Tour to Neocene
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The climate of Neocene epoch had become milder, than in Holocene.
The part of continental coasts had become hidden under water, the bottom of
ocean here and there has risen, and the level of ocean has a little increased.
It was has the big influence at the features of climate - it had become much
more damp, than earlier. The abundance of rains has caused displacement of borders
of natural zones - areas of deserts has become strongly reduced, and the area
of deciduous forests has extended. In equatorial belt of the Earth damp rainforests
now are dominating, and some plains in large river basins have turned to extensive
bogs. The increase of amount of rains has caused occurrence of large lakes and
rivers. And the most impressing result of climate changes has become occurrence
in Eurasia the huge saltish reservoir - Fourseas.
20 million earlier of this time the ice age radically has had an effect at the
geography of southern and southeast Europe: Mediterranean and Black seas, cut
off by tectonic processes from Atlantic, had dried up and had turned to small
hyper-salt reservoirs among extensive salt plains. But with increase of rains
amount these barren landscapes have come to life. In the Mediterranean the system
of salty bogs, on which the original animals who have adapted for so extreme
conditions live, was stretched out. And the Black sea is again full of water
and life though the history of its settling is more dramatic.
When Bosporus and Dardanelles straits were closed as a result of movements of
Earth's crust, and Asia Minor had collided with Europe, the Black sea had turned
to an isolated from the ocean reservoir and had mostly dried up. Shallow sea
of Azov had dried up even faster. The area of Caspian sea had been strongly
reduced, and Aral sea had turned to small similarity of the Mediterranean -
barren salty plain.
But in a Neocene the situation began to change for the better. Rains have filled
in the Caspian lowland, and soon Caspian sea has merged with Aral. In estuaries
of rivers inflowing into Caspium sea, some of species of the animals, capable
to exist in conditions of changeable salinity was kept. They have got rather
favorable chance for development, again having occupied the formed sea lake
with very low water salinity level. The sea was occupied even by descendants
of freshwater species. And the species of Black Sea was unlucky: the rivers
of the Black Sea basin have dried up during the ice age; therefore there are
nobody to occupy sea again filled by water - except for bacteria, protozoans
and several species of plankton crustaceans and algae, in the new Black sea
nobody had lived. But then big trouble has happened: strongly spread waters
of the Aral - Caspian basin have reached the Black sea and both basins have
united. New huge reservoir waters have formed, filling pools of four seas -
Black, Azov, Caspian and Aral seas. Association of pools had caused leap of
salinity because in hollow of the Black sea the huge amount of salts had been
accumulated. Besides reservoirs at the area of Black sea are rich in sulfides
and hydrogen sulphide – it was the heritage of Holocene epoch. The Black sea
was deep, but waters of it have mixed up poorly, that has caused occurrence
above a bottom of practically lifeless water layer. Such "heritage"
had became a problem for the species not resistible to salty and dirty water.
Someone from their number had receded in river mouths, some species had died
out. When position was stabilized, set of staying empty ecological niches had
formed, which had been filled by descendants of the survived species. Gradually
new reservoir appeared populated as plentifully, as in Holocene epoch.
In a Holocene at the African continent there was few Great African lakes, which
numerous fish population belonged mainly to cichlid family (Cichlidae). Other
groups of fishes inhabited these lakes, were less various, than cichlids. In
Fourseas the situation has practically repeated, with the only difference: instead
of cichlids gobies (Gobiidae), capable to endure changes of water salinity,
have became main group of lake ichthyofauna. Some species of this group have
survived in estuaries of the rivers at the integration of Black and Caspian
seas, and have become ancestors of fishes of Fourseas.
Waters of Fourseas numerous species of the diverse gobies inhabit. Some of them
live in thickets of plants, others live in water thickness or prefer to settle
at the bottom. Small gobies eat invertebrate animals, and larger species are
predators. The most numerous inhabitants of local waters, crustaceans, serve
as food for many species of fishes of Fourseas. Herbivorous fishes are rarity
in Fourseas, and their ecological niche was strongly occupied with various species
of crustaceans – scuds (or side-swimmers). The majority among side-swimmers
includes plankton species, filtering unicellular algae in thickness of water,
but also the large forms eating macrophytes are present. These species keep
in estuaries of large rivers where in water of poor salinity carpets of eel
grass, pondweed and cane spread. But the coastal zone is richly populated with
gobies of different species, the majority of which is not squeamish crustaceans.
However even the most gluttonous and ruthless hunters among gobies try to keep
closer to saving bottom and hide in more rich thickets when above sand and stones
the ominous shadow of seven-meter predator has sliding. Lazily moving by huge
crescent tail, the monster swims above thickets of plants. Long leaves of eel
grass and pondweeds wave from the waves spreading at movements of huge creature.
The small weak-sighted eyes located on each side of flat head, will hardly notice
fishes hidden in plants, but long wattles, supplied by organs of chemical feeling,
will give the full information about those creatures which cannot be seen. The
beams of the sun penetrating thickness of water, slide on each side of the monster,
decorated with longitudinal lines of osseous plates.
Such visitors seldom come deep into coastal thickets, preferring to keep in
open sea. This creature is the tsar-fish, the representative of the sturgeons
becoming rarity in Neocene. Here, in Fourseas, not having adequate competitors
from among sharks and osseous fishes, sturgeons have survived in plenty. And
the tsar-fish occupies a place of honour at top of an ecosystem, gathering its
share in populations of gobies.
Having swum among coastal thickets, the tsar-fish turns off in the high sea.
Gradually at the bottom under its stomach thickets of plants vanish, and then
the bottom is lost somewhere below, covered by thickness of water. Absolutely
other world - the world of plankton, the basic productive zone of Fourseas here
begins. Here, far away from the rivers carrying in the sea dregs and silt, in
transparent water microscopic algae sometimes coloring water greenish color
grow in huge amount. And here the food chain, which tsar-fish crowns by itself,
begins.
Plankton algae breed with improbable rate. Especially they are plentiful in
areas where the rivers carry out in the sea plenty of mineral and organic substances
which are washed away from ground. But other centre of variety of plankton sea
algae is the high sea where there are good conditions for growth: no oozy suspension
in water, constant salinity and intensive sunlight. Breeding with constancy
and regularity of clockwork, algae can fill by themselves all top layer of the
sea. But they never will make it, because the significant part of them will
be eaten by tiny inhabitants of thickness of water.
The most usual plankton animals of Fourseas are midgescuds. These crustaceans
continuously filter algae with the help of the mouth legs covered with bristles.
Breeding in plenty, they do not give algae to expand widely. The crustacean
spends the most part of life, soaring in thickness of water. It is little bit
heavier than water because of massive shell, therefore from time to time it
is compelled to move by legs to immerse not so fast to bottom layers of water.
Usually it simply places long legs in sides, and soars in water, as if the small
jellyfish. On legs of the crustacean there is the set of sensitive bristles
which give it the information about the movement of water around. It is very
important - in plankton not only vegetarians meet.
Midgescuds form large rich flights: in one liter of water up to 80 - 100 crustaceans
of different age may be. Such congestions drift to tens meters, mounting two-meter
thickness. Usually crustaceans are inactive, but sometimes their flight comes
in chaotic movement: crustaceans skip to sides, randomly bumping with each other.
It means only one thing: the attack of one of plankton predators. If to look
attentively, it is possible to see in water completely extremely appearing creature
with the body of dragonfly, long head, the branchy antennas similar to ragged
wings, and one large eye in the middle of forehead. Appearance makes clear that
this creature is the cladocer crustacean. This creature is twice larger than
scuds, and its jerky movements are the evidence of that it is a predator. Usually
strange creature soars in water thickness, drifting by current. But when in
its field of view the catch appears, the tiny monster quickens: it aims by cautious
movements of antennas at catch, and then by quick throw overtakes the prey -
usually young scud or fish fry. Ruthless jaws pierce in prey body and instantly
terminate it. The manner of hunting very much resembles habits of the hawk:
this creature also is named as the hawk leptodora. It is the descendant of one
of species of Leptodora - the large predatory cladocer crustacean from fresh
waters of Eurasia.
The hawk leptodora slowly devours catch - the young midgescud. The life of leptodora
in Fourseas is not bad - this species is significantly larger that the ancestor
had been only one centimeter long. But nevertheless it can easily fall prey
to other plankton animals. In plankton not only crustaceans live – larvae and
fry of various gobies make a significant part of plankton. All of them have
fantastical shape: their fins are decorated with the various outgrowths, allowing
soaring in water thickness. Larvae of gobies eat different infusorians and microscopic
worms - rotifers (Rotatoria), forming nannoplankton - the smallest plankton.
Larvae of gobies are inactive - they wait, while catch itself will swim up right
to the mouth. Then there follows the quick throw - and new expectation. Small
mobility allows saving forces, in this case the most part of nutrients is using
for growth of the organism. But it is fraught also with rather unpleasant consequences:
predatory crustaceans are not asleep.
Light is shimmering as the rainbow in spherical eye of the transparent hawk
leptodora. The crustacean recently has finished with the next prey, and now
it looks for new catch. Sight at the hawk leptodora is not so good - the crustacean
is short-sighted, but at the distance about 10 - 12 cm it confidently distinguishes
alive creatures fifth part of its own size long. When near soaring leptodora
the transparent larva of the goby floats, the crustacean badly sees it, but
organs of chemical feeling give out to the predator the location of prey. Fast
throw - and the larva writhes in prickly legs of predator. Having got hold of
the next dinner, the hawk leptodora begins the meal. By sharp mandibles it divides
into particles meat of catch, and then eats turned out gruel.
On the back of the hawk leptodora there is the large egg bag in which through
transparent walls about one and half tens eggs are visible. After 10 - 12 days
from them the new generation of gluttonous crustaceans will hatch. To tell the
truth, few of them attain the maturity - the majority, alas, will be eaten by
adult neighbours.
For one day the large hawk leptodora devours about 80 fry or ten adult midgescuds.
But also it did not become the king of predators among plankton animals. In
plankton of Fourseas there are fishes - glass-transparent plankton gobies. Though
they are only a little larger than the hawk leptodora, but surpass it by might.
Jaws of the plankton glass goby are armed with the sharp thrust teeth easily
piercing fragile shells of leptodoras. Gobies are practically transparent -
only dark eyes and peritoneum through which sun beams do not pass, indicate
their location in water thickness. Other organs and tissues of the animal are
completely transparent. Such transparent fish lived in the Asian tropical reservoirs
of Holocene epoch – it was the glass catfish (Kryptopterus bicirris). Therefore
it is quite possible for fishes to become the phantom - the invisible being.
Having noticed the hawk leptodora, the glass goby comes behind to not be noticed
and at the same time to avoid sharp mandibles of the crustacean. Carefully having
aimed, the small fish makes throw, trying to put the sting to the pleon of catch.
After the attack the goby does not turn loose the "bulldog" bite,
expecting while the hawk leptodora will die. Having convinced, that tenacious
legs and sharp jaws of predator do not threaten to it any more, the goby starts
to devour catch. More often it limits itself to tearing off and eating the pleon
and eating away the contents of thorax of the crustacean. Having filled a stomach,
the glass goby slowly continues to soar in water, having stretched wide fins.
It accumulates fat for the most important event in life – for spawning. Only
once at life this small fish can spawn and hatch fry. At females almost all
nutrients will be transformed to the portion of large eggs, and the body of
the male to spawning time changes by strange way: jaw bones extend, the mouth
expands, teeth decrease. The mouth of the male turns to the true mobile incubator
where fry are carrying. In shoals of plankton it is possible to see the “large-headed”
males busy with egg bearing. They strongly grow thin, and it seems, that the
head is attached to the fish obviously “not according by the size”. In mouth
of such males the precious laying is incubating. Felt the leptodora presence
near to itself, such male does not attack any more, and tries to swim out, carrying
away eggs. In rest the male “being in the family way” regularly ventilates eggs,
driving water through semi-opened mouth. Through walls of mouth it is possible
even to observe, how eggs are incubating, larvae move in a mouth of the daddy
and turn to the fry ready to independent life.
All time while fry are in the mouth of the male, it eats nothing, supporting
self-existence due to the nutrients saved up in the organism. Fat in the beginning
is using, then the gland and the intestinal tract reduction begins, and at last
stage muscles of its body start to atrophy.
Fry in the mouth of the male grow simultaneously - they emit the chemical substances
synchronizing development of hatch. And one fine day from the opened mouth of
the father the true school of fry ready to independent life comes up. At the
moment of fry going out the male turns to real “living mummy”. Changes in its
body are so great, that they become absolutely irreversible. Having executed
the duty to the future generations, the male perishes. Plankton midgescuds and
… hawk leptodoras, which have no objection to diversify the ration with carrion,
wait for this moment.
The big congestions of plankton in the high sea involve rather large fishes
eating water smallness. The high sea is inhabited with schools of large gobies,
evolved to pelagic habit of life. They pursue driven by wind and waves shoals
of plankton crustaceans and fry, eating only them. Pelagic silvergobies swim
in the big schools - up to hundred ones and more. From afar their silvery colouring
makes them practically invisible on the background of sea water, and the cloud
of plankton still worsens visibility, in addition protecting gobies.
Having found out the congestion of plankton, silvergobies begin hunting. They
open too much wide mouths and spread operculums wide. Branchial arches of fishes
turn to the original plankton net filtering large zooplankton. Midgescuds, leptodoras,
glass gobies - all these creatures get in this mouth-trap. The silvergoby moves
by tail, swimming through the cloud of plankton. Thus its pectoral fins are
opened like fans, assuring balance and elevating force.
On bodies of some gobies tiny long-bodied small fishes sit – they are gobies
too: bellysucker gobies. Their abdominal fins have turned to very powerful sucker,
safely keeping them on the body of the chosen host. The bellysucker goby clears
the body of the host fish from parasites, receiving thus the opportunity to
move freely together with silvergobies. And during the feeding of the host fish
the bellysucker goby can regale itself too not bad: for any seconds darting
off from the body of the silvergoby, it catches large crustaceans swimming near
the mouth of the host fish. While the host fish does not hunt, the bellysucker
goby can even get to it into the mouth, accurately clearing gills from parasitic
crustaceans and worms which infect silvergobies with the help of plankton larvae.
The school of silvergobies finishes feeding. Fishes accurately close mouths,
from time to time moving by the bottom jaw from side to side - so they pack
up the trap organs. Having folded pectoral fins, the school of fishes is swimming
near the surface. The sunlight transforms their bodies to inexpressive flat
silhouettes invisible from afar. But swimming fishes are given out with the
fluctuations of water spreading from school of gobies far away. And sensitive
organs of one inhabitant from Fourseas have marked this school.
Almost eight-meter long tsar – fish, slowly swam through thickness of water,
has quickened, when cells of its lateral line have felt movement of fish school.
Though it would not see gobies, even they had swim twice closer to it, the lateral
line has precisely prompted to the fish the direction and provisional distance
up to the school of prey. The long crescent tail has struck on water, and the
lazy creature had turned to the live torpedo. Had gathered speed, the tsar –
fish, as if the battering ram had ran to school of silvergobies. Its toothless
mouth has widely swept open, having grabbed at once some large fishes, and then
have promptly slammed. There is no sense to continue attack – the school has
swum out, and hunting for single fishes is energetically unprofitable. The attack
has taken only some seconds; after it the tsar-fish has again found greatness
and calmness of movements. In water at the place of swum out school of silvergobies
the bellysucker goby, unhooked from the host at the attack of predator, lonely
scurried here and there. And it has no other way, except for to go down to the
skin of the huge armored fish and to stick strongly to one of plates on predator’s
body.
Tsar-fishes not always live in the sea - once a year they rise upwards in the
rivers where at the pebble shallow waters spawning rituals of giants take place.
Eggs are buried in pebble and some days develop in relative safety from large
fishes. And tiny larvae and fry of tsar-fish get in the world full of dangers.
Millions of them perish literally in the first months of life, becoming prey
of fishes and water insects. But the survived ones can live a long time - from
above one and half hundreds years.
The young growth of tsar-fish grown to length 5 - 6 cm (after 1-st year of life)
migrates down in the sea and first time keeps in the freshened shallow waters
overgrown with water plants. Fry of tsar-fish are fattened by small scuds and
larvae of insects, and pass to feeding by fish fry later. But while they are
small, they represent the delicious dish for local predators.
Sandy shallow water is habitat of set of worms and larvae of mosquitoes. The
tsar-fish fry finds them, cautiously investigating the top layer of sand. It
literally touches sand by wattles supplied with set of chemoreceptors. And at
last the fry feels something edible: under sand the red larva of chironomid
midge moves. The fry picks up the portion of sand by long snout, and throws
it up. From the cloud of silt and sand at once few larvae jump out. Wriggling
and writing out "eights" in water, they vainly try to rescue themselves,
but the small fish quickly catches them all. The frightened away scud also disappears
in stomach of young predator. However the external calmness of landscape can
be deceptive: the enemy has nearby hidden, and it waits, while the fry of tsar-fish
will swim up more close. From sand pair of attentive eyes, turning after each
movement of planned catch, sticks up. And when the fry unfortunately swims up
too close, the shallow as if blows up: the flat head appears in cloud of silt
and sand, the huge mouth opens, and the current of water literally sucks the
fry in. Sharp teeth seize prey, not giving it the chance to rescue. Having swallowed
catch, the invisible predator leaves the shelter. From sand the huge wide head,
long trunk with big wing-shaped fins, and long tail appear. It is the stargazer
sandgoby: its eyes are shifted upwards, allowing the fish dug in sand to look
for catch. The fish about meter long slides above the bottom, flapping by pectoral
fins, as if by wings. Having found the new place for the ambush, the fish falls
on sand. Had crept a little on it, the fish digs in it by lateral movements
of body, and then throws on itself sand by fins. Soon silt settles on the bottom
and nothing gives out presence of predator. Only behind eyes, sticking up from
sand, the sediment layer waves, when the fish quietly takes water in the branchial
cavity and cautiously lets it out. The trap is placed.
The half meter long youngster of tsar-fish swims above the sandgoby laying in
an ambush. But the predator will not attack: such catch is rather large for
it. And in thickets of pondweed other hunter is hidden which is not to be averse
to attack the young tsar-fish. The zandergoby is an inactive predator, as well
as the majority of gobies. Due to the large size and the special anatomy of
mouth it can eat large fishes. And the young tsar-fish is not too tough to it.
Goggled eye the zandergoby observes the young tsar-fish engaged in search of
scuds and worms. Swimming above the bottom, it as if touches by wattles sand
and silt. Eyes of the fish look upwards and in sides, but wattles give the full
information about the hidden animals. From time to time the fish rushes on the
bottom and takes from sand the next scud or the wriggling mosquito larva. When
the large scud runs away from a tsar-fish by jumps, it swims up too close to
thickets of pondweed in excitement of pursuit.
Reaction of the zandergoby is momentary: it rushes out from an ambush and catches
the young tsar-fish across the trunk. However almost at once it sets catch free:
the young tsar-fish is densely covered with armour of osseous plates, and the
predator simply at once had broken some teeth. And the young tsar-fish has not
suffered almost: one of teeth has put to it an insignificant cut at the stomach.
In some days the wound will skin over.
Usually the gobies of other species not protected by shell serve as the catch
for the zandergoby. It hunts in coastal zone, and at times after storm it has
plentiful catch “on the dinner table”. The next storm have brought to the coastal
zone strangers from other ecosystem: school of pelagic silvergobies. Silvery
creatures look completely inappropriate in green-brown-yellow world of shallows
and thickets of plants. It had fallen to their share quite enough: at some fishes
scales are scratched, magnificent fan-shaped fins are tore off, on bodies of
several fishes there are deep grazes. Silvergobies are scared by unusual conditions:
they press close to each other, forming dense globe-shaped congestion. Their
sides brightly sparkle in sunlight, giving out to predators the location of
fish school. And predators do not keep long waiting: from greenish haze the
monster appears - adult, approximately six-meter long tsar-fish. It heads straight
to school of silvergobies. The huge mouth opens, in it at once three fishes
disappear, and the monster departures. But gobies do not swim away, as it would
be in the high sea. Disoriented by unusual conditions, they gather to sphere
heads inside even more densely. But the tsar-fish, as against these gobies,
feels like at home both in the high sea, and in coastal zone. And it uses the
moment, coming back to school of gobies. Attacking more and more times, it orderly
annihilates pelagic gobies. Eventually from flight only one fish had remained
in panic rushing here and there. At last it rushes to thickets... where its
head immediately ended up in strong bite of zandergoby’s jaws. Sharp teeth easily
stab skull of the silvergoby, and catch of the zandergoby instantly dies. The
predator starts to swallow prey orderly. Its jaws alternately move fish body
in wide gullet, hooking it by teeth located on the palate and jaw bones. Gradually
catch takes the place in stomach of the zandergoby, and the predator hides more
deeply in thicket. Certainly, it is still a predator, and the majority of fishes
will be afraid of it. But in the sea there are such fishes that are afraid of
nobody...
The tsar-fish, slowly moving by tail, swims above the bottom. Tips of its long
wattles feel bottom in searches of edible creatures. More and more clearly the
huge fish feels the smell of catch, however its small eyes see only few fry
of any goby swam above the head of giant. And they obviously do not correspond
to the smell which is felt by fish. Catch is somewhere beside, but it is hidden.
Some shrubs of plants waving near to the tsar-fish, can not hide large catch.
It means, that catch is somewhere under sand. And the tsar-fish starts to dig
it by lateral head movements. Literally at once from sand the large sandgoby
rushes up, up to last moment not leaving the shelter. Flapping by pectoral fins,
the fish tries to swim away, but the huge predator right here overtakes the
goby, presses to bottom and snaps it. Having crushed catch by jaws, the tsar-fish
re-seizes the goby from the head and swallows. Few seconds - and all is over.
The silt lifted by short fight of fishes slowly sediments on the bottom. And
the tsar-fish majestically leaves to the high sea.
Gradually the bottom starts to revive: scuds dug in sand move, tiny gobies swim.
And above thickets the young tsar-fish swims. While it is still small and easy
can become the anybody’s catch, but twenty years later all live beings will
hide and freeze horror-stricken when it will visit this area.
Bestiary |
Midgescud (Planctopulex chaetognathus)
Order: Amphipoda
The pelagic representative of order Amphipoda. Length of its
body is about 1.5 cm. This crustacean filters phytoplankton, breeds plentifully
in water thickness, forming large congestions. The animal eats with the help
of mouth legs covered densely with hairs. With the help of fleshy blades in
the basis of mouth legs the crustacean creates constant current of water through
hairs of mouth legs. Thus cells of algae and protozoans stick to them. From
time to time the crustacean scrapes by mandibles food gruel from mouth feet
and swallows it.
The crustacean spends all life in plankton. It soars in thickness of water,
having stretched legs covered with hairs. Hairs serve to slow down immersing
of the animal, and also serve as sensitive organs, allowing the crustacean to
trace movement of environmental water.
Diecious animal, but in the summer at the increasing of water temperature frequently
passes to parthenogenetic breeding. Eggs (up to 200 ones) are carrying in brood
pouch on the bottom side of the female body. Alternation of generations occurs
quickly - during 4 weeks the larvae hatch from eggs, stay in brood pouch of
mother and go out in water. Within 3 months the crustacean becomes the adult
and breeds at first time. During the life the female can make up to 10 clutches
2 months apart.
Hawk leptodora (Macroleptodora accipitrina)
Order: Phyllopoda
The representative of cladocer crustaceans (order Phyllopoda,
suborder Cladocera). Length of body is up to 3 cm. Body is translucent; it seems,
that the crustacean is made of glass. Through covers of body internal organs
are perfectly visible. Sight of this animal is perfectly advanced, though there
is only one large complex eye at the forward part of head. This is predating
species, attacking crustaceans and fish fry; for day it eats as much food, as
it weights itself. The animal spends the most part of time, soaring in thickness
of water, but for prey capture it is capable to make sharp throws. Long legs
and two spikes on the end of pleon facilitate soaring; the animal quickly swims
with the help of movements of the huge oar-like antennas covered with hairs.
It seizes catch by large forward leg pair covered with bristles from within.
Significant part of lifetime the crustacean breeds parthenogenetically, males
appear only in extreme conditions (cold snap, increase of water salinity in
the closed bays). Eggs are carrying in brood pouch on the back side. Larval
stage lasts 8 days, general life expectancy is about 1 month. The significant
part of larvae perishes as the result of cannibalism of adult individuals.
Stargazer sandgoby (Astrogobius arenarius)
Order: Percoid fishes (Perciformes)
Family: Gobiidae
Picture by Lambert
Initial picture by Pavel Volkov |
This large species of gobies (Gobiidae) is the benthic ambush predator. Length
of the body is up to 1 meter. Appearance of this creature is rather strange:
the fish resembles the usual goby strongly stretched in width. Head is large
(about 1/5 of general fish length), eyes are small. Wide mouth and eyes are
revolved upwards (by this feature the fish resembles Holocene stargazer fishes
(Uranoscopus)). Operculums are revolved on the top side of the body, from sand
they are protected by the skin plica. That the fish free could breathe, the
plica at the top part of operculum forms the respiratory tubule through which
water is sucked in branchial cavity at the closed mouth. If to look at the fish
hidden in sand, it is possible to see, how from sand pair of short skinny tubules
sticks up, and around them sand from time to time distend and falls down - it
is the water accurately pulling out from the branchial cavity. Pectoral fins
are wide, fan-shaped. With their help the fish buries in sand and throws it
on the body for masking. Abdominal fins are short, with overgrown bases, helping
the fish to be dug in sand. The prickly back fin is separated from soft one,
in the basis of spikes there are well developed poisonous glands. Body is flatten,
caudal peduncle is long and thin, tail fin is narrow. The fish moves basically
due to waves of pectoral fins, during swimming resembling the ray. Coloring
of the body corresponds to environment in which the fish lives: the top side
of body is colored sandy yellow with small brown speckles, bottom side is grayish
white. The male differs from the female by larger size, wide head, graceful
body and wider prickly back fin which basis is colored black color and is bordered
by narrow white strip.
Spawning takes place in sea shallow waters, the male incubates eggs (up to 100
- 150 large grains of roe) in mouth within 2 weeks. The young growth 2 days
stays in mouth of the male, when the yolk sac will resorb. The generated fry
about 1 cm long leaves the male for ever and further live independently. At
4-years age at length about 60 cm the fish becomes adult and is able to spawn.
Live duration is up to 15 - 18 years.
Zandergoby (Luciogobius stizostedion)
Order: Percoid fishes (Perciformes)
Family: Gobiidae
The ambush predator of the family of gobies (Gobiidae), ecological analogue
of pike perch and pike. Length of the body is about 80 cm. Body is rather high:
the height is approximately twice more than width. Mouth is wide, in it there
are large slightly recurved teeth. Mouth cut is slanting, corners of mouth are
lowered downwards. The jaw anatomy allows to push the caught prey in gullet
by alternate advance back moving. Fins are wide, back and anal fins are shifted
back to tail. The prickly back fin is submitted by the several short spikes
connected by reduced membrane. Coloring is cross-striped, on grey background
there is the pattern of vertical green strips and brown speckles – it corresponds
to color scale of underwater plant thickets - the favorite shelter of fishes.
At males the membrane, connecting jaw bones, is painted red color. When the
fish closes mouth, this coloring is not visible, but in spawning season one
of elements of courtship ritual is the demonstration of bright membrane.
Fish keeps in thickets of long-stalk plants, trapping and seizing catch by throw.
It can catch fishes of the size comparable to itself, eats them due to an extensible
stomach.
Spawning takes place in thickets of water plants. The male and the female clear
from silt and dirt the flat stone on which eggs are spawned. The female protects
clutch, fanning it with movements of fins, the male protects territory around
of the clutch, sometimes substituting the female.
Pelagic silvergoby (Argentogobiosoma pelagica)
Order: Percoid fishes (Perciformes)
Family: Gobiidae
Large fish of family of gobies (Gobiidae) - length of body
is up to 50 cm. It inhabits thickness of water, not swimming to the bottom.
Wide pectoral
fins
and very fat liver facilitate to the fish soaring in water. The body is lengthened,
slightly compressed from sides. The head is large (till 1/5 of general length
of the fish), but the most part of it is occupied by the complex filtering
system of overgrown branchial edges with which help the fish filters zooplankton.
Teeth are thin, hair-looking, very numerous - they "lock" mouth,
not allowing catch to swim out. Eyes are large, slightly shifted to the top
part of head.
Coloring is soft: body is silver-gray with bluish shade, back is darker. Such
coloring is typical for fishes of thickness of water. Pectoral fins are wide,
fan-shaped and translucent. Unpaired fins are wide, in the first back fin there
are three poisonous spikes. The tail fin is high - fish can swim quickly, escaping
from enemies.
The spawning takes place in thickness of water, the male incubates eggs in mouth.
In clutch there is up to 200 small eggs. Larvae spend in mouth of the male about
one week, later they pass to independent life. The larva looks originally: unpaired
fins merge together, "bordering" the body. They are very wide - more
than height of body. It facilitates soaring in water. The larva eats algae,
later - protozoans and zooplankton. At the age of 3-month the development of
filtering system and pectoral fins begins. Fish matures at 1 year, life expectancy
is till 8 years. At the age of 3 years the fish grows to length 40 - 45 cm,
later its growth is slowed down.
Plankton glass goby (Pterogobiops crystallinus)
Order: Percoid fishes (Perciformes)
Family: Gobiidae
This is tiny species of plankton fishes - length of body of
the female is about 3 cm, the male is 3,5 cm long. Body is practically transparent,
at the swimming fish at insufficient illumination only large eyes are visible.
Intestines are shielded by shining lining of peritoneum. Against the light at
this fish all bones and intestines are visible.
This species constantly lives in plankton. It doe not approach close to coast,
preferring to stay in the central part of Fourseas. It keeps in water due to
the plenty of fat in body - the density of body is equal to density of water.
Soaring is promoted also by wide pectoral fins which rays are divided to 2/3
of the length, and the membrane has outgrowths as the fringe. The body of this
fish is rather high, unpaired fins are wide. Spikes of back fin are strongly
jutting out from membrane, their prick is poisonous. Jaws are strong, with long
teeth in forward part. Teeth jut outside at the closed mouth.
Fish eats crustaceans and their larvae; sometimes it can attack even predatory
crustaceans.
Spawning takes place only once a life. The female spawns eggs in mouth to the
male and perishes after spawning. The male perishes after the fry hatching.
With approach of spawning season the body of fishes changes: intestine degenerates,
sexual glands actively develop. At males jaw bones expand, forming large brooding
chamber for larvae. In clutch it is up to 40 large grains of roe. Larvae hatch
after 3 days, but stay in mouth of the male about 2 weeks. Life expectancy is
only 2 years.
Bellysucker goby (Echeneogobius striatus)
Order: Percoid fishes (Perciformes)
Family: Gobiidae
This small fish (body length is up to 5 - 6 cm), living on
the body of large fishes, differs by the powerful abdominal sucker formed, as
at all gobies, overgrown bases of abdominal fins. The body is the streamline-shaped,
tail is very long. Unpaired fins are short, tail fin is narrow, abdominal fins
are reduced up to small hooks - the fish is adapted to attachment to the body
of large fishes, hardly swimming independently. Pectoral fins are wide, with
strong fleshy bases. During movement of the host fish they help the goby of
the present species to keep in stream of water. Eyes are small, capable to remove
inside of eye-sockets when the host fish accelerates movement. Such feature
well protects eyes of the fish from casual traumas. Coloring is golden yellow
with black longitudinal strips on the back and along each side. Eyes are blue.
The male is more graceful, large and "large-headed", than the female.
Eats the rests of catch of the host fish, tiny plankton organisms (fish catches
it, leaving the host for some moments). Also the fish renders the host of service
of the cleaner, gathering parasites even from eyes, gills and mouth of host
fish.
The bellysucker goby spawns, bearing eggs and fry in branchial cavity. In clutch
it is up to 50 grains of rather large roe. Process of spawning is very original:
thus fishes do not leave the body of the host fish. The female spawns eggs in
the mouth to the male, then the male transfers her spawned eggs from mouth to
mouth and moves forward the female. It emits soft roe in water, and the female
holds the position behind it to catch by mouth soft roe as much as possible.
In the mouth of the female there is the fertilization of eggs which later are
transferring to the male for incubating. The young growth stays in the mouth
of the male up to resorbtion of the yolk sac (about 4 days), then they swim
out. First few weeks of life the young growth spends in coastal thickets of
plants, then searches for the host fish.
Tsar-fish (Pseudohuso cataphractus)
Order: Acipenseriformes
Family: Acipenseridae
It is the largest fish
of Fourseas - the huge sturgeon fish growing to 7 - 8 meters long. This is the
descendant of widely expanded and hardy species of sturgeons – the sterlet (Acipenser
ruthenus). Due to short life cycle this species could survive in the changeable
environment with strong anthropogenous influence.
Body shape is the characteristic form of almost sturgeon fishes - unpaired fins
are shifted to tail, tail fin has almost equal lobes: the top blade is only
a little longer than bottom one. The skin is covered with shell plates along
ridge and sides. At young growth intervals between lines of plates are little
(the shell is almost solid), it rescues fry from predators. The head is flat
with long firm snout, allowing to dig out catch from sea bottom. The mouth is
inferior, widely opening and toothless. Eyes are small, located on each side
of head. Fish has long wattles on which numerous organs of chemical feeling
are placed. With the help of wattles the fish finds food even in oozy muddy
water or under the sand layer. The bottom side of body is almost white, top
side is greyish green with slight cross strips.
The fish is active predator, young growth eats larvae of insects and worms.
Later the fish starts to eat fry and small fish in thickness of water, the adult
fish hunts large single and schooling fishes.
Spawning takes place in rivers, in clutch there are up to 5 - 8 million tiny
grains of roe. Parents dig eggs in pebble and do not care of it any more. Fry
the first year lives in rivers, later it migrates down in the sea. Sexual maturity
at males is at 12 - 14, at females - at 15 - 17 years, to this time length of
the fish increases to 3 - 3,5 meters. Life duration is up to 150 - 180 years,
separate individuals pass also 200-year boundary.