter. Fry of ichthyophyseter lives at the depths of 30 – 50 meters and eats mainly crustaceans and small fishes. As fish grows, the reduction of eyes proceeds further and fish passes to life in depth. Its diet changes, and it passes to feeding on cephalopods. At the age of five years it reaches the length of two meters, and fish grows up to maximal size at the age of twenty years. Life expectancy of ichthyophyseter reaches 60 – 70 years.
Hornet catfish (Toxiglanis crabro)
Order: Catfishes (Siluriformes)
Family: Bagrid catfishes (Bagridae)
Habitat: Zinj Land, medium course of Indian Ocean basin rivers.
Zinj Land is huge subcontinent which broken away from Africa approximately 15 MY after the mankind extinction. It is separated from the basic continent with Tanganyica Passage which has passed just along the chain of Great African lakes. Salt water became an absolute obstacle for freshwater fishes, and species of Zinj Land began to evolve independently of African species. For 10 million years of isolation they had not formed any new family, but between Zinj Land and Africa there is no one common genus of freshwater fishes. Only representatives of migrating fishes may freely cross Tanganyica Passage and meet both in rivers of Africa and Zinj Land.
The rivers of Zinj Land are much shorter, rather than African ones, but conditions of life in them are more various: Zinj Land “had got” highest mountains of Africa. For freshwater fishes the communication between rivers of subcontinent flowing to the east (to Indian Ocean) and to the west (to Tanganyica Passage) is complicated, therefore in rivers of subcontinent the per cent of endemic fish species is rather high. But in any ecosystems struggle for survival is very sharp. Evolution process resulted in formation of diverse protective adaptations at fishes.
One of fishes living in rivers of eastern part of Zinj Land uses for self-defense poison – it is the reliable and repeatedly time-tested means. It belongs to bagrid catfishes for which sharp poisonous spikes in fins are characteristic. Poisonness and characteristic striped colouring have served as an occasion for the name: this fish is named hornet catfish. It is small fish (its length is about 12 – 15 cm) of contrast warning colouring. Out of spawning season these fishes have striped colouring – yellow with brown cross strips and white belly. Males differ from females in larger size and wider head.
At hornet catfish there is flat head with large shining eyes. On the top jaw of fish two long wattles in corners of mouth grow and two shorter ones stick up near nostrils. On the bottom jaw four short wattles grow. Fins of fish are pointed: it is preciously fast swimmer.
The hornet catfish differs in features of biology from many species of catfishes: it is diurnal fish hunting in schools in thickness of water to small fishes, tadpoles and water insects. At night hornet catfishes hide under floating leaves of water plants. At this time their colouring turns pale, and cross strips become narrow and faltering.
Poison is one of the basic means of protection at hornet catfishes. In back and pectoral fins of these fishes sharp spikes grow, in which basis advanced poisonous glands are located. Besides one more feature of this fish makes it similar to wasp: at this species the effective group protection is developed. Having noticed a predator, the fish of this species utters warning signal – it makes sharp scratching sound with the help of spikes of pectoral fins. At the alarm signal all fishes gather to spherical school (as at marine catfishes (Plotosus) of Holocene epoch). Angry fishes lift spikes, and their colouring becomes much more contrast. Hornet catfishes do not hide from the enemy – they entirely rely on efficiency of group demonstration. The sting of spikes of this catfish is dangerous to predatory fishes. The seized catfish spreads fins wide and sticks spikes in gullet walls of predator attacking him. The predatory fish can even die, having choked with such catfish. Therefore after attack on these catfishes predators had survived do not attack them any more.
When hornet catfishes are quiet, their school swims in river, having stretched to long rank. Fishes exchange sound signals and keep up movements of congeners, keeping a distance.
The spawning of these fishes takes place at night. After plentiful rains which serve as stimulus to spawning males of hornet catfishes gather to separate schools and “sing a chorus” involving females. Their colouring changes: in courtship dress male has black head and white lips, the body color stays like former one. Male ready to spawning shows to the female widely opened mouth, and thus with the help of pectoral fin spikes utters sounds similar to grasshopper chirring.
Demonstration of mouth till courtship display is not casual: it is connected to way of care of posterity at hornet catfish. Males bear eggs in mouth – such way of care of posterity appeared independently at fishes of various families and orders including catfishes of other families. Fertility of this species amounts about 100 large orange eggs incubated within one week. Males bearing eggs gather to dense school and keep in common: it helps them to protect against predators. Such school may total over hundred of fishes, and sometimes in one school it happens up to half thousand of males incubating eggs. At this time they have characteristic colouring – they are white with narrow vertical black strips on body and black top part of head. The forward part of back fin where the large poisonous spike is located gets reddish-brown color and is well appreciable from afar. When the predator comes nearer, fishes gather to spherical shoal and utter warning sounds in common. Loudness of alarm signal is proportional to the size of predator – all flight of fishes reacts to occurrence of large predator.
Helpless larvae hatch from eggs; they lay in mouth of the male motionlessly, yet yolk sac will resorb. At the fourth day of life when it occurs, larva turns to fry. First days of life fry have badly advanced spikes, but at this time they are reliably protected from enemies by care of the male. Fry distinguish the parent male by smell and keep nearby from it swimming out from its mouth. They start to feed, eating slime emitting on the body of the parent. About one week after larvae had turned to fry male hides them in mouth in case of danger (like fishes of cichlids (Cichlidae) family known to people acted). At this time schools of males with posterity move to shallows overgrown with plants where fry have an opportunity to feed on small animals.
Every day fry swim out of parental mouth for a longer time and depart from the male farther. Sooner or later they leave loving father absolutely and start to lead independent life. When the male will have no fry to keep, it starts to eat. For one year the male can bring up to three hatches of fry.
When fry become independent, at them spikes quickly develop, and young fishes become protected from predators. Passing to independent life, fry become cross-striped and group to schools. Schools may unite or broken depending on amount of forage. Main enemies of young hornet catfishes are larvae of water beetles and water bugs. They do not swallow small catfishes entirely, but exhaust avoiding poisonous spikes. But adult fishes have almost no enemies.
Wattle-walking catfish (Barbambulus verticalis)
Order: Catfishes (Siluriformes)
Family: Long-whiskered catfishes (Pimelodidae)
Habitat: tropical latitudes of South America, channels of Amazon and Hyppolithe rivers.
Picture by Amplion
In Neocene expansion of Atlantic Ocean had caused break of
isthmus of Panama and changes in geography of New World. South America is shifted
a little bit
farther to the south, and the southern extremity of continent is located
in zone of seasonal climate with rather cold snowy winter. But the north of
continent is still in zone of equatorial and tropical climate, and the grandiose
river systems carrying their waters to Atlantic are stretched here again.
Meandering on plains, Amazon river changed its channel many times during the
In 25 million years after extinction of mankind the part of former Amazon
basin became the basin of Hippolythe – one of former inflows of Amazon.
Huge rivers joining the circuit of inflows and lakes represent the places of rough evolution of freshwater animals. Usually live beings inhabit the top layer of river waters, rich in oxygen and well lighted. Here it is always enough of food – on the surface of water floating plants grow, and the bottom is covered with thickets of rooting hydrophytes. In wide channels, far from riverbanks, in transparent water the microscopic algae expand, giving food to pelagic fishes of various sizes, down to giant boltergillers (Potamocetus spp.).
But life is present not only at the top layer of water. Bottom “floors” of deep river channels are inhabited by creatures eating rests from the table of inhabitants of top layers of water. They live in the world where the sunlight can not penetrate at all, and eat few things, that fall from above. Food chains are short here, and specialization concerns only the way of search of food, but not a kind of the food.
One inhabitant of deep river channels of Amazonia is a strange fish spending more than half of life, standing on head. It is a wattle-walking catfish, the representative of diverse group of fishes characteristic for South America. This fish has rather strange manner of movement – in rest it takes vertical position and stands on head. Eight wattles surrounding mouth of fish are rather elastic, with muscled mobile bases. Their length exceeds length of body of fish including tail fin. On skin of wattles there is a great amount of chemoreceptors, and branchings of lateral line stretch to them. The role of wattles in life of this catfish is great: fish prefers not to swim, but “to creep” on wattles, moving them like spider legs. However the scared fish takes horizontal position and swims away, waving by the whole body. This fish lives in channels of large rivers at the depth over 20 meters, but in rivers which water carries a plenty of suspension and is non-transparent, these fishes live even at five-meter depth. At night these fishes can move to smaller depth in searches of food, but disappear in depth at the dawn.
The length of body of this catfish does not exceed 30 cm from which the flattened head with wide mouth makes about a quarter. Wattles may reach the length of up to 40 cm. Due to the anatomy of jaw bones the mouth of this catfish can extend forward as a tube to the half of head length. The body has cylindrical shape slightly narrowed to tail fin. The swimming-bladder and fat liver give to the body of fish the density close to density of water, therefore wattle-walking catfish appears almost “weightless” under water and wattles easily maintain weight of body of fish. Back fin is strongly shifted forward and its basis is approximately at the same level as pectoral fins. Not disturbed fish is able to swim in vertical position, making wavy movements by back and pectoral fins simultaneously. The moving back forward is carried out due to wavy movements of anal fin which stretches at half of length of fish. Fatty fin is very small and blade-like. In back and pectoral fins there are strong poisonous prickles.
Among senses at wattle-walking catfish senses of smell and touch are most advanced. Wandering on wattles on oozy river bed, fish receives from receptors the complete information on nearby presence of various animals – predators and prey. Sight does not play any significant role for this fish; eyes of adult individuals are underdeveloped. They are capable to distinguish light from darkness and too bright light frightens this fish. Colouring of this catfish is monotonous pale yellow; fins are transparent.
Wattle-walking catfish feeds on benthic invertebrates – crustaceans and to a lesser degree on larvae of insects which are rarer in deep sites of the rivers. The fish feels their presence with the help of receptors developed on wattles. Having defined the location of prey, fish cautiously “flies up” above the bottom with the help of fin movements, attacks prey from above and catches it by single movement of mouth.
Spawning of wattle-walking catfish occurs in pairs. Male involves the female, uttering loud squeaky sounds with the bases of prickles in pectoral fins. This species does not have complex spawning ritual. Male and the female “get acquainted”, touching each other by tips of wattles. During the spawning fishes adjoin stomaches, also keeping vertical position. Female lays eggs on male’s belly and leaves him; spawning repeats up to two times per year. In clutch it may be up to one thousand small eggs. Male bears them about one week, not ceasing to eat. Fry at once leave him, and male does not care of the posterity any more. Fry has other way of life, rather than adult fishes. Young fishes swim in top layers of water and at this time can settle to new habitats. They are almost transparent, and their eyes are normally advanced. They swim in horizontal position, but can hover in thickness of water for a short while, taking vertical position and spreading wattles apart. If the crustacean or fry of other species of fishes touches wattles, they make short throw and catch prey. As young fishes grow, they “settle” on bottom and gradually migrate in deep sites of river channel, being guided mainly by change of light exposure. Fishes of this species become sexually mature at the age of 1 year at length of about 17 cm.
synodontis (Synodontocephalus electrophorus)
Order: Catfishes (Siluriformes)
Family: Upside-down catfishes (Mochcidae)
Habitat: rivers of Central Africa.
Natural accident of the end of Holocene has affected mostly ecosystems of open ocean and large seas. Natural communities of rivers had not suffered almost, though the river ichthyofauna had lost only some species of large fishes, mainly predators. But when conditions were stabilized, and also climate gradually began to improve, new species of fishes have borrowed become empty ecological niches. One of the most original predators of rivers of Western Africa is electric synodontis.
It is very large fish - the length of body reaches one and half meters, and weight exceeds 20 kgs (females are a little bit larger than males). The body of the electric synodontis is flat: it is the bottom-dwelling fish, preferring to spend time in ambush, hiding among driftwood and water plants. Head is wide, with long wattles - length of wattles at the top jaw is up to 1 meter; on chin there are 4 feather-like barbs about 10 cm long. Eyes are small, shifted to sides of head. In wide mouth there is set of very small teeth - they do not allow to crack catch half-and-half (as at sharks), but help to keep it.
Fins of this fish are rather short and rounded. In back and pectoral fins ahead there are sharp poisonous spikes – the protection against large predators. Tail fin is wide and two-lobed: this fish is lazy swimmer, preferring to hunt from an ambush.
Smaller relatives of this river giant, catfishes of Synodontis genus differ in various coloring: spotty and striped, sometimes contrast bicolor. Electric synodontis during evolution had developed cryptic colouring of black and brown spots on grayish-green background. The bottom part of body of this catfish is yellowish-white.
The main hunting weapon of the electric synodontis is latent under skin. It is a layer of modified muscles, able to generate strong electric charge with which help fish stuns catch: smaller fishes and frogs. This fish also uses electric charges for protection against enemies: large predatory water turtles and lizards. In due time people had found at small African synodontis catfishes ability emit very weak electric charges. Obviously, one of numerous species of these catfishes during evolution had turned this ability for its own benefit, having strengthened power of electric batteries in many times. It had allowed it to occupy ecological niche in ecosystems of African rivers, earlier occupied by electric catfish (Malapterurus).
This catfish spends the most part of time at the river bottom. This fish inhabits shallow wood rivers and coastal area of large reservoirs. Electric synodontis keeps in places where small fishes and frogs - the basic forage of this predator – live in large number. Usually this fish hides in thickets of water plants or among driftwood, but at lack of shelters catfish simply can dig in layer of fallen leaves at the bottom. When in field of action of electric charge of this fish catch (fish up to 20 - 30 cm long, or frog) appears, catfish actuates the weapon, and after some seconds prey already fall on bottom, convulsively pulling. For a short time the catfish shows itself from shelter, grasps the paralyzed catch, and quickly swallows it. After hunting it needs time to have a rest and restore charge in electric organ.
But in spawning season these fishes do not hide at all, making courtship rituals. Males actively care for females, driving them by two – three ones. At this time cryptic colouring gives up the place to bright colors: throat and chest of the male become bright red, the body background brightens, and stains appear on it with the greater intensity. During caring males utter series of clicks and scratches with the help of spikes in pectoral fins. To the moment of spawning at females sides turn pale and become rounded from roe. More clearly female shows the readiness to spawning, more strongly the competition between males for the right to spawn with it proceeds. Males push away each other, sometimes put to the contender bites or grip its wattle. Eventually only one male will stay with the female, fertilizing spawned eggs.
At synodontises of Holocene epoch fishes more often simply dropped eggs at the bottom and did not care of it any more. In Great African lakes some species of synodontises simply put eggs stealthily for incubating to other species of fishes. Electric synodontises care of own posterity independently: female digs fertilized eggs in sand at the river bottom and protects a place of clutch within approximately week. All this time it eats of nothing. Being attacked by predators (more often it is large turtle or lizard), it protects future posterity with the help of impulses of an electric current.
Development of eggs proceeds about three days. But after hatching larvae sit in sandy nest approximately equal time, yet their yolk sac is resorbing. At hatching time the female by strong jet of water from mouth washes away the top layer of sand, accurately gathering by mouth and putting to the nest casually dropped out helpless larvae. After yolk sac resorbing larvae abandon nest for ever. They hide in thickets and eat small invertebrates. First some months of life their electric organ is not advanced, and they perish in great number from every possible predators, including from adult individuals of the same species. But at length about 6 – 8 cm they are already able to stun by charge fry of other fishes at the distance up to 10 cm. And special “signal of identification”, submitted by them at a meeting with neighbours, helps to avoid attack from the side of adult fishes. If the young fish succeed to survive, to the end of third year of life its length will reach one meter, and it’ll take part in spawning.
Root turtle catfish (Cystobiichthys radicans)
Order: Catfishes (Siluriformes)
Family: Pencil catfishes (Trichomycteridae)
Habitat: large rivers of South America – Amazon and Hyppolite.
Some groups of invertebrates are submitted exclusively by parasitic forms – for example, classes of tape worms and trematodes among flat worms, orders of fleas and lice among insects. In other groups representatives of few separate genera or species in the group submitted by free-living forms are parasites. Among vertebrate animals parasitic forms are rare exceptions. In Neocene only some mammals and birds turned to haematophags. In fresh waters of South America there is a blood-sucking species of neotenical tadpoles. But parasitism is most typical for fishes among vertebrates. Some catfishes of pencil catfish family are blood-sucking parasites, and among them in Neocene absolutely fantastic forms had evolved.
In cloacal bladder of elasmosaurine hydromedusa and other large turtles of South America one species of these catfishes parasitizes – the root turtle catfish, worm-like creature about 8 cm long. This fish lives in cloacal bladder and in adult condition leads sedentary habit of life. The parasitic way of life had leaved an imprint to anatomy of this catfish. It is blind depigmentated fish with transparent body through which walls interiors are visible. On stomach of fish the longitudinal plica of skin forms a line of suckers. This species eats exclusively blood of turtle – fish bites through epithelium of cloacal bladder and sucks blood, having densely attached by lips to wound.
One attribute gives out the presence of this parasite in turtle’s body: the long and strong shoot of tail fin formed by elongated fin rays and extending at the tip as a blade is put out from cloaca of reptile. It is penetrated with blood vessels, and through its surface gas exchange proceeds. The additional source of oxygen is blood of the turtle. This catfish has the special adaptation, permitting to extract oxygen. On the bottom side of body of the fish a plenty of fibers is developed; they take root into the epithelium of turtle (hence the specific name “radicans” meaning “taking roots”). Through them oxygen diffuses from blood of turtle. Due to uselessness gills of this species are greatly reduced, and branchial apertures are tightened by skin and are reduced up to two small holes above the bases of pectoral fins.
Pectoral fins of root turtle catfish have muscled bases, and the membrane between fin rays is reduced. Rays represent structures like claws with which help fish attaches to walls of cloacal bladder. Due to inhabiting inside turtle body this fish easily endures the necessity of turtle to go to the riverbank for egg laying. Therefore such catfishes parasitize in turtles of both genders.
Gender of root turtle catfish is not fixed genetically and may easily change in any direction depending on circumstances. Two any fishes appeared near each other in the same host animal turn to individuals of different genders and produce normal posterity. In connection with motionless way of life this species does not have courtship ritual and internal fertilization had developed. The cloaca of this catfish has ability to turn out and to extend as a tube. It forms similarity of penis at male and long extensible ovipositor at female. Male makes internal fertilization, and in ovoducts of female eggs start to develop. The female puts the ovipositor outside and lays fertilized eggs in water. At this time the embryo has already passed early stages of development. At absence of breeding partner fish develops as a hermaphrodite and lays normal fertilized eggs alone.
The fertility of root turtle catfish is rather big for such tiny fishes – within one week the female lays up to one hundred large eggs. Egg laying lasts some weeks in succession after one fertilization, and then female restores the physical condition, and male fertilizes it again. The young ones of this species lead strictly another way of life, rather than adult fishes: they are active planktonic predators eating fry of other fishes and also larvae of insects.
This species of fishes may exist as free-living stage for rather long time, reaching the length of 4 – 5 cm. At young individual in such condition eyes are well advanced; it is translucent and leads mobile mode of life for a long time, but at this time puberty is delayed. Frequently fish even dies “eternally young”, having not searched for host turtle and having not reached sexual maturity. Having found out a host turtle, catfish penetrates into its cloacal bladder and attaches to its wall. After the attachment the fast degeneration of unnecessary organs – eyes and fins – proceeds. On the belly side of body suckers and “roots” quickly develop, and then on tail additional respiring organ grows. For some weeks fish turns to true parasite, and then normally continues development and reaches sexual maturity. Too old individuals, however, can not go through such radical reorganization of an organism, and perish in body of host turtle.
Life expectancy of this catfish reaches 4 – 5 years.
Antiguan phoboclarias (Phoboclarias antiguae)
Order: Catfishes (Siluriformes)
Family: Airbreathing catfishes (Clariidae)
Habitat: fresh waters of Great Antigua – lakes and swamps.
In human epoch borders of faunistic and floristic areas appeared broken. People introduced various species of animals and plants to territory where these species could never appear by natural way. Frequently such activity resulted in degrading of ecosystems. Some of newcomer species had died out in epoch of global ecological crisis, but the part of species had survived, and their descendants had taken the place in ecosystems of Neocene.
In swamps and other freshwater reservoirs of Great Antigua Island one of descendants of animals introduced by people lives. It is the large catfish Antiguan phoboclarias, the descendant of clarias (Clarias batrachus) introduced from Asia to Florida. In human epoch clarias had got out of human control and had widely settled in freshwater reservoirs of Florida. In ice age this fish had got from Florida to Cuba, and then by temporary land bridges over small islets had reached islands formed Great Antigua in Neocene.
Antiguan phoboclarias is very large predatory fish (hence the name meaning “awful clarias”). The length of adult fish may reach two meters and even more (male is smaller and more graceful, than female). Body is very much lengthened, flexible and cylindrical. Low back fin lasts at all its length. Tail fin of fish merges with anal one. The skin of phoboclarias without scale is covered with plentiful slime. Colouring of this catfish usually is sandy yellow with small spots; stomach is white. Depending on color of environment this catfish can change colouring – on dark ground it turns dark brown with black spots. Change of colouring proceeds within several days after resettlement of catfish to other place.
Head of phoboclarias is flattened and wide. If necessary it may be used as a weapon – by impact of head the catfish is able to cripple animal swimming in water which it wants to eat. Due to wide mouth phoboclarias easily swallows chicken-sized animals.
This fish has badly developed sense of sight; small eyes are located on edges of head and are slightly shifted upwards. Bad sight at fish is filled with chemical sense – around of mouth of phoboclarias eight wattles about one meter long grow, and their surface is covered with set of receptors.
In pectoral fins of catfish spikes with poisonous slime grow. One prick of such spikes is enough to kill large dog-sized animal; therefore adult phoboclarias does not have enemies.
Phoboclarias, similarly to the majority of catfishes, does not like to swim long. It is a passive ambuscader trapping prey, having buried in ground almost completely. At the hidden fish only long wattles and a part of head with eyes is out of ground, therefore it is difficult to notice it among plants. When the fish or other prey of suitable size swims near, catfish rushes out from sand and catches it. Usually phoboclarias eats small fishes, aquatic insects and their larvae, frogs and tadpoles. But at an opportunity this fish eats animals got in water during flooding or crossing the reservoir. Also phoboclarias hunts ducks and other waterfowl. Hunting birds, it hides under leaves of water lilies and waits while the careless bird will move nearer to it. At this species cannibalism is advanced, and a significant part of posterity passed to independent life may be eaten by own relatives.
Phoboclarias is able to live almost in any freshwater reservoir with water of any quality. If in water there is no oxygen, approximately once per twenty minutes fish emerges to water surface and takes in mouth an air bubble – from it oxygen for breath is taken. It is especially important, if the fish lives in poor in oxygen water of swamp, in which there is plenty of rotten plants. From the ancestor, the clarias, phoboclarias had inherited the adaptation for breath by air – specially modified gills.
In rain season at fishes the courtship season begins. Its beginning is audible even at the coast of reservoir: male involves female, uttering melodious sounds – chirping trills. In shallow water it digs a nest – a hole about two meters in diameter and about half meter depth. Having cleared ground from dust, male begins courtship “songs”. It is very cautious at the presence of the female, and constantly keeps at some distance, always directing by head to her.
Fertility of the female makes up to 200 thousand of small eggs. After spawning male stays near the nest and protects eggs till five days, while fry will hatch. When fry will start to swim, male stays with them and protects the hatch during approximately two next weeks. At this fish the care of posterity is very strongly advanced: in case of danger male takes away eggs and fry in mouth. Also it acts so, if the reservoir where the nest is arranged dries up, or water level decreases. But it is only a part of that the adult fish can make for posterity. Clarid catfishes are able to creep overland, and phoboclarias can leave a reservoir, carrying away posterity. Keeping the posterity the adult catfish can creep overland till some days in searches of new habitats. During overland travel the body of fish becomes covered by viscous slime, helping to keep moisture; and in mouth eggs or fry become covered by liquid slime which slows the evaporation of water. The catfish feels a smell of water, and easily finds new reservoirs. If it had to move with eggs, in new residence it continues to incubate it in the mouth.
Young phoboclariases grow quickly, and at the age of about five years become sexually mature. Young fishes live in rich thickets of marsh vegetation where adult fishes can not eat them.
catfish (Silurus megachasmus)
Order: Catfishes (Siluriformes)
Family: Catfishes (Siluridae)
Habitat: Three-Rivers-Land, rivers of Fourseas basin, channels of large rivers and river shallows.
Picture by Alexey Tatarinov
During the ice age the majority of freshwater fishes of Europe
had died out. There were only few representatives of them kept in lakes at the
narrow strip between glacier and saline hollows at the place of Black, Caspian
and Aral seas. And only few fishes managed to recede farther to the south –
to Central Asia. There, in the rivers flowing from mountain glaciers, the rests
of the fish population of Eurasia had found a shelter. Among them the true giant,
wels catfish (Silurus glanis) predominated. When conditions began to change,
fishes from the Central Asian rivers began settling to Europe.
Descendants of wels catfish were among these settlers. They had not changed too strongly externally, but had turned to true monsters – wide-headed catfishes. The fish about 5 – 7 meters long, weighting about 800 kgs, having huge head and strong tail, became the true tyrant of the large rivers flowing to Fourseas. Even the tsarfishes swimming up-stream for spawning, try to keep closer to each other when this monster swims near them. The width of head of large individuals of this catfish reaches almost one meter. Having huge mouth, fish swallows entirely animals as large as small deer.
Wide-headed catfish hunts large fishes, arranging ambushes at the river bottom of the. But it also includes ground animals into the diet, having turned to original ecological analogue of the crocodile of (temperate latitudes. The fish arranges ambush at the shoaliness and catches the animal had come to watering place, sharply jumping out from water, For such giant it is rather easy to mask: colouring of fish represents the set of dark brown spots on background able to change shade from green up to brown. Eyes of wide-headed catfish are small and located on edges of head. Therefore it is rather inconveniently to it to see prey directly. But it easily feels its presence due to the circuit of the electroreceptors covering its head. And also on head of a fish the circuit of channels of lateral line, catching movement of water, is advanced. So the wide forehead of fish represents an original “screen” in which everything occuring in front of head of fish is reflected. Wattles of this catfish are reduced up to small outgrowths – two ones on upper lip, two in corners of mouth, and four ones grow on the lower jaw.
To track down prey is not all yet. The most important is to catch and to drown it, if the catfish hunts ground animals. And this catfish has solved this problem. Having seized prey, it bends body sharply and throws prey above itself in water, and then, having turned around, pushes from riverbank by tail, snatches prey and drowns it. Its reliable support is the tail compressed from sides, along which the anal fin stretches from below. The part of fin rays has turned to strong prickles. Sticking them into the bottom, catfish provides to itself a support for a throw even at the oozy river bed.
Teeth at wide-headed catfish are very small; they grow on jaws in some rows. It is impossible to bite through prey or to cut off a piece of flesh with such teeth, but this lack is quite compensated by pressure force of jaws. Fish can easily crush chest of harelope or other animal of similar size by single bite. Though wide-headed catfish can catch even rather large ground vertebrates, its basic prey includes fishes, large frogs and waterfowl which it seizes from under water.
Like all catfishes, wide-headed catfish loves warm water and shows especial vital activity in summer. Then it catches ground animals more actively, trapping them at the watering place. This fish also spawns at higher temperature of water, in second half of spring. Male is smaller, rather than female (he is approximately one meter shorter), and differs from her in more sated colouring. To time of spawning he gets contrast colouring: back darkens, and stomach turns almost white with separate dark spots.
Spawning takes place at well warmed up sites of shallow water. Male chooses a site well warmed up by sun, pulls out all vegetation there, digs not deep hole and begins courtship “dances” near it – he whirls on this site, uttering loud rumbling heard even from under water. Spawning takes place at night and it may be very rough: fishes jump out of water and fall back with loud splash. Care of posterity is entirely male’s duty: he incubates clutch (up to 50 thousand grains of roe) and raises fry in mouth. The female lays eggs into the nest, and in the same place male fertilizes clutch, but right after spawning he banishes the female and takes away all eggs into the mouth. During the execution of parental duties male does not eat at all within approximately three weeks. Rather developed young fishes leave his mouth; they will reach maturity only at ten years’ age at length of about 3 meters. Life expectancy of wide-headed catfish makes up to 150 years.
This species of fishes was discovered by Simon, the forum member.
Namadzu catfish (Psammosilurus namadzu)
Order: Catfishes (Siluriformes)
Family: Catfishes (Siluridae)
Habitat: Hokkaido island (Japan), lower reaches of rivers of the eastern side of island.
The rivers of Japan Archipelago are short and have plenty of waterfalls and rapids. The complex relief of islands promotes occurrence of plenty of isolated habitats. But the same circumstance limits number of populations of fishes and the size of predatory fishes inhabiting the rivers of islands. Еру сonsequence of it is the variety of small species of fishes and rather small amount of large predatory species. One of the largest species of Japan fishes lives in the rivers of eastукт part of Hokkaido island where rivers form a circuit of channels and running-water lakes. It is the representative of catfishes named namadzu catfish. It is named after huge catfish from Japanese legends, which movements people believed the reason of earthquakes.
Namadzu catfish is the long-bodied fish capable to dig in sand fast. The size of this fish is up to 150 cm; body of fish is long and snake-looking. About three quarters of body length the tail stalk makes; it is ended with small tail fin merged with well advanced anal fin stretching along the bottom side of tail. Small back fin is located near to nape of fish.
Namadzu catfish perfectly masks due to colouring – background colour of body is brownish-yellow; on it the set of dark specks is scattered, forming chaotic marble pattern. Male and female do not differ from each other in colouring. Female differs from male in more heavy constitution and in greater length. Head of this fish is flat and wide, with small eyes located near corners of mouth. Sight sense at namadzu is very bad. The catfish receives the most part of the information on world around through wattles on which the set of chemoreceptors is located. Wattles of namadzu are long, and there are three pairs of them: pair of long wattles (half of body length of fish) in corners of mouth, and four short ones (not exceeding the length of head) on chin.
Namadzu catfish is inactive, and spends the significant part of time, having almost completely dug in sand and vegetative dust at the bottom of reservoir. This catfish is ambush predator and traps prey, having left on surface of ground only head and part of back. Despite of inactive way of life, it is the quite good swimmer. In open water namadzu swims, coiling the whole body like eel. But among thickets or snags this fish uses absolutely other style of swimming more similar to way of movement of South American gymnotid fishes (Gymnotidae and related families) – along anal fin waves move one by one, and fish moves forward, cautiously moving apart stalks of plants by head. If necessary the direction of wave movement changes to opposite, and fish equally easily swims a tail forward. With the help of movements of anal fin namadzu is dug in sand, from where jumps out to catch prey.
This predator eats small fishes, crustaceans and frogs.
The courtship season passes roughly. In spring when water gets warm enough, male starts “playing”, declaring rights to the territory with the help of jumps from water. When the female comes to his territory, male takes contrast spotty colouring and begins to court her, swimming near her and keeping the body in parallel to the body of female. From time to time male makes wavy movements, enabling the female to estimate force of his movements. The couple of fishes clears a site of bottom of dust and with the help of movements of anal fin digs furrow in it. The female lays in it some tens thousand small eggs, and male at once fertilizes them. After spawning female swims out, and male ventilates eggs with movements of anal fin, soaring above the nest. When larvae hatch, male looks after them for some time while they will be able to swim independently. When larvae turn to fry, male stays with them, and “pastures” school of young ones during approximately one week.
Young fishes at the end of the first summer of life reach the length 25 – 30 mm and pass to feeding on insects and other invertebrates. In two years the young fish reaches the length of about 40 cm and begins to eat almost exclusively fishes and small crabs. At the age of 4 years young catfish becomes capable to spawning, and lifespan of this species may reach 60 – 70 years.
Branchial suckermouth (Branchiolorica molligaster)
Order: Catfishes (Siluriformes)
Family: Suckermouth catfishes (Loricariidae)
Habitat: basin of Amazon and Hyppolite; the blood-sucking parasite on fish gills.
Parasitic species are very common among invertebrates – some large groups of these animals are present only by parasites. Parasitic vertebrates are rather the rare exception, than a rule. Among fishes representatives of various orders passed to partial parasitism, but most deeply specialized parasites were pencil catfishes (Trichomycteridae) known in human epoch. In Neocene some other kinds of sanguivorous vertebrates added to their number. The original branchial tadpole (Branchiosuga nosferatu), neotenical species of amphibians became the parasite. And among fishes one more parasitic catfish, the close relative of leechcatfish (Hirudistomus cataphractus), branchial suckermouth had evolved. It is small species of fishes – general body length of adult individual is about 5 cm. It eats exclusively blood of fishes.
Branchial suckermouth lives on gills of large fishes (for example, boltergillers (Potamocetus spp.)). It is kept on gills of host fish with the help of hooks growing on rays of pectoral fins. The mouth of all loricariid catfishes is transformed to sucker, and only few changes had been required for transformation of scraping mouth to sucking one. In mouth of branchial suckermouth sharp corneous plates grow. With their help catfish bites through an epithelium of gills of host fish, and sticks to the wound by lips.
The body of branchial suckermouth has lengthened shape and is flattened from above. It had undergone strong changes in connection with the adaptation to parasitism. The armour of fish is strongly reduced and represents very thin transparent plates which do not adjoin to each other on the back part of the body. The skin on stomach of fish is depigmentated, and through belly wall interiors and intestines filled with semidigested blood are visible. The top side of body is grey with cross black strokes. Strangely enough, at this parasite there are rather large shining eyes: it has good sight. Besides on front edge of head of this fish the set of the fleecy outgrowths covered with chemoreceptors grows.
Abdominal fins are rather small, but pectoral ones are strongly advanced – they are principal organs of attachment to body of the host fish. Front rays of pectoral fins are thick, covered with set of tiny corneous thorns, and the tip of fin ray is bent like a hook. Branchial suckermouth clings to gills of host fish by it. Unpaired fins are rather small; on bottom lobe of narrow tail fin there is long threadlike outgrowth.
This catfish does not live on the same fish constantly. It is able to swim and prefers to move from one fish to another at night when fishes are less active. If this catfish does not find suitable host, it may appear completely defenseless surrounded by various predators. Therefore branchial suckermouth having no host behaves very cautiously and secretively. In the morning it is dug in layer of fallen leaves at the bottom of river, or hides in long roots of floating plants, and keeps a full immovability, not giving out itself until the last second, or … yet will find out the host fish. Then catfish promptly attacks it and clings to its body behind the operculum. Having chosen a right moment, branchial suckermouth cautiously slips under the operculum of host fish, and attaches to its branchial arches.
These catfishes spawn during all year. When sexually mature fishes ready to spawning meet, they begin simple courtship ritual. Male cautiously sticks to the body of female, unfastens some seconds later and moves forward a little. It moves this way along the body of the female from tail to head, yet will reach her nape. Then he cautiously starts to slip to side of the female (because at this moment the female is attached to branchial arch of host fish, male actually slips downwards and appears turned the stomach upwards), and touches by abdominal fin the skin on her stomach. The female lays on stomach of the male about 20 – 30 eggs which stick to skin of the male. Male fertilizes eggs and cautiously moves them to its head. He bears eggs on fleecy outgrowths on edges of head.
Fry hatch after 6 – 7 days of incubation. The first days of life they keep on stomach of male, and he protects them from the current of water moving through gills of host fish. Within several days young fishes gradually leave him. They hide among underwater plants and eat algal scurf. Since the second month of life, at the length of about 1 cm young branchial suckermouths start to attack medium-sized fishes.
suckermouth (Spealeoloricaria setosa)
Order: Catfishes (Siluriformes)
Family: Suckermouth catfishes (Loricariidae)
Habitat: caves of Yucatan, fresh water.
Picture by Tony Johnes
The family to which this species of fishes belongs is the
most numerous in order and simultaneously looks the exception by food predilections
among other families of predatory catfishes. Loricariid catfishes are very characteristic
fishes of New World. After break of Panama Isthmus the part of species had remained
in Central America where evolved independently from the majority of species
had stayed in South America. Some species of loricariid catfishes had adapted
to unusual habit of life: the parasitic
species of these fishes is found in South America, and there is a sanitary
species. But one species of Central American loricariid catfishes had settled
under ground, in extensive calcareous caves of Yucatan, and had successfully
adapted to unusual way of life.
Cave suckermouth prefers quickly flowing rivers and is especially numerous in places where the river current on ground surface hides in caves. In these places cave suckermouth finds enough food, being in habitual environment.
The shape of this fish shows the long history of settlement under the ground. Eyes of cave suckermouth are strongly reduced and are visible under skin only as dark spots. They are completely covered by skin and thin armour plates, and do not perceive light at all. In shape of fish presence of set of corneous bristles (hence the specific epithet “setosa”, meaning “bristly”) on lateral faces of head is remarkable. The armour at this catfish is kept: water in caves is strongly mineralized, and problem of armour construction does not arise. Neighbours of this species are crayfishes and crabs living in various caves, therefore additional protection is vital.
Body of cave suckermouth is strongly extended; it is about 15 cm long at the maximal width no more than 1 cm. At back edge of back fin at males the long string grows – it is strongly extended back ray of back fin. The same threadlike outgrowth is present at the bottom lobe of tail fin. Therefore catfish seems little bit larger, than actually is. The body of fish is colored pinkish white.
Pectoral fins at males and females are advanced equally well. At them there is a firm forward ray covered from the bottom side with set of frieze-like prickles. The bases of pectoral fins are shifted downwards. They are extended, lack of armour plates, and turned to strong suckers which keep this fish in rough underground streams.
Cave suckermouth has characteristic for loricariid catfishes scraping inferior mouth modified to sucker. This catfish eats bacteria and larvae of insects settling on stones. If in cave dead bodies of animals get from the surface, cave suckermouth willingly feeds on carrion. Also it eats bats had sunk in water which frequently drop from the ceiling of caves in which this species lives.
Caves differ in poor food resources, therefore populations of cave fishes are not numerous, and rate of breeding is very slow. But it is compensated by absence of large active predators; therefore the survival rate of posterity at cave fishes is rather great. Seasonal prevalence in spawning of cave suckermouth is absent, but breeding may repeat up to four times per year. Courtship games of these fishes differ in simplicity. Courting at the female, male keeps in parallel to her and by strong lateral movements of body turns waves to her body. The female estimates physical condition of the male by force of waves which it makes. Male broods a small amount of eggs (about 20 ones) in the mouth within several weeks; all this time it does not eat.
Young cave suckermouths become sexually mature at the age of about 10 months. Life expectancy of these fishes is no more than 6 years.
Mountain suckermouth (Platyhypostomus frigophilus)
Order: Catfishes (Siluriformes)
Family: Suckermouth catfishes (Loricariidae)
Habitat: Andes, mountain streams and cool rivers.
South America differs in large variety of catfishes; some families of these fishes are endemics of this continent. In Neocene when the climate became warm and damp, catfishes as many other freshwater fishes had started to evolve roughly and to develop new habitats. Andes, the high mountain ridge stretched along the whole Pacific coast of continent, became the house for some new species of fishes, including catfishes.
In cold quickly flowing water of mountain rivers, clean and rich in oxygen, large loricariid catfish – mountain suckermouth – lives. Length of this fish is about 40 cm – it is one of the largest representatives of family in Neocene epoch. This fish is perfectly adapted to life in fast current. The body of mountain suckermouth is strongly flattened; therefore when fish lays at the bottom, resistance to current is minimal. The shape of this catfish forces the current to press fish to the bottom.
Mountain suckermouth has wide head of rounded outlines with blunt snout. Small yellow eyes are shifted to edges of head and protected by bone “eyebrows”. Operculums are shifted to the bottom side of head. On the body of fish there are well advanced armour plates (it is the common feature of family), providing good protection against enemies and casual traumas against the stones moved by current. Colouring of body of mountain suckermouth serves for camouflage – it is grey with olive shade; on top side of the body there is “marble” pattern of cross irregular-shaped strips. When fish lays motionlessly on stones, it is almost not visible among patches of light at the bottom. Passive protection is the main vital strategy of this harmless fish. In case of danger mountain suckermouth prefers to hide at the bottom, and seeks safety in flight only at direct threat of life.
Unpaired fins of mountain suckermouth are wide and fanlike, with rounded tips. Tail fin of these fishes has colouring appreciable from apart: on dark grey background “trout” oculate spots, red with white border, are scattered. At large males this pattern is supplemented with white border on external edge of fin. These marks serve for warning of competitors and for courtship display. Also at males on bottom lobe of tail the long string formed by two strongly lengthened rays of tail fin grows. One more attribute of sexual dimorphism is characteristic for many representatives of loricariid catfishes, and mountain suckermouth is not exception here: at the male on edge of head long outgrowths grow; at this species they are appreciably corneous, firm and bristle-like. On forward part of head they are short; on each side of head they are much longer and grow in two lines, forming rich “whiskers”.
Pectoral fins of these catfishes are rigid and strong, with powerful front rays: they help fish to cling to stones. Fromt rays can be fixed in opened position, resting against stones, as an anchor.
The sucker-like mouth of this species of fishes is very strong; it helps to keep in current. Mountain suckermouth eats various kinds of food. This catfish scratches out from stones water mosses growing as pellicles, plants of Podostemaceae family, and also microscopic algae. Besides of plants mountain suckermouth eats larvae of insects – two-winged flies, dragonflies and caddis flies. Using wide head, catfish is able to overturn stones, searching for invertebrates. At an opportunity this fish eats dead bodies of animals had got in the river.
At the bases of abdominal fins of mountain suckermouth skin plica forms an additional sucker of semilunar shape. Using oral and belly suckers alternately and clinging by pectoral fins, this catfish is able to creep on stones, rising upwards in mountain rivers and even in low falls.
Mountain suckermouths spawn in places with weaker current, near stones, in underwater caves. Courtship games at them proceed not for long. Male displays to the female stretched back and tail fins, swimming in front of her head and from time to time pushing the female by side. Before spawning fishes keep in parallel to each other, and touch each other by tips of fins. The female lays eggs on bottom; male fertilizes them and at once gathers from stones, rowing up by outgrowths on head. In first minutes after fertilization jelly-like sticky layer starts to produce on the surface of eggs; with its help eggs stick to head of the male. Male broods eggs pasted to bristles from the bottom side of head till 8 – 9 days. Such speed of development of eggs is connected to low temperature of water in habitats of these fishes. Mountain suckermouths living in better warmed lower reaches of rivers rise upstream for spawning: at high temperature fry hatch weak. In first days of life fry keep on head of the male and sometimes escape from danger in its mouth. Till all brooding time male eats of nothing.
Young fishes become able to spawning at the age of two years, but active growth proceeds within first ten years of life.
Arafura mangrove catfish (Batrachoplotosus mangrophilus)
Order: Catfishes (Siluriformes)
Family: Stinging catfishes (Plotosidae)
Habitat: mangrove swamps of Arafura Lake.
Movement of lithosperic plate on which Australia and New Guinea are located, had caused rising of its northern edge. Arafura Sea had shoaled and gradually turned to extensive brackish lake separated from the ocean by multikilometer circuit of mangrove swamps and shallow channels. Salinity of water in them varies from slightly brackish during tropical downpours up to almost equal to oceanic one. In such conditions only few species of aquatic animals may exist normally – the majority of sea inhabitants does not endure fresh water, and freshwater animals do not suffer presence of salt in water. Nevertheless, there are fishes in mangrove channels. One of their representatives is Arafura mangrove catfish, the descendant of one species of sea stinging catfishes (Plotosus). When sea water began to turn fresh, the ancesor of this fish had not left it, and had adapted to life at coastal shallows, and then had moved to mangrove channels.
This species of catfishes is large eel-looking fish up to one meter long. The trunk of this catfish is compressed from sides, and the tail is bordered with merged back, tail and anal fins. With the help of strong tail fish can be dug in sand at outflow, and survive outside of water due to it till many hours. Head of this catfish is flat, with small eyes shifted to the sides. Wide mouth is surrounded with eight short wattles. This catfish has changeable colouring: in rest this fish is grey with numerous black spots on the top part of body, merging in twisting marble pattern on back and tail. Stomach and the bottom part of head at this catfish are white. At fright or at night black spots turn pale grey. In courtship dress male and female strongly differ from each other: female turns monotonously grey, and male has black back and sides, and white belly. On the background of black colouring its silvery eyes, surrounded with white spot, look especially impressively.
It is a predatory fish eating any prey, which it is able to seize and to swallow – smaller fishes, crabs and shrimps. Catfishes also eat animals fallen in water – mammals, reptiles and nestlings of small birds.
For protection against numerous predators living in mangrove forests, this catfish is armored with poisonous spikes growing in fins. This is a heritage got from ancestral species, which had been remarkable by their poisonness in human epoch. But in any case this species prefers to be imperceptible, and at danger is quickly dug in sand. Young fishes use this way of protection especially frequently.
As against to far ancestors lived at sea reeves in numerous schools, Arafura mangrove catfish is a solitary species, though it does not avoid the presence of congeners. It gathers to schools only for migrations connected to spawning. The adult fish lives in water of any salinity – from fresh up to oceanic water. But it spawns only in salt water, because too freshened water kills an embryo. For spawning catfishes wait for a time of the highest inflow in the month. With a tidal wave, filling channels of mangrove forest, adult fishes gather to schools and migrate to the depths of lake. At the depth of about 10 meters catfishes gather to shoals numbering many thousands of fishes, including individuals of both sexes. Within night fishes find each other, and courtship games begin in the morning. With the first rays of sun males turn black and white, and start to court after females. Competing for the female, males shove each other aside from her, pushing by sides. At this time their spikes are pressed to the body and are not used – their prick may be dangerous to congeners. During the courtship ritual male bites fins of the female and keeps near to her. The pair of fishes swims so till several hours, synchronizing ripening of eggs and soft roe. Directly to the moment of spawning the shoal is broken to the set of pairs.
Male and female throw up sexual products simultaneously, and male picks up by mouth large eggs – in clutch it may be up to 200 pea-sized eggs. Having spawned all eggs, females at once return to mangrove thickets, and males remain at spawning place. Male looks after posterity, brooding eggs in mouth. At this time males gather to schools and keep together at the distance from lake coast. They do not eat, and between them there is no competition, therefore in male school there are no fights.
The incubation lasts till about 50 hours, and some more days male carries helpless fry in mouth. In one week after spawning males swim up to the coast and let out posterity in thickets of aquatic plants. After that they return to rendered habitable places and do not care any more of posterity. At the age of 3 years young fishes become sexually mature. Life expectancy of this species makes over 30 years.
Usambara characid trout (Alestotrutta ussambarica)
Order: Characids (Characiformes)
Family: African tetras (Alestidae)
Habitat: mountain regions at the east of Zinj Land, mountain rivers.
When African continent had broken up along the Great Rift Valley line, all highest mountains of continent had stopped to belong to it. They had remained at the subcontinent named Zinj Land. Because of global ecological accident many ecosystems appeared destroyed, but it almost had not affected terrestrial and fresh-water ecosystems. Flora and fauna of Zinj Land developed completely separately from Africa till at least approximately ten millions years, from the moment of separating of subcontinent from continent. The variety of freshwater species of animals had kept almost at former level. Characid fishes are very characteristic for continental reservoirs of Africa to the south of Sahara and for New World (South America and the south of North America). They inhabit various reservoirs – from stagnant swamps up to cold mountain streams. They avoid only brackish water.
Significant spaces of Zinj Land are occupied by mountain landscapes. One of characteristic species of fishes lives in streams with quickly flowing clean and cold water – large trout-looking characid named Usambara characid trout. It is a fish about 60 – 70 cm long with torpedo-like body and pointed muzzle. It swims quickly and can “stand” in fast current near stones or bushes of water plants for a long, similarly to trout.
The basic colouring of body of characid trout is silvery blue. Fish has narrow black longitudinal strip on body, stretching from tip of muzzle through an eye up to the basis of tail fin. Also at characid trout there is darker back making fish imperceptible on the background of bottom at sight from above. Back fin of fish has pointed tip. At the male the height of fin exceeds height of body. Tail fin is high and crescent; it also has rigid rays.
Characid trout is insectivorous predator. This fish hunts down insects flying low above water, and jumps to catch them at height up to one meter. Characid trout has large eyes – sight plays a leading role in air hunting. Also fish searches for larvae of dragonflies and caddis flies at the bottom of streams. Occasionally characid trout hunts down small fishes, including its younger congeners. The mouth of characid trout is wide – its cut lasts up to level of front edge of eye. Jaws are armed with numerous thin pointed teeth.
Characid trouts spawn in current, spawning very large amount of eggs – up to 200 thousand small eggs. Male at these fishes is larger, but more graceful, than female. Its colouring differs in more intensive blue shade which is amplified on head, passing to dark blue on tip of muzzle. On this background at the male silvery “ear-ring” spots at operculums are clearly visible. In courtship season (during the thawing of mountain snows) male actively chases females, pressing them by body to the bottom. If the female is ready to breeding, she swims near the male within several hours. At this time at fishes sexual products intensively develop. At night or in early morning spawning begins. Fishes splash in stream, jumping out of water, and male chases the female, biting her tail. Just before the dawn time fishes spawn eggs, scattering them in current. This species of fishes does not care of posterity, and as required adult characid trouts can be cannibals. The young ones differ in habit of life from adult fishes. Young characid trouts keep in thickets of water plants. At them bottom jaw is short, and mouth is inferior. They scrape off larvae of insects and bacterial cover from stones. The young ones also differ in cross-striped colouring. As they grow, the middle part of strips stays dark, edges turn pale and fishes gradually get “adult” longitudinal-striped colouring.
The first spawning of young fishes takes place at the age of three years at length of body about 30 – 35 cm. This species reaches the usual size to the age of six years, and then growth of fish slows down. At the age of 20 years some fishes reach length of 80 cm, but it is the extreme rarity. Usually life expectancy of characid trout does not exceed 15 years.
Order: Characids (Characiformes)
Family: Trahiras (Etythrinidae)
Habitat: shallow fresh reservoirs in tropical zone of South America.
After climatic accidents of the end of Holocene and the beginning of Neocene many of earlier prospering groups of animals have died out. Such destiny has comprehended almost all crocodiles existing on Earth still from Triassic period of Mesozoic era. Only few representatives of this group live on Earth in Neocene epoch, and in many places where they had lived before, in ecological niche of large water predator absolutely other animals have replaced them. More often they are various turtles and lizards, but in South America where the forked chain of rivers and lakes was kept, the role of terrible water predator was undertaken by fishes. In Holocene epoch in basins of tropical South-American rivers trahiras, large and unaccommodating predatory fishes, reached sometimes one meter length, were settled. They trapped catch, having hidden in ambush among plants. Same tactics is successfully used by their descendant – huge tyrannocharax.
The length of almost cylindrical body of tyrannocharax reaches four and half meters: it is one of largest osseous fishes of Neocenic Earth. Huge head with extended snout and sharp teeth similar to recurved nails accounts about meter from this length. Weight of this monstrous fish can reach 300 - 350 kgs. The head is covered with dense armour of skin osteoscutes, that give to it additional durability and protect from casual damages which large catch can put to this predator. In the top part of head small black eyes and approximately in middle between eyes and tip of muzzle sensitive nostrils are located.
The constitution gives out in this fish the typical ambuscading predator not swimming long and far. Practically all time tyrannocharax spends having hidden among plentiful water vegetation at the depth about 1 – 1.5 meters. The pattern on its scales helps to remain unnoticed even to such enormous fish. On sides of tyrannocharax there is non-uniform mesh figure: on greenish-grey background there are black spots merging in vertical strips. Back of this fish is brown-black with small number of light spots.
Tail fin of tyrannocharax is short and rounded, and tail stalk is high and muscled. Such proportions are characteristic for fishes able to make sharp throw. The back fin lasts approximately from middle of back almost to the beginning of tail stalk; fatty fin is very small and rounded. Pectoral and abdominal fins of fish are advanced well and shifted downwards.
Living in shallow, strongly warmed up reservoirs, the large fish faces with one problem: the organism demands a lot of oxygen, and its contents in water is insignificant. Tyrannocharax solves this problem with the help of one adaptation inherited by it from ancestors. Swimming bladder of this fish is opened – it has turned to original lung. From time to time the huge fish cautiously emerges to the surface of water and breathes. After that the tyrannocharax can lay in ambush up to half an hour, giving itself out by nothing to possible victims. Lung helps fish to survive in conditions of drought: when reservoirs dry up, tyrannocharax can move from reservoir to another, bending by all body and helping itself by pectoral and abdominal fins. Thus the fish keeps branchial covers close, preserving gills from drying, and breathes exclusively with the help of lung.
Female is paler and fuller than male, and besides it is longer than male approximately at half-meter and heavier at 20 – 30 kgs. At such arrangement of forces, taking into account rather unaccommodating and aggressive character of fishes, the maximum of care is required from the male at relations with the female during spawning. Ritual of caring at tyrannocharaxes is rather long; male gradually accustoms female to his presence, keeping on edge of her territory. He is ready to recede any minute to respectful distance, when female shows attributes of displeasure from his presence. But in due course female gets used to the male, and he can come nearer to her cautiously. During caring the male becomes brighter: his body gets bright green color with velvet black strips, and the bottom part of head becomes bright red. Looking after the female, male swims near to her, having opened fins and uttering series of clicks heard from under water, especially at night.
The tyrannocharax belongs to phytophyls: this fish spawns eggs on leaves of small-leaved plants. Before spawning pair of fishes chooses thickets of any water plant with small leaves, and tears out all vegetation at the distance of two meters around it. After that courtship ritual begins; during it the male drives female in thickets and nestles against her side. After several trial attempts pair spawns eggs – about 20 thousand of rather large grains of roe.
The female practically at once leaves breeding bottom, and male stays to protect posterity. At this time he becomes almost entirely black, only on sides some green spots are appreciable. His aggression at this time increases so, that even female surpassing him by size, is compelled to recede away from clutch.
The incubating of eggs lasts about one week, and then male leaves clutch to the mercy of fate. First days larvae hide among plants, at three-day age start to swim and to eat small crustaceans. They quickly grow, and at length about 1 centimeter already can attack fry of other fishes. Cannibalism is typical to this species at any stage of development, therefore only few fishes live up to adult condition. Sexual maturity at young fishes comes at the age of about seven years; life expectancy reaches 50 years and more.
Tyrannocharax hunts large mammals, waterfowl and large fishes. Jaw might at this predator is those, that it can easily punch by teeth even carapace of small turtle. Usually fish hides near favorite watering places of large animals, and waits, while any animal will come in water too far. Then sharp throw follows, and prey disappears under water. At tyrannocharax there is iron jaw bite. But even if animal can escape, it most likely will die from loss of blood: sharp teeth of tyrannocharax put deep wounds. This fish catches waterfowl, seizing it from under water. Also tyrannocharax is not squeamish to eat small catch: nestlings of small birds fallen in water and small mammals, escaping from flood, can easily finish life in its teeth. The full fish swims to depth and lays for some days in deep whirlpool, digesting food.
Comb-jawed duckweed-hackler (Exodolabrus lemnivorus)
Order: Characids (Characiformes)
Family: Comb-lipped characids (Ctenolabiidae)
Habitat: Congo basin, lakes, bays and cutoff meanders.
Characids are one of groups of fishes common for Africa and South America. Though at these two continents even common families of these fishes had not remained, the relationship of African and South-American characids indicates former connection of Old and New World. In Africa the majority of characids is presented with predatory or omnivorous species, but representatives of citarinids family (Citarinidae) are exclusively vegetarians, despite of competition from the side of numerous cyprinid fishes. Till the ice age in equatorial zone of Africa many representatives of aborigial tropical fauna had been kept, and life in this place had always differed in variety. Therefore narrow food specialization had become the best solution in stable environment at rigid competition. In such conditions some African characids had turned to stenophagous species.
One of narrowest food specialists among herbivorous fishes of Africa is the comb-jawed duckweed-hackler. It is rather large fish reaching length about 30 cm. Duckweed-hackler constantly keeps near to surface of water; in this connection its body has got rather characteristic shape. The top part of body of this fish is flattened; head and back make practically straight line. The bottom part of body of duckweed-hackler, on the contrary, has rounded outlines. The body of fish is strongly compressed from sides due to what duckweed-hackler easily squeezes among roots of floating plants hanging down in thickness of water.
Tail of this fish is short and wide: duckweed-hackler does not like to swim far, but in case of necessity it can accelerate large speed, escaping from predators or arranging courtship display. Back fin of fish is short and triangular; flesh fin is low. Wide anal fin of this species has the important role in displays: having stretched and colored it brightly, male involves females, swimming near the surface of water.
The body of fish is colored yellowish with brown irregular-shaped spots and pale “leaf nerves”. In case of danger fish skilfully simulates rotten leaves, rushing on bottom and quickly digging in dust. When silt and settle sediment, the hidden fish becomes invisible. Duckweed-hackler can hide in bottom dust for some minutes. As a rule, it is enough, that predatory fish ceases to search for it.
Duckweed-hackler eats exclusively one kind of food: duckweed covering like continuous carpet the surface of tropical reservoirs. The mouth of this fish is perfectly adapted to such diet: it is shifted and oblique upwards. Top jaw of duckweed-hackler has a remarkable structure: teeth on it are very thin and numerous, forming true “palings”. They stick up on the internal surface of upper lip, and when the mouth is opened their edges are directed upwards and a little forward. Bottom jaw with thick fringy lip at the opened mouth is directed in parallel to water surface. Eating fish “draws” water surface by upper lip, gathering duckweed by thin teeth, as if like net. From time to time it closes mouth, and lower lip rakes gathered duckweed from top jaw and fish swallows it. Duckweed is rich in protein, but fish also eats tiny animals settling on duckweed.
Duckweed-hacklers protect the fodder site actively, and support it in cleanliness: they tear off leaves of water lilies and take away large floating plants, releasing living place for growth of duckweed. Each fish owns the certain site on water surface (approximately some tens square meters). It drives off congeners from site, showing itself in ray of sun light. However, at edges of fodder territories at these fishes necessarily there is secluded nook in which duckweed-hackler hides from predators.
In spawning season duckweed-hackler does not show strict intolerance to congeners. Females have a right to swim to another's territories, and males do not hide their location – they highly jump out of water, ploping down back loudly splashing. At duckweed-hacklers males are smaller than females, but they have larger head and are colored brighter. Courting after the female, male spreads anal fin on which the border of red color appears, and shows itself in sun rays. Preliminary it scatters plants floating on water surface to make the place of display lighter.
As against to the majority of citarinids and their relatives, duckweed-hacklers spawn in pairs. Male drives female above the bottom, and from time to time presses it to underwater objects. Sires spawn transparent not sticky eggs in water, and it sediments on bottom. Fertility of one female may reach 30 thousands of eggs. Adult fishes may eat a part of eggs, picking them up during the spawning act, but after spawning male banishes female and swims up to the surface of water. Therefore the significant part of eggs has an opportunity to develop at the bottom among dust.
Incubating lasts about two days, and about day larvae motionlessly hang on plants. Then they turn to fry and start to eat phytoplankton and protozoans. Till the first year of life young fishes reach length of 4 – 5 cm and win to themselves small fodder territories, usually in shallow water where adult fishes do not swim. Approximately to the third year of life duckweed-hackler reaches the usual size of adult fish and becomes able to spawning.
Barracuda phago (Necrophago sphyraenoides)
Order: Characids (Characiformes)
Family: Citarinids (Citarinidae)
Habitat: Congo, middle part of river channel.
Among inhabitants of African rivers characid fishes are very typical. They are less various, than species in South America, and occupy slightly other ecological niches. Among them there are many predatory species, and omnivorous and herbivorous ones frequently differ in large size. Small predatory fishes of genus Phago had occupied the special place among African characids. These creatures distinguished by furious and predatory behavior, had survived in mass extinction – being small fishes, they could keep rather numerous population till the falling of biological efficiency of reservoirs. Large river predators died out till the ice age – this process had completely exterminated crocodiles, for example. But after stabilization of environment conditions at small fishes the tremendous chance to force the way into large-sized class and to be among succeeding predators of Equatorial Africa rivers, competing with predatory turtles and lizards, had appeared.
Length of Phago and most part of its congeners of Holocene epoch did not exceed 20 – 30 cm. But their descendant, huge barracuda phago, became frightening inhabitant of Congo. It is the predatory fish reaching length up to 2 meters. Body of this predator is lengthened and streamline-shaped. Barracuda phago may accelerate large speed and easily resists to strong current. On sides of this fish body is covered with armour of thick scales – barracuda phagos are rather aggressive relatively to each other, and this adaptation for protection in intraspecific skirmishes is not superfluous for them. Scales form set of slanting cross lines on sides, and the body keeps sufficient flexibility and mobility.
Fins of barracuda phago are short and peaked, and fatty fin is very small. Unpaired fins are shifted to the back part of body – such feature is characteristic for fishes making fast throws. Tail fin of barracuda phago is high and rigid, adapted to accelerating of fast speed.
Barracuda phago has kept a diet, characteristic for ancestors: it is active predator. At it there is big head with long jaws on which numerous pointed teeth stick up. Due to the size this fish eats any animals which it may find in the river and swallow: fishes, shrimps, waterfowl and small ground animals had got in water. For this species cannibalism is very characteristic, therefore young fishes avoid meetings with adults: they keep in shallow rivers, mastering main channel till the process of growth.
Young and adult fishes have different ways of life and thereof at them the various colouring varying in process of growth was developed. Young fishes are more secretive, than adults: they spend a lot of time, hiding among roots of floating plants near the water surface. Therefore their colouring is cross-striped: on silvery background rough vertical strips stretch, hiding fishes among roots of plants. Adult fishes keep in river channel where there are not enough bushes of floating plants. Their body has monotonous silvery colouring.
Being a predator, barracuda phago is solitary fish. Each individual has extensive fodder territory in river channel and actively protects it from neighbours. Threatening the neighbour, the fish utters series of loud creaking sounds well heard from under water. If the contender does not abandon the occupied territory, fishes enter fight: they put bites to each other, drag each other by jaw and tear contender’s fins. Sometimes one of fishes may even kill the contender.
The loneliness of barracuda phago is broken in spawning season. Spawning at this species is schooling, as at many others characids: at this time all borders of individual possession are broken, and predators gather in large shoals numbering up to fifty adult fishes. Unique rescue for river inhabitants at this time is that during spawning the food behaviour at barracuda phago is suppressed. Therefore in shoals of adult fishes it is possible to find young fishes not yet completely left striped colouring.
During courtship games males pursue female by small group, uttering abrupt single clicks. At the culmination moment they densely nestle against the female from different sides, literally squeezing eggs out from it. Small transparent eggs are spawned in water, at once are fertilized, and males lose interest to the female. They abandon it, and start to drive other females, yet not spawned eggs. Having spawned eggs, females try to get rid of chasing from the side of males: they leave the common shoal and hide in thickets of floating plants, as if young growth.
Eggs develop in thickness of water, being gathered at coast or among small bushes of floating vegetation. The incubating lasts about 2 days. Larvae passively soar in thickness of water, becoming prey of various plankton crustaceans and small fishes. But part of them turns to fry a day after. Fry actively swims and hides among plants floating on water surface. Part of them perishes, when the watercourse carries away thickets of floating plants to the ocean. But some of them succeed to survive among thickets, washed to river banks. Growing up, young barracuda phagos migrate in rivers then to return to main channel as one of main predators of the river. They become sexual mature at the fifth year of life, at length about one meter. But at this time at them striped colouring is still kept. They completely develop and lose juvenile colouring up to seven years. Life expectancy of barracuda phago may reach 30 – 35 years.
eel (Caecogymnotella psammotalpa)
Order: Cyprinoid fishes (Cypriniformes), suborder Knifefishes (Gymnotoidei)
Family: Electric eels (Electrophoridae)
Habitat: South America, basins of Amazon and Hyppolithe rivers.
Picture by Lambert
In northern part of South America vast river systems represent
the home of various fishes. Some groups of fishes are endemic for South America,
in particular, original gymnotid fishes. All of them are flesh-eating ones,
and some use the electric discharge for hunting. However, the primary purpose
of electric field of these fishes was the orientation in conditions where sight
is useless – in muddy water, at night or in thickets of plants. One of gymnotid
fish species during the evolution had completely reduced sight sense which appeared
completely replaced by electric field in life of this fish.
At the bottom of South American rivers there are some species of digging fishes. Some of them eat mainly invertebrates, and others represent the active predators attacking smaller vertebrates – fishes and frogs. Largest of digging species of fishes is mole eel, blind species of electric eels adapted to life in top layer of river bottom. The body length of this fish reaches 1 meter; male is larger than female. The body of fish is lengthened, snake-like, similar to body of electric eel (Electrophorus electricus), its direct ancestor. But digging habit of life was substantially resulted in shape of mole eel. The anal fin of this species is underdeveloped; it represents only narrow edge along the bottom side of body, and does not take part in movement of fish, as at freely swimming gymnotids. Tips of fin rays jut out from fin plica and serve as a support when fish creeps through bottom sediments. Pigmentation of body is substantially lost: fish has pale colouring, and its skin has only slight pinkish-yellow shade. At young fishes skin is pale grey, and body is transparent. At adult fishes eyes had completely reduced, and there are only two dark spots under skin near to edges of mouth. At young fishes eyes are advanced much better; they are hidden under skin, but it is thin and transparent, therefore young fishes react to light, leaving from lightened places to darkness, and can distinguish the subjects contrasting with the general background. Young fishes live in thickets of plants and in shallow water, and are dug in sand only in case of danger though willingly creep in thickness of layer of fallen leaves covering bottom of rivers flowing in tropical forest. At the age of 1 year they pass to burrowing way of life and get shape of adult fishes, and at the third year of life they become able to breed.
The adult fish almost never leaves sand. It creeps in top layer of ground, coiling like snake. The tip of muzzle of mole eel is covered with very hard skin helping to carve its way in thickness of sand. Operculums of fish are supplied with leathery valves along the edge; it protects gills from contamination. However, this fish respires mainly with the help of skin (mole eel receives this way up to 60% of needed oxygen). At lack of oxygen or if the fish was dug deeply in ground, blood vessels of skin can dilate. Thus the body of fish gets visible pink color. If necessary, fish canrespire with the help of skin within several hours.
Mole eel orientates itself in surrounding world with the help of electric field. Creeping in ground, fish feels the changes of electric field connected to different electroconductivity of subjects (stones, live plants and driftwood). Mole eel defines the presence of other live beings nearby from it the same way. This fish has inherited from the ancestor the ability of generation of strong electric pulses. This skill is absolutely necessary for hunting and self-defense – fish stuns by discharges small fishes and crustaceans, and eats them. Also the strong electric pulse can paralyse or frighten off large predator hunting this fish.
Spawning of mole eel is not connected to the certain season. Male searches for the female ready to spawning, being guided by smell, and, having come nearer to her to safe distance, makes a series of weak electric pulses forming “the love message” to the female. If the female begins to answer male synchronously, the couple continues courting. By movements of forward part of body male and female dig a hole in which female spawns eggs (up to 500 eggs in the clutch). Male at once fertilizes them and then takes in mouth and broods during 4 – 5 days, cautiously pumping water through mouth. Larvae keep in male’s mouth within several days while yolk sac resolves at them. Young fishes lead active life in shallow water near the riverbanks, moving to deeper sites of river channel as they grow up. They also are predators, and eat small fishes and larvae of insects.
Rainbow silverscaler (Argentopleura iridescens)
Order: Cyprinoids (Cypriniformes)
Family: Cyprinids (Cyprinidae)
Habitat: deep part of Fourseas.
Cyprinoids are mainly freshwater fishes, though separate representatives of order can live any time in sea water. And some freshwater species regularly come to sea water for feeding. Earlier such species of cyprinoids lived in Black, Caspian and Aral seas. And, when Fourseas had appeared in Neocene at the territory of Southern Europe, some species of cyprinid fishes survived during mass extinction, had mastered this new environment.
One of main pelagic species of Fourseas belongs to cyprinids. It is silverscaler, the descendant of roach (Rutilus rutilus). This fish appreciably differs from the ancestor, first of all by size and habit of life.
Silverscaler is schooling fish about one meter long, weighting about 15 kg. At it there are muscled body and wide two-lobed tail fin. It is a fish of silvery colouring with bluish shade and strong iridescent shine on sides. Back is appreciably darker than sides, and iridescent shine is swept less up on it. Back fin is short, high and transparent; on it there is a coal-black cross strip – with the help of this natural label fishes of present species distinguish congeners at the large distance. To be less appreciable for predators, fishes simply lower back fin, and become imperceptible on the background of blue water. The mouth is rather small, but it can extend forward as a tube. This fish is mainly zoophagous – it eats invertebrates and fry of fishes (primarily gobies). As at all cyprinids, at silverscaler there are no teeth, but on branchial arches sharp pharyngeal teeth permitting crushing of armors of crustaceans and to keep small fishes are advanced.
Silverscalers keep in huge schools numbering up to hundred of fishes and more. Schools usually include fishes of approximately equal size and age. The expressed leader is not present in them. The school synchronously moves in thickness of water, and scatters in sides as if dissolving in blue haze of water at approach of predator (for example, the tsarfish, the largest inhabitant of Fourseas). When danger is over, fishes gather, signaling to neighbours by movements of back fins.
The spawning of silverscalers takes place in the spring in reeds among thickets of pondweed and eel grass. Fertility of the adult female is up to 100 thousand eggs. The spawning proceeds very roughly: fishes jump out from water, plop down with loud splash; males in schools of four - five individuals chase females ready to spawning. In spawning season males have elements of spawning dress: on their operculums “pearl rash” appears, and the tail fin has red colouring. In spawning season fishes become easily excitable and any sharp burst results to their active jumping out from water in great number. Fishes prefer to spawn approximately in the beginning of spring while water plants only have started to grow, and water is cold and rich in oxygen. There is one more reason in it: in cold water appetite of predators is reduced, and the larvae will be in relatively safety.
Similarly to the majority of cyprinids, these fishes do not care of eggs, and the part of eggs may be had simply eaten by congeners.
The incubating lasts about two weeks. For this time the significant part of eggs is eaten by various animals. The larva hangs on plants two more days, and then turns to fry. Schools of fry of silverscaler leave the coastal zone and pass to life in high sea. To the age of five years fishes reach the length 50 – 60 cm and become sexual mature. Life expectancy at this species may be up to 35 – 40 years.
Potamolabeo (Potamolabeo platycephalus)
Order: Cyprinoid fishes (Cypriniformes)
Family: Cyprinids (Cyprinidae)
Habitat: Zinj Land, fast-flowing mountain rivers and streams.
Zinj Land had separated from Africa by break line marked even in prehistoric time by Great Rift Valley. This enormous land mass, separated from the main continent, includes territories on which in human epoch eastern part of Ethiopia, Somalia, Kenya, Tanzania and the north of Mozambique were placed. In human epoch it was the district including mountainous areas and savanna with additions of woods. Having separated from the continent, Zinj Land had carried away Kilimanjaro, the highest mountain of continent. Rivers of this huge island are short, but flow in warm district favorable to development of diverse life forms. Because of isolation rivers of island are rich in endemic species of fishes. Many interesting species of fishes live in cool mountain rivers. One of these species shows excellent fitness to life in rough current. It is potamolabeo, “stream labeo”, the descendant of cyprinid fishes of genus Labeo, lived in African rivers in Holocene.
Potamolabeo is rather large fish: length of adult individual is up to 30 cm. At this fish sexual dimorphism is well expressed – it is the unusual phenomenon in cyprinid family. The female is larger than male, but at the male head is relatively bigger. Also on operculums of the male the several lines of small spikes increasing in courtship season grow.
Potamolabeo looks very clumsily: the fish seems made of two parts of completely different fishes. At this fish there are massive flat head, slightly convex eyes and constantly opened mouth looking like sucker. On lips of fish some numbers of corneous denticles develop – similarly to all cyprinids, potamolabeo has no true teeth. Operculums of this fish are shifted downwards, and gills are protected from below from sand by additional skin valves.
Body of fish is thin and low. Wide pectoral fins serve potamolabeo as rudders of depth. This fish lives in fast flowing water; therefore, having slightly turned fins, it can emerge or nestle against the bottom easily, not spending superfluous efforts. The first ray of pectoral and abdominal fins at fishes of both sexes is thick, strong, and saw-like jagged, having a spike on the tip. At males spike is thicker, rather than at females.
Back fin of potamolabeo is very bright – red with black speckles. Its basis is short, and fin rays are long. This fin has the function of warning signal, equally important both for the male, and for the female. Therefore back fin is equally bright at representatives of both sexes.
Strong current is a factor of environment difficult to struggle with it. In current fishes develop two basic tactics of behaviour: they either become fast swimmers to move against the stream, staying on place, or avoid the current. Potamolabeo had chosen the second way: this massive fish swims hardly and does not emerge without special necessities. All efforts of fish are directed on being kept at the bottom and to not be carried away by rough current. This fish keeps by spikes of fins for stones, and the counter stream presses fish to stones. Swimming bladder at potamolabeo is lack.
This fish keeps on stony areas of rivers. Potamolabeo eats algae, water mosses and larvae of insects attaching to stones. Also it can clean off microscopic seaweed growing on leaves of underwater plants living in flowing water. Except for corneous denticles, on bottom jaw the corneous edges develop, assisting to scrape off algae. For digestion of such poorly nutritious food at fish the long intestines had developed – its length fifteen times exceeds length of fish body. Being filled with food, intestines also raise density of fish and facilitate resistance to current.
Feeding by so specific kind of forage had caused the certain changes in habit of life of potamolabeo. Potamolabeo is territorial and aggressive. Each fish has territory the area about 10 square meters; the fish knows borders of territory and furiously protects them from neighbours. Bushes of plants and large stones serve as boundary marks. If the stranger interferes in limits of territory of fish, the owner of territory quickly lifts and lowers back fin some times. It is a signal, that the stranger is noticed, and simultaneously it is the requirement to leave the territory which is already occupied. If the stranger does not leave territory, the fish owning a site, swims towards to the contender, having opened back fin. This is the warning of opportunity to fight. Fights at potamolabeo are very severe: fish accelerates speed and puts to the opponent ramming impacts by a head. Such impact, if it is put to the operculum area, may even kill the contender. There is one more, more harmless reception of struggle – the fish picks up the opponent by head, lifts it above the bottom and by strong impact of snout throws upwards. Current picks up the infringer of territory and carries it to some distance from the site occupied by with a fish.
In spawning season male leaves its territory and spawns with the female in her territory. As a rule, the male chooses the female living in the neighbourhood. Courtship at these fishes is simple and even a little bit formal: the male simply drives the female, trying to swim forward and to touch its head by spikes growing on operculums. Accepting the courting, the female trembles by pectoral fins and presses back fin to the back. Pair of fishes simply scatters eggs at the bottom and does not care of them. For one spawning the pair spawns more than 200 thousands eggs. Eggs fail between stones and are incubating in conditions of good supply by oxygen till about two weeks. The first some minutes after fertilization the shell of eggs is not sticky, but further it swells and on its surface slime appears, which pastes eggs to stones and driftwood. Larvae of potamolabeo are inactive. They hide in cracks between stones and eat bacterial slime and particles of organic substances. Larger fry keep secretively under stones or in bushes of water plants. Young fishes migrate in shallow streams where there are no adult fishes, and gradually grow there. At this stage of life many fishes become victims of various water predators. As they grow, they settle in deeper sites of river channel and occupy individual sites. Young fishes take part in spawning at one-year-old age.
Mudsleeper (Dormicyprinus robustus)
Order: Cyprinoid fishes (Cypriniformes)
Family: Cyprinids (Cyprinidae)
Habitat: Meganesia, savanna areas to the west from Eyre Gulf; temporary reservoirs.
Picture by Carlos Pizcueta (Electreel)
Not all species of animals and plants introduced by people
to various places of the Earth had died out during global ecological crisis
at the boundary of
Holocene and Neocene. At various continents in Neocene flora and fauna it
is possible to meet species descended from species introduced to these regions
by people millions years ago. Ecosystems of islands and Australia, continent,
for long time being in isolation, suffered from introducing of alien species
especially strongly. In Neocene at the territory of Meganesia (continent
Australia and New Guinea) many species being descendants of non-native species
live. In ichthyofauna of Meganesia one of their representatives is the large
cyprinoid fish named mudsleeper. It is the descendant of of carp (Cyprinus
carpio) introduced by people, which had exellently adapted to extreme conditions
of new motherland.
Freshwater reservoirs in Meganesia are concentrated at the north and at the east, along Great Dividing Ridge. Farther at the west there is wide brackish-water Eyre Gulf; from the west only temporary rivers which may dry up completely for some months run into this gulf. In such reservoirs this fish is dominant species of ichthyofauna.
Body length of mudsleeper is about 40 cm. Body of this fish is prolonged; head is flattened and rather small. The fin shape of this species is characteristic for slowly swimming omnivorous cyprinids – all its fins are rounded and have soft rays. Only in back fin some forward rays have grown together to one strong prickle on which front edge small denticles develop. Colouring of body of mudsleeper is beautiful: there is golden-brown background with vertical greenish-black strips, one of which stretches across the eye. Fins are transparent with reddish-orange shade.
This species of fishes is omnivorous, and equally willingly eats insects, aquatic vegetation and even dead animals had sunk during rains.
The remarkable skill of its ancestor, the ability to go through temporary drying of reservoir, had received the further development at this species. Mudsleeper can survive till about 15 months, having dug in ground of the dried up reservoir to the depth of about one meter. At this time in organism of fish significant physiological changes proceed. Shortly before complete drying of reservoir muscles of fish as if impregnate with water and become slightly watery. It is the stock of water necessary for successful surviving in drought. When water level falls so, that it does not provide the survival of fish, it starts to dig in ground the vertical shaft to the depth up to one meter. Usually the individuals living in droughter conditions hide deeper, than ones from populations of the coast of Eyre Gulf. Having reached the needed depth, fish forms the small chamber, in which falls into anabiosis, by movements of body. In chamber fish is turned as a ring, having covered operculums by tail fin from below. The body of fish starts to produce slime plentifully. Thus water is gradually “squeezed out” of muscles. Slime is produced in small amount up to the end of term of anabiosis, therefore to the end of dry season fish seems dried alive. At this time fish grows thin strongly; even its eyes fall in, but blood in any case is kept liquid. During anabiosis the body is covered with “cocoon” in which there is only one small aperture which opens to the mouth. External surface of cocoon represents the hardened crust of sand and clay stuck to strong cover by protein fractions of slime. During the rain when the ground is impregnated with water enough, the cocoon becomes soggy quickly, and fish absorbs water through skin of stomach and gills. When muscles restore approximately 50% of the lost moisture, fish starts to get out of ground captivity.
Right after filling of reservoirs by water mudsleepers arrange noisy courtship games. In day time they are slow and hide among quickly growing plants, but in the evening males one by one or in small groups jump from water and loudly splash back, involving females. At night males start to chase females and to drive them to thickets of underwater plants. Nestling to females, males force them to spawn eggs. Fertility of these fishes makes over 50 thousand eggs.
At the majority of cyprinoid fishes the care of posterity is limited only by spawning of plenty of eggs in place favorable for its incubation. Mudsleeper had not departed this “tradition”. The young ones hatch after 3 – 4 days and start to develop very quickly. Young fishes are mainly zoophagous - they had to grow up as much as possible while the reservoir is not dried up. They eat larvae of insects, small crustaceans (their eggs go through drought in dried up silt), and larger ones devour their own congeners. Having such diet some individuals grow to the length of 13 – 15 cm to the time of drying of reservoir. At such size they have a great chance to survive in drought in anabiosis. Small individuals also have chance to survive: many of them successfully live the first years of life in not drying up ponds in lower reaches of rivers. These fishes do not endure salt water and do not live in Eyre Gulf.
At the third year of life mudsleeper reaches a sexual maturity. Life expectancy of this species may reach 40 years and more – ageing of a fish is sharply slowed down while it falls into anabiosis.
Rainbow salmocyprinus (Salmocyprinus irideus)
Order: Cyprinoid fishes (Cypriniformes)
Family: Cyprinids (Cyprinidae)
Habitat: India, upper courses of rivers flowing down from southern slopes of Himalayas.
Significant amount of small species of freshwater fishes had rather successfully endured the epoch of human domination. Destruction of habitats had resulted in extinction of some local endemic species, but in several hundreds thousand years they had been replaced with descendants of survived species. And some descendants of small fishes began to grow up promptly. This process had beem promoted by the emptying of ecological niches caused by overfishing of large fishes and destruction of their habitats. Among large species of fishes of Hindustan the schooling fish length up to 50 cm is especially remarkable; its sides shine in all colors of rainbow with obvious prevalence of lilac and violet. It is rainbow salmocyprinus, the descendant of rose danio (Brachydanio roseus), the species widely distributed in human epoch as aquarium fish.
The descendant of this species is changed in great degree. The fish has considerably increased in size compared to tiny ancestor, but has kept adherence to schooling way of life. Schools of salmocyprinus total up to one hundred individuals, and during the spawning season they gather to many thousands shoals. Body of salmocyprinus is muscled, slender, with short head and unpaired fins shifted to back part of body. This fish has superior mouth, pushing forward and upwards like a short tube. In corners of mouth two long mobile wattles grow. At night when the fish sleeps, wattles are turned forward and serve for the notification about approach of danger – a plenty of chemoreceptors and the cells feeling movement of water is located on them.
The body of these fishes is coloured very attractively. Sides have metal shine, and back is dark grey and matte. Colouring of sides is pinkish-lilac with blue and greenish shade. Beyond the spawning season male does not differ from the female in colouring. The female is little bit larger, rather than male, and her stomach is fuller. In courtship season male changes colouring to more sated one – sides turn rich pink, the top parts of sides are lilac turning to violet colouring of back. Fins at fishes of both sexes are transparent with bluish shine.
This fish eats food which may be gathered from surface of water – larvae of insects and other invertebrates living among floating plants, and also duckweed rich in proteins.
The ancestor of this species, rose danio, willingly spawned in fast flowing water. At salmocyprinus this feature of behaviour has received the further development: this species spawns in fast current in cool mountain rivers, as a salmon (hence the generic name, meaning “salmon – carp”). In spring, when in Himalayas snow thawing begins, the mountain rivers turn to rough streams. Feeling changes in chemical composition of water, schools of these fishes gather to many thousands shoals. Males get bright iridescent colouring but keep in common with females in united schools yet. Spawning places of this species represent thickets of small-leaved hydrophytes in upper courses of rivers at the shoaliness. Fishes swim upstream, overcoming small falls with strong jumps.
At the spawning places schools broke to small groups including about ten of fishes - approximately fifty-fifty males and females. Spawning begins in the morning. Males drive females in thickets of underwater plants and fertilize spawned eggs. By several movements of tail fishes straighten plants trampled down during the act of spawning, and leave thickets, giving up the place to new groups. After spawning fishes hide in deep holes and among large stones, in places protected from predators. Having had a rest after spawning, fishes move to middle watercourse. As against the majority of salmons, salmocyprinus can spawn many times repeatedly.
Fertility of one female makes up to 100000 small transparent eggs. Approximately in one week from them transparent larvae hatch. The first days of life larvae do not eat: yolk sac resolves at them. Having turned to fry they continue life in thickets of plants, eating microscopic aquatic animals. Fry gradually migrate downstream. At the age of 4 months, at length of 5 – 6 cm young fishes get pinkish shade on scales. At this time they gather to numerous shoals, numbering tens thousand individuals, and eat planktonic crustaceans. As they grow, their mouth from terminal becomes superior one, and at the age of about one year fishes pass to diet of adult individuals.
Rainbow salmocyprinus reaches sexual maturity at the age of 3 – 4 years. In upper courses of rivers this species frequently forms smaller slow-growing form spawning together with fishes of the normal size. Lifespan of these fishes makes about 20 years.
fish (Ichthyomanatus crassilabrus)
Order: Cyprinoid fish (Cypriniformes)
Family: Suckerfishes (Catostomidae)
Habitat: lakes and rivers of southern part of North America.
Picture by Alexey Tatarinov
In Eurasia and Africa cyprinoid fishes were characteristic
component of Holocene ichthyofauna. In North America fishes of this family had
also lived, but they had been represented only by small species. And the place
occupied by cyprinids in ecosystems of Eurasia had been occupied in New World
by representatives of suckerfishes – representatives of other family of fishes.
Suckerfishes are fishes of clean rivers and lakes. In human epoch number of many of their species had sharply decreased because of pollution of reservoirs, and some species had been destroyed completely. During the ice age few survived species prospered in cool lakes, and till the global warming they had widely settled in all North America. When the climate began to change, descendants of northern suckerfishes had to maintain an impact of heat-loving fishes from the south. Some suckerfish species had died out or had receded to the north in such conditions, but anothers managed to survive and to occupy various ecological niches in new ecosystems.
In subtropical and tropical waters of North America to the east from Great Plains extensive river systems stretch; earlier the Mississipi basin was here. Here and in smaller river systems of Gulf of Mexico basin, one species of suckerfishes lives, having no analogues in ichthyofauna of North America. Presence of this fish can be defined by moving of leaves and stalks of plants: when this fish eats plants, stalks of reed move and fall in water, and from bottom clubs of silt rise. Occasionally in sun light wide scaly back with large fin shines, or wide-foreheaded head is shown. By behaviour mode and the role in ecosystems this fish resembles the manatee (Trichechus manatus), herbivorous water mammal, rare in Holocene and extinct completely to Neocene. This water inhabitant is named manatee fish.
The length of manatee fish is over 4 meters, and weight reaches one and half tons: it is largest freshwater fish of North America of Neocene epoch, and it is possible, the largest freshwater fish of the world. This is peaceful sluggish creature and the exclusive vegetarian. Manatee fish has massive body covered with large scales. This species of fishes is not able to swim quickly, but it is not necessary for adult fish: manatee fish had reached the size characteristic for these fishes, has practically no enemies. Tail fin is short, two-lobed with rounded blades. Tail is thick and high. Pectoral and abdominal fins of this fish have strong bases and very thick beams - they help the manatee fish to make the way through thickets of reed and among roots of trees. Manatee fish has bad sight and small eyes are located near to corners of mouth. This fish orientates with the help of sense of smell.
Body of this fish is colored dark green, and stomach is grey. On back and sides small brown spots are scattered. On back they are more numerous and merge, forming “marble” pattern. All fins are grayish. Male does not differ from the female in colouring; it is only smaller and slender a little.
One more feature which makes manatee fish a little similar to the mammal prototype is its mouth. At manatee fish there are fleshy mobile lips covered with numerous fleecy outgrowths. With their help the fish pulls out water plants with roots, and then swallows it entirely. Vegetative forage is poorly nutritious, therefore to increase the efficiency of digestion fish has got very long intestines – the length of bowels is about 30 meters. In it vegetative food is digested as if on the conveyor. The stomach at this fish is not expressed. Manatee fish eats practically till all day, consuming up to 30 kg of water plants per day. Using its dung infusorians and bacteria breed; they are eaten by plankton crustaceans and larvae of fishes serving as forage for various predatory fishes and water insects. Therefore reservoirs where the manatee fish lives differ in large productivity.
In reservoirs where heaten water contains not enough oxygen or in silty water manatee fish uses air breath. The mechanism of it is extremely imperfect, but effective. Having felt an asphyxia, fish emerges to water surface and ventilates gills actively: it simply swallows air from surface and blows it through gills as strong jet. Such activity of set of manatee fishes living in the same reservoir helps to avoid asphyxia in hot season and benefits to other inhabitants of reservoirs. One more advantage to inhabitants of lakes and slowly flowing rivers is that manatee fishes eat floating water plants. For this purpose the huge fish is overturned upside down and gathers plants, sucking them by mouth. From time to time the fish strongly compresses operculums, noisily throwing out from mouth casually swallowed air. Floating plants evaporate a lot of water, therefore, controlling their growth, manatee fishes slow down turning of reservoir to swamp.
At large species there is very slow cycle of reproduction, and manatee fish is not exception here. First time the female of this species spawns only at the age of about 12 years. Despite of the adaptation to life in warm and slowly flowing reservoirs, manatee fish has kept characteristic for suckerfishes attachment to the cool clean rivers which is shown during the spawning. To spawn eggs fish leave inundated lakes and coastal shallows during the river flood, gather in main channel and swim in schools to upper flows of rivers to pebble shallows. In these places there is a simultaneous and rough spawning. Males involving females jump out of water and loudly slap tails. They gather small groups and drive females ready to spawning. But usually one of males drives off other ones and spawns with the female alone. This species of fishes spawns a lot of roe – the adult female spawns more than 10 million eggs. Breeding fishes dig eggs in pebble and do not come back to it any more. The most part of spawned eggs perishes of different kind of water animals: crayfishes, small fish and snails. Fry hatch in one week. Young fishes swim to places with slow current where spend first months of life. At first they eat algal films and their mouth has the sucker shape. Growing up, young fishes start to eat filamentous algae and leaflets of water plants. The most part of young fishes perishes of various predators, but few individuals had reached 4 – 5-years age and length about 40 cm already have an every prospect to reach sexual maturity. At the age of 8 years young manatee fish reaches length of 1 meter and from above one and half meters to maturity approach. This species differs in enviable longevity: the average fish of this species may live till 150 years and more.
rainbow fish (Discotaenia multicolor)
Order: Aterinoids (Ateriniformes)
Family: Rainbow fishes (Melanotaeniidae)
Habitat: freshwater reservoirs of Northern Meganesia, thickets of aquatic plants.
Movement of Australian continent to the north and its collision with New Guinea had caused active processes of mountain forming which had transformed Arafura Sea and Gulf of Carpentaria to lakes separated from each other and from ocean by land areas. Rains and rivers had gradually filled these reservoirs with fresh water, and salt sea water had filtered out from them in ocean through cracks in rocks. Only lowermost layers of water in these large lakes have slightly brackish water, as if in memory of that once they were a part of sea.
In reservoirs Meganesia continent of Neocene fishes prosper; these ones are descendants of species inhabited this area in Holocene a long time ago. They are mainly representatives of Aterinoid fish order - various descendants of rainbow fishes (Melanotaenia) and forms related to them (however, among ichthyologists there was also an opinion, that rainbow fishes belong to another order, to Mullets (Mugiliformes)). Similarly to cichlids in Africa (in Holocene epoch) and to Neocene live-bearing fishes of Caribbean Sea, rainbow fishes had evolved to plenty of various species, mainly predators or omnivorous species.
Disk rainbow fish is some kind of “angelfish” among rainbow fishes. It is an omnivorous fish about 10 - 15 cm long, living in thickets of plants. Here this fish hides from enemies and searches for food – larvae of insects and freshwater shrimps. Body of disk rainbow fish is short, but very high: fish at a sight from side seems almost round, only head and tail break disk-like shape a little. Such body shape is characteristic for fishes living among stalks of water plants – having such constitution it is impossible to swim fast, but it is possible to maneuver easily in rich thickets. The body of disk rainbow fish is colored very brightly: scales on body have green metal shine, on operculum there is red “neon” spot, allowing to identify neighbours (at males it is brighter, than at females), and unpaired fins are transparent green with blue border on edge of tail. Body is covered with narrow and twisting cross strips of black color: it helps to mask among vertical stalks of plants.
The mouth of disk rainbow fish is small; it can extend to small tube: by such mouth it is more conveniently to gather attaching larvae of midges and mosquitoes making a basis of diet of this species from plant stalks.
Disk rainbow fishes breed, dropping eggs above thickets of small-leaved plants. For spawning they gather to big shoals (up to 200 fishes and more). Males begin school formation, gathering to groups and appealingly swimming above thickets of water plants. Gradually new males and females join them. The school swims above plants, from time to time quickening, synchronously turning and twirling. Movements of school of fishes ready to spawning resemble fantastic bewitching dance. Vital processes of separate individuals are synchronized so, and females begin ready to spawn practically simultaneously. Each female in time of “common dance” is surrounded by two - three males (usually there are more males than females in school). Then at the culmination moment “dance” interrupts and prompt race begins. Females spawn eggs, and males following them, fertilize them. Eggs fall in thickets of plants, and fishes do not worry any more about their destiny. Having spawned a portion of eggs, female has a rest any time, having replaced race to “dance”, and then spawning repeats. Usually female has exhausted egg stock, leaves school, hiding in thickets. But it does not worry males: from vicinities new males and females swim to school. Such “dancing madness” proceeds some days in succession, and then fishes gradually calm down and again live reticent life in plants.
If eggs will not be eaten with numerous predators and simply foddies loving gratuitous entertainment, in day from them tiny larvae will hatch. They hang on plants about day (yet a yolk sac will resorb), and then turn to active gluttonous fry. At the age of half-year young fish has length about 5 cm and colouring, characteristic for adult fishes (only without red spots on operculums), and at seven-month age it already can breed.
rainbow pike (Esocitaenia angustistoma)
Order: Aterinoid fishes (Ateriniformes)
Family: Rainbow fishes (Melanotaeniidae)
Habitat: freshwater reservoirs of Northern Meganesia (lake of Carpentary), thickets of underwater plants.
Being out of competition in various conditions of inhabiting, species of live organisms quickly divides to some new forms, occupying various habitats, weakening thus a competition among themselves. Such process is named “adaptive radiation”. In Australian-New Guinean region such phenomenon is shown by fishes: representatives of family of rainbow fishes. Among them species had mastered most various habitats and habit of life have appeared. One of species of this family, the wide-mouthed rainbow pike, had turned to active predator of brackish lake formed at the place of Gulf of Carpentaria.
This solitary species of fishes had occupied ecological niche of pikes and other ambush predators. In this connection at the rainbow pike the characteristic shape was formed. Body of fish is oblong and almost cylindrical; length is up to 60 - 80 m. Tail fin is two-lobed, wide and short. Unpaired fins are shifted in back half of body, prickly and soft back fins are connected. Abdominal fins are very short, located approximately under pectoral ones. Rainbow pike swims reluctantly, but can stand per many hours in ambush at the bottom, waiting while catch itself will approach to it close enough to prey it.
Head at this fish is large with wide mouth, extending to short tube. On jawsthere are about hundred small needle-like teeth permitting to keep easily slippery fish or firm shrimp (they make a basis of food of rainbow pike).
The body of this fish is colored with “marble” pattern imitating stones overgrown by seaweed and solar patches of light on them: the basic background is sandy-yellow with cross green and white irregular-shaped “dabs”. At each individual they form unique individual pattern. Besides the shade of coloring can vary depending on color of environmental site of bottom: from almost entirely green color with white and yellowish-green spots up to almost monochromic sandy-yellow color with white “dabs”. At night the fish as if appreciates ancestral colouring: it turns pale, and along the middle line of body the clear black longitudinal strip appears: ancestors of rainbow pike were australian and New Giunean rainbow fishes (Melanotaenia), named so for this feature (“Melanotaenia” in Latin means “black-striped”: many species have longitudinal black strip in colouring).
Each fish occupies at the bottom the certain territory, preserving it against neighbours. As borders of territories various underwater objects, and simple sites of the bottom, not overgrown by plants, serve. If on border the neighbour appears, the owner of territory swims up from thickets, uttering series of clicks. Usually such signal happens enough to drive the stranger off. The fish banishes especially persistent newcomers by sharp throw, braking and turning off aside near to stranger. If the stranger is not going to leave, the turn and ramming impact by snout in area of operculum follows.
During spawning borders of territories as if cease to exist: rainbow pikes earlier were selfish and bilious singles, gather to schools of some tens fishes. Spawning is stimulated with rains freshened the top layer of lake water, and also with bright sunlight. Males shine with bright red fins and golden spots on sides. Fishes spawn in groups, spreading eggs above leaves of aquatic plants near coast. Spawning passes roughly: fishes keen on pursuit one after another jump out from water at meter height and plop down back with loud splash. Each female can spawn approximately 500 - 600 grains of roe for one breeding cycle. After the ending of spawning fishes swim out to their sites, and each of them precisely remembers borders of the possession and ruthlessly expels strangers, which had time to lodge at this site of bottom, from the territory. Approximately month later spawning repeats. But, despite of such fertility, fry of rainbow pikes meet among plants in shallow waters of Carpentaria Lake much less often, than fry of other species of fishes.
Eggs develop within approximately two weeks. Because fishes do not care of posterity, for this time the most part of eggs appear had eaten by various inhabitants of lake. Larvae grow disjointedly, and among fry of rainbow pike cannibalism is not a rarity, and fry frequently become preys of adult fishes. If the young fish managed to reach half-year age and length about 20 cm, it has quite good chances to live up to 10 - 12 years – it is the age limit of wide-mouthed rainbow pikes.
Long-termed archontobranchius (Archontobranchius longaevus)
Order: Cyprinodontiformes (Cyprinodontiformes)
Family: Killyfishes (Cyprinodontidae)
Habitat: north of Zinj Land, shallow rivers and lakes.
For tropical zone of the Earth so-called “annual” fishes are very characteristic. It is the large group of small species of cyprinodontiform fishes living till only one season, and surviving in drought as dormant eggs. In Old and New World there was a set of species of these fishes. Sometimes they could be met even in pools, existing only few weeks in rain season. The part of species of “annual” fishes had successfully gone through climatic changes of the boundary of Neocene and Holocene. In Neocene the active speciation of this group connected to expansion of area of tropical climate and split of African continent began. One species had gone on the unusual way of evolution - it turned to “perennial” species again, and had considerably increased in size. The ancestor of this fish belonged to number of small fishes of genus Notobranchius. Its descendant looks hereby Methuselah in comparison with ancestral forms: duration of its life makes about 15 years. For this feature the fish is named archontobranchius.
Archontobranchius lives in rivers of northern part of Zinj Land having slow current, strongly overgrown with water plants and well warmed by sun. It is a solitary fish aggressive to congeners out of spawning season.
The length of body of archontobranchius reaches 30 – 35 cm. This fish is a little similar to the goby: at archontobranchius there is massive body slightly compressed from sides, and large head with wide mouth turned upwards. Unpaired fins are rounded and shifted to back half of body. Tail fin is two-lobed, with small cut at back edge. Pectoral fins of males are wide and fan-shaped. The body of fish is covered with very small scales.
At archontobranchius the sexual dimorphism in size and colouring of body is well expressed. The male is larger and more aggressive, than the female, and it is painted much brighter, than the female. The back of fishes of both sexes is brown with black speckles – fish is less appreciable so for air predators. At male sides are blue with slanting faltering red strips. Eyes of male are bright blue and shining. On its pectoral fins there is a pattern of
small black spots on red background, forming faltering cross lines.
Female is colored more modest, rather than male – at it there is “marble” brown colouring with grayish-green irregular-shaped spots; eyes are grey with slight shine. In populations the number of males is less, than the number of females – the significant part of males perishes because of bright colouring in beaks of fish-eating birds.
Archontobranchius is carnivorous fish; its food is made by water insects and their larvae, and also shrimps and fry of fishes. This fish hunts catch, which keeps near the surface of water.
The spawning of this fish passes very originally: in it features, characteristic for ancestors of archontobranchius were kept and had received the surprising continuation. This fish breeds at flood of the rivers, during the peak of rain season. Archontobranchiuses spawn in pairs, digging eggs in silt in shallow water. Fishes spawn in the morning, while fish-eating birds have not woken up yet. At this time shallow water literally boil from pairs of spawning fishes which hasten to lay eggs while sun is not rose high enough. Spawning pair jumps out from depth of reservoir to the shallow water, and is literally twisted in layer of coastal mud. At this moment male covers the female by the body, snapping her by pectoral fin or operculum. The female digs out in silt the furrow by sharp movements of head and breast and immediately lays in it small eggs (in clutch it may be up to 500 eggs). The male on the spot fertilizes eggs, and pair of fishes, spinning in silt, buries eggs. For one act of spawning fishes make in mud some furrows and lay in them all caviar which is produced by female. After spawning adult fishes slip from shallow water and swim out to depth. They hide under floating leaves of water plants and restore forces after tiresome spawning. The female spawns only once for a rain season; and one male can repeat spawning with different females some times having breaks approximately in two days. Right after spawning fishes feed more actively, and at females the forming of new portion of eggs begins, but its development stops up to new rain season. Rain water serves as stimulus for the further egg ripening.
Eggs of archontobranchius are small, but the period of their incubating stretches almost to one year. Conditions of egg incubating of this species of fishes are original: in some days after spawning shallows dry up, and eggs appears in layer of liquid mud, or even simply on land. It does not kill them: egg of this fish easily tolerates drying due to dense shell. This feature inherited from ancestors, allows archontobranchius to settle actively. Eggs can be transferred in dry season by wind or on legs of animals to long distances. Sometimes water birds carry eggs on paws over sea passages, and archontobranchiuses may be met even at Madagascar, in Arabia and at the African coast of Tanganyica Passage. But there constant populations of this fish are not formed – practically all immigrants fall victims of local species of fishes and fish-eating birds. But in conditions of seasonal climate at the north of Zinj Land, when the rain season is replaced by drought, archontobranchius is out of competition.
Adult archontobranchiuses live in rivers and lakes which in drought may turn to stinking ponds with dirty water. These fishes are steady against lack of oxygen dissolved in water. They can respire, grasping an air bubble from the surface of water. When the fish holds air bubble in mouth, oxygen from it gets in blood through gills. When the reservoir dries up strongly, archontobranchius digs itself in silt and rotten plants, and respires with the help of skin. This fish has the certain abilities to forecasting a drought: having a presentiment of rough drought, fishes dig in silt deeper, and fall into catalepsy.
When the rain season comes, adult fishes leave the refuges. They at once start to hunt various insects flying to water, and even try to catch butterflies and dragonflies flying above water. During the rain season from eggs fry hatch. The part of them may appear in temporary reservoirs unsuitable for life, but some ones may get in other rivers and lakes where there are good conditions for life. Fry is very tiny – the length of just hatched fry does not exceed 2 – 3 mm. But they grow quickly, and to the end of the second month of life reach the length of 4 – 5 cm. At the age of about half-year young fish already can take part in spawning.
snail cleaner (Helicichthys hygeius)
Order: Cyprinodontiformes (Cyprinodontiformes)
Family: Live-bearers (Poeciliidae)
Habitat: Great Antigua, slowly flowing rivers, ponds and bogs.
Sometimes health of certain animal may depend on other species
of live beings, and sometimes the connection may look too strange. Vertebrates
are hosts of various helminths. Life cycle of these parasitic worms is connected
to change of various hosts at different stages of development of worm. Frequently
larvae of helminths parasitize in freshwater snails during any time, and then
pass from them to the final host.
At Great Antigua many species of animals live, and some their parasites pass the part of life cycle in large freshwater snails of families Ampullariidae, Viviparidae and others. But the evolution had given to snails the unexpected assistant – one local fishes.
Small translucent fish about 25 millimeters long constantly keeps near large snails. The body of this fish has only some dark spots on back, and on side thin longitudinal silver strip stretching from eye up to the basis of tail fin is visible. It is a symbiote of snails, tiny snail cleaner. The body of snail cleaner is prolonged and thin due to what fish can penetrate into pallial cavity of snail, not causing it of anxiety. The pointed head of snail cleaner permits this fish to clear delicate snail gills of parasites accurately. Fish constantly keeps near the snail, not swimming out from it more than to 10-15 centimeters. Only in case of extreme danger snail cleaner can leave a snail “cared” by it, but after that it necessarily searches to itself for the new host mollusc. If danger threatens to the fish, it hides in shell of snail. Sometimes it even squeezes into shell of snail when mollusk retracts into it, and waits danger, having covered in pallial cavity of snail. Enemies of tiny snail cleaner are water beetles, bugs and leeches.
Tiny snail cleaner eats various invertebrates found near snails and on its body. It eats rotifers and smallest larvae of midges and mosquitoes. This fish is able to eat planarias, harming to snails strongly, without harm for itself. Other fishes do not eat planarias because of their poisonous slime. But the biggest benefit of this fish is received not only by snails cleared by it, but also by various species of vertebrates of Great Antigua. Tiny snail cleaner, in addition, eats swimming larvae of helminths searching for snails to pass the next stage of life cycle. Therefore contamination by helminths of vertebrats of Great Antigua in habitats of tiny snail cleaner is much lower, than in similar areas where this fish is not present at the same number of snails.
Tiny snail cleaner belongs to viviparous species. The complex ritual previous to pairing is lack at this species. Male and female are coupled at the meeting of their host snails. The sperm received by female, keeps viability for a long time, therefore female is able to bring posterity within several months after the only pairing. Embryos in ovoducts of female do not lose connection with it up to last moment before birth. Stimulus for their birth is the presence of large snail having no symbiote fish. When such snail comes nearer to closer distance, the female of tiny snail cleaner leaves its own host snail and quickly gives rise to one well developed young fish for other snail. The anal fin of female of tiny snail cleaner has lengthened front edge and resembles the male gonopodium a little. At the birth moment the edge of fin turns off in tube like an ovipositor. With its help the female places newborn fry right in pallial cavity of snail. After the fry birth it quickly swims back to its own host snail. Fertility of the female can make up to fifty young fishes for three months of life. Sometimes within one day the female gives rise up to three young ones in shells of different snails. Right after the last birth in her organism next embryo starts to develop.
Transparent young tiny snail cleaners are completely independent and very active. They clear host snail of parasites, and the first weeks of life hide in its shell. At bi-monthly age young tiny snail cleaner reaches sexual maturity. Life expectancy of this fish seldom exceeds 20 months.
Barbed cave live-bearer (Caecopoecilichthys barbatus)
Order: Cyprinodontiformes (Cyprinodontiformes)
Family: Live-bearers (Poeciliidae)
Habitat: caves of Central America (Yucatan).
In Neocene viviparous fishes of Poeciliidae family have a true evolutionary blossoming. Among them many freshwater species had evolved, and the significant number of these fishes had developed sea inhabitancy. Among poeciliids in human epoch there were some species of low-specialized troglobionts – cave species made only first steps in development of gloomy world of caves.
From human epoch millions years had passed. In Neocene among live-bearers the true cave species deeply specialized to such habit of life, barbed cave live-bearer, had evolved. It lives in underground waters of Yucatan Peninsula and was widely settled in various caves due to unpretentiousness and endurance.
It is rather large species of fishes at which the sexual dimorphism is clearly expressed: the female is much larger, than male. Length of female is about 15 sm, male is only about 10 cm long. Female and male very strongly differ from each other not only in size, but also in shape, and also in features of behaviour. Female is massive and has deep body. It swoms slower and eats larger prey. Male is faster and has prolonged body. It has smaller mouth and eats small aquatic animals.
The shape of barbed cave live-bearer is the evidence of millions years of evolution in underground habitats. It is completely blind fish at which even rudiments of eyes was not kept. Only two holes on head indicate former presence of eyes at far ancestors of this species. Instead of lost sight this species has well advanced organs of lateral line and set of receptors located on head. Related to barbed cave live-bearer fishes living in rivers and sea have no wattles, but at cave live-bearer around of mouth the outgrowths similar to short wattles are developed. They are especially numerous on bottom jaw, because of what this species has received the specific epithet “barbatus” – “barbed”. The length of these outgrowths reaches 20 – 25 mm; they are plentifully covered with sensory cells.
The body of barbed cave live-bearer is lack of pigmentation and has pinkish-white color. The skin of fish is covered with thin transparent scale. Fins are wide; back and anal fins are shifted back, to tail. At males anal fin is turned to long mobile gonopodium which basis is covered with small scales. The length of gonopodium makes about half of length of male’s body. Tail fin is trapezoid; at its back edge there is small cutting dividing it to lobes. Pectoral fins are fan-shaped and mobile.
This species of fishes is widely settled in underground waters of Yucatan and adjoining areas of Central America. It is connected with the fact that barbed cave live-bearer can live in water of various salinity – from fresh up to oceanic. Using sea caves, it settles from one underground river into another one.
Barbed cave live-bearer represents strongly expressed predator. At this one wide mouth able to extend to tube and literally to suck prey is developed. This fish eats larvae of insects and other water animals living in caves. If from vaults of cave bat drops and falls in water, bearded cave live-bearer willingly eats them, especially representatives of small species or cubs. It swallows prey entirely – in conditions of caves as in ocean depths it is practically impossible to have strict diet or to eat more or less regularly, therefore the present species of fishes uses poor food resources of cave to the full. Jaw bones are connected by mobile ligaments, and gullet and stomach can stretch strongly.
Similarly to all relatives, this fish is viviparous. However, breeding rate at barbed cave live-bearer is much slower, than at fishes living in open reservoirs. The female of this species gives rise only to one young fish at once. But fry is very big – its length reaches one third of length of female, and it has all chances to survive. Nevertheless, females of barbed cave live-bearer frequently attack young fishes of its species. Within one year the female bears posterity no more than four times, but it is enough of it to provide reproduction of species in conditions of rather isolated reservoir with poor food resources. Right after birth male and female do not differ from each other in size, but further male finishes growth earlier and matures faster. However, in connection to cannibalism of females, the number of males in population is insignificant – it mounts about a quarter of the whole population. Young fishes mature at the age of 1 year, and life expectancy makes not less than 8 years.
Dwarf stomatobius, “mouth fish” (Stomatobius pusillus)
Order: Cyprinodontiformes (Cyprinodontiformes)
Family: Live-bearers (Gambusiidae)
Habitat: Zinj Land, rivers.
During evolution live organisms develop freakish forms of mutual relation – from symbiosis up to parasitism and superparasitism in various displays. One of freakish ways of coexistence with other species was developed by tiny viviparous fish living in Zinj Land – dwarf stomatobius, the descendant of guppy (Poecilia reticulata) which had been widely settled in tropics of the Earth by people for struggle against malarial mosquitoes. This species of fishes differs from the ancestor in very dim colouring and special way of life. This species has entered relations of commensalisms with disproporcichla (Disproporcichla micrandra), large fish living in the same places. Stomatobius lives in one of the most reliable shelters in the river – in the mouth of large females of these fishes when those ones brood their fry. Less often stomatobius fishes settle in mouths of other representatives of cichlid family. Life in mouth of the representative of so protected species bears the great benefits: it is reliable protection against the majority of predators of small and medium size, and also carries constant supply by food.
The shape of stomatobius is adapted in top degree to imitation of disproporcichla fry. It is tiny fish (length of adult individual does not exceed 15 mm) with the translucent short body, short fins and rather large eyes. As fish grows, its colouring becomes similar to colouring of the host fish fry. Sight sense has the important role in imitation of host fry – during the growth fish imitates changes of host fry colouring. Life of stomatobius is very short – no more than one month from birth to death. It grows and changes synchronously with fry, imitating one of them, and is fed on the same food, as they are – on infusorians, tiniest worms and larvae of crustaceans. This species behaves tolerantly in relation to fry of host fish, and only competes to them for food, but not in the greater degree, than young fishes compete to each other.
Life cycle of stomatobius is closely connected to presence of mouthbrooding fishes near to it. If such fishes are not present, the development of fry of this species is considerably delayed – it develops physiologically, but growth is considerably slowed down. It happens, that in such condition females of stomatobius reach sexual maturity and they are fertilized by “homeless” males. But, though the fertilization occurs normally, ovocytes in ovaries of the female do not develop while she will start to grow.
If the female succeeds to find a couple of cichlids preparing for brooding, it stays near to them, waiting for a right moment and driving potential competitors away. If there is no host fish of suitable species beside, stomatobius fishes behave to each other rather peacefully, but the presence of the necessary fish changes the behaviour of stomatobius. Females differ in greater aggression, but let males fertilize themselves. Spawning of potential hosts and the excretion into the water of the chemical substances, accompanying this event, render stimulating influence on the female. She starts making cautious, but active attempts to get in mouth of brooding fish. As a rule, she makes it at night, cautiously penetrating under the operculum of the host fish. If not disproporcichla is chosen as the host, stomatobius correctly defines by smell what individual is brooding eggs. When the host fish opens operculums, stomatobius squeezes under them and gets into the mouth. This fish almost on the spot starts to benefit the host fish, gathering parasites attached to gill arches.
If the fertilized female has penetrated into the mouth of host fish, she almost at once starts to spawn posterity. Eggs and embryoes develop in her ovaries as on the conveyor, and with a current of water through gills stomatobius fry leaves a mouth of the host.
When host fry leaves the parent, stomatobius is also compelled to leave a refuge and to lead independent life. At this time, if the female was not fertilized before its settlement in mouth of the host fish, at them the courtship season begins: males, having changed camouflage colouring to courtship dress, gather in thickets of plants. Courtship colouring of the male is monotonous bluish-silvery with dark matte back. Females come to their smell, then fertilization follows, and within the next two weeks the female spawns up to fifty youngs one by one. Two types of development of stomatobius females are, probably, the beginning of division into two separate species, at one of which fertilization takes place before the life in mouth of the host fish, and after it at another one.
The idea about existence of this fish was proposed by Simon, the forum member.
River needle-jawed live-bearer (Potamobelone acutirostris)
Order: Cyprinodontiformes (Cyprinodontiformes)
Family: Predatory live-bearers (Rapaciliidae)
Habitat: rivers of Great Antigua.
At the boundary of Holocene and Neocene the most productive communities of ocean, coral reeves and plankton, had suffered irreparable damage as a result of catastrophic processes happened in biosphere. With their disappearance in crisis period the biological variety of oceans had sharply decreased. When conditions acceptable to life had started to restore, survived species had started to evolve actively. Caribbean Sea and Antilles became the center of active speciation of live-bearing fishes. Their ability to live in fresh and sea water, and also high survival rate of posterity were the features determined their evolutionary success.
In shallow waters of Caribbean Sea, in rivers and estuaries live-bearing fishes make an appreciable part of the variety of ichthyofauna. In rivers of Antilles species of fishes of other families were kept, but live-bearers make a considerable part of ichthyofauna there. Some river live-bearers have related species in Caribbean sea. The needle-jawed live-bearer living in lower reaches of rivers of Great Antigua is the close relative of sea lancemouth. This fish lives in deep parts of river channel and occasionally leaves in brackish water of rivers mouth.
The body length of river needle-jawed live-bearer reaches half meter at weight about 400 gramms. Colouring of sides of this fish is silvery with slanting cross strips; back is dark green. Eyes at fishes of both genders are red. River needle-jawed live-bearer keeps in shadow of plants floating on the water surface, or under tree trunks floating in the river. When fish leaves shelter, its colouring becomes uniform silvery.
The most remarkable feature in appearance of this species is the structure of jaws: they are extended and pointed at tips; the bottom jaw is longer than top one and has triangular section. On its bottom side sharp keel stretches. The bottom jaw serves as the hunting weapon: fish pins catch up with the help of this adaptation. Protecting itself against predator, river needle-jawed live-bearer puts to aggressor deep stab and slash wounds by jaws. This tactics of defense makes it very dangerous species: this fish is very excitable and sometimes attacks ground animals swimming in water, taking it for aggressor. By this feature river needle-jawed live-bearer is similar to swordfish of Holocene epoch, which had also attacked objects had not represented any danger for it.
Similarly to many predators, river needle-jawed live-bearer is solitary species. But it is not aggressive relatively to congeners and does not avoid their neighbourhood. At places rich in food this species forms small congestions changeable by structure without any hierarchy. The social behaviour at this species is not advanced; therefore this fish does not form true schools and does not pay attention to adult congeners only because they are too large to be a food.
River needle-jawed live-bearer eats mainly fish. It catches prey up with fast rush and tries to put to it wound by bottom jaw. The swallowed catch has characteristic traces of attack: stab and slash wounds. Small catch may be literally cut half-and-half by impact of the bottom jaw. River needle-jawed live-bearer can eat its own fry.
The male of this species is smaller than female and its “sword” is shorter. It eats smaller catch and keeps in shallow waters of rivers and in shallows of river mouth. Male eats not only pelagic catch; it frequently digs by bottom jaw invertebrates at the bottom of shallow rivers. Females live in deeper places of rivers, therefore for pairing male leaves habitats and moves to river channel. To involve the female male makes high vertical jumps above the water surface.
Courting for the female, male becomes brightly colored: stomach gets nacreous shine, anal fin and gonopodium turn black, and the tip of “sword” becomes red. Male swims near the female, pushing its back and sides. If the female is ready to pairing, it stops and inclines to the side, turning cloaca to the male.
Spermatozoids of male keep viability for very long time, and fertilized ovocites may run the diapause. As a rule, one pairing with the male is enough to the female to give birth up to three hatches of fry. Once in three weeks the female gives rise up to five large youngs (up to 5 cm long) with short jaws. First few weeks of life at young fish long bottom jaw characteristic for species grows, and then on its bottom side “keel” starts to grow. Young fishes of this species are also active predators. They eat at first larvae of small insects, then fishes and water beetles. Because adult fishes are cannibals, young ones hide from adult fishes of their own species. For this purpose young fishes simply turn vertical pose among roots of floating plants. Adult fish prefers to not attack animals seeming to it too “high” – it estimates the angular size of object in vertical dimension. Therefore it does not attack such young fish even seeing it. Due to such simple tactics the part of fry may escape of attacks of adult fishes.
Young fishes become able to breeding at the age of 11 – 13 months, and life expectancy of this species reaches 20 years (females live for longer time, rather than males).
Dwarf lancemouth (Nanobelone esociformis)
Order: Cyprinodontiformes (Cyprinodontiformes)
Family: Predatory live-bearers (Rapaciliidae)
Habitat: Great Antigua, streams and shallow rivers in forest.
Climatic changes and anthropogenous pressure had resulted in extinction of many species of large fishes in fauna of rivers of Caribbean Sea basin. Their place was occupied by unpretentious and quickly breeding small species among which viviparous fishes of live-bearers family (Poeciliidae) dominated. In Neocene they realized the received advantage, having formed some independent families of viviparous fishes differing by anatomy and habit of life. Various representatives of these families inhabit fresh waters of Central America, Caribbean Sea, Panama Passage and even Pacific coast of America. In various habitats speciation of these fishes actively passes, and among them rather strictly specialized species evolve.
In shallow forest streams of Great Antigua island small live-bearing fish lives – dwarf lancemouth. Despite of size (the length of body of the male is about 5 cm; females grow up to 8 cm), it is active top-skimmer predator, the relative of terrible sea species of lancemouth. But dwarf lancemouth may represent the threat only for larvae of mosquitoes and various small insects fallen in water.
The body of this tiny fish indicates prompt and ruthless predator. It is arrow-like and strongly extended. Unpaired fins are shifted back; abdominal fins are reduced up to several thick fin rays. On internal side of abdominal fins of the male short sharp spikes develop. Head of this small fish is flat and narrow, with goggled mobile eyes; bottom jaw is only a little longer, than top one.
Colouring of body of this fish is longitudinal-striped, silvery with black strokes. Male and female out of breeding season differ not only in size, but also in colouring of eyes. At males iris of the eye is bright blue, at females eyes are black.
This fish lives in forest rivers and streams, keeping in shallow water under leaves of marsh plants hanging above water. It eats insects (the basic forage is mosquito larvae), and can eat fry of other fishes.
For courtship display male chooses sites where through forest canopy sunlight shines. At the male ready to pairing appreciable dark blue shade appears on back. Male shows to the female back shining dark blue color and eyes sparkling in sunlight. It is not afraid of attack from above: sunlight shines on surface of water, and it hides presence of the male. It is capable to fertilize several females in succession, and the period of courtship proceeds at him till about one week. At fertilization of females the male actively uses abdominal fins with spikes. With their help the male “saddles” the female, jumping to her back and squeezing her body right behind operculums. Preparation for pairing ritual resembles rodeo a little: the male tries to keep as long, as it is possible, on the female which tries to shake from itself the importunate male. If the male kept on a back of the female long enough, she stops “gallop”, and freezes at the surface of water, having slightly bent on one side: it is a signal to pairing. At this moment male “jumps off” from her, fertilizes the female fast, and again is engaged in courtship display, showing itself in beam of sunlight.
The male is territorial; it drives off other males from the site. If it is necessary, it furiously battles to them: male bites contenders to fins, and tries to seize by jaws for tips of their jaws. If the male succeeds to do it, the opponent appears disarmed: it can not open mouth. Using it, the unpunished site owner drags him for some time, and then lets off at the border of territory.
Fertility of dwarf lancemouth is very small – usually at the female only 1 – 2 young fishes are born simultaneously. Birth of fry repeats each 2 weeks. Small fertility does not represent threat to survival of species: it is compensated by high degree of survival rate of young growth: the newborn fry reaches third of length of parental individual, and congeners or posterity of other fishes will not eat it any more. The newborn fry at once can eat fry of other fishes and larvae of insects. It grows quickly, and already at four-monthly age the female of dwarf lancemouth gives rise to posterity the first time. Life expectancy of this species in wild does not exceed two years.
Segregated callopoeciliops (Callopoeciliops dispar)
Order: Cyprinodontiformes (Cyprinodontiformes)
Family: Deep-bodied live-bearers (Altipoeciliidae)
Habitat: fresh waters of Central America.
In early Neocene when coral reeves degraded and the richest fauna of sea shallos had disappeared, in Caribbean Sea the active adaptive radiation of live-bearing fishes began. They had appreciable advantages in comparison with sea species – these fishes were less specialized rather than their sea neighbours and were able to live both in fresh and in sea water. Being mainly small and tiny animals they had kept a sufficient variety after the global ecological crisis, and at early Neocene had sufficient potential for new evolutionary break. In conditions of rather low competition in restored ecosystems of early Neocene the tendencies shown at the level of species and genera differences were realized to the full, having formed great number of species differing by ecology and habit of life, and belonging to several families.
Differences of various species include other features except for anatomy, for example behavioural features. Different courtship rituals of the male reliably interfere with crossing of closely related species that also have resulted in formation of some species of live-bearing fishes of Neocene. The additional factor of isolation was various shapes of copulating organ, the gonopodium, in some cases preventing pairing of different species and occurrence of hybrids.
Males and females of live-bearing fishes often differ in colouring and size strongly. It is especially precisely shown at fishes from fresh waters of Central America belonging to genus Callopoeciliops (“the beautiful fish similar to Poecilia”). Their males and females would be hardly for classificating as representatives of the same species basing at the appearance, therefore this species had received the specific name “segregated”.
The body of callopoeciliopses is high, of rounded outlines, compressed from sides, especially at males: it is a common attribute of all representatives of Altipoeciliidae (“deep-bodied poecilias”) family. Callopoeciliopses are externally similar to a crucian, and lead a similar habit of life, eating vegetative forage and small animals in shallow rivers of Central America.
Back fin of these fishes is high and pointed; its forward rays are thick. On fin some small “pearl” spots shining in sun light are scattered, permitting to representatives of species to find out each other. At females the basis of back fin has black spot.
For these fishes the sharp sexual dimorphism in colouring and size is very characteristic. The female of this species is large (up to 20 cm long), grayish with several black spots stretching like a chain along sides. Its back is greyish green – it helps to disappear from predatory birds attacking from above. The male of segregated callopoeciliops is smaller, rather than female: its length is about 10 cm. In quiet condition male is spotty, bluish with black spots on back and head. In rivers of Central America there are many fishes much brighter in colouring, but not many of them may surpass the callopoeciliops male in multicoloring in courtship season. During the courtship ritual at the male of this fish bright courtship dress hiding in usual life is shown. The male of segregated callopoeciliops differs in very variative colouring – color of different individuals varies from entirely cherry red up to cobalt blue and emerald-green with numerous transitions between such vatieties. Frequently there are bicoloured fishes at which head or fins have another color, rather than body, and also fishes of transitive colouring. Occasionally among males black individuals with color shine and also fishes with black spots on colored background appear. The integrity of colouring is broken a little with eyes – at fishes of both genders and any colouring they are silvery and shining.
When the male is not occupied with courtship display, its bright colouring is shown poorly – the shade on scales is swept up only, and black individuals are simply darker a little than usual males. Courting at the female, male is colored especially brightly and tries to show itself to the female as favourable, as possible. It tries to keep in bright sunlight to make colouring as better visible, as it is possible. In courtship season the whole loop of males of different colors, up to ten fishes, stretches behind the female ready to pairing. They compete among themselves: push each other away from the female, having at the moment of clush darked shade. Sometimes the strongest male seizes tails and fins of contenders, biting and breaking them off.
Female does not interfere with battles of males and behaves phlegmatically enough and indifferently in their environment. It couples to several males in succession; therefore ritual fights of males do not guarantee at all, that strongest of them will have the posterity.
Because all deep-bodied live-bearers are rather deep-bodied fishes, it is more difficult to them to pair, rather than to live-bearing fishes of usual shape. But at them one original adaptation facilitating this important process is developed. The pectoral fin of the male has thick strong top ray with small bristles. At pairing with the female male clings by this fin its pectoral fin, and till the pairing hangs for some seconds on the female. Sometimes at once two males cling to one female – one fish on each side of its body. But only one of them can enter soft roe into its genital ducts. In courtship season pectoral fins of females appear torn because of active male courts, but they restore quickly.
Out of pairing season fishes of different genders keep separately. Schools of females swim in main river channel, and small males hide in underwater thickets at shallow water and lead secretive habit of life. Males come to females when their schools come nearer to the coast. Rains are stimulus to pairing: noise of rain and the rise of oxygen contents in water result fishes in excitation. After rains continuing till some days in succession, males start to color brightly, and females gather in shallow waters.
Fry develop in organism of the female rather quickly: usually female spawns fry each two weeks till the half-year. Young fishes are tiny (no longer than 8 – 11 mm), but their number is large: up to 200 ones in one pack. The soft roe of males keeps viability in oviducts of the female for a long time, but without additional pairings the amount of fry decreases in each new pack. But fry of last packs are even twice larger, rather than in first one.
Fry of callopoeciliops gather to schools kept up to adult condition, and hide among rich underwater vegetation. During the mass breeding of these fishes in river gulfs shoals of thousands of young fishes swim. Males of this species grow slowly in comparison with females. Young fishes reach sexual maturity in different time: males at one-year-old age already take part in courtship games, and female is ready to fertilisation only at the age of one and half, or even in two years.
Gradually shoals of young fishes divide by size and gender. Males form separate school and remain to live in thickets of underwater plants, and females schools swim to deep areas of rivers farther from coast. They willingly keep under “rafts” of floating plants, feeding there on larvae of insects and eating young roots.
hypotenuse fish (Hypotenusichthys aculeatus)
Order: Cyprinodontiformes (Cyprinodontiformes)
Family: Vertical, or Head-standing live-bearers (Verticalichthyidae)
Habitat: mountain rivers of Central America and the south of North America (Mexico).
Picture by Fanboyphilosopher
In Neocene live-bearers have reached the great evolutionary success in tropics
of New World. Various species of these fishes live in rivers and in sea, turned
to vegetarians and predators, giants and dwarfs. They have developed various
ecological niches and have fancifully changed in order to use resources of their
habitat in the best way. Among them the unusual family of head-standing live-bearers
had appeared; the representatives of this group in normal position keep body
vertically, head downwards.
The transitive form from fishes of habitual shape to verticalichthyids is kept in mountain rivers of Central America. It is unusually looking fish which is named spiny hypotenuse fish for original appearance. It is the representative of live-bearers living in current and eating tiny animals and algal pellicles growing on firm substratum.
The body of spiny hypotenuse fish has triangular outlines from sideview. The backbone of this fish in normal position is positioned at the angle of about forty degrees to substratum. The outline of stomach is almost horizontal, and approximately from the beginning of anal fin the contour of body is sharply bent upwards at the right angle to line of stomach. Head of this fish is wide and flattened. The part of stomach, directly adjoining to substratum, is slightly concave and forms a sucker which helps to attach to surface of substratum. Body of fish at the level of abdominal cavity is almost triangular in cross section. When hypotenuse fish stands a head against current, water stream presses it to substratum. The top part of back is narrow and compressed from sides, and tail stalk is deep. The length of adult fish does not exceed 20 cm.
The back fin of spiny hypotenuse fish in the degree of development represents a transitive stage between normally advanced fin of typical fishes and strongly reduced fin of head-standing live-bearers. Fin rays in it are thicken and short, and the membrane is reduced – it covers only the bottom half of each ray (hence the name – fin rays are prickly). Tail fin is short and deep, blaed-like, with elastic poorly branching fin rays. Its bottom part adjoins to the anal fin stretching along the entire “cathetus” of fish from below upwards. At males first (actually they are bottom, located at the substratum) fin rays are transformed into copulating body – gonopodium. Belly fins are very reduced and hook-like, numbering only 4 – 5 thick rays which have almost merged together. They are additional bodies of attachment, and also serve for keeping of the partner during the copulation. The bases of belly fins are fleshy and mobile. Pectoral fins are wide and fan-shaped.
Spiny hypotenuse fish swims very badly. If current breaks it from substratum, it at once falls on bottom and tries to attach to stones or to driftwood. In thickness of water it swims very slowly and clumsily.
The scraping mouth of this species is half moon-shaped. Lips are thick and fleecy; they serve for scraping of algae and sedentary animals from substratum. Small eyes are located near corners of mouth. At the feeding fish moves forward by short jerks, moving by tail and anal fins.
The body of spiny hypotenuse fish is colored silvery-grey with blue shade. Back is dark blue; on sides small black irregular-shaped spots are scattered. In courtship season anal fin of male turns bright red with transparent edge and dark spots at the basis. Courting the female, males attach near to her, pushing each other away, and try to hook by belly fins against belly fin of the female. Sometimes at once two males succeed to do it, and they begin original “struggle” by gonopodiums, pushing the contender away from cloaca of the female. Copulating male stays with the female for a long time, not allowing to another males to copulate with her.
Pregnancy lasts for about two weeks. In ovoducts of the female embryos start the development not simultaneously, and after the only pairing the female gives rise to one young fish in each three days within half-year. Newborn fish of this species about 2 cm long has the shape typical for fishes. It has only underdeveloped sucker on stomach. At week age it begins to attach to plants and stones, gathering food from them. At bi-monthly age the young fish represents a tiny copy of adult individuals. At the age of 16 – 17 months the young hypotenuse fish becomes sexually mature.
Close species of hypotenuse fishes inhabit rivers of Central and North America:
Motley hypotenuse fish, or driftwood fish (Hypotenusichthys maculatus) lives in slowly flowing forest rivers running into gulf of Mexico. It has short and deeper body of rhomboid outlines about 12 cm long. Colouring of this fish resembles the surface of driftwood pierced by larvae and overgrown with moss: the basic background is brown with several randomly scattered black spots and light brown strokes; wide black stroke always stretches across the eye. Tail and back fins are transparent. The belly sucker represents two longitudinal plicas of skin. This fish keeps more often among driftwood or the flooded tree trunks, and scrapes tiny animals and algae layer from the surface of driftwood.
Overturned hypotenuse fish (Hypotenusichthys reversus) inhabits flatland rivers and lakes of Central America, overgrown with floating plants. It is the smallest species of the genus – the length of adult individual does not exceed 5 - 6 cm. It leads way of life unusual to this group of fishes: this species uses sucker for attaching to the bottom side of leaves of floating plants where it eats small animals. Body of this fish is short and deep, “humped”, almost square in shape; the backbone of fish stretches diagonally in this “square”. On the belly side of body there is well advanced sucker looking like longitudinal plica of skin. The belly fins are transformed into attachment devices and help fish to attach to thickets of small-leaved floating plants. They represent long hooks with tiny denses on the internal side. Their length makes approximately one third of general length (“diagonal”) of fish. Head is short and deep, but mouth is of scraping type, like at other species of genus. Colouring of body of this fish is silvery with marble green pattern, helping to hide among plants. On tail fin there is a large oculate spot – false “eye” of yellow color with black center. This fish is able to swim better, rather than other species of the genus, but only at short distance. After fast jerk it tries to hide in thickets of plants.
Mangrove verticalichthys (Verticalichthys striatus)
Order: Cyprinodontiformes (Cyprinodontiformes)
Family: Head-standing live-bearers (Verticalichthyidae)
Habitat: mangrove thrickets at the coast of Caribbean Sea, coast of Great Antigua.
In Neocene viviparous fishes of tropical areas of America had reached the particular variety. In human epoch they were presented by rather small species, but some Neocene live-bearers became true giants. Among them both sea and freshwater species had evolved. Some species of Neocene live-bearers had got morphology strange and unusual to fishes. These ones are species presenting vertical, or head-standing live-bearers family – their manner of movement has determined their name. In rest head-standing live-bearers keep body almost vertically, or having small inclination. Being scared, they seek safety in flight in usual for fishes horizontal position.
Mangrove verticalichthys is the largest species of family. Its length reaches 40 – 45 cm, and height of body is only 5 cm. The body of fish is strongly extended, and head with small mouth makes approximately the fifth part of the total length of fish.
Fins of verticalichthys are advanced in such a manner that normally helps it to move in vertical position. At this fish anal fin stretching along the bottom side of body is strongly advanced; because of it cloaca of fish is shifted forward on breast. Actually at swimming fish anal fin is directed back. It waves, and fish slowly swims forward. The forward part of male’s anal fin is transformed to gonopodium with mobile muscled basis. Wide and mobile pectoral fins help fish to keep balance. Also with their help verticalichthys can move upwards and downwards, gathering forage from the bottom. Tail fin is short and wide; when fish swims in vertical position, it is compressed, and body of fish seems pointed from above. At occurrence of danger fish turns to horizontal position and swims to shelter with the help of tail fin. Back fin of fish is reduced and represents low leathery crest with rudiments of fin rays.
At females abdominal fins are small and rounded, and at males they are transformed to hook-like captures, permitting to keep the female. Fin rays are strong and supplied from the inside with set of small denticles.
Colouring of mangrove verticalichthys is chocolate-brown with several thin longitudinal strips of white color on sides. One of strips stretches from tip of snout across an eye (additionally masking it) up to the basis of tail fin. Pectoral fins are transparent.
Verticalichthys fishes keep solitarily or in small groups in mangrove thickets. They are able to move dexterously in vertical position among roots of mangrove trees. Striped colouring helps them to mask good in such environment. These fishes can live in water of various degrees of salinity – from almost completely fresh water in river mouths up to ocean water of normal salinity. During outflow these fishes can remain at shoaliness. In this case they dig in ground with the help of movements of anal fin, and lay, having put outside only a head.
Food of verticalichthys is made of various small aquatic animals – worms, crustaceans, molluscs and tiny fishes. In fresh water they eat larvae of water insects. Head of this fish is extended and has small mouth. Mouth can be extended as a small tube, helping to dig small animals out of ground.
Verticalichthys fishes breed during all year. Fishes pair in vertical position, turned by stomach to stomach of each other. At this time male keeps female by abdominal fins. In two months after pairing female gives birth posterity - 5 – 6 rather large translucent young fishes; till one year it bears posterity 3 – 4 times. Newborn verticalichthys fishes have body shape characteristic for these fishes, but swim in horizontal position more often, than adult fishes. Also at young fishes back fin is more advanced, but decreases later. Young ones of verticalichthys keep in thickets of water plants, preferring the freshened areas of mangrove thickets and river mouths. Gradually on body of young fishes dark longitudinal strips appear. In older age they extend and turn brown color, and intervals between them lose transparency. At the age of about 4 months young fish gets colouring characteristic for adult individuals, and at the tenth month of life young fish can take part in breeding.
Close species live in coastal waters of Caribbean Sea:
Acrobat live-bearer (Algopoecilia acrobata) living among seaweed thickets differs in massive constitution and rather short body. It is one of primitive kinds of the family, keeping a lot of features of usual fishes.
Golden needlefish (Chrysospinichthys melanostriatus) is a small fish living in rivers at southern coast of North America. This species very seldom goes to brackish water of river mouths and absolutely never swims to sea. The body length of adult individual is about 20 cm, and body height seldom exceeds 15 mm. Golden needlefish has very long head – it makes one third of total length of fish and has small mouth at the tip. The body of this fish is colored golden-yellow and has expressed metal shine. Along each side from tip of snout up to edge of tail fin the deep black strip lasts. All fins are transparent, except for black strip on tail fin.
Abdominal fins both at males and at females are reduced and turned to attachment organs. Abdominal fin at this fish represents two strongly thicken fin rays covered with bristles from the inside. With the help of these fins males keep females at pairing, and fishes of both genders cling to plants to keep in watercourse.
The female of golden needlefish gives rise up to 4 – 5 large fry at once, but within one year it bears up to six broods. Fry of this species is transparent, large and short-headed, only a few similar to adult individuals.
Pelagic verticalichthys (Euverticalichthys meropelagicus) is a small fish: total body length is about 25 cm. Colouring of body is silver-gray with thin and slightly twisting longitudinal strips of dark grey color on sides. This species lives far from coast, in thickets of sea spinach – characteristic floating plant of Caribbean Sea. Pelagic verticalichthys constantly keeps in thickets of this plant, and, as against to the majority of species, keeps the most part of time turned a head up. This fish eats small crustaceans, gathering them from leaves and roots of sea spinach. Also this fish eats fry of other species of Caribbean live-bearers. The mouth of pelagic verticalichthys can extend to tube, soaking up prey in a split second.
Abdominal fins at fishes of both genders are transformed to hooks with which help fishes keep each other at pairing, and also cling to roots of sea spinach during the storm. This fish swims with the help of fluctuations of ribbon-like anal fin which has fleshy basis and length of about one third of total length of fish. Fertility of these fishes makes only one young fish once per ten – twelve days. But the length of such fry is about half of mother’s length, and survival rate of such large posterity is much higher, than at the set of tiny fry. Newborn pelagic verticalichthys at once can eat fry and other kinds of food characteristic for adult fishes.
Great false swordfish (Xenoxiphias magnificus)
Order: Needlefishes (Beloniformes)
Family: False swordfishes (Xenoxiphiidae)
Habitat: tropical and temperate waters of all oceans; in summer in warm currents comes to the border of polar waters.
In early Neocene, after “plankton accident”, when productivity of ocean started to increase, various groups of fishes began to evolve in direction of pelagization. Among them there were needlefishes – the group of long-jawed sea and brackish-water fishes. In Neocene their descendants became specialized pelagic fishes making special family of false swordfishes. It includes various species – from schooling pelagic ones up to semi-deepwater fishes. And the most remarkable representative of this family lives in warm waters of all oceans is great false swordfish, very large fish similar to swordfish (Xiphias) of Holocene epoch. It is one of the largest osseous fishes up to 6 meters long (including rostrum), weighting up to 300 kgs.
Great false swordfish is perfectly adapted to inhabiting in open ocean. It has short strong body of “scomber-like” shape – rather deep, with short strong tail stalk. Unpaired fins of this fish are shifted in back half of body. They are narrow and peaked. Pectoral fins of false swordfish are crescent and have very rigid forward rays. At movement they act as elevators and serve for balance.
The most remarkable feature, which has determined the name of fish, is its rostrum. Upper jaw of this fish is longer, than bottom one; it is peaked and very firm. The length of rostrum makes about one third of general length of fish. Bottom jaw hardly reaches half of length of top one. It is wider and slightly covers rostrum from sides. On the bottom jaw there is a firm skinny keel stretching back to breast.
The skin is firm, covered with small scale, and also is similar to emery paper to the touch. Such rough skin smooths over turbulence of water, reducing thus resistance at movement. Colouring of body of great false swordfish is blue with silvery stomach. On root of tail there is black triangular spot turned by top to the head.
Great false swordfish is fast fish of top layers of water. It can accelerate movement up to 100 kms per hour, chasing prey. Having gathered speed, fish can jump out of water, making jumps up to 10 meters long. This species eats smaller fish and squids, but there are cases when this fish attacks sea birds flying above surface of water, and punches them by rostrum. Great false swordfish does not have any tooth in mouth, and swallows prey entirely.
In clutch of this fish it totals up to 100 million eggs. Many sea fishes are pelagophils – they spawn eggs in water and do not care of posterity. Great false swordfish represents the exception of this rule. It spawns eggs on objects floating on surface of waters – this behavioural feature had remained from needlefishes, its ancestors. For spawning male finds tree trunk floating in water and protects it from congeners, waiting for appearing of female. It involves females to its territory by high vertical jumps, loudly splashing in water. The female ready to spawning quickly reacts to such appeal. The pair of fishes spawns eggs on roots or branches of tree trunk, and clutch stays on them as a long tape of slime quickly swelling in water. Inside it there are tiny eggs which develop during 2 – 3 days. Fry of great false swordfish is lack of characteristic rostrum. Young fishes live in plankton till 5 months, gradually taking the body shape characteristic for adult individual. The one-year-old fish has length of about 20 cm, and rostrum makes about the fifth part of it. By ten years the fish reaches length of 4 meters, and six-meter specimens are old, twenty years old individuals.
sarganella (Sarganella brevirostris)
Order: Needlefishes (Beloniformes)
Family: False swordfishes (Xenoxiphiidae)
Habitat: Atlantic ocean, temperate, subtropical and tropical latitudes of both hemispheres.
Picture by Fanboyphilosopher
False swordfishes are characteristic pelagic sea fishes of
Neocene epoch. They are descendants of needlefishes and form various, but unite
by origin group. The common features of these fishes are short or moderately
lengthened body (in contrast to very long body of needlefishes), high crescentic
tail fin, narrow and rigid pectoral fins. All species of false swordfishes are
zoophagous fishes. Large species (for example, great
false swordfish (Xenoxiphias magnificus)) are solitary predators and eat
large prey, and smaller species are schooling planktophags eating crustaceans,
small fish and cephalopods.
Small species of these fishes are ecological analogues of mackerel and other pelagic fishes of Holocene. In contrast to giants of family, these species have short pointed snout. Typical representatives of schooling false swordfishes are sarganellas. They are medium-sized fishes – the length of representatives of various species changes from 20 up to 70 cm. They have moderately long body, flattened top part of body, and projecting leathery keel stretching from throat prior to the beginning of anal fin. Scales are very small and deeply buried in skin. Rostrum of sarganellas is very short – its length does not exceed the length of head.
Fins of sarganellas have the shape characteristic for quickly swimming fishes. Pectoral fins at them are narrow and long (their length is approximately equal to length of head in common with rostrum), and abdominal ones are strongly reduced. Back and anal fins are peaked and shifted to back half of body. Tail fin is high and narrow; it has the characteristic crescent form and is very resilient. Sarganellas can accelerate momentum over 60 kms per hour, and at the short distance they make throws at speed over 80 kms per hour.
Far from coast in Atlantic schools of one of sarganellas species live; it reaches the length of about 50 cm. The body of these fishes has silvery-blue color with metal shine, and tips of top and bottom lobes of tail are colored black. It is short-beaked sarganella, the most “snub-nosed” species of the genus. Its toothless jaws are very short and form only approximate similarity of “sword”, characteristic for false swordfishes, more resembling thickened bird’s beak.
Short-beaked sarganella eats small pelagic animals – crustaceans, herring squids and fry of various fishes. This fish swims very quickly and catches up the most high-speed pelagic animals. Attacking small schooling prey, fish puts to it wounds by jaws, not slowing down its own movement. Hunting of sarganellas for such animals resembles beating more – fishes surround a shoal of prey and swim around it, as if incidentally striking impacts to prey. Jaws of these fishes can compress strongly and crack armours and skulls of prey. Fishes swimming right after first ones pick up animals wounded or killed by fishes swimming ahead. But, when the school of sarganellas surrounds prey and forms a ring, first fishes get the prey killed by individuals swimming ahead. Because of such hunting tactics sarganellas can eat small prey effectively only in school. The school of these fishes is lack of the leader, and any fish can be both among attacking ones, and among “marauders”. Attacking larger fishes and squids, which do not form dense congestions, sarganellas operate independently from each other, and swallow only their own prey.
These fishes inherited from needlefishes the way of spawning. Though sarganella belongs to pelagic fishes, it spawns eggs on plants – usually on floating algae. Frequently these fishes migrate for spawning to algal fields, developing plentifully near to New Azora island. As in the most cases the meeting of suitable substratum for spawning is accidental, these fishes developed one more adaptation for spawning. Eggs at sarganellas develop in small portions (up to 4 – 5 thousand ones simultaneously, that is too smal amount for pelagic fish), but they keep viability for a long time, keeping in ovaries of the female. The meeting of floating plants is the most powerful spawning stimulus. Having searched the suitable substratum, sexually mature fishes begin spontaneous spawning which passes very roughly. Males within several minutes turn brightly colored (their colouring becomes more sated, and on the body some indistinct vertical strips appear), and females gather to unisex school. Males start to display their force, making high jumps from water and sparkling in sunlight by shining sides. When their excitation reaches apogee, they rush to school of females, and start to pursue females one by one or in pairs. Swimming above plants, females spawn portions of eggs, which on the spot become fertilized by males. During 15 – 20 minutes spawning is finished, and fishes abandon eggs, not caring about posterity.
Posterity of sarganellas represents tiniest pelagic larvae. They are predators and grow very quickly. Larvae of sarganella eat fry of other species of fishes, shrimps and larvae of cephalopods. By the end of the second year of life fishes reach approximately 80 % of length of an adult individual and start to breed. Life expectancy of short-beaked sarganella seldom exceeds 7 years, and small species start to lay eggs at one-year-old age and live no more than 4 years.
Sarganellas are typical species of fishes of open ocean, but among them there are species meeting near to coast. In Neocene epoch some kinds of these fishes live in World ocean. Pacific, or golden sarganella (Sarganella chrysopectoralis) replaces the Atlantic species in tropics and subtropics of Pacific – from Panama passage up to Indonesia. Occasionally these fishes swim to Caribbean Sea and equatorial area of Atlantic. It differs in appreciable golden shade of scale and in larger size – about 60 cm. Males of this species in courtship colouring shine pure gold, even with reddish shade. Black tail fin contrasts with this background. Pacific sarganella is an active predator; its prey includes pelagic octopuses and squids, and also large fish. These sarganellas do not form numerous schools, and their congestions number no more than two tens individuals.
Hawaiian sarganella (Sarganella hawaiiensis) lives in northern part of Pacific Ocean, from the latitude of Hawaiian Islands and along the Asian coast up to Big Kurils, and comes into sea of Okhotsk in summer. It is a small species of the genus – the largest individuals are up to 30 cm long. But the small size is compensated by high number: schools of this sarganella total up to 300 – 500 thousand individuals. Colouring of fishes is silvery with three thin longitudinal strips on every side and dark back; one dark strip passes from tip of snout across the eye to root of tail. These fishes eat small planktonic crustaceans and fish fry. Hawaiian sarganella spawns in the summer at the northern border of an area – in coastal areas of Pacific Ocean, in thickets of brown algae.
Pointed sarganella (Sarganella acuta) lives in tropical Indo-Pacific region. It is usual at coast of Meganesia and islands of Indonesia, and also in tropical area of Indian Ocean. These fishes do not leave from coast, and their small schools frequently come to reeves to hunt local fishes. The present fish is the largest species of the genus – the average length of adult individual is up to 70 cm. Body is more prolonged, than at other species; this species is similar by constitution and habits to barracudas (Sphyraena) of Holocene epoch. Body colouring is blue with black cross strips. This fish does not avoid fresh water and frequently catches prey in river mouths and mangrove thickets.
Southern sarganella (Sarganella australis) is the hardiest species of this genus. It lives in southern part of the Atlantic, Indian and Pacific oceans, in the area of temperate climate. In summer schools of these fishes come far to the south, to coast of Antarctica. It is the smallest species of sarganellas – large individuals seldom exceed 25 cm in length. The body of present species of fishes is silvery, and tail fin has black strip on back edge. The rostrum is a little shorter than length of other part of head. Southern sarganella breeds in thickets of brown algae at the coast of South America and Falkland Islands.
herring mullet (Clupeomugil pentastriatus)
Order: Mullets (Mugiliformes)
Family: Pelagic mullets (Pelagomugilidae)
Habitat: Tanganyika passage, top layers of water.
Mass extinction at the boundary of Holocene and Neocene has had the most fatally effect at the structure of ichthyofauna. During natural accidents which had determined change of epoch in most degree, there was a catastrophic decreasing of amount of plankton organisms. It was followed with extinction of animals depended on plankton as food source, or passed through plankton stage in life cycle. In particular, pelagic species of fishes - scombroid fishes, tunas, herrings had completely died out. When number of plankton had increased, former eaters had irrevocably died out, but from among benthic and coastal fishes less injured from natural accidents, new pelagic species had started to form. They had mastered rich resources of ocean, having evolved plenty of new species.
Striped herring mullet is the descendant of any coastal mullet fishes. It is medium-sized fish about 20 cm long. Its body is rather narrow and extended: this fish can swim quickly. Large head with widely opening mouth accounts about 1/5 of body length. Fins of herring mullet are moderately long; there are two back fins: soft back fin is well advanced, from prickly back fin five sharp separate spikes serving for protection against enemies remained. Tail fin is forked and wide. The body of fish is covered with small scales, silvery-colored with five blue longitudinal strips. Such colouring is characteristic for some schooling fishes: it prevents predator to distinguish contours of separate fish on the background of other ones. Middle strip is very long: it stretches from tip of snout through an eye (masking it) to tail fin.
Herring mullets live in high sea, not approaching closely to coast. They keep from surface up to depth of 30 meters in huge schools numbering up to 20 - 30 thousand fishes. Fishes eat exclusively plankton crustaceans and fry of other species of fishes.
Spawning occurs two times per one year: the basic one in spring, additional one (the amount of spawned eggs is approximately half less than in spring) in summer. Fertility of basic spawning is over 60 thousand grains of roe. For breeding herring mullets swim to the central part of Tanganyika passage where a plenty of plankton breeds. Such abundance appears possible due to rivers washing off in waters of passage huge amount of organic substances from coast. Near to coast water is slightly muddy from suspension taken out by rivers, but far from coast plankton organisms plentifully breed, providing to herring mullets food at any stage of development. Herring mullets spawn in schools, practically simultaneously spawning in water cloud of eggs and soft roe. In school right before spawning pairs form: each male chooses to itself the female and keeps near to it. Sometimes male snaps the female’s pectoral fin, and she is compelled to “tow” him. But such behavior of fishes proceeds not for long time, and spawning soon begins.
Small eggs develop about one day at the surface of water, very small larvae at once start to eat: in the beginning microscopic phytoplankton, then larger and mobile zooplankton. Fry of this species form one-age schools, kept for a long time, sometimes for all life. Herring mullet grows very quickly: at bi-monthly age length of fry is about 5 cm, one-year-old fishes up to 15 cm long already can breed. Life expectancy is little: no more than 5 years, and 80 % of fishes do not reach even the 3-rd year of life.
Order: Mullets (Mugiliformes)
Family: Pelagic mullets (Pelagomugilidae)
Habitat: waters of Central America, tropical Atlantic, Caribbean Sea.
Picture by FanboyPhilosopher
Alongside with needlefishes mullets are the successful group
of fishes which have occupied open ocean and waters far from the coast after
“planktonic accident”. Among them fast swimming analogues of tunas and other
pelagic fishes had evolved. And some of pelagic mullets became dangerous predators,
the terror of small pelagic fishes.
One of the largest bony fishes of Neocene is arrownose, the inhabitant of tropical waters of Atlantic and Pacific oceans near the coast of New World. It is the huge pelagic fish reaching almost four-meter length, the far descendant of mullets.
In body outlines this fish is very similar to shark. Only homocercal tail and strongly lengthened snout give to this species some external difference from sharks at first look.
Body of arrownose has streamlined shape adapted to fast swimming. Forward back fin is high and has rigid rays. The second back fin is separated to some rigid triangular finlets suppressing turbulence of water during the movement of fish. Pectoral fins are narrow, lengthened, peaked, and have fleshy bases. During the swimming they nestle against sides of body, and the role of stabilizers is incured with the belly fins shifted forward, which are longer and wider than pectoral ones. Tail stalk is deep; tail fin is also deep, forked and rigid. It is an attribute of the good swimmer – arrownose is able to accelerate momentum up to 50 - 60 kms per hour and to swim in this mode during several hours, and also to make short throws at speed up to 80 kms per hour. The body of arrownose is covered with large rough scales. Colouring of body of fish is silver-grey; back has the expressed greenish shade. Fins are translucent with dark grey edges.
For arrownose the shape of its head is characteristic. The upper jaw of fish is long, pointed, with cutting lateral edges and slightly protruding keel on the top side. The bottom side of snout is only slightly convex. The snout is covered with rigid rough skin, which helps to suppress water turbulence. Besides the snout is used by fish during the hunting. Large eyes are located in forward part of head, at the snout base. Cutting edge of snout stretches above eyes as rigid “eyebrows”.
Arrownose is a predatory fish eating smaller aquatic animals. Usually its prey includes schooling pelagic fishes and cephalopods. Attacking fish “cuts” them by impacts of head, rushing in their school. Impact of edge of snout in high gear is enough to put deep cut wound or to cut smaller fish half-and-half. Arrownose swims around of school of fishes or molluscs, not giving them an opportunity to escale in flight, and from time to time rushes through the school, striking impacts by snout. After attack fish quietly swims at the place of fight and eats wounded ones and pieces of bodies of prey.
Jaws of arrownose are toothless; firm lips partly replace teeth functionally. On lower jaw symphysis there is the peaked triangular outgrowth which is enters the dredging on the upper jaw; it helps to keep pieces of food.
Arrownose keeps above continental shelf and frequently swims close to coast. It is a solitary fish which relates neutrally to relatives of the similar size – near large school of prey some arrowheads of approximately equal size can feed at once. Young arrowheads frequently become prey of adult individuals.
The spawning season of arrowhead lasts for all year. Males ready to spawning declare themselves, jumping from water vertically and falling back with loud splash. For this purpose they choose floating subjects – tree trunks and the bushes carried out to sea from the continent. In this feature the atavistic element of behaviour of fish is shown: ancestors of arrownose from the mullet stock had similar feature of behaviour – propensity to jumps above floating subjects.
Courtship ritual includes male’s pursuit of the female and biting of her back fin. Sometimes the female not ready to spawning escapes from male’s jaws, leaving to him a sizeable piece of back fin. The female ready to spawning swims for some hours in succession (usually the whole night) side by side with male, and at this time fishes eat of nothing. At the culmination moment, in early morning, female spawns up to 50 million tiny eggs. Male fertilizes eggs, and adult fishes do not care of posterity any more.
Larvae hatch after 36 – 40 hours. They are completely helpless and eat the tiniest protozoans. The significant part of them perishes within several weeks after hatching. Growing up, fry becomes an active planktonic predator. At one-year-old age arrownose reaches the length of 25 – 30 cm and gradually passes from plankton to nekton. The greatest growing rate at this fish takes place in the first 10 years of life; during this period fish reaches the length over two meters. At the same time it becomes sexually mature. Life expectancy of this species makes about 40 years.
river horsefish (Potamohippidium acuticaudis)
Order: Pipefishes (Syngnathiformes)
Family: Pipefishes and sea horses (Syngnathidae)
Habitat: rivers of Japan Islands, thickets of underwater plants.
Picture by Fanboyphilosopher
Changes in biosphere happened at the boundary of Holocene
and Neocene had affected the direction of evolution of various live creatures.
Some of sea animals had disappeared (extinction had especially strongly affected
pelagic species or species spending in plankton even a part of life cycle),
others had kept in isolated sites of earlier extensive area. Some animals had
compelled to replace habitats to survive. At Japan Islands in Neocene the river
species of sea horses had appeared. This species of fishes had settled in rivers
of Japan from Inner Japan Sea during the ice age at the boundary of Holocene
and Neocene (actually it had repeated the way of needlefish from Caspium Sea
and Black Sea settled in rivers of Europe in Holocene epoch). When the sea level
had decreased, between islands isthmuses had appeared; they had transformed
Inner Japan Sea to gulf with slightly freshened water. The part of sea inhabitants
had died out, others had moved to the entry of this gulf, and some fish species
including ancestors of Japanese river horsefish had settled in rivers.
This fish differs from sea neighbours only a little. Japanese river horsefish reaches length about 40 cm from which long flexible tail accounts more than half. Head of this fish is mobile and has long pipe-like snout on which tip the small toothless mouth opens. All fins of this fish are transparent, and river horsefish swims mainly due to wavy movements of back fin.
Japanese river horsefish lives in thickets of underwater plants. This harmless fish eats crustaceans and fry of fishes, and is not able to swim quickly. Therefore main defence of Japanese river horsefish is the ability to masking. The body of fish is colored green with longitudinal yellowish strips. On the body there are some dark irregular-shaped spots.
Colouring of fish is supplemented with the fantastical body shape: from head up to the middle of back the crest of small leaf-looking outgrowths stretches. Near eyes of fish “moustaches”, two long peaked outgrowths doubled at the basis, grow. On sides of fish there are two parallel rows of small outgrowths. When the fish is in danger, it clings by tail to stalks of plants, and rocks according their waving in water.
Not all predators search for catch with the help of sight. Some of them badly see at all, but have sharp sense of smell. Even the most skillful masking does not save from such “pathfinders”. Therefore additionally to ability to hide Japanese river horsefish had developed means of active protection. On its long tail which is able to be bent in any direction, from above, from below and on each side sharp spikes grow. While the fish is not disturbed, they help to cling to plants. But if the fish is seized, it starts to defend. The river horsefish seized by predator is twisted by tail around of the enemy, trying to prick it, and strongly gripes the ring. Such reception may be enough for many local predatory fishes to let this fish off. Even water birds not always can swallow this fish alive: in bird’s throat the river horsefish twists to ring and also starts to rotate tail from side to side, causing strong pain.
Similarly to all sea horses, at this species the leaging role in breeding is played by the male. It bears posterity in brood pouch on stomach, and feeds posterity through blood – blood vessels sprout to each grain of roe in brood pouch, and larvae receive an additional feeding. At this species fertility is rather small: only 50 – 60 eggs. But the posterity hatches very large – the length of newborn river horsefishes reaches 2 – 3 cm. They develop in brood pouch of the male within one month, and begin independent life right after births. Felt the approach of delivery male searches for river bays with slow current overgrown with small-leaved water plants. Here the newborn posterity finds plentiful food like tiny plankton crustaceans, rotifers and large infusorians.
Order: Pipefishes (Sygnathiformes)
Family: Charibda fishes (Ichthyocharibdidae)
Habitat: sea waters of the Southern hemisphere in areas of temperate and cold climate.
Picture by FanboyPhilosopher
Evolution can be compared to a kind of game, where on par with
the rules and regularities the element of chance acts. It is for this reason
that among the inhabitants of earth can sometimes appear bizarre and extravagant
creatures, adapted, however, to their habitats.
One of these experiments in evolution is the North Atlantic Sea Wyvern (Vivernocampus titan) – a huge fish which is a descendant of the sea horse. In the Southern Hemisphere the whim of evolution has caused the appearance of another being, equally bizarre and distantly related to this species. The cold sea waters of the Southern hemisphere are inhabited by the charibda – a giant pelagic needle-shaped fish reaching the length of 3 meters with a thickness up to 20 cm. Despite its size, this fish is a very poor swimmer and is, in fact, technically plankton.
The charibda slowly drifts in the current, very rarely approaching the coast. Only in severe storms these strange fish are thrown to the shore, where they are helpless and quickly die.
The charibda in appearance resembles a snake, clad in a shell of bone rings. The shell’s scutes, however, are very thin, and on the lower side of the body they are even reduced. The buoyancy of the fish is provided by a fatty liver and a large amount of fat in the body. The unit weight of the fish is almost equal to that of water, and the charibda can easily maneuver in water. But its muscles are very weak and impregnated with fat, so the fish is unable to swim against the current.
The spine of the fish is very flexible, so it can roll up into rings and knots, rubbing on its own body and getting rid of parasites. The tail is a little less than two thirds the length of the fish.
Charibda fins are relatively small in size. The caudal fin is reduced to one short, thick spine. The dorsal fin is fan-shaped, with a strong fleshy base. This is the main propulsion of the fish; making undulating waves of the dorsal fin, the charibda can slowly move through the water column. Broad pectoral fins-also with strong bases-are turning rudders and help the fish keep its balance.
The head of the charibda bears features characteristic to members of the order. The fish has movable large eyes which can be rotated in different directions. The snout is elongated and tubiform, with a small mouth at the end. The opercles form a suction device. Abruptly opening them, the fish can draw in water as well as food organisms.
The charibda feeds exclusively on planktonic organisms: jellyfish, salps, worms, and crustaceans. When feeding the fish sucks them in entirely, hence the name. The gills of young fish form a filter device, allowing them to pump in a large volume of water and suck in clusters of small animals: crustaceans and fish fry. The charibda is immune to the poison of jellyfish and planktonic starfish.
The charibda has a soft colouring: silvery-gray with a greenish tinge; fins are transparent. Males and females do not differ in color.
Charybda reproduction is confined to the spring. Males and females find each other by smell and a male wraps his tail around a female, waiting for her mature eggs. At this time he drives away rivals with his head. The fecundity of this species is very high: up to 150,000 eggs. The female lays her eggs in the male’s brood pouch and does not care for her offspring. The inner surface of the brood pouch is covered with villi; the blood vessels grow through them to the eggs and provide them with extra nutrients.
Juveniles hatch of their eggs after 15-20 days and after another 2 days they leave the brood pouch. The length of the fry at the exit from the pouch is 3 mm. They passively float in the water and only eat prey which is in close proximity to the mouth. A significant part of young fish dies before reaching even the fifth of the length of an adult. Sexual maturity occurs in young fish at the age of 3-4 years; a lifetime is more than 50 years.
Translated by FanboyPhilosopher
Glass false angelfish (Pseudophyllum crystallinus)
Order: Percoid fishes (Perciformes)
Family: Snooks (Centropomidae)
Habitat: down flow of Zinj Land rivers, thickets of underwater and coastal plants.
Mangrove thickets are the special inhabitancy – here inhabitants of sea and freshwater inhabitants meet. Fluctuations of salinity and water level create the certain difficulties for live creatures adapted to constant parameters of inhabitancy. But the part of mangrove thickets inhabitants has adapted to endure changes of water salinity and prospers in changeable world of mangrove woods. Among fishes inhabiting these places there are gluttonous predators and peaceful omnivorous fishes. Some inhabitants of mangrove thickets have adapted to endure inflows and outflows and live in mangrove woods constantly; other species come into this biotope only temporarily.
At the distant border mangrove woods where influence of ocean is felt only till the highest inflow the vegetation is more similar to river one. Here the bottom is covered with thickets of underwater grassy plants, and at the coast rich bushes of high marsh grasses grow – reed reaching height of three meters and more. Among stalks of reed the set of insect larvae lives and on plants bryozoans and hydroid polyps sit – they are recent fugitives from the sea. That minimal salinity of water which turns out at mixing tidal waves with the water of the river quite suffices to them.
The set of small animals involves in these places one surprising fish, the descendant of glassfishes (Chanda), characteristic inhabitants of brackish waters. This fish is a high-bodied predator of lower reaches of rivers and mangrove thickets. This fish is a little similar to angelfishes (Pterophyllum) belong to cichlids family (Cichlidae) known to people. Similarity of habit of life had made these fishes very similar to each other.
Body of glass false angelfish is very deep (20 cm and more at length about 15 cm) and transparent – this feature is inherited from the glassfish. Interiors of fish are opaque, but they are disguised by shining film of peritoneum. Eyes of false angelfish are big and silvery.
Living among rich thickets of reed, this fish has short body. But unpaired fins of this species are very high. In back fin sharp poisonous spikes grow. The membrane between them is strongly reduced, therefore prickly fin rays may move freely. In anal fin first three rays are also prickly. It is the only active protection of this fragile looking fish. Abdominal fins of false angelfish are long – their tips reach top of anal fin. They consist of two thicken rays and serve for balance maintenance. On the second ray of these fins tiny sharp spikes located in some lines are advanced. With their help fish clings to stalks of plants for better resisting to strong tidal wave or current till the high water. At danger glass false angelfish freezes among reed stalks and on the body of fish grey vertical strips appear. In skin of fish there are chromatophores which are contracted in rest. At irritation or excitation of fish they open, giving to fish striped colouring.
False angelfish eats tiny animals – swimming larvae of mosquitoes, larvae of water beetles, worms. Its mouth is small but it can protract forward as a tube. When it is protracting, the current of water inside of mouth appears – this way the fish sucks in small swimming animals. Teeth are tiny and bristle-like – they serve for tearing off attaching catch from substratum. In fresh reservoirs false angelfish breaks from plants hydras, in brackish water of river mouthes it eats tentacles of hydroid polyps living here. This fish is tolerant to their poison.
This fish spawns in river estuaries choosing shallow gulfs with quiet and slightly brackish water. Eggs at these fishes are looked after by male which is larger, rather than female. The spawning may repeat up to 4 times in succession within half-year, and then male has a rest. In courtship dress it becomes striped, and edges of high unpaired fins get blue color. The courting male “dances” around the female, touching it by tips of abdominal fins. The female ready to spawning turns almost completely transparent and inclines the body on one side, showing to the male the belly as a sign of submission. The female pastes very small eggs on stalks and leaves of plants preliminary cleared by male, and at once leaves nest. Male stays to care for posterity: it fans eggs with fins and clears of dust. If necessary the male drives off other fishes having too closely swam to eggs. When larvae start to swim, male leaves the post. Larva of glass false angelfish is very small. It passively soars in water and eats plankton animal – rotifers and large infusorians. The significant amount of larvae perishes: larvae of advanced age become active hunters and eat smaller fry. At monthly larvae unpaired fins start to increase, and the body gets the shape characteristic for adult fishes. At the age of about half-year young false angelfish reaches length 6 – 8 cm, and one-year-old fish begins able to spawn.
glassfish (Megachanda pellucida)
Order: Percoid fishes (Perciformes)
Family: Snooks (Centropomidae)
Habitat: Tanganyika passage, thickets of seaweed in coastal zone.
Coastal waters of Tanganyika passage, slightly freshened by river waters, are fine place for life of numerous fishes. Far away from river mouthes where salinity of water is only a little below normal sea one, the bottom is covered with rich thickets of seaweed of various shapes. Among them there are species similar to palm leaves, fans, grape bunches and clusters of mushrooms. In this seaweed various species of small fishes, crabs and shrimps find shelter and food, and, in turn, predators, settling here, eat them. One of largest predators in underwater thickets is giant glassfish.
In Holocene many various species of glassfishes inhabited fresh and brackish waters of African and Asian coasts of Indian Ocean. But these species usually did not exceed 5 – 10 cm in length, and the species 18 cm long could be considered among them as the giant. But it would look a crumb near to one of Neocenic relatives, the giant glassfish, strange fish about 80 cm long.
Continuing “family tradition”, this species of fishes have kept a transparency characteristic for glassfishes: through its skin the skeleton is perfectly looked, and interiors are disguised from curious sight by silvery opaque film of peritoneum. But the constitution was made as a sacrifice of body transparency: body of fish is very deep and thin: at length 80 cm thickness of body is only 3 - 4 cm. The transparency of body helps this fish to mask among seaweed from catch and probable predators. For protection against attack of other fishes in back and anal fins of this fish strong poisonous spikes stick up.
At this fish, similarly to its Holocene relatives, there is very large head with big extensible mouth. When the giant glassfish attacks prey, its mouth extends like a tube and soaks up fish or other small animal.
Habitats of giant glassfishes are thickets of seaweed at the depth from 2 up to 10 meters in rather well warmed up shallow sites. Usually these fishes hide among seaweed and wait, while possible catch will come nearer to distance of successful throw. If it is a little of catch, fish can search for it itself. Favorite forage of giant glassfishes is shrimps and small fishes. When the perch is in an ambush, it is very difficult to find it out: its body is very high and transparent; therefore it is almost not distinguishing on the background of waving seaweed.
But except for advantages thin high body creates problems: when storm rages, it is difficult for such fishes to resist to disaster. Therefore giant glassfishes differ in good ability to weather forecasting: instinctively feeling approach of storm, fishes search for shelter. Usually before storm schools of these fishes leave seaweed and swim down to the deepest places of coast – to underwater canyons and caves, and also in cracks of rocks, where it is possible to hide from breaker impacts.
Giant glassfishes breed similarly to ancestors, in brackish water of coastal bays and river mouths. At these fishes spawning is paired: male finds a bush of water plant, clears its leaves and adjoining territory of dust, and then starts to involve female. To time of spawning it has a wide silvery-blue strip on soft back fin. When near to bush female appears, male swims up to it and starts to push her by side to the plant prepared for spawning. If female is ready to breeding, she responds on courtships of the male. The generated pair some time in common cleans bush and patrols its vicinities, driving neighbours away. After that, when eggs at the female will ripe, spawning begins. Female spawns eggs (about 50 thousand small grains of roe) on leaves of plant and at once leaves it. Male fertilizes eggs and protects them within one week – up to fry hatching. When posterity hatches and starts to swim, male abandons it, and fry appear leaved to their own. Within first two weeks of life their life is rather passive: young perches soar in thickness of water and eat plankton which appears literally “right under their very nose”. But then they turn in active predators, devouring even their own smaller neighbours. At one-year-old age young perches grow up to length of 5 cm. But in three years they already reach length of half meter and become sexual matured. Life expectancy of this species is up to 8 – 11 years.
monster perch (Deinolates vorax)
Order: Percoid fishes (Perciformes)
Family: Snooks (Centropomidae)
Habitat: Tanganyika passage, mangrove thickets and stony areas near coast.
Picture by Amplion
In XX century of human era to the African Victoria Lake the
giant Nile perch (Lates niloticus) had been introduced; and later it had practically
exterminated populations of local species of cichlids. Probably, such thoughtless
step from the part of man has given to this species of predatory fishes an
every prospect of survival in the future. When Great African lakes had turned
to sea gulf, and later to passage, the new species of predators, giant monster
perch, the lineal descendant the giant Nile perch, had occupied shore mangrove
thickets. Great African lakes in which this species evolved, are in equatorial
zone of Earth, therefore this representative of heat-loving fishes had
managed to survive.
This fish is huge solitary predator of sea and brackish waters, the original analogue of sea groupers. The length of body of giant monster perch reaches 2 – 2.5 meters at weight up to 200 kgs.
During inflow the wide zone of mangrove thickets, especially plentiful on east coast of Tanganyika passage turns to circuit of small islands. Marsh and overland inhabitants of these places hide in holes or get on trees, and sea fishes visit in these places for feeding. Schools of fishes move in passages between trees, gathering insects fallen in water. But they can become food for one of the most gluttonous local predators.
Fish looking like rotten stump of tree trunk waits for nothing suspecting small fishes in shadow of mangrove roots. Its scale is spotted with pattern of longitudinal twisting strips giving similarity to bark, and on head small skinny outgrowths, masking eyes and nostrils, grow. When any small fish swims up too close, instantly wide mouth opens, and it is literally tightened to teeth of predator by stream of water. Throw happens so fast, that only cloud of silt and some fallen leaves twirling in water show that here something had taken place. Having swallowed catch, fish freezes again, having folded fins. If the sunlight, having appeared through foliage, falls on body of predator, fish moves in shadow and continues patient expectation.
It is the giant monster perch, one of most gluttonous predators of Tanganyika passage. During outflow the fish quickens a little: continuing expectation, it is possible sometimes to appear in shallow water. Huge fish emerges from bottom and then it can be examined in more detail.
At giant monster perch there is massive head with wide mouth oblique upwards. On jaws numerous small sharp teeth grow. Small eyes of fish are shifted to the top third of head, and are disguised by skinny outgrowths “eyebrows” similar to seaweed. The first back fin of fish is high, triangular; spikes strongly jut out from its membrane. Two-lobed tail fin of giant monster perch is wide and rather short. The body is deep, short and compressed from sides: it permits a fish to maneuver between roots of mangrove trees: in mangrove thickets the maneuverability is more important than high speed.
Colouring of giant monster perch helps fish to mask among roots and trunks: body is colored soft brown with plenty of twisting dark longitudinal stripes, and only bottom part of stomach has silvery shine. Cryptic colouring is supplemented with plenty of outgrowths on head of fish: along head a line of knob-looking outgrowths passes, under eyes and in corners of mouth also there are some skin warts giving to fish strange and fantastical appearance.
The giant monster perch lives in water of varying salinity, normally feeling like both in sea, and in fresh water. The fish spends the most part of time, having half dug in sand. Then because of colouring and shape it is easily possible to mix it up with rotten tree trunk, and small fishes swim up to predator to the certain death, deceived by its shape.
This species spawns in fresh water, making migrations to river estuaries. In spawning season courtship dress of males becomes brighter: brown background is replaced by copper-red, and strips become narrower. At females the stomach considerably brightens, showing thus readiness of these fishes for spawning. Males and females swim up in rivers by common schools, but males quickly leave school and search for places for spawning.
The giant monster perch spawns eggs on roots of trees washed away by water, or on bushes of small-leaved plants. Being found suitable place, male starts to invite swimming near it females to spawning. He opens pectoral and abdominal fins forming as though “collar” around of his head, and utters sounds similar to growling and bark. When one of females shows intention to spawn, pair clears together the substratum chosen by male, and drives off from it all neighbours. Spawning occurs in the evening, then female leaves the river, and male protects eggs up to fry hatching. In clutch of giant monster perch can be up to 200 thousand of small transparent grains of roe.
Fry of giant monster perch is very small, and their big part perishes from every possible predator already at first days of life. But survived individuals have an every prospect to survive: they feed with every possible river plankton, and do not squeamish with their own neighbours, being behind in growth. At this time colouring of fishes is cross-striped – black strips on silvery background. In due time strips break off to irregular-shaped spots which to the moment of migration from rivers merge in longitudinal strips, characteristic for adult fishes. The background also changes from silvery to dark one. Young fishes live the first half-year of life in the river, but then, having reached size about 10 cm, gradually start to migrate to zone of mangrove thickets. Here young fishes should face real danger second time in life: mangrove thickets are occupied by adult fishes which will not suffer competitors, and can simply to have eaten small fishes of the species. Therefore young giant monster perches search shelter in those places where adult fishes can not squeeze through.
The part of young fishes can stay to live in rivers for ever, forming small sedentary form reaching length about 1 meter. Such fishes usually can not compete to larger neighbours, evolved in sea, and spawn upstream, or at shallow sites of rivers. But their posterity is quite viable, and in good conditions reaches the usual size for this species.
At the age of five years at length of body about meter these fishes become mature. And lifespan of giant monster perch may reach 40 years.
Great songperch (Percantor musicalis)
Order: Percoid fishes (Perciformes)
Family: Grunters (Teraponidae)
Habitat: Arafura Lake.
Grunters (Teraponidae), the family of euryhaline percoid fishes, were characteristic representatives of Australian and New Guinean ichthyofauna in human epoch. Some of them rose for feeding in upper courses of rivers, but migrated to estuaries and the sea coast for spawning. When New Guinea and Australia had merged to unite Meganesia continent, populations of these fishes appeared isolated in two lakes – older and almost fresh-water Carpentaria lake and younger brackish-water Arafura lake which is separated from ocean by extensive areas of mangrove forests. Some species of fishes had left these reservoirs at the stage of their formation, others had died out at decreasing of water salinity, and one more part of species had managed to adapt to new conditions of inhabiting. Among fishes had achieved success, grunters were formed lot of species in these lakes. In courtship season these species fill lakes with “songs” which are audible sometimes even above the surface of water.
Grunters are pelagophils – they spawn a plenty of tiny eggs which are a little bit denser, rather than water. Living in common, different species of these fishes could easily hybridize at joint spawning. The necessity to distinguish the congeners has resulted in occurrence during the evolution of the “songs” sharply differing in sounding at related species of these fishes. Representatives of the same genus of these fishes, songperches, represent an example of ethological isolation of the species living in same place. Some species, similar externally, but differing by ecology, size and some elements of colouring, live in Arafura Lake. However, the sharpest distinctions between these species are shown during the courtship “concerts” which serve for gathering of representatives of the species and synchronization of their biological rhythms. The necessity of recognizing of congeners is closely connected to the choice of spawning places: all songperches use for spawning sites of lake far from river mouths, where there is constant salinity of water and depth is no more 10 – 15 meters.
The most typical species in this group is great songperch inhabiting coastal biotops of lake along the edge of mangrove forests and thickets of pandanus. At the border of two habitats schools of fishes of this species find a plenty of food – small shrimps, worms and snails.
Great songperch is rather large fish: the length of its body reaches half meter, and weight of adult individual is about 5 kg. It has deep body compressed from sides allowing such large fish to penetrate easily deep into mangrove thickets. Head of this fish has wedge-like shape, and rather small mouth can extend forward, allowing gathering of small animals from surface of mangrove roots. Eyes are shifted upwards and are located on border of last third of head.
Colouring of this species is modest enough: slight greenish shade on silvery scale without strips. Contrast black spots are located on head (forehead and area around of eyes) and on tail (vertical strip at the back edge of tail fin and stripe on tail stalk). Unpaired fins are transparent; spiny part of back fin differs in lengthened fin rays. Pricks of spines growing in first back fin and in anal fin are very painful.
Schools of these fishes total up to hundred fishes, and in courtship season they gather in many thousands shoals. Fishes distinguish relatives using sounds uttered by them. Because closely related species of songperches utter different sounds, fishes correctly distinguish congeners and join them. Mistakes happen at night more often when fishes are not so active and do not utter sounds. But in the morning the stranger, having caught a voice of another species, at once leaves the school – otherwise its voice causes aggressive behaviour in fishes of another species, and it may be strongly bitten or will receive some ramming impacts by head. Having gathered in numerous school, songperches stop feeding and spend a significant part of time for loud synchronous “singing”. Such sound sets original rate to biological rhythms of fishes, and synchronizes their readiness for spawning. Night before spawning passes noisily: fishes continue uttering of sounds even in darkness, and keep activity (and one of species even day time colouring). In the morning rough spawning begins, and females spawn a plenty of eggs – up to 100 thousand small grains of roe. Males fertilize eggs, and the school of fishes swims to depth. The care of posterity at this species is absent. After spawning number of school does not stay constant: former congestions separate, and in the same school after spawning fishes from five and more schools existed before spawning may swim.
The larva hatches approximately in 36 hours. The first days of life it soars in water and eats nanoplankton. At the age of one week gradual transformation into fry begins. Juvenile colouring of songperches is cross-striped; when they grow, strips on the body turn pale and vanish, only marks on head and tail are kept. At one-year-old age fishes reach about one third of length of adult individual, and at the age of three years they take part in breeding. Life expectancy of great songperch and other large species reaches 20 years; small species are mature in 1 year age and live no more than 10 years.
Some other species of songperches live in Arafura Lake:
Chime songperch (Percantor resonator) is schooling fish up to 30 cm long. Voice of this species may be easily recognized – it represents single musical sounds of low tone resembling tolls. Colouring of body of this species is silvery-blue; on head there is a wide area of black color, including lateral parts of head, forehead and the bases of operculums. The tip of muzzle, lips, lower jaw and edges of operculums have the same colouring, as body. Also the tail fin of this species has black colouring with colorless border. The present species lives in schools numbering up to 200 – 300 individuals and keeps far from the coast. These fishes eat small pelagic invertebrates and fry of other species of fishes.
Sparrow, or twittering songperch (Percantor passerinus) is the smallest species of the genus: the length of adult individual does not exceed 15 cm. Body of this species is rather short; head has high forehead with the fat pillow stretching to the beginning of back fin. Its courtship song represents short series of chirping sounds of high frequency similar to twittering of small bird. The fish is colored very attractively: body has a distinct greenish-blue shade, eyes are surrounded by dark spots, making an impression of “glasses”, and on back part of body and tail there are thin vertical strips. In courtship season these strips almost disappear, but the tail stalk is colored black. Twittering songperches almost constantly live in mangrove thickets and eat small fishes and shrimps.
Cricket songperch (Percantor aquagryllus), a fish about 20 cm long, has more prolonged body, rather than other species of genus. It has golden colouring of body, and on head and forward part of body it has black saddle-shaped spot stretching from back edge of eye up to the end of first third of spiny back fin. This spot stretches down to the basis of pectoral fins. On tail stalk there is also small saddle-shaped spot of black color. In courtship season this fish utters long series of clicks similar to chirring of cricket. Schools of the present species, numbering over hundred of individuals, keep in mouths of rivers and frequently rise in middle watercourse, but return to the lake for spawning. This species is a predator and eats small fishes and shrimps, hunting them in top layers of water and especially in thickets of floating plants.
Glass-clincking songperch (Percantor crystallinus) is named not for appearance at all. It is a fish of coal-black color with silver-gray forehead and sides of head; fins are transparent, only their bases have black color. It is the only species of genus, so sharply differing by colouring from other songperches. But such colouring is characteristic for fishes of this species in daytime. At night it becomes pale grey with five vertical strips on body and white head. The length of body reaches 25 – 30 cm. The characteristic voice of this fish is similar to melodious ringing of vineglass which is repeated in long series. Glass-clincking songperch lives in mangrove thickets, eats small fishes and gathers in schools numbering of some tens of individuals.
Sawyer songperch (Percantor serrator) is easily distinguished in courtship season because of long series of abrupt sounds similar to sound of a saw. It is medium-sized species, about 30 cm long. Colouring of body is silvery with bluish shade. Snout and lower jaw are black; on the back end of body there is thin vertical strip stretching from soft part of back fin up to back edge of anal fin. Tail stalk and back edges of back and anal fins have some small dark spots. This fish gathers in schools numbering no more of fifty of individuals, and eats benthic invertebrates and small fishes. The present species frequently swims to mouths of rivers and gathers at the border of thickets of aquatic plants, searching for larvae of insects.
Barking songperch (Percantor latraris) is one of the small species of genus: length of adult individual is no more than 18 cm. This species lives mainly in more freshened eastern part of lake where influence of inflow is less felt, and inhabits thickets of pandanus and reed. Separate schools of this species come into the western part of Arafura Lake, but prefer to keep in river mouths. This species has the characteristic deep body compressed from sides and double strips on head: one strip stretches across the tip of snout, and another one lasts across the eye. From the beginning of a back fin frequently one more strip stretches downwards, but more often it does not reach even the basis of pectoral fins. On tail stalk dark spots appear only on occassion. The basic colouring of body is silvery with slight lilacky shade appreciable only at bright light. The courtship song represents the loud abrupt sounds similar to bark of small dog. Mouth of barking songperch is small: this species eats mainly small invertebrates inhabiting thickets of aquatic plants. This species gathers in small schools numbering of some tens of individuals.
Caravel fish (Scaphoichthys caravella)
Order: Percoid fishes (Perciformes)
Family: Serranids (Serranidae)
Habitat: Indian ocean, from tropics up to moderately cold areas.
After extinction of whalebone whales and “planktonic accident” caused by global changes of climate at the boundary of Holocene and Neocene ecological niches of pelagic animals turned free that time were occupied with descendants of coastal fishes. Survived small species of groupers passed to large dimensional class; their huge mouth allowed grasping small fishes and cephalopods in a plenty at once. Transition from benthonic to pelagic way of life took place at fishes of various groups repeatedly: already in human epoch the pelagic manta ray (Manta birostris) was known, though its relatives are benthic fishes. In Neocene other inhabitants of thickness of water had appeared; among them the caravel fish, large (body length up to 4 – 6 meters) fish, the descendant of one of Holocene species of groupers, is one of the most unusual species.
Caravel fish has more extended and streamline body in comparison with an ancestor, with powerful tail that allows it to make fast throws. The head with huge mouth makes about 1/4 of general body lengths. Prickly part of back fin at this species is increased and represents a kind of “sail” up to 2 – 2.5 m high, with rounded top edge. “Sail” has contrast colouring of black cross strips and concentric “oculate” spot in back part on brightly shining silvery background. It is used in order to drive prey in dense shoal from which it is easier to eat. Also demonstration of “sail” allows to disorient predators: sharply stretching fin, fish seems larger, rather than actually, and the oculate spot distracts attention of attacking predator from the vital body parts of fish. Colouring of back of this species is steel-blue; belly and sides are silvery.
This fish is good swimmer though in speed it concedes to sharks and to anothers fast swimming pelagic fishes. Similarly to tunas and some sharks of Holocene epoch, like mako shark and great white shark, caravel fish is capable to maintain temperature of body some degrees higher above suroundinf environment due to intensive work of muscles that allows it to feed both in warm, and in cold, but rich in food waters. It has deep forked tail fin, rigid front rays of anal fin; and narrow belly fins are shifted under the bases of pectoral ones and can nestle against the body, being hidden in special longitudinal plica of skin on stomach.
This species lives in top layers of water of Indian Ocean and dives for prey to depths no more then 50 – 60 m. Caravel fish is settled from tropical and equatorial zone almost up to the coast of Antarctica. In the south it may be met mainly in summer when water is warmer. For spawning these fishes migrate to coast of islands of Indonesia, to coastal reeves. Adult individuals live in groups of 3 – 6 individuals. The structure of each group always includes one male, and other individuals are females. It is connected to feature inherited by caravel fish from the ancestor: the gender at these fishes is not fixed genetically and can vary many times in ontogenesis. A dominant individual in group becomes a male. If male leaves school or perishes, his place becomes occupied by alpha female which turns to full-grown male in some weeks.
Caravel fishes eat small schooling fishes and squids, and in waters of Antarctic Region they feed on numerous species of pelagic crustaceans – “the red robber” (Gregariomyzis planctophagus). Hunting individuals surround a shoal of prey and swim around it, lifting and lowering back fins. Thus they drive prey in dense sphere and do not allow it to escape. Periodically one of individuals rushes into congestion of prey, and like huge vacuum cleaner, sucks it in with water. Then water flows out through gills, and the food is filtered by branchial stamens and is swallowed.
The courtship period at this species is strongly dragged out – at the coastal reeves schools of caravel fishes may be met at any time of year. But especially intensive courtship games take place in winter when schools of fattened fishes return from Antarctic waters. In courtship period the back fin of males is colored bright golden, and colouring of body becomes more contrast and intensive. Spawning occurs near to coral reeves during the day time inflow. At this time schools of many tens large fishes approach to the coast. Males, appearing near each other, begin demonstrations of force to each other. They open back fins and try to push each other aside from the chosen site of reef. Frequently stronger male pushes the contender almost half out from water. At this time above water numerous brightly colored back fins of males rise, which the more modestly colored fins of females join.
Spawning takes place above sandy sites at the bottom. Each female spawns huge amount of tiny eggs – up to 40 – 50 million grains of roe, packed in dense slime cords. Male fertilizes eggs and they begin to inflate, absorbing surrounding water. At this time some sites of reef become covered entirely by jellylike paste of eggs under which crabs, shrimps and tiny fishes are trapped. Eggs develop within two days, and tiny helpless young ones leave them. Young caravel fishes live at the reef, like groupers of Holocene epoch, eating small fishes and invertebrates. They are absolutely not similar to the parents – they have cross-striped body and short back fin. They are very quickly growing predators. They need a plenty of food and devouring of their own smaller congeners is in the order of things for them. At one-year-old age, after reaching of length of 0.5 meter young fishes move to open ocean where join schools of adult individuals. In this case they at once starts to develop as females. Sometimes schools of approximately one-age individuals are formed. In this case the gender depends on place of individual in hierarchy.
This species of fishes was discovered by Andrey, the forum member.
Order: Percoid fishes (Perciformes)
Family: Sea swallows (Monodactylidae)
Habitat: Tanganyika passage, coastal zone.
Formation of Tanganyika passage which had separated East Africa (Zinj Land) from other continental platform, began, in effect, from formation in break of Earth crust of whole circuit of Great African lakes: Tanganyika, Nyassa (Malawi), Victoria, and some more several smaller lakes. In due course they had merged to one deep long lake, and then edge of rift had revealed in the south, and ocean waters had rushed to freshwater reservoir. Then narrow gulf had turned to passage, having revealed to all length and completely having separated East Africa from other continent.
When it had taken place, numerous unique species of freshwater fishes evolved in lakes, either have died out, or have receded in rivers, but the formed basin started to be occupied by sea fishes from the south and the north. Among former freshwater inhabitants of these places, however, some species, which also had mastered salt water of passage, were to found. But all the same the significant part of species inhabiting passage, belongs to sea fish families. Psamaphe, the representative of sea swallows family, is one of them.
Psamaphe named after nymph from antique mythology is large predatory fish: length of its body from muzzle tip up to tail tip is about 1 meter. As at all representatives of family to which it belongs, the body of psamaphe is very much extended in height: at meter length the height of fish is up to one and half meters and more. Back and anal fins are peaked, tail is crescent. Pectoral fins are long, pointed, slightly bent, and abdominal fins are reduced up to small spikes (it is characteristic attribute of family). The constitution of fish indicates the fish as excellent swimmer.
At this fish there are large eyes and mouth able to streth in tube for capture of catch. Psamaphe eats small fishes and large plankton crustaceans, catches shrimps and others large, swimming in thickness of water, crustaceans.
The body of psamaphe is colored silvery-blue with dark irregular-shaped spots on back and sides. At the edge of unpaired fins there are wide yellow strips, at males having appreciable orange shade. Males are larger than females, at them there are more abrupt forehead and long fins.
In sea psamaphe prefers top layers of water up to depth 15 - 20 meters. These fishes dive deeper only at the beginning of storm. Psamaphes keep in large schools – up to 20 - 40 fishes of equal age and size. Such way of life helps them in hunting: predators overtake school of crustaceans or small fishes, push them aside from shelters at the bottom, surround and orderly start to catch prey one by one. Sometimes psamaphes approach to the coast and even come in mangrove thickets: these fishes are not avoid of lowered salinity of water, and near coast it is possible to catch many various edible live creatures. For getting animals dug in sand psamaphe has original hunting reception - fish “stands on head” above bottom and by sharp movements of fins creates a wave, which sweep sand in sides. Thus small inhabitants of silt try to rescue by flight, finding out themselves to the predator.
Psamaphes breed in schools in mangrove thickets. Males become appreciably brighter and more contrast than females; strip on their unpaired fins becomes red-orange. By group of two - three ones males surround female ready to spawning and “leap” her away from school to roots of mangrove trees. After short chasing they nestle to the female, and she jets out portion of eggs which are fertilized by males immediately. Then spawned female has a rest, and males chase the next female. Fertility of one female can reach 50 thousand of small grains of roe. The spawning proceeds some days then school swims out to the sea. 2 days later larvae hatch from eggs. They passively hover some hours in thickness of water, and then start to swim and eat actively. After one week larvae turn to fry similar to adult fish by outlines. Fry quickly grow, at bi-monthly age reaching length 2 - 3 cm, and at one-year-old age about 15 cm. The first year of life young growth spends in mangrove thickets, then schools leave in high sea. Active growth proceeds within the first 5 years of life, at this time fish reaches length 60 - 70 cm and begins able to breed.
cleaner chromis (Neonochromis medicus)
Order: Percoid fishes (Perciformes)
Family: Cichlids (Cichlidae)
Habitat: Tanganyika passage, river mouths with thickets of water plants.
Before split of Africa the territory becoming coast of Tanganyika passage, was the huge valley serving as a receptacle to chain of Great African Lakes. These lakes were richly inhabited by huge amount of various species of fishes among which representatives of cichlids family prevailed. After split of continent and filling of Great Rift Valley with sea water the part of cichlids species has survived, having receded from lakes to rivers. But later some cichlids had adapted to life in sea water of Tanganyika passage.
One of sea species of cichlids is sparkling cleaner chromis. It is a small fish (length of body is about 12 – 15 cm), living alone or in pairs in river estuaries where water is only slightly brackish, and still there are aquatic flowering plants. By constitution it is similar to the majority of lake cichlids dwelt in Holocene in thickets of plants: body is rather deep; head is large (about of 1/5 of all fish length), with big eyes. Prickly part of back fin at males is very high (about 2/3 of body height), on it there are some bright red irregular-shaped spots. It serves as warning signal for other males that the territory is occupied – pair of fishes is territorial; they aggressively banish neighbours, trying to lodge nearby. At the female such ornament is not present. Other unpaired fins are translucent with bluish shine.
Feature of the cleaner chromis is its diet consisting mostly from parasitic worms and crustaceans which are gathering by fishes from skin of other fish species. This species lives in thickets of plants; pair of fishes occupies a large appreciable bush near which they spend “reception” of clients – large fishes, cleaning them from parasites. For “advertising of services” at chromises the attribute making them very appreciable from afar is developed: bright blue “neon” strip on cyaneous body. When fishes swim near the bush of plants serving for them as shelter, shine of their sides involves “client” fishes. From the central part of passage large schools of fishes frequently swim to river mouths for the sanitation – freshened water has pernicious influence to parasites. And cleaner chromises help fishes to have quick and warranted sanitation.
The mouth of this species of fishes is transformed into scraping grater: strongly turned out lips are covered with set of tiny corneous denticles permitting to scrape off particles of dying off tissue on fins and wounds, to clear gills of worms have stuck to them, to hook and pull out parasitic crustacean has taken root under skin.
Fishes have come to clearing, patiently tolerate all actions of cleaners though sometimes pull because of pain if the cleaner chromis carelessly clears graze of rags of died out skin. Sometimes “client” fishes conceive fights, pushing each other away from the fish - cleaner.
Pair of fishes spawns twice per one year on the chosen plant – large eggs (up to 200 ones) are spawned on leaves. Before spawning male actively cleans leaves, from time to time “inviting” the female to itself. He is colored bright, “crown” on fin becomes almost entirely red. The spawning usually begins in the evening though ceremonies previous to it can take place in the afternoon. Male actively shows to the female cleared leaves, drives off from them fishes and shrimps (sometimes simply making false lunges against nonexistent enemies). In the evening pair of fishes starts to spawn eggs: the female swims along the leaf, laying grains of roe in “line”, and the male swims almost side by side with her, fertilizing spawned eggs. Both parents carefully protect clutch, driving away probable enemies. At this time bright colouring of cleaners grows dull: blue “neon” strip completely disappears, being replaced by line of vertical strokes. During caring of posterity these fishes try to not draw attention of yesterday's “clients”: at approaching of large fishes parents hide in thickets. The posterity hatches after 3 days, and parents at once bring them to the small hole dug out under roots of chosen plant, that current will not carry fry away.
After one week fry starts to swim actively. Colouring of young fishes while resembles parental by nothing: they are black with longitudinal line of white points. Such colouring will be kept at them up to monthly age when they’ll leave parents. At a young fish passed to independent life, to three-monthly age white points start to increase and to merge to one longitude strip. Their colouring changes also: an appreciable blue shine is seemed. Half-year-old fish already can breed. At this age its colouring is already similar to colouring of adult fish, but at males “crown” on back fin will appear only at the end of first year of life.
or comb-toothed cleaner (Ctenognathochromis figaro)
Order: Percoid fishes (Perciformes)
Family: Cichlids (Cichlidae)
Habitat: Tanganyika passage, coastal waters.
As against the previous species of fishes, this fish is not the homebody, but the wanderer of coastal waters. It does not have constant territory; it swims among stones and thickets of vegetation, searching for food in different places. Similarly to the sparkling cleaner chromis, this fish relieves other water animals of parasites though the significant part of diet at this fish is made by tiny sedentary sea animals. This species prefers to clean turtles and large pelagic fishes keeping in places where the sparkling cleaner chromis does not live – far from sites of sea with freshened water.
Figaro is very similar externally to the cleaner chromis though at the closer examination distinctions are clearly visible. This fish neither at males, nor at females does not have “crown” of lengthened fin rays. Distinctions in structure of mouth are well appreciable: at this species lips are narrow and smooth, but the bottom jaw is flat and saw-edged in front: it is a main instrument of getting of forage (name Ctenognathochromis means “chromis with comb-looking jaw”). Colouring of fish is very similar to coloring of sparkling cleaner chromis: it is a result of phenomenon, known to people as Muller’s mimicry. Thus natural selection favors to formation and preservation at various species of features of external similarity while both species are equally protected from attack of predators. For cleaner fishes of Tanganyika passage this protection is their role of cleaner in ecosystems. Predatory fishes do not touch all fishes of similar coloring, having shining blue strips on sides.
In details of colouring figaro nevertheless has differences from colouring of sparkling cleaner chromis: the body of this fish is not bright blue, but grey, and neon strip is much wider and longer. It reaches tail fin, and on branchial cover is supplemented with round shining spot.
Fishes of this species do not form constant pairs, meeting only for fulfillment of courtship ritual. For this purpose male builds special “dance pavilion”: he cuts out all seaweed on any flat stone, then literally “polishes” by jaw its surface. After that male starts to invite females, performing in thickness of water above the cleared platform the special dance, swimming along eight-shaped trajectory. He supplements these movements by advertisement sounds – loud clicks. Usually some females living in the neighborhood respond to this signal. They swim together to “dance pavilion” of male, then the male starts to perform the following “figure”: semi-laying on one side, he whirls on the surface of stone, flashing by blue strip. Female ready to spawning joins him, and pair of fishes makes some circles together. Further the generated pair expels all superfluous females and starts spawning. Eggs (up to 100 ones) are spawned on stone. Male fertilizes them, and then female takes all clutch in mouth. Male any more does not takes part in care of posterity. He banishes female, has a rest for some days, clearing “dance pavilion”, and then spawns with the next female.
Female incubating eggs hides anywhere at its territory in cavity between stones. During egg incubating she does not eat. Eggs develop in mouth of the female about 10 days. Hatched larvae even one week stay in mouth of the female, and then start to swim and feed under her supervision. In two weeks they swim out from mother and live independently. The original feature protecting them from predators is early shown blue neon strip on body. Due to this even the youngest fish feels like in safety even near to large predators. Young fishes at once start to work as cleaners, rendering the services at first to small fishes, and then, in process of growth, to larger ones. Sexual maturity appears approximately at one-year-old age.
Small-maled disproporcichla (Disproporcichla micrandra)
Order: Percoid fishes (Perciformes)
Family: Cichlids (Cichlidae)
Habitat: forest rivers of Zinj Land.
The species variability of fishes of cichlid family had reduced to Neocene. It was the result of splitting of Africa to continental mainland and Zinj Land. The line of break in Holocene epoch was marked by chain of Great African Lakes differed in variety of cichlid fauna. When waters of Indian Ocean had filled in Great Rift Valley, many species of cichlids had died out. Some species of these fishes managed to recede to rivers – they became ancestors of various Neocene cichlids.
Representatives of cichlid family are distinguished among bony fishes by various forms of family relations and complex behaviour providing isolation between the species living in the same reservoirs. In Holocene epoch it was possible to distinguish precisely some species of cichlids by features of behaviour at rather similar features of their anatomy. In Neocene at cichlids various tendencies in development of relations between genders were kept. Besides the forms of relations existed in Holocene between fishes of different genders, completely new, earlier not existed ones had appeared.
In short and rapid rivers of Zinj Land one interesting cichlid of Neocene lives, at which mutual relation between genders have got completely fantastical character. This fish is named small-maled disproporcichla, and its specific features completely justify the name.
The female of this species is rather large – it reaches the length of 45 – 50 cm and more. The female differs in rather large head with wide mouth and thick lips. Out of spawning period the female has rather soft colouring – gray-brown with darker back, pale vertical strips and black “mask”. Lips of the female out of spawning period are light grey, and on fins grey points and irregular-shaped spots are scattered. During the spawning its colouring turns brighter and more contrast: the body gets the shade of red clay, vertical strips become black, and lips turn snow-white. The female of disproporcichla is a predator eating small fish and shrimps.
The male of this fish sharply differs from the female. At first sight it is possible to mistake it as the representative of completely other species, and even genus of fishes. Length of the male is only about 10 cm including fins. It has dark blue body with cyan metal shine; on anal fin of male large “egg spots” of orange color are scattered. During the spawning he stretches anal fin and swims right before head of the female, displaying to her these spots. Head of the male is short and high with small mouth. On its forehead the large fat outgrowth is located – it is an attribute of maturity and good physical condition. Eyes of the male have clear silvery shine, and they are surrounded with dark spot, remotely similar to black “mask” of the female. Male eats small water animals.
The ratio between genders at disproporcichla depends on temperature and acidity of water. In soft and acidic water (for example, in rainforest rivers) the ratio of genders at growing up posterity makes approximately three males to one female. In fresh water of neutral acidity the ratio of genders makes approximately 1:1. Therefore more often in population young males prevail a little. While they had not found the female, at them the chance to perish from predators is great. The female means protection and safety for them. Therefore the male gets attached not as much to territory, as much to the female living at this area. He continuously follows the female and behaves very aggressively, driving possible contenders away from the female.
Disproporcichla lives in wood rivers overgrown with water vegetation along riverbanks. Among plants fishes find shelter and rear posterity. The spawning of disproporcichla passes originally. Stimulus for a spawning is the rise of temperature of water up to +30°С. During courtship displays male stimulates the female to egg spawning, showing to her “egg spots” on anal fin. For this purpose he literally nestles by side against the head of the female, and stretches fins, overlapping by them a field of vision of the female. Also he pinches the female by lips for bases of pectoral fins and pushes her to side by all body. At the culmination moment of courtship displays male moves to the tail of the female and swims along all her body, having nestled to her by side. Under action of such stimulation the female spawns a portion of large eggs. In clutch of disproporcichla it may be up to 200 – 250 eggs spawned at once.
Having spawned eggs, the female at once takes them away to throat pouch for incubating. And this moment the male actively includes to the process of spawning. He squeezes in mouth of the female (female lips turning white during the spawning serve as the stimulus for this purpose), and fertilizes eggs right in her mouth. After that the male cautiously leaves the mouth of the female, and keeps permanently near to her. From time to time male gets in mouth of the female and searches for sterile eggs. He takes eggs in mouth and clears them of parasites and dirt.
Term of incubating makes about three weeks. This entire time female eats of nothing. Male protects her from other males - at disproporcichla female aggression relatively to males of the species is reduced, therefore stranger male can easily “enter trust” and destroy another's eggs. When from eggs young fishes hatch, they keep for some time in mouth of the female, and the male regularly examines them. Approximately at one week age they start to swim, and cares increase at the male. It “pastures” posterity and protects hatch from small predators, such as water bugs, larvae of dragonflies and beetles, if necessary. At danger it quickly returns posterity to the mouth of the female.
First days of life young fishes have no gender – at these fishes the gender is not determined genetically. Further depending on conditions of environment and degree of development they turn to males and females. Males in development quickly stop in growth, but get bright colouring rather early. Because of it the part of them perishes from predators, but the male founded the female, provides safety till entire further life to itself. Life expectancy of females of these fishes makes over 30 years. The male lives less, rather than female – till 15 years.
Cuckoo chromis (Cuculichromis parasiticus)
Order: Percoid fishes (Perciformes)
Family: Cichlids (Cichlidae)
Habitat: forest rivers of Zinj Land.
In early Neocene, when the great split of African continent took place, numerous species and subspecies of cichlids evolved for millions of years of isolation in Great African Lakes, had got a serious problem. Earlier people caught representatives of these species, then had introduced in some lakes predatory fishes preyed lake endemics and had undermined their forage reserve. But geological forces had put much more serious problem to fishes. Lakes had turned first to narrow gulf of Indian Ocean, and then turned to Tanganyica Passage. This event had completely separated Eastern Africa (Zinj Land) from the basic continent. In these conditions the majority of endemic fishes had died out, but some species of fishes had managed to adapt to life in rivers flowed earlier into lakes, and then into Tanganyica passage. Cichlids also were among them.
Due to high adaptive potential cichlids had developed a plenty of biotopes in reservoirs of Zinj Land. Among them even extremely strictly specialized species had appeared.
The amazing cichlid Disproporcichla lives in rivers of Zinj Land – at this fish male is many times smaller, than female. The female of disproporcichla is a predator representing danger to small fishes and shrimps. It reliably protects the posterity, and the male, tiny creature of dark blue colouring, uses her protection. At the aggression and predatory behaviour the female of disproporcichla has one “weak point”, which is caused by her instincts. She does not touch the male of own species and consequently does not attack fishes having more or less similarity to him. The species of small cichlids, cuckoo chromis, the descendant of certain species of chromises of Tanganyica Lake missed in Neocene, dexterously uses it, skilfully imitating the male of disproporcichla.
It is fish only 5 – 6 centimeters long. The male is a little bit larger, than the female, and it has rather large head. Out of spawning season both genders of this fish have the colouring strongly distinguished from colouring of the male of disproporcichla – fishes have the bright orange colouring with small black spots forming “marble” pattern, black back, vertical dark brown strip stretching across the eye; dark iris of eye. Having such colouring they diligently avoid meetings with the female of disproporcichla which may swallow them easily. But the male of this fish does not pay attention to them at all, because it does not see competitors in them. But in spawning season both fishes change colouring and body shape. At fishes of both genders fat “helmet” on head grows, and colouring turns to dark blue with slight metal shine. They differ from the male of disproporcichla in lighter forehead and dark eyes (at the male of disproporcichla eyes shine silver). On anal fin these fishes also have “egg spots”, but they are black. Having such colouring cuckoo chromis rather successfully imitates the male of disproporcichla. And in courtship season the relation of disproporcichla to these fishes varies to opposite one. The disproporcichla female has boundless confidence to dexterous imitators, but the male begins to see contenders in them, and furiously attacks them.
The purpose of this “masquerade” is simple, but its achievement is much more difficult. The task of cuckoo chromises is to place stealthily eggs during the spawning right in mouth to disproporcichla incubating own clutch. They use similarity to the male of this species to penetrate into the mouth of female and to lay eggs in clutch, having had eaten a part of disproporcichla’s eggs. The spawning of these fishes begins almost simultaneously with spawning of disproporcichlas. The pair of fishes simply waits, while the disproporcichla female will take eggs in mouth for incubating. Then the female of cuckoo chromis under the guise of the male of disproporcichla penetrates into her mouth, eats a part of eggs and lays her own eggs. At this time the male distracts the disproporcichla male, showing bright colouring at some distance from spawning fishes. After that action partners exchange roles, and male of cuckoo chromis fertilizes eggs right mouth of disproporcichla female, while the female withdraws aside disproporcichla male. Having finished the spawning, pair of these fishes departures and quickly changes colouring, giving disproporcichlas an opportunity to care of their posterity.
Fry of cuckoo chromis hatch earlier, than posterity of disproporcichla. But they do not attack fry of host species. They stay in mouth of disproporcichla until the hatched posterity of disproporcichla will start to swim. First days fry of both species keep in one common school, in common using protection of female and care of male of disproporcichla. Approximately in two weeks the posterity of cuckoo chromis leaves foster parents and passes to independent life. Young fishes become adult at the age of two years.
Cuckoo chromises live in pairs. They prefer to live at the edge of territory of breeding pair of disproporcichlas and not to catch eyes of the male of this fish just before the spawning time. They are very cautious, and at first signs of danger hide in underwater vegetation. These fishes eat small aquatic animals – larvae of insects, leeches and other worms.
Sharp-toothed cichlopike (Esocichla
Order: Percoid fishes (Perciformes)
Family: Cichlids (Cichlidae)
Habitat: Zinj Land, rivers of the western part of subcontinent.
In Holocene fishes of cichlid family dominated or made a significant part of specific structure of ichthyofauna in some reservoirs of the Earth. In Neocene due to global ecological crisis the role of these fishes in ecosystems has exchanged. The destiny of cichlids in New World is to be rather small peaceful fishes. In this part of the world characid fishes, reaching the monstrous size, dominate in reservoirs. Split of Africa had caused disappearance of the majority of species of endemic cichlids inhabited Great African Lakes when these lakes became a part of Tanganyica Passage. Isolation at Zinj Land had resulted in active adaptive radiation of cichlids among which ecological analogues of fishes of other groups had appeared. One species of cichlids, living in Zinj Land, had occupied an ecological niche of large freshwater predatory fish. Arrow-like body and large head with long jaws have made this fish similar to pike, that has determined its name – the cichlopike. In Holocene epoch pike-like cichlids of genus Crenicichla lived in South America. But external similarity of cichlopike from Zinj Land and pikes of Eurasia and North America is even more.
Cichlopike constantly lives in fresh water. Using marshy sites of forest it had settled along whole western coast of Zinj Land, in rivers running into Tanganyica Passage. She is rather large fish reaching one meter length. At it the sexual dimorphism is expressed: male is larger and more slender, rather than the female, and it also is colored much brighter.
Body of cichlopike is arrow-shaped, with short tail and wide tail fin. Forward part of body is strongly extended and flat; head is also flattened a little. Mouth of cichlopike is wide and extending to short tube. Due to such structure of mouth fish eats small catch, which has appeared nearby – it is enough to it to open the mouth and the prey is engulfed in it by strong stream of water. Eyes of cichlopike are big: fish hunts in day time, and mainly with the help of sight.
The prickly part of back fin is presented only by short spikes connected by rudimentary membrane. A line of these spikes stretches approximately from the nape to the beginning of soft part of back fin. The soft part of back fin and anal fin are shifted back and pulled together to tail. Such structure is typical for fish overtaking catch by fast throw from an ambush. Back of cichlopike is dark grey; sides are silvery with greenish shade and plenty of dark vertical strips. For giving of signals to neighbours this fish has bright recognition marks on anal fin and the bottom part of tail fin, especially appreciable at males. Anal fin of male is red with several white spots; at female it is red-brown without spots.
Cichlopike avoids muddy water and reservoirs strongly overgrown with underwater vegetation. It lives in clean water with slow current, and usually slowly swims near water surface. Favourite place of an ambush at cichlopike is roots of floating plants which small thickets drift with the current. Cichlopike is not specialized relatively to food, and eats practically any creature which it can swallow. It hunts frogs, pelagic fishes and shrimps, and also catches small ground vertebrates appeared in water – birds, reptiles and mammals. Each fish occupies the certain site in the river, but hides in its various parts where at present there are floating plants. Adult fishes regularly declare the rights to territory, jumping out from water and plopping down with loud splash. Such feature of behaviour causes in fishes living in the neighbourhood, something like “chain reaction”: when one fish plops down in water, individuals living in the neighbourhood with it, also jump out from water, as if reminding about their own presence.
At cichlopike constant pairs are not forming. This fish spawns on sandy bottom, choosing the shallow sites of river closed from looks of aerial and ground predators by floating plants. The male occupies the certain territory, and settles it: it pulls out all plants preventing him, digs by mouth small hole in sand and invites to it females swimming near. At this time his body darkens and turns graphite-grey, and eyes get silvery shine. Anal and tail fins, and also back part of back fin become cherry-red. Involving the female to the nest made by him, male swims around the hole, and emerges to water surface, displaying itself. Fishes spawn in hole, and male at once takes away fertilized eggs in mouth for incubating.
In clutch of cichlopike it may be up to 100 rather large eggs. The posterity hatches approximately in 10 days, and keeps in mouth of the male till about one week while the yolk sac resolves. All this time the male eats of nothing, and hides from large predators among underwater vegetation or at the bottom.
Fry able to swim keep near the male, and it protects posterity till about ten days. During this period in case of danger fry hide in mouth of the male. Rearing posterity, male keeps in thickets of floating plants where it is easier to young growth to find food. Young fishes eat larvae of insects and shrimps. They grow quickly – to the age of half-year young fish reaches length of 10 cm, and for the next year grows up to 30 cm. Till the first year of life young fishes live in thickets of underwater plants, but later pass to life at the water surface. At one-year-old cichlopike body shape typical for these fishes starts to express – jaws and forward part of body extend quickly, and back fin and tail slow down in growth. At the age of 5 years, at length about 60 centimeters cichlopikes become sexual matured. They reach the size typical for this species at the age of about 10 years. Life expectancy of cichlopike reaches 35 – 40 years.
mayaichthys (Mayaichthys patronus)
Order: Percoid fishes (Perciformes)
Family: Cichlids (Cichlidae)
Habitat: South America, shallow rivers of tropical zone.
After global climatic changes at the border of Holocene and Neocene among fish population of rivers of South America there were significant changes. The majority of heat-loving fish species had died out, and the variety of some groups of fishes was essentially reduced. After the restoration of conditions acceptable to life of heat-loving fauna at different groups of fishes the chance to grasp domination in Amason basin had appeared; and characid fishes have taken advantage more successfully than others. In Neocene characids became most awful predators of South-American rivers, and another earlier multifarious group, cichlids, has appreciably yield positions: among them there are few large species, and their variety was essentially reduced in comparison with Holocene epoch. But they survive among various characids due to occurrence and perfection of effective ways of posterity care. At these fishes much more fry survive, rather than at more fruitful characids spreading eggs to the mercy of fate or not caring about fry.
Among Neocenic cichlids it is a lot of species, developing during evolution original receptions of care of posterity. Among them the mayaichthys, the descendant of one cichlasoma species (Cichlasoma), bearing eggs on the body, is especially remarkable.
Mayaichthys is medium-sized fish: about 25 cm long. The body of this species is deep and short, strongly compressed from sides, rounded, and covered with small scales. This fish is colored rather brightly: forward part of body is golden-yellow (at males - copper-red), back one is green. On body wide black faltering longitudinal strip passes. During spawning head of male becomes brighter, getting violet shade, and strip on body, on the contrary, fades. Head of mayaichthys is rather large, at males on forehead the big fat cushion grows. In season of spawning this cushion increases and sticks forward, as ram.
Mayaichthys is rather sluggish fish: its favorite habitat includes thickets of aquatic plants in well warmed up shallow rivers. This fish swims rather slowly: at it there are wide rounded fins and rounded tail.
Mouth of mayaichthys is rather small: the basic food of this fish is larvae of midges and mosquitoes, and also other water insects. Sometimes mayaichthyses eat small snails, leeches and other worms.
As well as all cichlids, to mayaichthyses the care of posterity, shown very originally, is peculiar. During spawning on body of fishes the special nutritious slime is secreting. To people such feature at discuses (Simphysodon), angelfishes (Pterophyllum) and some other cichlids was known. But all these cichlids spawned eggs on any substratum, and only fed with it hatched fry. The care of posterity at mayaichthyses had turned further. The female spawns eggs on stone or cleared leaves of plant. But after it the male carries by mouth eggs spawned by female on her sides, pastes to slime and fertilizes. The incubating of eggs proceeds within one week. All this time the female hides in thickets, trying to not give out its presence, and does not eat at all. Male in this period protects environmental territory, driving away not only small fishes, but also the fishes surpassing him in size. Showing the aggression, he opens mouth and spreads branchial covers in sides. At such moment brilliant blue spots latent under skin plicas become well appreciable. If the newcomer does not leave, male supports the threat with ram impact of forehead with thick fat cushion.
Embryos develop in the beginning due to stocks of yolk. The yolk sac of the embryo quickly becomes empty, but completely does not disappear. Yet not hatched larva nestles by it against skin of the mother, and starts to eat her slime. For this purpose on surface of yolk sac fibers which, as if roots, penetrate into slime produced by skin of the female, develop. Through blood vessels nutrients absorb in blood of larva, and it grows intensively. Due to fibers eggs keep on sides of female rather strongly, not dropping down even at sharp jerks of adult fish. When fry is ready to hatch and start to shake from themselves rests of egg shell, male accurately helps them, cautiously removing it. Also he in due time examines the female, removing from her sides became white not fertilized grains of roe.
Long development and additional feed have favorably an effect for larvae of mayaichthyses: after hatching they are able to swim and eat actively almost at once, having passed critical for other fishes stage of helpless inactive larva. When fry of mayaichthyses start to swim, they eat also slime of male which takes an active part in cultivation of larvae. The fish, ready to feed posterity, darkens and rises side by side with fish on which young growth sits. It serves as a signal for fry, and they pass to other parent.
Young mayaichthyses do not depend on presence in right moment of any special species of live forage, and the interest of their survival rate is very high: about 80 % of larvae lives up to independence. At the age of two weeks they cease to feed with slime of parents, gradually passing to feeding by small water animals. At this age young small fishes are translucent, colored yellowish with black longitudinal strip. Female drives flight of fry in thickets, and male keeps behind, adjusting fry lagging behind and swimming in sides. But gradually it is more and more difficult to them to keep flight of fry together and sooner or later young fishes one by one abandon parents. At the age of 16 - 18 months young fishes become adults. At them colouring, characteristic for this species is gradually shown, but males will get magnificent fat “crowns” only at two-year-old age. Then at them the reddish shade in colouring will appear.
aspredocichla (Aspredocichla pseudoaspredo)
Order: Percoid fishes (Perciformes)
Family: Cichlids (Cichlidae)
Habitat: South America, rivers of tropical zone.
During evolution various species of fishes of Cichlidae family have developed surprising ways of care of posterity. Among them there are species protecting and fanning them by fins eggs laid on leaves of plants and stones. Some species brood eggs in mouth, keeping strict fast. There are child-loving parents feeding fry with nutritious slime secreting on body, and there are also ones simply “fosteraging” eggs to related species of fishes. But in Neocene among cichlids the nurse aspredocichla has appeared, which, perhaps, has surpassed in child-loving all its relatives.
This fish uses the same way of care of posterity which South-American catfish Aspredo and its neighbour, the frog of Pipa genus have developed independently from each other. At these species of animals eggs develop on skin, and developing embryos are supplied with feed due to parent organism. Blood vessels sprout in skin, and surround grains of roe, supplying them with substances necessary for life.
Externally the aspredocichla has only distant similarity to mayaichthys: at it there are the same short body about 25 - 30 cm long, and wide rounded fins. But constitution of the aspredocichla is more powerful: its body is almost cylindrical; head is large with big mouth. The body of these fishes is colored bluish-green with light yellow stomach. Separate scales on back of the male at movement literally flash by blue sparks. Occasionally same scales are present at females, but in much smaller quantity. The back fin of male is bordered by red strip which becomes even wider and brighter to the moment of spawning.
The body of fishes is covered with large relief scales. However on chest of the female there is an extensive site of scaleless skin. Its role in life of these fishes is really invaluable: it serves for egg incubating.
Aspredocichla lives in wood rivers of South America, preferring to keep among plants. It is a predator eating various small animals – larvae of dragonflies, water beetles, small snails and fry of fishes.
In spawning season colouring of the male is changing: it darkens, and the bottom part of body from throat up to pectoral fins becomes almost white. On background of velvet-black back of the male bright blue flashes seem especially brightly when the male stands in ray of sunlight, falling in water through crones of trees. On his head to time of spawning the big fat cushion similar to helmet grows. The male chooses bush of plant with wide leaves, and clears territory around of it: it drags dust by mouth, breaks off from bush yellowed leaves, tears out stalks of plants in radius about half meter from bush. On bush the male accurately clears some leaves by lips, and then starts courtship demonstrations. The male in courtship dress is remarkable on the background of greenery of bush. Having straightened fins, he swims around of it, from time to time rushing towards to fishes swimming near.
If the met fish is the female ready to spawning, the male starts to entice her to the plant. He swirls around of the chosen female, having straightened fins and from time to time stopping to show itself. Female answers to his courtship, also changing colouring: her back becomes black, and stomach turns white. During courtship games skin on chest and throat of the female becomes pinkish because of dilatation of blood vessels, that it serves as additional stimulus for the male. The female also shows to the male belly full of eggs. The male “leads” her to prepared leaves of plant where spawning takes place.
During spawning eggs are laying on leaves, and male fertilizes them. After all eggs are spawned, the female swims up to the male, having turned to him by side and having bent. Pink color of the bottom part of female body stimulates the following act of reproductive behavior of fishes: male cautiously gathers eggs in a mouth by small portions, and accurately displays them on chest of the female. When one side of the female is covered with eggs, she turns by other side, and the male repeats the actions while all eggs will appear on body of the female. In full clutch at these fishes it happens up to 80 - 100 large grains of roe, and all of them are accurately displayed by the male on throat and chest of the female. At grains of roe there are sticky shells, and they strongly enough keep on her body.
Contact of eggs and skin causes the certain physiological reaction at the fish, as a result of which blood vessels sprout in top layer of skin and close approach to shells of eggs. The skin partly swells, and eggs appear plunged in it at half. Thus not fertilized grains of roe are torn away.
The female with eggs hides in any shelter, and male incurs care of her. He gathers food, cautiously swims up to the female and feeds her, giving food from mouth in mouth.
Development of eggs lasts about one week. At this time the female strongly grows thin, despite of care of the male. The developing posterity exhausts the female, but larvae of this species safely passes critical for many fishes stage of helpless larva.
Fry of aspredocichla is rather large: about 1 cm long. Young growth at once starts to swim and eat actively. First time it is translucent, and on the body there only pigmented specks are appreciable. Later spots merge to a longitudinal strip.
The larvae first some days of life eat slime of parents: in the beginning the care of them is incurred by the male, and the female grows fat, restoring after egg bearing. In case of danger parents hide fry in mouth even then when young small fishes reach length 2 cm.
Young fishes have quite good chances of survival at young age due to care of parents. But rather few from them will live up to maturity - three-year age. The maximal life expectancy of the aspredocichla is about 14 – 16 years.
goby (Calamogobius striatus)
Order: Percoid fishes (Perciformes)
Family: Gobies (Gobiidae)
Habitat: coastal reed thickets of Fourseas.
Picture by Tony Johnes
In Neocene in territory of South-Eastern Europe the huge brackish
reservoir – Fourseas – had appeared literally from nonexistence. Waters of glaciers
had thaw in early Neocene, and flowing of European rivers had formed it. Having
filled in hollows of former Black, Azov, Caspian and Aral seas, this reservoir
isolated from the ocean renders strong influence to the climate of western part
Descendants of some survived European species of fishes inhabit Fourseas. They mainly belong to gobies though in ichthyofauna there are also representatives of other fish families. Fourseas became original “laboratory” of nature: here there is a process of active speciation of gobies, which could occupy various habitats. Among them there are ground predators and hunters for invertebrate, and also various pelagic forms.
The reed goby is one of species inhabiting Fourseas. This fish lives in coastal reed thickets, bordering by wide strip northern coast of Fourseas. The reed goby has perfectly adapted to such residence: it is unpretentious to salinity of water, easily tolerating complete desalination, steadier against lack of oxygen and undemanding to cleanliness of water, surviving even in brown stinky slush among rotting plants. And its appearance and habits literally permit this fish to merge with environmental plants and to become completely imperceptible both for predator, and for catch.
The body of reed goby is long, narrowed to the tail, and rather thick. The length of adult fish may reach 20 cm (male is larger than the female). The fish spends the most part of time, having attached to stalks of plants vertically. The reed goby uses for this purpose abdominal fins which at all species of this family are joined and transformed to strong sucker. Pectoral fins with strong fleshy bases permit to keep for the near stalks.
Living in such conditions, the fish has got excellent cryptic colouring: on brown background there are longitudinal yellowish strips. But masking is not unique protection of the reed goby: spikes of the first back fin are well advanced, and in them ducts of poisonous glands pass.
This fish is a predator eating fry of other fishes and various invertebrates: larvae of insects, crustaceans and leeches. Mouth of the reed goby is rather wide, and the fish can easily seize catch almost in half of its own length. Jaws of the reed goby are supplied with sharp teeth. Eyes of this goby are large and mobile; they provide to predator the full circular field of view.
In spawning season (in the middle of spring) the mouth of this goby turns from fatal trap to cradle: the male incubates eggs in mouth. This is preceded with complex courtship ritual during which males fight for the female, seizing each other by jaws and trying to expel the contender from the territory. The winner male begins courtship: it changes color (becomes almost black with longitudinal white strips), and “sits” on stalk of reed near to the female, showing to her opened fins. The female turns pale and compresses fins as a sign of submission. After that the female spawns eggs, and the male fertilizes it and takes in mouth for incubating. Within two weeks while there is an egg incubating, the male behaves very cautiously and secretively: it eats of nothing, carefully hiding in reeds. Larvae spend in his mouth about two - three days, and then turn to fry and leave a mouth of the father. This goby does not protect fry, and many young fishes become victims of water insects. At these fishes the cannibalism also is advanced.
Life expectancy at this species can reach ten years and more.
Pennonback goby (Vexillogobius hortulanus)
Order: Percoid fishes (Perciformes)
Family: Gobies (Gobiidae)
Habitat: Fourseas, thickets of water plants in estuaries of rivers.
Fourseas became the place of life of set of goby species related to each other, had evolved from several related species. They had survived in lower courses of rivers and brackish lakes formed in ice age at the place of Caspian and Black seas. During speciation at various species of gobies the adaptations, permitting to distinguish representatives of their own species from neighbors, had developed.
One species, at which such adaptations are especially well advanced, lives at sandy shallows, among thickets of eel grass and pondweed. This small fish is difficult for noticing, because usually representatives of this species of gobies dig in sand, waiting for catch: fry and large crustaceans. But if in field of view of hidden fish the congener appears, the lawful owner of territory warns it about its own presence: it opens the first back fin on which there are long fin rays and membrane forming bright “tag”. For such feature this fish is named pennonback goby. With the help of this fin the fish communicates with congeners, confidently distinguishing them among set of species of Fourseas gobies. It is the small fish: the length of body of the adult male does not exceed 15 cm, and the female is even smaller.
Body of the pennonback goby is lengthened, with thick tail and wide tail fin. Due to muscled constitution the fish is able to dig itself in sand literally by one movement. When dregs sediments, the fish appears practically imperceptible: from sand the tip of muzzle, protruding eyes and back jut out only. The back fin at this time is pressed to the body, and it is also imperceptible. But, when the noteworthy prey comes nearer to it, the goby makes sharp throw, snaps it, and instantly jumps in sand again.
The body of the pennonback goby has cryptic sandy colouring: on light yellow background a set of brown speckles is scattered merging to vague striped pattern. On back there is more speckles, and stomach of fish is almost completely white. Eyes of the pennonback goby also are perfectly disguised: the iris of the eye has the same pattern of speckles, therefore the hidden fish looks simply like continuation of sand. Pectoral, back and anal fins also have cryptic coloring.
But, if the goby will decide to warn contenders about its presence, it is difficult to not notice it. Back fin of this fish is very high: its height makes approximately half of common length of fish. Its forward part also has a cryptic “sandy” pattern, but the most part of “flag” at males has contrast and bright color: black with large white spots. On edges of fin the color changes from black to purple, and top and back edges are edged by bright red strip. Females have smaller “flag”, and in its coloring only black and white colors are combined.
This species of fishes is territorial: each fish occupies in the shallow water the certain site overgrown with water grasses, and zealously preserves it against strangers, showing if necessary bright back fin.
This goby spawns eggs in plants, and the laying is looked after by the male. He possesses the leading part in courtship ritual of these fishes. Spawning games take place in the beginning of summer, when water is warm enough. The male clears the chosen bush of dust and snails and tears out environmental plants so, that the bush appears surrounded with a strip of clean sand (a specific epithet “hortulanus” means “gardener”). After that courtship demonstrations begin: male entices females, showing them bright back fin. If the female has become interested, the male conducts her to the prepared plant. As a sign of absence of aggression the male “shivers” slightly lowered back fin. Courtship games pass roughly, being accompanied by “races” and easy lip biting. After all eggs (in clutch there is about 300 grains of roe) appear spawned, male expels female and starts to protect clutch. He preserves it against various fishes and large scuds, driving them away by impacts of head. Eggs develop about five - six days, then larvae swim out, and the male, having cleared a bush, starts to entice new females. For a season he takes part in spawning up to three times. Young fishes become sexual matured at the second year of life.
In winter when water at northern coast of Fourseas becomes cold, this fish leaves on depth and hibernates, having dug in sand. At this time pennonback gobies are inactive and form numerous congestions. In areas of rocky bottom fishes hibernate in deep cracks. At the southern coast of Fourseas pennonback gobies keep activity almost the year round.
heterogobius (Heterogobius batophilus)
Order: Percoid fishes (Perciformes)
Family: Gobies (Gobiidae)
Habitat: Atlantic ocean, temperate latitudes, depth up to 2 kilometers.
Picture by Timothy Morris, colorization by Alexander Smyslov
Исходный рисунок Тима Морриса
At the boundary of Holocene and Neocene ecosystems of open
ocean had suffered great losses because of “plankton accident” – sharp decrease
of number and variety of plankton organisms caused by catastrophic changes in
ecosystem of planet. As the result inhabitants of open ocean, and also species
passed a part of life cycle in plankton had strongly suffered. Especially strong
damage was put to deep-water fauna for which plankton and pelagic animals of
top layers of water were a unique source of organic substances.
In Neocene become empty depths of oceans appeared populated again. Among the most successful immigrants in the world of depths there were gobies. These inhabitants of benthos moved down in depths along the continental slope, and then had developed pelagic habit of life already as deep-water animals. One of such gobies is the abyssal heterogobius living in Atlantic.
This species has received the name (literally meaning “the different goby”) because of sharp distinction in shape and habit of life of male and female. The female of abyssal heterogobius has the shape partly similar to shape of deep-water anglerfishes (Lophiiformes) of Holocene epoch. Its length is about 20 cm, from which the head with huge mouth amounts about third. The mouth of this fish is oblique upwards and can be extended to short tube – jaw bones of fish are connected by elastic membrane. Teeth of this goby are long, needle-shaped and bent hook-like – it is easy to keep catch by such teeth. Heterogobius eats pelagic fishes, octopuses and other invertebrates.
Eyes of the female of heterogobius are very small, and sight of fish is rather bad. Sight is practically useless at life in depth, but sharp sense of smell and rich circuit of lateral line channels advanced on head quite replace it to the female of heterogobius. Nostrils of fish are surrounded with thin leaf-looking outgrowths of skin dissected at edges. This adaptation considerably increases olfactory surface of nostrils. The body of fish is covered with naked slimy skin of grey color through which large blood vessels are visible. On stomach skin is thin and easily extensible, and through it interiors of fish are visible. The female of heterogobius can swallow catch of weight approximately identical with it.
Unpaired fins of female of deep-water heterogobius are short and rounded. Pectoral fins, on the contrary, are long (their length is approximately equal to the body length of fish) and fanlike. Having stretched them, fish passively soars in thickness of water, waiting for approach of catch. Fin rays are connected by thin delicate membrane.
The male of heterogobius considerably differs from the female by shape and way of life. It represents a creature about 2 cm long attaching to gills of the female. It sucks blood of the female and completely depends on it by way of feeding and development. Through blood it receives from the female hormonal signals about her physiological condition, and at the readiness of the female for spawning it produces sperm. The male is, in effect, the individual which early has stopped the growth. These fishes hatch from eggs having no gender, and the gender of maturing fish is determined by its subsequent life. The single individual always turns to the female. The growing female emits the special substance involving young individuals of this species in water. Using such trace young sexless fish searches the individuals turned to females.
The individual, managed to attach to the female turns to male under influence of hormonal signals coming from the blood. Hormones of the female suppress the “female” program of development of young fish, and it turns to male. Hormones of the female also suppress growth of the individual attached to it, and the male stays dwarf. Its contribution to reproduction is also important, but the maintenance of the high-grade large male in conditions of limited food resources is biologically inexpedient, and it turns to the true appendage on the body of the female, able only to breeding.
Hooked teeth of the male allow it to keep for the branchial arch of the female. In development the body of male deeply degenerates: in adult condition it is blind, lack of fins (from them only bristle-like rudiments of fin rays remain), and organs of lateral line also disappear at him. Gullet of the male turns out forward and sticks to gills of the female. This way blood of female does not get in water through branchial apertures of the male, and does not involve predators. Operculums of male are reduced, and at movement of the female water freely wash his gills. In such condition he is not able more to independent existence though it does not adhere to the female body as it was at deep-water anglerfishes of Holocene epoch.
Abyssal heterogobius bears eggs in mouth. Female regularly spawns portions of 300 – 400 eggs. The breeding cycle of this species is connected not to seasonal changes which are not felt in depths of ocean, and with physiological condition of adult female. Female at once grasps eggs laid in thickness of water in mouth and bears them in branchial cavity during 3 – 4 months, not feeding thus. At the moment of spawning male shows the certain activity: it bends body, penetrates into branchial cavity of female, and lets out soft roe, fertilizing eggs placed in mouth of the female. During the bearing of posterity the female grows thin. At this time she can reduce feeding of the male – blood vessel nourishing him grows thin and degenerates. It happens, that male not receiving an additional feed during the egg incubating of the female, perishes. But in this case any other young fish of suitable age and physiological condition can replace him.
The young growth leaves parental mouth, and leads independent life in top layers of water rich in forage. As young fishes grow, they settle deeper.
mudskipper (Batrachophoca gigantea)
Order: Percoid fishes (Perciformes)
Family: Mudskippers (Periophthalmidae)
Habitat: Hawaii, littoral zone between reeves and the coast.
Picture by Fanboyphilosopher
Mudskippers are fishes unusual in many respects. By their
way of life they show that fish is capable to develop even the environment atypical
for its ancestors, if it will have no competitors. They have occupied mangrove
swamps – a specific inhabitancy in which they did not have competitors, because
amphibians do not suffer salt water. Mudskippers became very similar to frogs
in some features of appearance and behaviour, but all the same they still are
fishes. In epoch of late Holocene congelation many species of these fishes had
died out, as the climate became much colder, and the areas of mangrove swamps,
suitable for inhabiting of these fishes, had been reduced. Mudskippers had survived
only in Southeast Asia where areas of mangrove forests had kept.
In early Neocene active adaptive radiation and settling of descendants of few survived species of these fishes had begun. Mudskippers had began to develop newly forming mangrove forests actively. One species of these fishes had developed an interesting way of settling – it began to settle on floating trunks of trees. In parallel this species had developed the ability to brood eggs in mouth that had allowed it to “tear off” the coast completely and to turn to true sea traveller. Descendants of “wandering” mudskippers had settled mainly at the islands of tropical zone of Pacific Ocean to the south of equator. In northern hemisphere they had only one successful attempt of settling, but these fishes had mastered this opportunity in fullest degree: they had occupied Hawaii. Development of new extensive habitats was accompanied by active speciation, and as a result of it some related species of these “amphibious” fishes differing from each other in behaviour and ecology live at the coasts and reeves of Hawaii.
Due to protruding eyes and the propensity to live at the shoaliness these fishes are very similar to frogs externally. But nevertheless one of species of Hawaiian mudskippers is difficult for confusing with frog: this is a true monster of about one meter long, weighting of 25 kgs, the largest species of mudskippers ever living on the Earth. It is possible to confuse from afar these animals laying at the sea shoaliness with small seals; therefore they are named seal mudskippers. Their name Batrachophoca means “frog seal” and precisely reflects the appearance and habits of these creatures. Seal mudskipper is too heavy to jump; therefore it simply creeps at the littoral zone with the help of strong pectoral fins, helping to itself with pushes of tail. And its glittering slimy skin and head with wide mouth and protruding eyes give to it any similarity to frog. But operculums and fins normally advanced at this one precisely specify it as a fish.
Seal mudskipper has very big head with wide mouth and strong jaws. Above thick upper lip two fleshy short wattles directed down stick out. The male’s head is very large and looks disproportionate relatively to forward part of body. On male’s nape there is a pair of bone lumps which are used in courtship tournaments.
This fish is a predator like all its relatives. Due to sharp sight this huge mudskipper notices dangers in good time and hides in water. And mobile golden eyes with round pupils, sticking out at top of head, provide to it the complete circular field of view. Under water this fish also searches for prey with the help of sight. The jaw grip at eal mudskipper is very strong: this predator can easily splinter head of fish about half meter long by one bite and swallow it entirely.
The lengthened body of seal mudskipper is dimly colored: on brownish-olive background dark grey irregular-shaped spots are scattered; on back they are more numerous, than on stomach. It makes fish not too appreciable from apart. But the seal mudskipper not always needs to be imperceptible: each fish of this species occupies the certain territory and protects it from relatives. For the prevention of territorial conflicts fishes display visual signals to each other if the border of territory appears broken. For this purpose fishes use first back fin appreciable from apart. It is high, has short basis and is similar to flag in colouring – on white background large black spots are scattered. Raising this fin vertically, fish signals to contenders that the territory is occupied. At males back fin is higher, rather than at females, and there are more spots on it. In near fight fishes use one more means of intimidation of the opponent: conflicting fishes stretch in sides and completely straighten operculums. Then red spots on white background become appreciable; they are located on soft tissues and at quiet fish are hidden in skin plicas. If demonstrations had not conceived effect, fish expels the contender from the territory by impacts of head and tail.
Seal mudskipper eats all species of animals which can be found in littoral zone. It has a special way of getting of food, effectively using opportunities of the changeable habitat. This fish differs in complex building behaviour: each seal mudskipper builds for itself deep hole for life, surrounding it with bank of stones and sand. During the inflow fish creeps away from hole to the shoalinesses where it lays, having put out from water half of body, and displays back fin to contenders. In addition to the living hole of about half meter depth, fish makes in the territory some trap holes of about one meter depth. During the outflow fishes, crabs and small octopuses had not time to leave littoral zone gather in them. Seal mudskipper eats them: during outflow seal mudskipper creeps from one trapping hole to another, renews them, pulling out stones fallen inside by mouth and re-building their walls. Also it catches the fishes and other sea animals caught in trap.
The courtship season at these fishes stretches for all year. As a rule, around of male’s territory there are some sites where females live. The female at this species is smaller, rather than male, and her head is not so large. The female ready to spawning creeps to male’s territory, expressing the submission by her pose: she keeps back fin lowered to back, and makes characteristic “nodding” movements by head. Male displays to her the force and the good physical shape, having opened a back fin, having inflated operculums and having risen on strong pectoral fins. If male can not keep such poses for a long time (that means it is weak physically), female starts to rise back fin in reply to his court, displaying thus the counter aggression and unwillingness to submit. Such continuation of ritual can result in transient fight, and the female returns to her territory.
Well advanced male, having shown the physical shape, invites female to follow him, pushing her by sides to the living hole. Here female spawns very large eggs; male fertilizes them and at once takes in mouth. In clutch of this species it may be up to 300 yellowish eggs of small cherry size. Brooding eggs, male eats of nothing and becomes very aggressive. In posterity brooding time its colouring changes: head blackens, and spots on back fin become larger. It rushes on any of the relatives appeared nearby, and strikes them strong impacts by tail and sides. It happens, that male furiously attacks even the birds having rest in his territory.
The young ones hatch from eggs in one week after spawning. The first days of life young mudskippers stay in male’s mouth, while their yolk sac is resorbing. Then he lets them out in the living hole, and does not care of them any more. After brooding of posterity male is fattened for about one month, and starts courting the females again. For one year the spawning cycle repeats 4 – 5 times.
Young fishes search to themselves for shelter in a littoral zone – they frequently become prey larger congeners. To grow up to adult condition and to start spawning it is needed of about six years for young seal mudskipper. For this time the majority of fishes of this species becomes prey of various predators. Only quickness rescues them from various dangers, but the adult fish has almost nobody to be afraid due to size and ability to live in places where large predators can not reach. Seal mudskipper can live over 30 years.
Sargassum large-toothed blenny (Algoblennius inconspicuus)
Order: Percoid fishes (Perciformes)
Family: Blennies (Blennidae)
Habitat: Atlantic Ocean, thickets of floating algae near New Azora Island.
In human time congestions of Sargassum algae (Sargassum) floating near ocean surface formed a favorable inhabitancy for various animals. Among these creatures it was possible to meet original descendants of shore animals living actually in open ocean.
At the boundary of Holocene and Neocene, when character of sea currents had changed, the quantity of floating sargassum algae has decreased because of cooling of ocean water. But in Neocene, after stabilization of conditions and global warming, fields of seaweed have again plentifully filled in the central part of Atlantic. They grow in huge whirlpool which is slowly “twisting” by warm Gulf Stream current to the north, and its cold “double” Anti-Gulf Stream flowing along the European coast to the south.
Thickets of floating algae are the specific environment: here it is not important to be able to swim quickly, but ability to creep and mask is very important. Therefore fishes living in this place, in the majority are very bad swimmers. But almost all of them are skilful masters of masking.
Sargassum large-toothed blenny is the typical inhabitant of floating algae. At it there is rather short and high body. General length of fish is about 20 cm at height up to 10 cm. The tail fin is almost joined with anal and back fins; it is rather wide and fan-shaped: it is the feature indicating that the fish swims reluctantly.
At this fish there are large head and big mouth slightly oblique upwards. Eyes of this blenny are directed forward: sight of this fish is three-dimensional. Eyes of sargassum large-toothed blenny badly distinguish colors, but are especially sensitive to movements: so it easily defines presence of small animals have hidden among algae. These features tell that sargassum large-toothed blenny is a gluttonous predator in the algae world. It is an ecological analogue of sargassum anglerfish (Histrio histrio) from the order Antennariiformes. And external similarity of these species is the result of convergence.
One more feature of similarity of this blenny with sargass anglerfish is the special structure of pectoral fins. They have expanded fleshy bases due to what can grasp sarments of seaweed. As a rule, the fish keeps in thickets, having pressed sarments of algae by fins to sides. In case of necessity of moving to small distance, the fish creeps among algae, moving them apart by fins, as if by paws.
Similarly to Holocene algae inhabitants, sargassum large-toothed blenny differs in original colouring including features of camouflage: its body is colored yellowish – grey and is covered with dark brown irregular-shaped spots. Above eyes of fish there are leaf-looking outgrowths of orange color with the rough white edges, simulating dying off parts of seaweed. In back fin forward beams are lengthened, on them there are separate skinny “tags” strengthening masking develop.
Sargassum large-toothed blenny is a solitary predator. Due to sharp teeth in forward part of a mouth it easily can kill fish or shrimp of half of its own length. Usually this fish waits catch, motionlessly sitting among seaweed, and “coming to life” when the possible prey will come nearer almost in an emphasis.
Each fish of this species suffers neighbours near to itself only in spawning season. Spawning at these fishes proceeds in couples. Male is larger than female; it also differs in brighter colouring and advanced outgrowths above eyes (frequently near large outgrowth there are some smaller ones). Usually male himself interferes in possession of females, and chooses to itself the spawning partner. Per one year there are about three clutches, usually the spawning occurs in the summer and an early autumn.
The strong parental instinct is peculiar to these fishes. At this species the male cares of posterity: it bears eggs in a mouth, touching and ventilating them. At this time it becomes more cautious, and hides in thicket of seaweed. The egg incubating (in clutch there are about two hundred rather large grains of roe) lasts about one week, and two or three days the young growth is hidden in mouth of the male. Later young fry leave its mouth, and next time they can return there only as a catch: the male does not care of fry, and at an opportunity willingly will to have eaten the neighbour of the smaller size.
bathycrystallichthys (Bathycrystallichthys unlucens)
Order: Percoid fishes (Perciformes)
Family: Blennies (Blenniidae)
Habitat: Pacific Ocean, depths from 500 up to 1000 meters.
Picture by Timothy Morris
Various blennies were characteristic coastal fishes of Pacific
Ocean. Some species of these bottom-dwelling fishes lived in cold “forests”
of brown algae, and others preferred coral reeves. Wide area of family and high
ecological plasticity had permitted this group of fishes to survive during mass
extinction and to occupy forming ecosystems of early Neocene epoch. At the extinction
of deepwater ichthyofauna after “plankton accident” blennies had started to
develop ocean abyssal zone. Among them strange species like jellyfish
blenny (Medusoblennius holopelagicus) had evolved. Some species of blennies
had penetrated to deep water along the continental slope and as already true
deep-water fishes had “taken off” bottom, developing thickness of water.
Rather large pelagic predator, non-glowing bathycrystallichthys belongs to blennies. It is a fish about 40 sm long with deep body, large head and pointed tail. Unpaired fins border the body of this fish as one continuous strip. Pectoral fins of bathycrystallichthys are fanlike; they have thin long fin rays and transparent membrane. Having stretched them, fish passively soars in thickness of water waiting for approaching of prey.
The body of bathycrystallichthys is absolutely lack of natural pigmentation and is translucent – if at the depth where this fish lives, there is a good lighting, through skin and aqueous muscles it would be possible to see its interiors and a skeleton.
Bathycrystallichthys has large head with well advanced jaws and big eyes. Very sensitive eyes of this fish catch the slightest flash of light emitting by deepwater animals. Like to almost all inhabitants of deep, bathycrystallichthys is a carnivore. Its teeth are thin and numerous; they jut out from mouth of this fish, even when the mouth is closed. Bathycrystallichthys eats various invertebrates, obviously preferring soft-bodied cephalopods and fishes. Occasionally this fish catches jellyfishes and swimming worms, but never hunts crustaceans.
Many fishes living in depths have their own organs of luminescence. They eitherr develop the substance luciferin which shines at the reaction with luciferase enzyme, or give a shelter to symbiotic luminous bacteria in special organs and use their ability to glow. Bathycrystallichthys is not able to glow independently and has no symbiotic bacteria. Nevertheless, it is not lonely during the hunt in depths. The success in attraction of prey at this species depends on strange symbiosis with special species of annelids, stomach lightworm (Gasteronereis luciferus). This worm is capable to glow very brightly, and its light, clearly visible through translucent body of fish, involves prey. The way of coexistence of fish and worm is interesting: worm lives partly in its stomach, having fixed by the back end of body for branchial arches of fish, as if by anchor. Prey is shared between symbiotes: part of forage had got in stomach is eaten by worm, and other part is digested by fish. If bathycrystallichthys eats large prey and swallows it entirely, worm does not suffer from it. It has firm covers of body, and does not endure inconveniences from existence in hardly filled stomach of fish.
Bathycrystallichthys had developed the original way of care of posterity: during spawning female pastes a cluster of small transparent eggs on chest and stomach of the male. He fertilizes eggs and bears them up to fry hatch. Young ones of these fishes develop in top layers of water. The probability of meeting of larvae of symbiotic worms, which attach to gills of young fishes and gradually develop, is greater here. Growing up young fish migrates to depth, and worm gradually starts to produce glowing substance. When the worm perishes for any reasons, fish starts to live half-starving and also can die: in depths of ocean the probability to meet larvae of stomach lightworm is close to zero.
The idea about existence of this species of fishes is proposed by Simon, the forum member.
European snakefish (Serpentozoarces europaea)
Order: Percoid fishes (Perciformes)
Family: Eelpouts (Zoarcidae)
Habitat: rivers and swamps of Central, East and North Europe, temperate and cold climatic zones.
Picture by Alexander Smyslov
Seas of North Europe underwent significant changes at the
boundary of Holocene and Neocene. The congelation had held down the north of
Eurasia by continuous
ice cover, having buried under it Baltic Sea and coast of Northern Sea (in
ice age the ocean level had decreased, and the sea had substantionally receded).
Inhabitants of sea coasts had been compelled to adapt to changing conditions,
or died out. The part of species had receded following the sea, and the another
part had passed to life in fresh water of rivers and lakes. Among survived
species there were various crustaceans and some fishes. When climate had
changed again, these species had occupied new habitats already in new quality.
One of such fugitives from a glacier lives in fresh waters of Europe – it is European snakefish, the freshwater species of eelpouts. Ancestors of this fish had completely left the sea in glacial epoch at the boundary of Holocene and Neocene – they appeared are off from northern seas by coming glaciers, and compelled to adapt to inhabiting in fresh water. The majority of sea fishes can not make it because of problems in development of eggs and fry. But eelpouts had easily made it – they belong to viviparous fishes, and in their life cycle there is no the stage of egg sensitive to change of external factors. Therefore right till some millenia populations of eelpouts completely passed full cycle of development in fresh water had appeared in Europe.
The snakefish has kept features of appearance characteristic for its ancestors. It is a fish more than one and half meters long with reduced unpaired fins which edge its back and tail as a continuous narrow border. In forward part of back fin there are some spikes with poisonous slime serving for protection against enemies. Pectoral fins have fleshy bases, and fin rays are strong and elastic. With their help snakefish pushes from roughnesses of ground during the movement on land and makes the way through thickets of underwater plants.
The skin of European snakefish is naked, but covered with a layer of viscous slime. It prevents the drying when fish appears on land. Besides the skin of snakefish is penetrated with a circuit of capillaries, and through it fish receives a significant part of oxygen. Colouring of skin is spotty, green with black “marble” pattern; stomach is white.
Head of snakefish is flat and wide, with slightly bulging eyes and wide mouth. Teeth are pointed and thin.
Snakefish settles in marshlands where small reservoirs alternate with sites of land. The majority of fishes does not live in such places, therefore snakefish is almost out of competition. In summer reservoirs, in which it settles, may dry up. But snakefish is well adapted to such difficulties. It can easily creep overland, respiring with the help of skin. This fish creeps pushing by bends of body and helping itself by pectoral fins. Snakefish can creep within several days in searches of water. If weather is too hot, fish hides in shady place and may escape from heat even in holes of rodents.
Snakefish is a predator. In water it eats small fish, frogs and crustaceans. Frequently snakefish traps them in shallow water, having dug in ground, or having hidden among plants. Also this fish can catch sluggish insects, snails and earthworms on land.
This species of fishes has kept ability to vivipary had helped to survive to its ancestors till the ice age. Pairing at snakefishes takes place in autumn, and female hibernates, while in its ovaries the posterity develops. Young ones of snakefish receive an additional feed – products of secretion of female’s ovoducts walls. Due to it the posterity of snakefish is born already completely developed and ready to independent life. In spring when the high water comes to an end, the female gives rise to about ten large young fishes, reaching approximately one fifth of the length of female.
spiny eel (Psammomastacembelus echidnops)
Order: Spiny eels (Synbranchiformes)
Family: Spiny eels (Mastacembelidae)
Habitat: Tanganyika passage, sandy shallows in river estuaries.
Mouths of rivers are a fine place for hunting. Here on sandy shallows there is a set of edible live beings – small fishes coming from the sea, inhabitants of the river and dead bodies of ground animals, carrying away by river. One of most favorable strategies of life in such conditions is to rise a head against current and to wait patiently. Usually expectation is renumerated rather quickly: current frequently takes out in sea fry, larvae of insects and small animals had fallen in water.
If to look narrowly at the surface of sand of river shallows where fresh river water meets with salt sea one, in some places it is possible to see how sand moves. In it the superficial, quickly smoothing down groove meanders: under sand certain oblong flexible body creeps. From time to time on surface of sand in cloud of dregs the head of the sand inhabitant appears. This creature is a coiled fish about half meter long with top jaw sticking forward and tiny eyes – the sandy spiny eel.
Spiny eels are characteristic fishes of Africa and Southern Asia. They are similar to eels, but spikes on back are the rest of prickly back fin, characteristic for percoid fishes. After Great Split of Africa and separating of the Zinj Land from it these fishes, especially numerous in Great African Lakes, partly had died out, and partly had survived, having receded in the rivers. Some species, able to endure salt water, had mastered life in lower reaches of rivers. The sandy spiny eel is one of such species.
Similarly to many representatives of family, this species is digging fish as if “swimming” in thickness of sand, digging burrows with the help of firm top jaw extended forward. In thickness of sand the most part of life of this fish takes place, and it has dint on its appearance: eyes of sandy spiny eel are tiny, “weak-sighted”, with very thick cornea. Fish is very short-sighted, but as indemnification for bad sight at it the sense of smell is excellently advanced. The sandy spiny eel frequently sits in ambush, having dug in sand so, that only eyes and nostrils jut outside. This fish is bad swimmer for long distances: all fins of it are very short. But the body of this species is powerful and muscled, band-shaped in back part – with the help of wide tail this spiny eel easily digs for itself road in sand and in case of danger instantly can dig in it. Colouring of its body simulates the color of environment: creamy-white body with “marble” beige pattern and separate black and brown speckles.
Sandy spiny eel is a predator. It hunts small fishes and shrimps from an ambush in sand, catching them by sharp throw. Trapping catch, fish is dug in the uppermost layer of sand and exposes outside only a head. Sharp sense of smell prompts the fish when in immediate proximity from it crab or shrimp runs on sand. Then sharp throw instantly follows, and catch convulsively beats in jaws of fish. Having crumpled with crunch its catch by jaws, the spiny eel swallows it entirely, and continues the waiting in sand. It is not frightened even with outflow: this fish easily sustains recession of water, and perfectly feels in moist silt sand in succession of many hours. If the sun has dried the top layer of sand, this spiny eel simply digs in moist layers in depth, waiting for inflow.
But being well adapted to life in estuaries of rivers and at the coast of Tanganyika passage this species of fishes nevertheless is the descendant of freshwater fishes. And it has had an effect in features of biology of sandy spiny eel - it spawns in river headstreams. At night, with the highest inflow, these fishes leave sand and with a tidal wave swim to river mouths. In outflow they dig in river bottom and some time get accustomed to fresh water where they should execute the duty to the future generations. In colouring of fishes there are remarkable changes: from “sandy” it becomes striped and contrast - on light background green vertical strips appear, on tail forming irregular pattern. Gradually fishes start to gather in schools and to move upstream, choosing for this purpose night and richest thickets of plants along riverbanks. For some nights they reach river upstreams (rivers of the East-African subcontinent are short) where in thickets of marsh plants spawning takes place. Males rise in rivers more unanimously and faster: it is connected with features of their courtship behavior. Usually one female spawns with two - three males. Fishes rise to surface of water, wriggling and even plaiting together. They get into thicket of long-stem plants (water moss, bladderwort, or others small-leaved plants) in shallow water, and spread eggs on them. After spawning females quickly leave the rivers and swim down to the sea and males remain to expect new females.
In 3 days from eggs transparent larvae hatch. About two weeks they hide among plants, and then start to leave plants and to search for food in silt. Approximately to half-year age (at length about 20 cm) they begin movement from river upstream to river mouth. At two-year-old age ones will have the luck to survive, will return to the river for spawning.
Angler sole (Lophiosolea piscatorius)
Order: Flatfishes (Pleuronectiformes)
Family: Soles (Soleidae)
Habitat: Tanganyika passage, mangrove thickets and sandy shallows; also it can come in river mouths and to live some time in fresh water.
During ecological crisis at the boundary of Holocene and Neocene among sea fishes such species had survived, which had an opportunity to exist in ecosystems, less suffered from accident – in benthos and rivers. Therefore there was the chance of survival at plenty of shallow flatfish species. Though fishes of this group spawn in sea water, and the larva spends first days of life in plankton, they quickly pass this stage and early begin able to live even in completely fresh water. In rivers there are different flounder species, in tropics among them there are soles (Soleidae) to which the angler sole belongs.
This species had kept the body shape typical for family: short rounded head and sharp tail. Usually these fishes are right-hand, though about 15 - 20 per cents of population are “lefthanders”. The length of body of this fish is rather small – about 20 cm. Mouth is skew, eyes are located this kind: one is near a corner of mouth, another one is near tip of muzzle. Eyes are large, raised above body surface on small eminences. They stick up from sand when the fish is dug in it, trapping catch. Colouring of the eyed side of body can vary over wide range: from dark-grey up to yellowish and almost white, with spots or without spots depending on color of bottom. Usual colouring of fish in rest is yellowish-grey with randomly scattered black spots. The male is smaller than female, at him there are more oblong body and large head.
As against to related species passively expecting when catch itself will come nearer to the distance of exact throw, this sole can allure catch, for what at it the original adaptation is developed. On pectoral fin of the painted side of body the first ray is not attached to others. It can move independently of others due to several muscles in its basis. On the end of this fin ray there is a rag of fin membrane, alluring small fishes. The pectoral fin is shifted forward to middle of branchial cover. On the eyeless side of body skin is light pink or white, the pectoral fin is strongly reduced: from it some fin rays are kept. Tail fin has partly grown together with back and anal ones.
The angler sole prefers to keep on sandy shallows in rivers estuaries and at coasts of passage. It easily maintains desalination of water and even comes into lower reaches of rivers. But for spawning these soles leave shallows in river estuaries and swim to coast of passage where water has normal salinity. The male begins courtship for the female, actively chasing her; it is not a rarity when at once two males chase for the female. Male snaps front edge of anal fin of female, and does not release it for some time, being dragged behind the female on the bottom. When the female lies down on bottom, the male releases her fin and “stands” above her, driving other males away and even rushing to fishes of other species.
For egg spawning pair of fishes for a short time leaves bottom, quickly emerges almost to the surface of water, simultaneously “throws” eggs and soft roe and as promptly falls on a bottom and buries in sand. Their care of posterity comes to an end at this moment.
Larvae leave egg shells in two days, in one week they turn to translucent asymmetrical fry and pass to life of adult individuals. First time fry eats small crustaceans and worms. At four-monthly age they reach length of 7 - 8 cm and then at them the bait of “fishing tackle” starts to form.
Sexual maturity comes at the age of 8 - 10 months at body length about 15 cm. Life expectancy is no more than 5 years.
Large-headed sole (Cryptosolea macroceps)
Order: Flatfishes (Pleuronectiformes)
Family: Soles (Soleidae)
Habitat: Atlantic Ocean, thickets of algae to the south of New Azora island.
In Neocene circulation of ocean currents has undergone some changes: in Atlantic two circulations of water masses have appeared. One of them is located in southern part of ocean, and the second one is in the top water layers to the south-west from New Azora island - top of the Middle-Atlantic ridge. Here the water from depth sated with phosphates and nitrates rises to surface of ocean along slopes of mountain ridge. It causes plentiful growth of bushy brown algae similar to Sargassum algae of Holocene epoch. Floating algae is a fine habitat for set of species of fishes. Basically, descendants of coastal species whose fry and larvae were brought here by currents, live here. Among them even the special species of the flounder has lost connection with bottom habitats have appeared.
Large-headed sole is this flounder living among seaweed. At it there is a wide body with acute tail. Tail fin as such is not present, back and anal fins grow together on the pointed back end of body: it is a common attribute of family. Certainly, it is not the attribute of good swimmer, but this flatfish species, as well as the majority of inhabitants of algal “fields”, does not like to swim long and quickly. Length of large-headed sole is up to 25 cm.
On unpaired fins (back and anal) some forward beams are transformed to finger-shaped outgrowths with which help the fish keeps in plant thickets. Large-headed sole swims badly, but dexterously moves among plants, using these increased fin rays. Tips of fin rays have turned even to a semblance of claws, helping this fish to cling to seaweed. The fish spends a significant part of time, having strongly grasped by “fingers” for thalli of seaweed. Art of masking allows to large-headed sole to exist in such conditions extraneous to flounders at first sight. The fish is a predator, and traps catch (crustaceans and small fishes), masking among seaweed. Eyeless and eye-having sides at this species of fishes are colored equally (it makes large-headed sole the exception among flounders) reddish-brown with orange-yellow and dark-brown spots imitating light and shadow among seaweed. In case of necessity the fish easily changes color from light yellow up to almost black. Such masking permits fish to expect possible catch, not involving undesirable attention.
The head of fish is rather large, the most part of it a sliding mouth extending to long tube accounts. When catch of suitable size appears close, the fish by lightning movement extends mouth, and sucks in it the prey. Eyes of this fish are large, located on one side of body. They strongly stick up above the surface of body, and are similar to eyes of frog. Due to such eyes this flounder has the good circular field of view. Almost identical amount of right- and left-sided fishes in population is typical for large-headed sole.
These fishes breed similarly to all flounders: they spawn in water and not care of posterity. Male is smaller than female, but during courtship ritual it behaves more actively than female: male chases her, nestling to her by eyeless side. The male always chooses the female by its own similarity: it prefers female at which eyes are on the same side of body. In spawning season the male becomes brighter, and he shows to female bright colouring of the eyeless side of body, “hovering” above the female. For one breeding season (in warm season, since April till October) the female of this species can spawn eggs up to six - seven times, and single fertility makes about five thousand small grains of roe.
Black-winged cyclops flounder (Disparopsichthys cyclops)
Order: Flounders (Pleuronectiformes)
Family: Cyclops flounders, or Unequal-eyed flounders (Disparopsichthydae)
Habitat: tropical areas of Pacific Ocean, top layers of water.
In epoch of ecological accidents smallest inhabitants of Earth, plankton organisms, frequently suffer. But plankton community is one of the most important thing for the biosphere of Earth. The phytoplankton provides restoration of stocks of oxygen in atmosphere in greater degree, than tropical woods. And well-being of zooplankton infringes interests of the majority of inhabitants of ocean in various degree: some species completely depend on plankton as food, and others spend a part of life cycle in plankton. Therefore during mass extinction of plankton organisms at the boundary of Holocene and Neocene ocean inhabitants of thickness of water had died out after them, and in early Neocene their ecological niches appeared free. Therefore at once many species have started to take their place in ecosystem of ocean.
Among new inhabitants of open ocean representatives of various groups had appeared, but nevertheless flounders seem the most unexpected inhabitants of thickness of water. Despite of their specialization to bentonic habit of life, these fishes spend a part of life, soaring in thickness of water at the stage of fry. When in sea a plenty of plankton had appeared again, some survived species of flounders from coastal waters more and more “were late” at the stage of fry, and soon completely passed to life in thickness of water. So the separate family of flounders living in thickness of water had gradually evolved. But singularity of these fishes consists not only in habit of life, but also in anatomy: at these flounders there are eyes of different sizes. Such phenomenon in human epoch was known at some squids, but at vertebrates it was showed for the first time. However, flounders just differ in asymmetry of body; therefore eyes of different sizes do not look especially unnaturally at them.
Among these flounders there are approximately fifty-fifty left- and right-sided individuals. One eye has remained at these fishes on the side of body peculiar to it. It is small-sized and also looks directly upwards. But the second one moving in process of individual development to other side of body, as if had stopped halfway, having remained at the stage, characteristic for flounder fry: it is on the middle line of body. And this eye in many respects determines unusual and monstrous shape of these flounders. It is big, round, and also directed right forward. Therefore flounder also has received the name (in translation from Greek “Cyclops” means “round-eyed”). Due to the size this eye provides the excellent field of view. Besides it is mobile and can turn in eye-socket.
Mouth at all species of cyclops flounders is wide; jaws are supplemented with sharp teeth: these fishes are predators. Jaws are able to be slightly extended forward when the flounder grips catch – small fishes and large plankton crustaceans.
The black-winged cyclops flounder has short and wide body. This fish swims rather slowly, flapping by lengthened forward rays of back and anal fins. But if it is necessary, fish can swim with the help of tail fin waves. For protection against enemies the body of cyclops flounder has a line of small bone scutes with spike in the middle, placed on middle line of body along the eyed side. The blind side of body at these fishes is colored bluish color with strong shine. It masks fishes from an attack from below: the blind side merges with patches of sunlight on the water surface. The eyed side of body at cyclops flounder is motley – grey with brownish spots. On forward part of back and anal fins there are longitudinal dark grey strips. During spawning period at males of this species stripes on fins become velvet-black, and is had determined the specific name of fish.
This fish spends a lot of time above sea shallows, gathering to schools of some tens fishes. It feeds mainly by small fishes, shrimps and large plankton organisms.
The spawning takes place in top layers of water well heated by sun. It repeats two times per one year, and in warm years it may happen up to three times. During courtship rituals males gather to unisex flights. They “soar” under the surface of water, having opened fins, and involving females by black strips on fins, well appreciable in sunlight. They chase females ready to spawning by flights, simultaneously fertilizing eggs spawned by it. For one spawning the female can spawn up to two millions tiny grains of roe. Similarly to all flounder species this fish does not care of posterity.
Young fishes become sexual matured at the third year of life, and general life expectancy of this species makes up to 20 years.
Far from coast the close species of this family lives: flying cyclops flounder (Pterodisparoptichthys prolongisomus). It differs from black-winged cyclops flounder by features of anatomy: at it one abdominal fin is strongly advanced, and the tail fin has grown together with back and anal ones, as at soles. This flounder is more specialized to pelagic habit of life, than black-winged cyclops flounder. It swims quickly, flapping, as if by wings, by abdominal fin and muscled forward part of back fin which is detached from other fin. Like black-winged cyclops flounder, it is a schooling fish gathering to huge schools numbering hundreds and thousand of individuals. This fish never swims up close to coast.
gurnard (Pelagotrigla vespertilio)
Order: Goblingfishes (Scorpaeniformes)
Family: Gurnards (Triglidae)
Habitat: Tanganyika passage, superficial layers of water.
Mass extinction at the boundary of Holocene and Neocene, caused by natural cataclysms, has put serious impact to population of plankton organisms. Sharp decreasing of their number has entailed extinction of plenty of species of fishes depending on them. Basically they were pelagic fishes. Inhabitants of sea shallow waters and rivers were luckier: ecosystems in which they lived, not so much depend on plankton, as communities of open ocean. Therefore in such places rather variable ichthyofauna, among which there were ancestors of pelagic fishes of Neocene, was kept.
The thickness of water was occupied basically by species from coastal waters though among pelagic fishes there are even descendants of ground fishes. One of such species is the pipistrelle gurnard. It is fish about half meter long, soaring in top layers of water of Tanganyika passage.
Wide pectoral fins “inherited” by pipistrelle gurnard from benthic ancestors, have acquired now other function: the fish moves in thickness of water, flapping by them, as by wings. Bases of fins became very strong and were displaced upwards that the body of fish began steadier at “underwater flight”. Bases of pectoral fins have grown together in solid bone structure serving as a basis for muscles, moving by fins. Free rays of pectoral fins (“legs”, characteristic for bottom-dwelling species of gurnards) became very long and thin: they have turned to organs of touch sense, with which help fish communicates with neighbours and scrutinizes floating objects. On them a plenty of bodies of taste is developed, therefore fish can find out, whether object interested it is edible, not snapping it. Because the pipistrelle gurnard became an active swimmer, its body began easier: it is very narrow and deep, swimming bladder began more voluminous, and characteristic bone armour on forward part of body is strongly reduced.
In the first back fin of the pipistrelle gurnard eight poisonous spikes stick up, and one more is in anal fin. Such protection permits fish to not be afraid of predators furrowing waters of Tanganyika passage. Threatening a predator, going to attack, the pipistrelle gurnard “stands on head”, having turned to it by back and having exposed forward spikes. Simultaneously it widely opens pectoral fins similarly to wings of butterfly, and flaps them, moving to a predator wave of water. If the predatory fish will venture to attack the pipistrelle gurnard, it may receive some strong stings of poisonous spikes.
The pipistrelle gurnard “sounds” the threat, uttering loud abrupt sounds. And to secure itself more reliably against further attacks, fish has characteristic bright colouring. Pectoral fins are bordered by black strip, and on their surface there is large red spot. The silvery body of fish has characteristic contrast pattern of cross velvet-black strips. On unpaired fins there are lines of large black spots. Such colouring will be remembered for a long time to the predator having had received sting of poisonous spikes of gurnard.
Certainly, contrast colouring of pipistrelle gurnard could frighten off from it possible catch if the gurnard should be predator, but this fish eats rather specific food. The pipistrelle gurnard eats the mucous and spineless invertebrates living in thickness of water - jellyfishes, comb jellies and salpas. The mouth of this fish can extend to tube when it attacks the next translucent prey. Teeth of pipistrelle gurnard are strongly reduced: they are similar to bunches of bristles sticking up at the center of top and bottom lips.
For feeding by such specific catch at this fish the interesting adaptation was developed: strong immunity to poisons of jellyfishes and siphonophores. Even very young small fish can “plunder” fatally poisonous for other fishes tentacles of siphonophores without harm for itself, gathering small animals caught in them. And the adult gurnard will to have eaten also feelers with great pleasure.
All life of pipistrelle gurnard passes in thickness of water, courtship games also take place here. Males of pipistrelle gurnard distinguishing from females by bone combs above eyes and wider fins, perform rolling “love serenades”. Sometimes between them short skirmishes flare up, at which males are “butting” with the help of combs. When the female full of eggs, swims nearer to the male, he begins to sing special “aria of the groom”, similar to chirring of cricket. If the female is ready to spawning, she joins the male, and fishes sing some time a duet.
Fishes spawn plenty (about 300 thousand) small grains of roe and after that do not care at all of destiny of posterity. Glass-transparent fry spends first two months in plankton, eating larvae and eggs of other fishes. Frequently they join the large jellyfish and keep under its bell, from time to time stealing the small catch caught by it. At the age of three months at them adult colouring starts to be shown – at first separate pigmented areas appear, merging later to strips. Half-year old fish reaches length about 30 cm and already can breed. Males at this time get red spots on fins – mark of sexual maturity.
Impostor boxfish (Platyostracion imitator)
Order: Tobies (Tetraodontiformes)
Family: Boxfishes (Ostraciidae)
Habitat: reeves of Pacific Ocean in tropical and subtropical zones.
Reeves prospering in well warmed up shallow waters of Pacific Ocean are a place of congestion of various species of live creatures. The variety of food sources and shelter abundance results in appearing of numerous species of live creatures, and many of them may be strictly specialized. At reeves as rather peaceful plant-eating or omnivorous fishes and crustaceans, as obvious predators of various species live. Small inhabitants of reef stay in very unprofitable position – they risk to appear anyone's dinner almost every minute. Therefore till the evolution process they had developed various strategies of survival.
One species of crustaceans, the grooming crab, is in relative safety due to the role playing by this one at reeves. This crustacean renders fishes of cleaner service; therefore the majority of fishes does not attack it, and even trusts this animal to clean vulnerable areas of body like gills and eyes. Imitation of such well protected species is a good way of survival, and one fish had dexterously developed the imitaion of the shape and movement of grooming crab, avoiding attacks of the majority of reef inhabitants. It is the representative of brightly colored and protected by firm shell boxfishes, the impostor boxfish. This fish imitates the grooming crab, but does not render body clearing services to fishes. Similarly to it in Holocene some sea blennies imitated cleaner wrasses using the protection of these fishes from predators. But sea blennies attacked fishes, and this boxfish only uses protective similarity in coloring and behavior to the grooming crab to which practically all fishes of reef behave favourably.
The impostor boxfish is a small fish: length of its body is about 8 cm. The body of this fish is covered with armour, flattened and looking rounded at sight from above. Coloring of impostor boxfish is the main feature of its masking. Fish is almost entirely black, and its back is white with black spots. Pectoral fins of impostor boxfish are wide and fan-shaped, having red spots on edges. When the fish is swimming above the reef surface, movements of its pectoral fins are similar a little to movements of swimming legs of grooming crab.
Eyes of this fish are glogged, mobile and “frog-like”. Due to such feature fish can easily see everything happening behind it. The tail of this boxfish is very short, with a small fin serving only for turns. The impostor boxfish swims very slowly and tries not to depart far from reef where it is protected by instinctive behavior of other fishes not attacking the grooming crab. Despite of security this fish constantly keeps near to cracks and deepenings, hiding there when predators like the dorado croaker swim to reeves.
Impostor boxfish swimming among shells is very similar to grooming crab waiting for “clients”. But as against its arthropod prototype, this fish is not interested in cleanliness of fishes swimming around of it at all. Impostor boxfish eats small invertebrates biting them off from the reef surface by strong beak-like jaws. However, some most impatient fishes confuse the imitator and “original” and start to push this boxfish by head to drive its attention to them. Usually this fish does not react aggressively to these actions, but sometimes impostor boxfish should frighten off excessively importunate fishes. The disturbed impostor boxfish applies the reception characteristic to all its congeners: fish emits out poisonous liquid with strong irritating action which forces large fishes to keep aloof from the boxfish. Such feature of fish, strangely enough, is favourable not only to the boxfish, but also for crab: it suppresses possible aggression of “client” fishes relatvely to grooming crab. But nevertheless the impostor boxfish prefers to hide from large predators in crevices of reef.
The spawning of this species is paired and takes place at night. Male finds on reef surface small hole suitable by size, clears it and starts to involve females with the special crunching sounds. Female spawns eggs (about 400 tiny grains of roe) and at once abandons the clutch; male looks at eggs alone. It had to drive away from nest small fishes and crabs and to push away sea urchins. Protecting clutch, it can easily attack the fish exceeding its own size. For the period of clutch care male changes colouring – it becomes light yellow with dark irregular-shaped spots. This way it is not disturbed by fishes confusing it with grooming crab – some of them are much stronger than it and can ravage its clutch.
Permanent watch of the male on clutch lasts approximately till one week. At this time larvae hatch from eggs, turn to fry and start to swim out. They will lead about one month in plankton above the reef, and the majority of them will perish. Having managed to survive young fish returns to reef and settles in any shelter. The young growth of impostor boxfish has cryptic colouring – grey with black speckles. Till the growth speckles increase and merge, and the back turns lighter. The body of young fishes is short and almost cubic-shaped; later it extends and becomes disc-like. Having reached length of 2 cm, young impostor boxfishes start to simulate grooming crabs.
Armoured reefscraper (Scrapognathus armatus)
Order: Tobies (Tetraodontiformes)
Family: Boxfishes (Ostraciidae)
Habitat: tropics of Pacific Ocean, coastal reeves.
Reeves give a rich choice of food for animals living there. But on the other hand, abundance of food derivates a plenty of consumers, and as a consequence aggravates a competition between them. Therefore in such environment the appearing of various highly specialized animals eating only one or few kinds of food is possible. This strategy of survival has both strong, and weak sides. The greatest advantage of strict feeding specialization is almost complete absence of the competition to other species. And the basic lack is the dependence on an only source of food and impossibility of the passing to other food if the basic food vanishes. Nevertheless, such strategy of life is very common among reef inhabitants.
Reeves around of islands of Pacific Ocean are formed mostly by sponges and limestone-forming algae of various species. Coelenterates are presented here by not numerous species, and the great amount of limestone is delivered to reef with giant molluscs. At the surface of shells of large sea inhabitants the set of tiny creatures settles – polyps, molluscs, sessile crustaceans. They catch and filter from water food particles and tiny planktonic animals, and become food for other creatures.
The fish armoured reefscraper, widely settled in tropical zone of Pacific Ocean, eats small sessile animals. It slowly creeps on surface of reef, leaving behind itself a surface cleared of sessile animals.
Reefscraper has original appearance, characteristic for benthic fishes. It has wide and flattened body of rounded outlines, about 15 cm long. Head is covered from above with strong bone armour. This fish has camouflage colouring of the top part of a body – greyish-green with brown spots on head. The bottom part of body, imperceptible at usual position of fish at the bottom, on the contrary, has very appreciable colouring – it is white with set of black irregular-shaped lines forming wavy labyrinth-like pattern.
Eyes of armoured reefscraper are shifted upwards and are located in “openings” of the armour. They are mobile and can turn in various sides, like at mudskipper fishes (Periophthalmus). In case of danger fish retracts eyes under the armour. Gill apertures are also shifted upwards and open behind eyes in the same openings of the armour. They are protected by skin valves. Armoured reefscraper has inferior mouth. Instead of teeth lost a long time ago even by ancestors of this species, in jaws strong bone plates grow, with which help fish scrapes food from the surface of reef. The digestive path is long; in forward part (before the stomach) it has sac-like expanded outgrowth with strongly extensible walls.
The body of armoured reefscraper is covered with small armour plates, and on sides there are two or three lines of cross crests formed by their outgrowths. The stomach is not protected by armour and is covered with extensible skin. In case of danger fish hides into the crevice of reef and is inflated, swallowing water in pharyngeal sac. At inflated fish crests on sides rest against walls of refuge and prevent the predator to pull it out.
Armoured reefscraper is not famous in its abilities to swimming; therefore it keeps mainly near shelters. Usually armoured reefscraper slowly creeps on surface of a reef, cleaning off various tiny sessile animals and the top layer of growing limestone-forming algae from the surface. Moving by transparent pectoral fins shifted upwards, this fish presses body against the surface of reef. The body of fish seems strange, because weak and short tail fin is skewed upwards and inactive. When fish is quiet, it is closed, but if the congener interferes on the territory of fish, it stretches tail fin, and at this moment its contrast colouring becomes appreciable – black cross strokes on white background. The tail fin does not help fish in swimming, and its function was undertaken with well advanced anal fin with muscled basis. Frightened by bottom-dwelling predators, this fish can make sharp forward rush. Due to the shape of head it emerges above the reef, and then in process of decrease of speed slowly falls on the bottom.
This fish lives in warm climatic zone where seasonal changes are not expressed. Therefore the courtship season at these fishes stretches for all year. Male of armoured reefscraper is smaller a little, rather than female, but its colouring is more contrast. Male ready to spawning gets dark colouring: its back becomes black, and on this background shining yellow eyes are clearly visible. It displays himself to the female, having inflated body and swimming above the bottom. Thus the pattern on its stomach becomes clearry appreciable. As a sign of submission female turns paler and becomes bluish-gray.
For spawning male gnaws out in substratum a hole of the size almost equal to outlines of its own body. Female spawns there up to 5 – 6 thousand eggs, and male begins protecting of clutch, covering it by the body. He ventilates clutch with an original way: having slightly opened gills, fish gathers water in mouth, and then, having closed branchial valves, “blows” water under body, to the clutch. In this way male is on duty near the clutch within five days. For this time from eggs fry hatch and spend in nest about one day. Then young fishes pass to independent life, and male abandons the nest.
Young fishes have normally advanced tail fin. But as they grow, the back fin is shortened, and anal one expands and turns shifted back. Tail becomes simply the “flag” which does not take part in movement. Metamorphosis is finished at the second month of life. In same time fish gets characteristic camouflage colouring. Pattern on stomach and striped colouring of tail appear only when sexual maturity comes, at the age of 8 months.
Great crownfish (Astrosoma medusiphaga)
Order: Tobies (Tetraodontiformes)
Family: Crownfishes (Astrosomidae)
Habitat: Pacific Ocean, subtropical and warm-temperate areas of Northern hemisphere.
Mass extinction of pelagic fishes of global ocean has resulted to situation, when in few millenia at once the set of ecological niches appeared free. Till this original period of “ecological anarchy” a lot of species of coastal and bentic fishes began to adapt to pelagic habit of life. During the subsequent millions years some genealogical lines superseded others, and a number of such lines has remained only the small number of well adapted variants successfully competing to representatives of other groups.
The amazing species of pelagic fishes lives in top layers of water at the north of Pacific Ocean. At first sight it is very difficult to define fish in this one – the body shape of this creature is so atypical. But some attributes obviously specify a place of this species among fishes – short tail with fanlike tail fin, large mobile eyes, pair of branchial apertures covered with skin valves, and continuously wavying fins – back one, anal one and the pair of pectoral ones. This fish is great crownfish, the strange pelagic representative of family descended from boxfishes (Ostracyonidae).
The body of great crownfish has outlines atypical for fishes. It is strongly extended, covered with bony armour, as at ancestors from boxfish family. But the shell of this fish is adapted to passive soaring in thickness of water. It has oval outlines and is strongly extended – the width of fish concedes to length only a little. Diameter of body reaches 90 – 100 cm, and sometimes fish may be larger. Some pairs of long and pointed bone spikes symmetrically sticking above eyes, before branchial apertures, on sides of the body and on each side of short tail give this fish similarity to crown. Tips of these thorns are directed from the centre of a body like beams, and slightly raised upwards. The length of spikes reaches 40 cm. One more small pair of spikes grows at the basis of tail and is directed back and a little to sides. Such means of passive protection help fish to avoid an attack of sharks and other predators, because it complicates their attack. The back of fish is covered with strong armour in which there are only apertures for eyes and rabbet in back part of body for back fin and tail. The bottom part of body is covered with armour made of separate plates. On sides and stomach of fish plates are supplied with short thorns. Skin between plates is easily stretching, and fish can inflate stomach, swallowing a plenty of water in special outgrowth which branches from the gullet and stretches under skin along the stomach. Colouring of this fish is bluish-grey; tips of thorns are white. On back of fish the small number of dark spots is scattered; male has greater number of them, rather than female. Fins are transparent.
Additional contrivance of passive protection is the poisonous liquid of brown-yellow color; fish emits it out from the special bladder opening to cloaca. It is especially toxic for cephalopods, and with its help fish protects itself from attacks of squids at the most part of life cycle when it becomes large enough to represent interest as food for them.
Armour strongly reduces mobility of fish, and great crownfish belongs to plankton despite of the size. To reduce weight of body and to improve buoyancy there are many cavities filled with porous bone tissue impregnated with fat in armour of fish. Due to it fish easily soars in water, directing the movement with the help of fins. Usually this fish swims, making wavy movements by short and rounded pectoral fins. If it is necessary to swim faster, great crownfish uses back and anal fins. Tail serves only for turns. Tail fin is short and its basis is wide and fleshy.
Great crownfish is the true pelagic fish, and appears in coastal areas only after long storm. It eats jellyfishes and shrimps, frequently eating large jellyfishes in common with symbiotes living on them and prey pasted to tentacles. This fish has no teeth, and two sharp horn plates are advanced instead of them.
Great crownfish is not aggressive to relatives, but prefers to lead solitary habit of life. This fish forms pairs only to short time of spawning. Male is smaller, than female. At the meeting with female ready to breeding he quickly changes colouring and turns ink-violet with white tips of spikes. He swims around the female, displaying himself and being ready to recede before aggression from her side at any moment. If the female does not show aggression, male begins the following stage of courtship. He swims on the female from above, and presses her by the body, trying to “plunge” her. If female dumps him, male may snap at one of her spikes and hang on it. Having proved its physical perfection, male swims up from female’s body and fishes swim together till some time, and then spontaneously spawn the true cloud of eggs (up to one million ones) and soft roe. Female can repeat spawning up to three times per year, but each time the amount of eggs becomes lesser. In winter time fishes are fattened.
Parents do not care of the posterity. Larvae of great crownfish develop in plankton and undergo significant change of the shape. At first their body is similar to body of usual boxfishes, later lateral edges expand and body becomes disc-like, facilitating the soaring in water. At the size of about 4 cm poisonous gland develops at fish. And at the length of about 6 cm on the body of fish spikes giving the characteristic appearance to adult individuals start to form.
Xenofugu (Xenofugu rapax)
Order: Tobies (Tetraodontiformes)
Family: Tobies (Tetraodontidae)
Habitat: Japan Islands, the south of Big Kurils, lower reaches and river mouths.
Tobies (Tetraodon) of Holocene epoch were basically heat-loving sea fishes and frequently inhabited reeves. But some species frequently settled in rivers and could pass a complete life cycle in fresh water. Many freshwater species of these fishes lived in Holocene in tropical and subtropical latitudes at vatious continents. All tobies are rather heat-loving fishes, therefore till the ice age at the boundary of Holocene and Neocene their number had decreased, and fishes had receded from high latitudes to equator. In Neocene when the climate turned warmer, the new moving of descendants of survived sea tobies to extending subtropic areas began. New freshwater species of these fishes related to sea ones had gradually appeared.
In rivers of Japan Islands one of toby species occupied an ecological niche of medium-sized predator. This fish is named xenofugu – it shows that this creature is not connected by direct relationship with the toby known in human epoch named “fugu” in Japan.
Length of this fish is about half meter. Xenofugu lives in rivers, but occasionally swims out to sea. In spring, till the period of heavy rains, when the top layer of water is considerably freshened, these fishes can swim far in sea and cross through rather narrow sea passages, migrating from island to another one. Therefore at all islands forming continuous circuit along the northwest coast of Pacific Ocean the same species of this fish lives, not forming local forms. In warm years these fishes swim far to the north – separate fishes meet even near southern coast of Kamchatka. They can make some generations in rivers of peninsula but they managed to settle here for a long time only once.
In rivers of Kamchatka where water is warmed up by volcanic heat, there is one stable population of this species ranked as a subspecies - volcanic xenofugu (X. rapax vulcanophilus) differing from the basic species in smaller size (about 20 cm long) and dark colouring.
Body of xenofugu is extended; it has lost rounded shape characteristic for these fishes. The head of this fish is similar to frog’s one: it is wide and flat with glogged “frog” eyes able to turn various sides. The back part of body is compressed from sides. Back and anal fins of fish are the basic movement organs. They are shifted back, and their bases are strong and muscled, especially at anal fin. Tail fin is fan-shaped and short. As at all tobies, it serves only for turns. Xenofugu swims slowly, but can make fast single rushes for catch. Usually it is inactive and prefers to arrange ambushes at the river bottom.
Colouring of top side of xenofugu’s body is cryptic: on grey background there are large and small brown spots and many tiny white points are scattered. The bottom side of fish’s body is snow-white. At volcanic subspecies from Kamchatka top of body is dark grey with black speckles, stomach is bluish-grey, and near eyes there are two white spots.
This fish is able to puff with the help of intestines outgrowth – such feature is characteristic for family. But xenofugu makes it only at threat of life or till the courtship displays. The skin of fish is soft, elastic, covered with thick layer of slime, and on stomach the set of short spikes grows. When the fish is puffed, they are protruded, protecting fish. Also this fish is very poisonous – in its tissues, interiors and peritoneum tetrodotoxine accumulates.
All tobies are carnivorous species, and xenofugu is not exception here: it eats invertebrates and fish. Being illegible in feeding, this species eats any animals which may be overcome – fishes, frogs, shrimps and crabs. Sometimes xenofugu attacks chicks of waterfowl and eats small mammals appeared in water. Teeth at xenofugu are lack as at all tobies; sharp osseous plates replace them. They are strong enough to crush firm crab carapace.
Usually this fish arranges ambushes at the bottom, being dug in sand and silt with the help of movements of anal fin and lateral movements of body. Having buried to required depth, fish throws on itself ground dust by strong pectoral fins and waits for approaching of suitable prey. The hidden fish even breathes very cautiously – having slightly opened mouth and branchial apertures, fish freely allows water to wash gills, only occasionally passing through gills a new portion of water. When small animal is approaching, fish jumps out from ambush and snaps catch.
Xenofugu passes all life cycle in fresh water. Separate fishes spawn in river estuaries where the influence of sea inflow is felt, but usually fishes breed in the same place where they live. Courtship displays are begun by males. The male of xenofugu is larger, rather than female, and plays a dominant role till the spawning. It finds and clears flat stone of dirt, and then begins courtship demonstrations near it. The smooth stone with small deepening from above is especially attractive to the male. It is a tribute to the past: tobies bred digging in sand a hole for eggs. Competing males puff and try to push each other out of chosen stone. Thus they are colored brightly: the background of top part of body brightens, and small spots merge to large dabs.
Eggs are laid on stone. Clutch may number up to 5 thousand tiny grains of roe. At this species constant pairs are not formed, and male right after spawning expels the female from the territory. Male carefully looks at posterity: it keeps near to the clutch, ventilates it by fin movements and throws out dust brought by current. Eggs of this fish are additionally protected from enemies: they are poisonous and colored bright yellow. Fry hatch approximately in two days, and abandon the nest three days later. Larvae of xenofugu are small and first time keep near the male. Male looks after posterity some next days, driving away from fry school even very large animals – it happens that the male in parental care zeal bites legs of large mammals came in water. Gradually fry leave the male and begin independent life. Young xenofugus hide and feed among plants. They grow rather slowly and reach the maturity approximately at four-year-old age.
disk-toby (Ostracyopsitta reticulata)
Order: Tobies (Tetraodontiformes)
Family: Armoured tobies (Neostracyonidae)
Habitat: reeves of tropical zone of Pacific Ocean.
Picture by Fanboyphilosopher
At the boundary of Holocene and Neocene the Earth has gone
through great ecological catastrophe, as a result of which madreporarian corals,
the main group of reef-building invertebrates, had been wiped off the face of
the Earth. After them the richest fauna of reef animals, completely or in part
depended on growth and prosperity of corals, had died out. In Neocene the place
of coral reeves was occupied by ecosystems made by absolutely different organisms.
And they had been developed by representatives of new fauna. Among inhabitants
of reeves of Pacific Ocean disk-tobies are remarkable – brightly colored fishes
swimming in schools. They are descendants of pufferfishes (Tetraodon), changed
solitary way of life to social, and changed externally in great degree.
Body of disk-tobies is deep, has rounded outlines and is squeezed from sides. On back and stomach of these fishes body forms leathery keels promoting keeping of balance. All species of disk-tobies are small: in typical case about 20 cm long, and even smaller in the majority. But among them there are some “giant” species. They lack belly fins, and back and anal fins are shifted back. The fish swims forward due to their wavy movements, easily changing direction of movement and manoeuvring between sponges and mollusk shells. Tail fin of these fishes is short and leathery; it does not take part in movement, and with its help fish only makes turns. Pectoral fins are shifted upwards, and the centre of gravity at this fish is displaced downwards; therefore it is rather difficult even for dead fish to emerge up a belly.
The body of disk-tobies lacks of scales, but is protected against enemies with thin armour plates. They do not form any continuous protective armour as at boxfishes, and therefore do not complicate movement of fish. Between plates there are areas of extensible skin of contrast color. When fish is attacked, it swallows water, filling the special outgrowth of digestive path, turning strongly inflated. This feature is inherited by it from pufferfish ancestors. At inflated fish bright sites of skin stretch and become well appreciable. Skin of these fishes lacks of scales and has very bright and garish coloration with contrast strips and spots. It is warning colouring: meat of fishes is poisonous, and in addition in case of danger fish splashes out a jet of dark colored poisonous secretion.
Head of disk-tobies is short and deep; eyes are large. Jaws of fish represent a firm “beak”, with which help fish cracks fodder organisms with firm skeleton: sponges, armours of crustaceans and shells of molluscs. At the reeves disk-tobies of some species keep in large schools numbering up to fifty of fishes, and others live in families or solitarily. Each school, pair or single fish has the certain territory, and patrols it in process of growth of fodder organisms.
For spawning school of schooling species breaks to separate pairs, and solitary or harem species form breeding groups. At these fishes family is kept only for the period of spawning. For spawning fishes make nests in shelters, furiously protecting territory around of nest from congeners. Fry hatch in some days, and parents abandon the nest, forming new schools.
The young growth spends first time at the reef, grouping in numerous schoals of equal-sized ones. As they grow, they join schools of adult fishes, or (in case of solitary species) occupy a certain territory at the reef.
Reticulate disk-toby is a schooling species of fishes and keeps in congestions numbering up to hundred of fishes and more. It is one of medium-sized species; the length of adult individual may be no more than 35 – 40 cm, and usually smaller. Similarly to all schooling disk-tobies this fish has rather dim colouring: back and sides are blue; on bottom part of body there are light green spots separated by dark intervals forming characteristic mesh pattern. When the disturbed fish is inflated, dark skin between plates of armour is stretched, and fish becomes much more appreciable, displaying itself to predator. The iris of the eye is light, but on tail fin there is dark spot of “false eye”. This species eats sedentary worms and sponges, and bone plates on its jaws form firm “beak”.
At the reeves of Pacific Ocean close species live:
Parrot disk-toby (Ostracyopsitta psittaculus) is the smallest species of the genus: the adult fish reaches the length of about 5 cm. In body shape and colouring this fish resembles coral butterfly fishes of genus Chaetodon died out to Neocene. Body of this species is deep and strongly laterally compressed. Colouring of fish is contrast, black with big white spots (at mature fishes it resembles more any black grid on white background); unpaired fins are transparent, tail fin is fan-shaped and has red border along the edge. Head of fish of any age is black with large dark eyes and red strip around of “beak”. This fish keeps solitarily in cracks of reef and eats small crustaceans. Each fish of this species has territory with shelters where it hides in case of danger. If the enemy tries to take fish from it, this disk-toby inflates body and get densely “jammed” in shelter. This species actively protects territory against congeners, uttering squeaky warning sounds.
Honey disk-toby (Ostracyopsitta melisoma) is one of medium-sized fishes: body length of adult individual is about 20 cm including tail. This fish is named because of characteristic colouring: on yellowish-brown background on head, breast and stomach there is brown mesh pattern, remotely similar to honeycombs. Unpaired fins are transparent, and it gives to fish original appearance. Honey disk-tobies settle at the reef solitarily and eat mainly polyps, small snails and other soft-bodied invertebrates. Honey disk-tobies protect territory against congeners, uttering abrupt clicks.
Mourning disk-toby (Ostracyopsitta funebris) belongs to medium-sized species: it is up to 30 cm long. This fish has black colouring with white spots of various sizes near the tail stalk – at different individuals their number and sizes vary. Lips are also snow-white. Mourning disk-tobies keep at reeves in schools numbering up to hundred of fishes and more, and eat various small animals. They are rather peaceful to congeners; schools of this species have no constant territory and easily unite and break. The schooling behaviour provides reliable protection: mourning disk-tobies can actively defend against predators, biting them strongly. And the school of these fishes can drive back even very large predator. Contrast spots around of lips warn a predator of ability of this fish to defence. Spots on tail represent the “amplifier” of this colouring, creating the illusion of protection from both ends, and do not give a predator of an opportunity to orient and to attack fish from unprotected end.
Moonlight disk-toby (Ostracyopsitta lunaris) is the largest species of the genus: the length of its body is more than half meter. This fish has rather modest caesious color with metal shade. Only on sides there are the sites of dark skin, forming irregular mesh pattern and strongly stretching when fish displays itself to aggressor. Also on tail fin of fish there are some round black spots. Fishes of this species live in small schools numbering no more, than ten individuals, and swim rather slowly. This species eats mainly invertebrates with firm covers: crustaceans and molluscs. Occasionally these fishes can attack wounded and ill fishes, but do not pay attention to healthy ones.
Dirigible fish (Paramola zeppelin)
Order: Tobies (Tetraodontiformes)
Family: False sunfishes (Paramolidae)
Habitat: reeves of Pacific Ocean.
Picture by Alexey Tatarinov
Improvement by Carlos Pizcueta (Electreel)
In Neocene ecosystems of tropical sea shallows developed
practically anew. Coral reeves of Holocene represented the fine balanced community
in which many
species occupied very strictly shared ecological niches. Thus, during the
global ecological crisis at the boundary of Holocene and Neocene, when the
part of species of reef-building corals had died out or became a rarity,
the huge amount of reef inhabitants had become extinct.
In Neocene highly productive communities of sea shallows had appeared again. Like ones of human epoch they are populated with numerous species of fishes and invertebrates. In human epoch tobies (Tetraodontidae) and parrot fishes (Scaridae) were specialized durophagous species – animals eating organisms having firm body covers (crustaceans, molluscs) or internal skeleton (corals). At reeves of Neocene the niche of durophagous species is occupied by other fishes. In Indian Ocean it is huge crushing trunkfish (Titanostracion destructor), and at reeves of Pacific Ocean its distant relative, massive dirigible fish, lives.
The length of this fish reaches 160 cm at weight of up to 120 kg. At the first sight on dirigible fish it is possible to note its obvious similarity to sunfishes of human epoch (genera Mola, Masturus and Ranzania). But Holocene sunfishes, peaceful devourers of plankton lived at open ocean, had died out a long time ago, and their place in ecosystems was occupied by freakish creatures belong to other systematic groups. Dirigible fish is similar to sunfishes, but is only their very distant relative. It descends from tobies (Tetraodon) of Holocene epoch.
The body of dirigible fish has the shape close to cylindrical in cross-section. Head of this fish is short and deep, and strong jaws are located in its bottom part. Instead of teeth in mouth very firm plates grow, with which help the dirigible fish cracks shells and armours of animals used for food. The skin of dirigible fish is colored gray-blue with darker irregular-shaped spots.
Development of fins at dirigible fish gives to it significant external similarity to sunfish, but it is a result not of direct relationship, but of parallelism in evolution. Tail fin of dirigible fish is reduced up to leathery vertical plate with rudiments of fin rays. Tail stalk of fish is short and expanded; therefore back part of fish between back edges of back and anal fins seems cut off on to a vertical. The back and anal fins having lobe-like shape with rounded tips are principal organs of movement of dirigible fish; during the swimming they move wavy. Dirigible fish can freely swim back to front, and, despite of large size, is able to maneuver at the reef easily. It swims slowly as eats inactive food – mollusks (bivalves and gastropods), and also large crustaceans. Swimming fish resembles dirigible balloon – hence the specific epithet in scientific name and common name of fish. Shortly before storm dirigible fishes leave reef and swim down to depth.
Life at the reef is full of dangers. In Neocene in tropical zone of ocean sharkodiles (Carcharosuchus deinodontus), monstrous sea crocodiles belong to last representatives of the group rule. The adult sharkodile avoids appearing in shallow water, but younger individuals frequently hunt at reeves. Dirigible fish is too sluggish to escape from them in flight; therefore it relies to passive protection. Skin of dirigible fish is very firm and viscous - at the bite young sharkodile may simply break some teeth. Besides large bladder containing poisonous dark brown liquid opens to cloaca of dirigible fish. The basic poisonous substance is tetrodotoxine: ability to produce it is inherited by dirigible fish from tobies, its ancestors. Muscles of this fish also contain a plenty of poison.
Dirigible fish breeds, laying at the reef a plenty of ground eggs. Male chooses suitable site of reef, digs out or deepens a hole at the bottom, and starts to involve the female, uttering sound similar to gnashing with the help of jaw plates. Its colouring becomes very contrast: background colouring turns blue, and spots blacken. The female spawns in nest prepared by male up to 500 thousand of tiny eggs, and male protects the clutch within three days while fry will start to swim.
Young dirigible fishes are not similar to adults, and resemble fry of typical tobies more. They have tail, and tail fin is normally advanced. As fishes grow, the tail part of body simply stops in development and the partial reduction of fin begins.
Firemouth (Abyssodon flammeostomus)
Order: Tobies (Tetraodontiformes)
Family: Abyssal tobies (Abyssodontidae)
Habitat: Pacific Ocean, depths about 2000 meters.
Picture by Carlos Pizcueta
The majority of biotopes of Earth directly or indirectly
receives energy of the sun. Only at the bottom of ocean near to underwater
volcanos there are
complexes of the live organisms existing due to geothermal processes. But
they look exception in the biosphere dependent on the sun. Even in places where
the sunlight is not present, live creatures depend on it. One of such ecosystems
is developed in ocean depths. Sea water quickly detains sunlight, and photosynthesizing
organisms are not found in depths of ocean. But inhabitants of depths completely
depend on efficiency of top layers of water – they eat falling from above
organisms and their own neighbours making vertical migrations. Therefore
in time of “plankton accident” the mass extinction of deepwater fauna happened.
After disappearance of typical deepwater forms new species, descendants of
coastal species had started to occupy their place in ecosystems of Neocene.
Pufferfishes, or tobies (Tetraodon), very adaptive predators, were among settlers in depths. Obviously, they had settled in depths of ocean from continental slopes, then “took off” a bottom and pased to pelagic life (possible, ancestors of deep-water anglerfishes Lophiiformes had done the same way before them). One descendant of deep-water tobies had turned to specialized predator of thickness of water. The fish had got characteristic features of deepwater inhabitants: its bones became soft, and around of mouth organs of luminescence had appeared. For this feature the fish has received the name “firemouth”.
The length of this fish does not exceed 20 cm – as a rule, deep-water fishes do not reach the large size. Body of firemouth is soft, and its consistence is tender. It is rounded and also seems “bloated”: when the fish is swimming, the skin slightly waves. In skeleton bones are substantially replaced with cartilage – it is the typical feature of deepwater fishes. Eyes are very small, and sight of firemouth is bad. But lack of sight is compensated by very much advanced sense of smell. The sensitive area of olfactory holes is stretched to internal surface of big skinny outgrowths surrounding nostrils. They are very movable, and also work as “ears”, helping to the fish to orient itself in darkness of depths. Skin of fish is elastic and easily extensible. It is grayish – pink and seems chemically decoloured. Through skin of firemouth internal organs and large blood vessels are visible. The skin of tobies living in shallow waters is covered with a plenty of corneous spikes, which rise when fish is inflated with water or air. On the body of firemouth some corneous plates with sharp spikes in the centre had remained from this adaptation.
All deepwater fishes are predators or scavengers – herbivorous species among them are not present. At firemouth jaws are large, surrounded with a ring of small organs of bioluminescence. Instead of teeth at firemouth sharp plates grow as at all representatives of the order: it is the firmest part of fish body. With the help of luminous organs firemouth beckons fishes and invertebrates right to the mouth. This predator kills catch by characteristic bite in head and swallows entirely due to very extensible stomach.
The basic organs of movement of firemouth are back and anal fins – fish swims with the help of their waves. At these fins there are mobile muscled bases, and vertebrae in places of muscle attachment have big vertical outgrowths. Tail fin is considerably reduced, continuing the tendency common for representatives of the order. Pectoral fins of fish are shifted upwards and help to turn on the spot. Pushes of water through branchial apertures help this fish to move forward.
At deep-water fishes males, as a rule, are much smaller, than females are, and some species even became hermaphrodites. At firemouths “equality of gnders” is kept: it is connected with the distribution of roles of fishes in the spawning. Spawning at firemouths occurs in pair, and some features of breeding inherited from coastal ancestors were kept. The majority of pelagic fishes differs in great fertility – they produce huge amount of tiny eggs, and do not care any more of posterity. At firemouths the female lays only some hundreds of rather large eggs (their diameter is up to 3 mm). Fishes find each other by smell and flashes of light. Photophores of the female ready to spawning emit blue light seen from apart. Male finds female and begins courtship dance, touching to the female by fins and slightly biting her tail. The female pastes eggs on stomach of the male, and simultaneously he fertilizes it. At the culmination moment of courtship games when the female starts to spawn eggs, male emits cloud of soft roe, and pair of fishes “spins” in it. At this moment the fertilisation happens. Fertilized eggs are pasted to skin of the male and dead grains of roe peel off later. The male only carries eggs on itself, but does not look after posterity. Hatching fry at once leaves it, and begins independent life.
Order: Tobies (Tetraodontiformes)
Family: Abyssal tobies (Abyssodontidae)
Habitat: northern part of Pacific Ocean, depth about 2000 meters.
Picture by Timothy Morris, colorization by Alexander Smyslov
Initial picture by Timothy Morris
Deep-water habitats entirely depend on efficiency of top layers
of water. Therefore in epoch of ecological crisis at the boundary of Holocene
and Neocene mass extinction has mentioned deep-water fauna even in greater degree,
than shallow water one. Actually, in Neocene deep-water fauna began to form
practically from zero. At this time in abyss representatives of groups of animals
earlier not met in this habitat began to appear. Among new species of deep-water
fauna representatives of tobies order, which were shallow sea and freshwater
forms earlier, have appeared. In the course of evolution tobies had developed
life in sea depths, becoming the similarity of anglerfishes (Lophiiformes) known
in Holocene epoch.
Among tobies there are some deep-water species. One of them is firemouth, whose mouth is surrounded with luminous organs. It has close relative, crownmouth, differing in more specialized organs of luminescence. At the crownmouth luminous organs are located around of mouth on long elastic stems, forming the “crown” (hence the name of fish). With the help of these luminous organs crownmouth is able to imitate various sea animals. Having hung in thickness of water headfirst and having lowered luminous bodies like the closed umbrella, crownmouth imitates luminous deep-water jellyfishes. The bases of stems of luminous organs are mobile, and sometimes fish moves by them chaotically, involving catch. At this moment they are similar from apart to congestion of small luminous animals like shrimps. Hence the specific name of fish “constellation”, meaning “constellation”. Luminous organs produce blue light which is seen in sea water from apart. Having own “illumination”, crownmouth differs in weak sight, but sense of smell at this fish is advanced very well.
Crownmouth is sluggish swimmer. It is fish of spherical form with short fins and wide mouth. Length of body of crownmouth is about 15 cm; tail of fish is short with wide fin. Osseous plates, replacing to all tobies absent teeth, at crownmouth are more advanced, than at related firemouth: they form some pointed outgrowths like teeth. These plates are the strongest part of body, and other skeleton of fish is soft, gristle-like and elastic. It is the prominent feature of deep-water fishes appeared independently at various unrelated groups of deep-water fishes.
The skin of fish is colored black – so crownmouth is not appreciable in light of its own fires. As well as all deep-water animals, crownmouth attacks various catch, as opposed to fishes of shallow waters which can be specialized stenophagous species. Crownmouth eats any catch which it is able to swallow – usually it eats fishes up to 20 – 25 cm long, octopuses and other large invertebrates. Teeth-like outgrowths on jaw plates help fish to kill quickly any catch – they equally easy break shell of shrimp, pierce skull of fish or cut soft viscous flesh of octopus. To kill catch is only half of hunting success; it is not less important to manage to use it. The crownmouth does not encounter difficulties, swallowing catch. Alternately working by jaws and alternately sticking in catch jaw plates, this fish as if “stains” itself on catch, thus its mouth is strongly stretched. Jaws of crownmouth are not adapted to biting off food, therefore any prey, even the largest one, is swallowed by this fish entirely. In the other hand, due to stretched skin and soft bones it can swallow various animals. Catch goes on in stomach, which also is strongly stretching.
It is not only catch under water. Predators also come involved with light of fires of crownmouth, but the fish is able to protect itself from them. It uses the reception traditional for tobies: fish strongly puffs body, swallowing water. The skin of crownmouth is covered with plenty of corneous thorns. When the fish is inflated, they rise and spread wide. It is very effective protection - at many predators there are easily extensible mouths and stomachs which are easy for injuring. Therefore the predator, as a rule, refuses to attack prickly fish.
The male of crownmouth is smaller, than female. In depths of ocean there are no seasons, and crownmouths can spawn at any time. The male swims better, than the female – its body is more oblong, and stems of luminous organs are shorter. It searches for the female ready to spawning, by smell. Having found out the necessary individual, the male executes for it special “presentation” with the help of fires; it is necessary to prevent the attack of the female. Also he emits from cloaca the special chemical substance, braking aggression of the female.
Spawning eggs, fishes nestle stomachs against each other; thus the female is overturned by back downwards. Eggs of crownmouth are pelagic, with fat drop. In clutch there are some tens thousand very small eggs. Spawned eggs at once emerge, float through cloud of soft roe emitted by male, and within several hours rise to the surface of water. At this time a lot of eggs perishes from various predators. Fry develop in top layers of water, in plankton. Young crownmouths are absolutely not similar to adult fishes: they are creatures with flattened triangular head making about half of length of fry. Corners of head, sticking back, are extended to long strings – it facilitates soaring in thickness of water. Young crownmouths are passive plankton predators. As they grow, fishes swim down in deeper layers of water and get shape, characteristic for adult fish. Life expectancy of crownmouth can make about 18 years.
Chameleon clingfish (Labresox chamaeleonoides)
Order: Clingfishes (Gobiesociformes)
Family: Clingfishes (Gobiesocidae)
Habitat: reeves of Pacific Ocean, Hawaii.
Reeves in tropical zone of seas are a place of concentration of various live beings. Reef boicenose includes many kinds among which there is strict competition. During the evolution process at reeves various highly specialized species had appeared – thus the competition between them is weakened. At reeves there is one especial ecological niche which is occupied by cleaner creature, eating ectoparasites of other reef inhabitants. In human epoch fishes of wrasse family (Labridae) and some species of shrimps realized sanitary service at the reef. At the reeves of Neocene epoch crabs had appeared among cleaners – one representative of swimming crabs (Portunidae) family. Besides it, chameleon clingfish, the specialized representative of the group of inactive fishes characteristic for coastal zone, renders services of cleaner to fishes. Hence its name: “Labrus” is the scientific name of wrasses, fishes rendered cleaner services to other fishes in Holocene epoch.
Chameleon clingfish is rather small kind of fishes – its length does not exceed 8 – 11 cm. It has flattened body supplied with strong sucker on belly side, formed by grown together bases of abdominal fins. The head of this fish is strongly flattened and rounded in front; mouth of scraping type is located on its bottom side. Nostrils are positioned between large glogged eyes. Their site is marked by two bushy nasal valves – skin outgrowths. Unpaired fins of this fish are grown together in unite structure bordering back part of body of this fish.
Colouring of chameleon clingfish is bright and appreciable: yellow with large black points. But fish gets such colouring only in rest, which happens very seldom at its habit of life. This fish is completely harmless, and its main protection against enemies is a skill to hide and to change colouring, skilfully masking in imitation of colors of environment.
Chameleon clingfish is specialized to body clearing of large fishes. Usually it settles near well appreciable elements of reef – near separate shells or blocks of limestone. Here it waits for “clients” – large fishes requiring for clearing of skin from parasites. They find out this fish by its specific colouring, and, having swum up to it, freeze, having turned sideways to the cleaner. Having received such signal, chameleon clingfish sticks to their sides and begins clearing of fish. Thus it changes color, imitating colouring of served fish. Having cleared fish from parasites, this fish “jumps off” and becomes bright again.
Mouth of chameleon clingfish is scraping; lips are covered with numerous corneous bristles, helping to clear skin of the client fish. Due to flat head this fish can get under operculums of the client fish to clear gills of parasites and dust.
Chameleon clingfishes lead strictly solitary habit of life. They occupy small territories, and food comes to them on sides of client fishes itself. But in any case they do not suffer the presence of congeners and competing animals leading similar way of life (for example, cleaner crabs), and behave to them aggressively. This fish is tolerant to congeners only when they are ready to spawning. This species of fishes is hermaphrodite, and easily changes sex during the life, sometimes multiple times within one year. At the preparation for spawning the breeding pair forms of fishes living in the next territories. Spawning is preceded with rough courtship games during which fishes chase each other and fish, playing a part of male, pushes the female by side. Female lays eggs in hole on reef surface, preliminary prepared by male. In clutch there are about 200 large eggs strongly inflating in water. Only male cares of posterity. For the period of egg incubation it stops to care of fishes, gets camouflage colouring and almost permanently stays near the nest, fanning eggs by fins and driving away small predators. The incubation lasts about 40 hours, and 3 days after the posterity starts to swim and leaves nest. Young fishes become sexually mature at the age of 1 year.
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