Tour to Neocene


73. Terror of the lake



Translated by Jackson Orzekowski
Edited by Timothy Morris and Pavel Volkov

Meganesia represents a continent located in the southern hemisphere sandwiched between the Pacific Ocean in the east and the Indian Ocean in the west. In the human epoch, depending on changes in sea level during the ice age, the whole landmass appeared and broke for several times. When Homo sapiens first appeared on this land during the ice age, the continent was whole. Later, as the massive glaciers of the northern hemisphere began to melt, sea levels rose, and the united landmass separated into the continent of Australia and the island of New Guinea. At the same time other forces were at work in the land down under, forces occurring deep beneath the thickness of the earth's crust. The lithospheric plate, on which Australia and New Guinea rested, slowly moved north towards the equator. The northern edge of this lithospheric plate rose slightly, and this had a great influence on the geography of the continent. In the south, the large shallow Eyre Gulf penetrated far inland. In the north, the geography of the mainland has undergone even more significant changes. Australia and New Guinea have reunited, reforming the single landmass of Meganesia. This has caused the Arafura Sea to become shallower, while the water in this sea has become greatly desalinated. In the Neocene, its connection with the ocean has weakened significantly, being maintained only through a series of small channels located in a vast belt of mangrove forests and swamps. The nearby Gulf of Carpentaria became separated from the ocean even earlier than the Arafura Sea, and by the Neocene had undergone even more dramatic changes. The water of the gulf has become even more desalinated than in Arafura Lake, and it is surrounded by extensive wetlands and mangrove forests. As a result, Gulf Carpentaria has transformed into Lake Carpentaria.
In the deep layers of Lake Carpentaria, the water is still slightly brackish – it is a legacy of this reservoir's maritime past. Freshwater descendants of marine animals also live here: stingrays, blowfishes, pipefishes and silversides. Some of them live only in the depths of the lake, staying in layers of saltier water, but most still inhabit shallow water, where the water is rich in oxygen, and life is plentiful and diverse. A significant amount of organic remains enters the depths of Lake Carpentaria; therefore the darkest deep-water parts of the lake are poor in life – oxygen is in obvious deficit here since it is spent on decay. From time to time, bubbles of methane and hydrogen sulfide burst out of the silt strata, quickly floating up and imploding on the surface. Someday the rich and diverse world of Lake Carpentaria will perish – the basin of the lake will be filled with organic remains, petrifying over time. This will turn the lake into a shallow swamp, split into many small bodies of water, before eventually causing Lake Carpentaria to disappear completely, with a dense tropical forest growing in its place.
However, these changes are still millions of years away. In the present, the lake prospers, the productivity of its upper layers are enough to support a diverse life, from shallow water down to the gloomy depths. The upper layers of lake water have a green tint due to an abundance of multiplying microscopic algae, which serve as food for planktonic crustaceans. Forests of underwater plants grow in shallow waters. At some distance from the coast, eel grass of enormous size form dense sod, resembling thickets of seaweed. Tuberous plants flourish in the coastal zone, including aponogetons and water lilies. Their leaves form especially dense thickets opposite the swampy shores, where herbivores have fewer opportunities to descend into the water for feeding. At sandbanks, tuberous plants recede further from the coast, and the leaves of the water lilies sway on the surface of the lake over two to three meters deep. In some places, the shores of Lake Carpentaria are overgrown with tall reeds, and the soil is riddled with their thin branching rhizomes.
Plants serve as food for a wide variety of animals – from crustaceans to large mammals. These herbivores are in turn preyed upon by a host of predatory organisms, some of them being huge.
In the water, among thickets of pondweed with long, strong stems, a snake’s skin sways. Judging by its preservation, this snake had shed its skin recently. Obviously, the snake swam intentionally into the thicket of pondweed so that the friction of the stalks, which are resistant to tearing, helped to shed its exfoliated corneous epidermis. Due to the fact that the snake molted in the water, its skin did not break from its own weight and has preserved the imprint of the appearance of the former owner. At the front end, a characteristic pattern of shields covering the head is noticeable. Among them, two wide transparent windows formed by a smooth horny film are clearly distinguishable. During life, they covered the eyes of the reptile. The discarded snakeskin sways in the waves, catching one end of the edge of the thicket. Perhaps in some other case it might seem like something ordinary, except for the size of the slough – its length is about ten meters.
The skin belonged to the most unusual and dangerous inhabitant of Lake Carpentaria – a gigantic python species that switched to an aquatic lifestyle. This is the eingana, the top predator of the lake. Moreover, the shed skin, swaying in the water, belongs to a young individual. An adult of this species can reach a length of twenty meters with a body thickness of about a meter. Such a giant has nothing to fear, and an adult eingana enjoys all the rights and privileges of being the supreme predator of the ecosystem.
Lake Carpentaria and the surrounding marshes are located in an area of heavy rainfall, and rivers are constantly flowing from the mountains, ensuring the stability of the water level in the lake. The shores of the lake and swamps are overgrown with tropical rainforest, and these places are literally boiling with life. The existence of many forest dwellers depend on the lake. Small forest birds arrive at the watering hole, behaving cautiously near the water. From time to time, flocks of colorful parrots appear on the shores of the lake, filling the vicinities with their loud calls.
A bird’s-eye view opens up a wonderful perspective of the lake, the waters of which have a greenish tint, especially clear under the rays of the morning sun. In the shallow coastal waters, water lilies grow, the thickets of which are abundantly colored with white, yellow and pink flowers. Against the background of the sandy bottom, thickets of pondweed stand out in darker spots. Schools of fish form dark spots changing their shape the whole time. If something scares them away, the school sharply changes its direction of movement, its sides shining in the rays of the sun.
It seems like a heap of smooth gray stones lays in the shallows near the coast. However, these “stones” move slowly along the coast, moving towards and away from one another. These things belong to the number of the largest local herbivores called bovipotamuses. Their presence on the territory of Meganesia is a result of human influence to the nature of the Earth. Bovipotamuses are the aquatic descendants of Asiatic water buffaloes. Marsupials cannot master aquatic habitats in full degree because of the brood pouch, where joeys are carried for a long time. Buffaloes, which are placental mammals, faced competition from marsupials and descendants of camels (also introduced by humans) in drier habitats, but found themselves practically without competition from the other herbivorous mammals of the continent when it came to living in lakes and swamps. The further specialization to living a semi-aquatic lifestyle has led to the emergence of bulky bovipotamuses, excellent swimmers and divers, and also tireless vegetation devourers. Maybe, without the insatiable appetite of bovipotamuses, the lake coasts would be overgrown heavily with impenetrable thickets of marsh plants. These huge herbivores thin out these plants, making these coastal thickets comfortable for life of other animals.
Bovipotamuses are perfectly adapted to life in the water. The skin of these mammals is almost hairless – only a thick mane of elongated hair grows on the neck along the spine and the tip of the tail is crowned with a tuft. On land, bovipotamus looks clumsy: this beast is of a stocky build, with a massive body, a large head and relatively short legs. But under the water, these animals literally transform: their bodies slide in the water easily and even gracefully. Wide hooves that look awkward when walking on the land now rake in the water, the animal swimming and diving with ease. Under water, the hooves expand and the extensible skin that ties the animal’s toes together helps it paddle through the water. Bovipotamuses, satiated after a night of feeding on the shore spend the morning at rest, basking in the water. The whole herd of them lies at a shallow depth, barely touching the bottom of the lake with their hooves. Bovipotamus’ eyes and nostrils sit on the top of its flattened head, making them visible on the surface even when the rest of its body is submerged. In large adults, the neck and shoulders also protrude above the water. Their wet manes stick to their skin in clumps, and small midges hover over them. Calves, which cannot reach the bottom with their feet, plunge into the water deeper than the adults, with only their heads sticking out on the surface of the water. Some of the calves simply lay their head on the back of their mother and doze, lazily moving their legs in their sleep. Adult animals ruminate slowly. Curiously, horns of bovipotamus are relatively poorly developed – their bases are close together and greatly expanded, forming something like a corneous helmet. This feature helps them move through the forest, pushing apart the branches of the bushes and protecting their eyes from wounds. In males, the ends of the horns are directed to the sides, an in females, horns are shortened and represent simply small pointed outgrowths directed down more often.
While bovipotamuses bask in the lake, they fail to notice an ominously writhing shadow approaching them. An adult eingana, a snake about eighteen meters long, is swimming along the coast, looking for a warmer place after a cool night. It is a reptile, and warmth is important for its life. However, the snake is not hunting. The huge reptile does not hide its presence: it emerges to the surface and pokes its head out of the water. Leathery valves open, and eingana exhales air in a strident whistle, and then inhales a breath of fresh air.
Bovipotamuses have keen hearing, so the animals, having barely heard the noise of the breathing reptile, instantly wake up. They do not see the huge snake, but the sound of breathing of eingana is associated with danger even among these simple-minded giants. Panic immediately takes hold of the herd, the adult and their calves rushing to the shore, causing a massive stampede. The adults bellow in terror, while cubs, crushed by the sides of adults, moo in fright. As bovipotamuses scramble ashore in a chaotic stampede, rising clouds of silt and sand from the bottom with their hooves, turning the green water plants into crumbs and trampled reeds. From there, they can get a better look at the cause of their panic – a giant snake wriggling smoothly in the water among the clouds of silt. The eingana is not hunting – if it were necessary, it would attack its prey from under the water. Instead, the snake is busy with an equally important matter. This is a pregnant adult female, and she needs to warm herself – it is an adult female, and its many month long pregnancy comes to an end. Although the Eingana is a descendant of pythons, it does not lay eggs, but gives birth to live young. This is an inevitable consequence of its adaptation to life in the water – it would be extremely difficult for large females to get out onto dry land to lay eggs, and it would be even more difficult to protect the clutch from enemies and take care of it. Viviparity and the transition to an aquatic lifestyle removed the size limitation from this snake’s ancestors, and as a result, eingana has turned into one of the Neocene’s largest reptiles.
The eingana female has long felt the movements of the babies in her belly. Now, as her body heats up in the warm waters of the lake, the movements of the juveniles in her belly become more active. It seems, it is a proper time for them to be born.
Waves of muscle contractions run through the body of the giant reptile. The body of the female eingana involuntarily bends, preparing to give birth to the offspring. Finally, after another wave of muscle contractions, the first snakeling escapes from the womb of the giant snake. At birth, it is still covered with a thin film, penetrated with blood vessels, but in the very first seconds after birth, juvenile breaks through it and leaves it, wriggling its entire body. Its length at birth is already about two meters. Several small fish, attracted by the smell of blood, rush in different directions when the newborn snake swims. The young reptile emerges to the surface of the water and takes its first breath. Following the first baby from the womb of the reptile, two more appear, one after the other. Like their sibling, they cast off the embryonic membranes and swim away. Within half an hour, the labor continues, the giant female eingana giving birth to two dozen cubs. This is the maximum fertility of an adult reptile of this species: the female is in top physical condition and has reached the full potential inherent in its nature.
The babies try to leave their mother as soon as possible. Wriggling, they quickly swim away and hide in the greenish water of the lake. The female, still in a stressful state, pays no attention to them. But later, having recovered from the stress and turning hungry after delivery, she will not hesitate to feed on her own offspring. Cannibalism is not uncommon in eingana populations. Therefore, young snakes of this species keep to the shallows, where adults rarely appear and suitable prey is more abundant.
In some places near the shores, the surface of the lake is covered with patches of floating plants. In the quiet shallow bays, ubiquitous duckweed grows, and in areas facing open water, another plant thrives – a local variety of water hyacinth (Eichornia), a descendant of a species introduced by humans. This plant forms rather dense clouds of floating “islands” that dampen waves and serve as a refuge for a variety of aquatic animals. Among the fluffy roots of water hyacinths, fish and shrimp hide from enemies, and the surface of the plants serves as a home for various invertebrates – mainly for insects. If the floating “islands” of the water hyacinth are washed ashore, bovipotamuses will willingly feed on them. To some extent, these animals restrain the growth of floating vegetation. The water hyacinth carpets are so thick that small herons can walk on them without falling through. These birds often use floating plants as a convenient hunting ground.
The shallow areas of the lake are well lit and warm, and here the upper layer of water acquires a greenish tint due to the microscopic algae developing in the water. This is one of the components of the foundation of the food pyramid, the top of which is crowned by the monstrous eingana. Due to their high rate of reproduction, algae can provide food for a variety of invertebrates – small cladocerans, rotifers and worms. Lacustrine plankton teems in the water, but most of the creatures that make up it have a transparent body and are poorly visible in the water. Only in the rays of the sun can one observe the tiny creatures scurrying about in the water column. However, some of the lake’s inhabitants do not need to see their food – they have a completely different way of feeding.
A shoal of small transparent creatures swims in the water column at a depth of about half a meter. At first glance, they look like small fish, but upon closer inspection, this similarity turns out to be deceiving. Their bodies are covered with chitinous shells, they have developed antennae and several pairs of articulated legs that perform various functions. This is another characteristic inhabitant of Lake Carpentaria, the bristle-legged shrimp. The structure of its legs is unusual for decapod crustaceans, and its lifestyle is clearly atypical for Atyidae family to which it belongs. In the human epoch, related species of Atyidae shrimps were large and heavy-built creatures that lived at the bottom and among plants, filtering edible particles from the water using two pairs of modified front legs. The ability of water filtering is preserved in the bristle-legged shrimp, but the lifestyle of this creature is completely different. In due course of evolution, it turned slimmer, and it allows this crustacean to populate the water column and master feeding on the lake plankton.
Bristle-legged shrimps spend a significant part of their life filtering their food. For this reason, they have two front pairs of walking legs modified into a trapping apparatus. They are covered with numerous hairs, and the shrimp constantly waves them rhythmically. Due to these movements, these shrimps can swim and gather planktonic animals at the same time. From time to time, the shrimps scrape off the accumulated food with their maxillipedes and swallow it.
The waters of Lake Carpentaria are slightly brackish – this is an evidence of its past when the lake was a bay of saltwater. In the depths there are layers of salt water, but the upper layer of water is heavily desalinated by rivers and rainwater. Residual salinity is present here, but the amount of salt is so low that it does not interfere with the growth of aquatic plants. And due to that same salt, the offspring of many invertebrate species can develop successfully in the water of the lake. Bristle-legged shrimps breed far from river mouths, and planktonic larvae of this species develop in the water column. It is possible that the shrimps themselves eat, along with other food, some of their own larvae at the planktonic stage of development. But their fertility is high enough to compensate for these and other losses, and their species thrives.
A school of bristle-legged shrimps feeds, slowly moving in the water column. Shrimps keep their distance from one another, gathering plankton. In the shallows, the water warms up and is well-illuminated, and it promotes the growth of unicellular algae. Small invertebrates thrive here – rotifers, microscopic cladocerans and insect larvae; therefore, shrimps have more than enough food for themselves. However, they must be careful – a predator may appear from where it is least expected.
An island of water hyacinth thickets floats on the surface of the water. This plant constantly grows long sarments, on which plantlets develop. Therefore, even a single plant can form a floating island of plants very soon. Long fluffy roots hang down from it in the water column, among which fry of fish and juvenile shrimps usually hide from predators. Feeling no danger, bristle-legged shrimps continue feeding. From time to time, one or another shrimp changes its position in the school and moves to a site richer in plankton. To do this, the crustacean waves its third pair of walking legs. Unlike the first two pairs of legs, these legs are wide and flat. In the ancestors of this species, they served for fixing on the substrate, but in the bristle-legged shrimp, they turned to fins. With several synchronous strokes of these legs, the shrimp swims to a new place, after which it continues to feed. At rest, its swimming legs serve as stabilizers – elevators and rudders.
While bristle-legged shrimp feed in peace, they fail to notice that they are being watched. A different shrimp is hiding on the island of floating plants among the roots. It does not feed on plankton but seeks more substantial prey. It is a large barracuda prawn, about 25 centimeters long, a formidable predator for its weight class. It does not chase its prey during the hunt, rather, it relies on the accuracy of its strike, in which all its forces are put. An ambush predator, it waits for prey of proper size to come within striking distance.
An islet of water hyacinth drifts on the water, driven by the wind. Bristle-legged shrimps are oblivious to the danger and continue filtering the water. The barracuda prawn is patient, waiting for a favorable set of circumstances only. As the wind carries its shelter towards its target, it is possible for it to expect for a success in hunting.
Barracuda prawn is a very distant relative of the bristle-legged shrimp and belongs to a completely different shrimp family. Unlike bristle-legged shrimps, this species is armed with strong claws, a cutting-edge weapon equipped with a pointed spike. When prey gets into such claws, there is no hope for escape.
The barracuda prawn sees its prey and senses its movements with the help of sensitive bristles growing on the antennae. It prepares to the attack and opens its claws. Trying not to give itself away with unnecessary movement, the barracuda prawn remains motionless. Only its large eyes on the stalks tremble slightly, betraying its tension. Gripping the roots of the water hyacinth, the shrimp hangs upside down. Thanks to this, it sees almost everything that happens under its body. Barracuda prawn observes bristle-legged shrimps carefully, choosing its target. The wind is on its side, and soon the drifting raft of water hyacinth appears right above the school of bristle-legged shrimps.
Having chosen its prey, the barracuda prawn swiftly attacks the school of bristle-legged shrimps. Due to its camouflage longitudinal striped coloration, the predatory shrimp remains invisible until it launches itself at the prey. There is no hope for the bristle-legged shrimp, it is already too late. Having run into the school of bristle-legged shrimps, the predatory crustacean drives them into a hysteric flight. However, one individual has not managed to avoid a fatal encounter with the predator. A large female, carrying a portion of eggs on its abdomen, was not agile enough, and one claw of the barracuda prawn closed across its body. The claw teeth pierce the shell of the prey; one of them penetrated deep into its body, tearing the ventral nerve cord and paralyzing the prey. There was a faint crunch, the legs of the caught shrimp trembling with violent convulsions. The hunt is over.
Holding the prey in its claw, the barracuda prawn moves its abdominal legs and swims back into its hiding place. Turning its back down, it clings to the roots of the water hyacinth and climbs deeper into the thickets, so as not to attract the attention of random fish that might try to take away its prey. Its maxillipedes covered with hard jags literally saw through the shell of the prey with ease, and the predatory shrimp quickly tears it into pieces and scrapes all the edible particles out of the shell, rendering the prey a lifeless husk.
The predators that inhabit the shallow coastal waters of Lake Carpentaria belong to many different groups of animals. Among them there are not only good swimmers, but also creatures, for which the appearing in water is highly unlikely.
The thickets of floating plants are extremely dense in some places. Due to the spongy, air-saturated tissue of the leaves or stems, these plants easily float on the surface and do not sink, even when small birds perch on them to drink. This particular aspect of these plants is used by one of the most unusual predators that inhabits the shores of Lake Carpentaria.
... The sun has just begun its journey across the sky, and the air has warmed only a little after the chill of night. Not even all the birds in the surrounding forests have woken up, and nocturnal predators have only recently came into daytime dream. This time is the most favorable for hunting for this unusual inhabitant of the lake. A tiny fluffy ball of yellowish-white color runs along the leaves of floating plants. This creature with long slender legs deftly jumps over the leaves of the water lily, spread over the surface of the water. It is so light that the leaf does not even bend when this animal runs over it. This creature moves on four slender legs, keeping its balance with the help of a hairless thin tail. It has an elongated head with movable ears and a flexible proboscis-like nose. This creature is one of the many descendants of the marsupial mice of the human era. A tiny creature, only a little bit larger than a bumble-bee, is actually a ferocious predator, and sometimes the size of its possible prey does not stop it.
The marsupial shrew runs along the leaves of aquatic plants, sniffing and looking for signs of the presence of other inhabitants in the floating thickets. This tiny marsupial is so light that even small leaves can support its weight. With this key adaptation, the marsupial shrew easily examines almost all the thickets of floating plants, except, perhaps, the continuous thickets of duckweed. The flexible sensitive nose of the animal is constantly in motion: a warm-blooded creature of this size literally burns up food in its stomach. A fast metabolism requires a constant search for food, and the Marsupial Shrew can eat twice its own weight in a single day. There is one essential circumstance that makes it difficult for this particular individual to find food: it is an adult female with cubs in her pouch. Therefore, she cannot dive, chasing fish fry and small shrimp under the water, as males of this species do. Instead, she will plunge her head into the water in search of prey.
Small snails creep on the underside of a water lily leaf, scraping microscopic algae and small sedentary animals. They breed in large numbers and are often eaten by other creatures. The marsupial shrew can hunt snails – it is an easy and tasty catch. When the marsupial runs along the surface of the leaf, the snails feel only slight vibration, which is not associated with danger in their primitive behavior. The marsupial shrew runs along the edge of the leaf: sooner or later one of these snails will appear here, and it will be easy to catch it.
A large ramshorn snail crawls onto the surface of the water. It belongs to the group of pulmonate mollusks, and from time to time must renew its air supply. A thick conical tentacle carefully examines the surface of the water, before the mollusk crawls out from under the leaf of the water lily and breathes, exposing the edge of its shell from the water, where a hole opens, leading to its pulmonary cavity.
When the sensitive nose of the marsupial shrew touches the snail’s body, the snail jerks itself into its shell and firmly adheres to the lower surface of the water lily. The marsupial shrew boldly thrusts her head into the water and grabs the snail’s shell with her teeth. Backing up, she pulls the shell towards her, bending the edge of the water lily leaf at the same time. With abrupt lateral movements of the head, the marsupial shrew begins to tear the mollusk from the leaf. The frenzied vigor of the tiny creature eventually meets with success, and she rolls back to the middle of the leaf of the plant, holding a shell in her teeth. In a final attempt to defend itself, the snail released a large amount of sticky mucus from its shell. The marsupial shrew throws down the shell and begins cleaning its face hastily with high-pitched sneezing. The animal then grabs the edge of the shell with its teeth and begins to gnaw at it, breaking off pieces. In a few minutes, the marsupial shrew reaches the snail’s body and pulls it out of the shell with one sharp movement. She eats the prey even faster and throws the emptied shell on the leaf.
Finding food can be dangerous for such a tiny creature. In the thickets of floating plants, there are inhabitants that can tear off the head of this animal with a single blow. In addition, they are in their native element under water, and the marsupial shrew cannot hold its breath even for a minute. However, the marsupial has speed on its side, which allows it to cope with the larger aquatic animals.
A small barracuda prawn hangs on the roots of a water hyacinth, waiting for suitable prey to approach. But instead of this, the female of the marsupial shrew approaches to its ambush above the water. The ramshorn snail was eaten about a quarter of an hour ago, and now the animal is hungry again. The marsupial shrew descends along the leaves of the plants to the water. Among the leaf stalks swollen like bubbles, insect larvae can be found. This is not a bad meal either, but it takes too much time to collect this food to be worth the effort.
The barracuda prawn, less than half of its adult size, is already well equipped for hunting. The grip of its claws may not be as strong as that of the adults, but they are just as deadly for prey of a suitable size. Despite her size, she will be able to defend herself in case of attack. But everything will depend on how the situation plays out, and one false move can ruin the entire hunt.
The marsupial shrew’s nose sinks into the water, and the creature’s nostrils automatically close. However, sensitive vibrissae help the animal receive information about what cannot be seen. The tip of the animal's nose slightly touches the feathery antenna of the young barracuda prawn. This is followed by an instant reaction – the marsupial shrew thrusts its head into the water, snatching the abdomen of the prawn hidden in ambush with its teeth and pulls it out of the water. The attack takes only a second: the hunting tactics of the marsupial shrew relies on fast, devastating strike. The prawn, thrown out of the water in the violent tussle, finds itself out of its native habitat, and its abdomen beats the air idly, while the animal tumbles among leaves of water hyacinth. The sharp teeth of the marsupial shrew grab the body of the prawn and the shell is crunched in the shrew’s teeth. Having bitten the prey, which was twice as long as itself, the marsupial shrew bounces back, avoiding the claws of the predatory prawn. She must be careful: she has two rather developed cubs in her brood pouch, and her maternal instinct keeps her from more decisive actions. In addition, its prey is still full of strength and its claws are potentially lethal. Within a minute, the marsupial shrew strikes the prawn repeatedly, attempting to immobilize it. Finally, the movements of the prawn became weaker, and the abdomen beats become less frequent. As life leaves the body of the prawn, the marsupial shrew can start eating. She manages to provide herself with food for the next few hours at little cost: the prawn had only scratched her nose, with several drops of blood flow out of the wound.
After licking the wound and cleaning fur a little, the marsupial shrew proceeds to eat its dinner. Sharp teeth bite into the meat of the prawn, and the animal greedily eats the contents of its shell. This is food that is extremely necessary for a creature with such a fast metabolism. The marsupial shrew feeds hastily, trying to eat as much and as quickly as possible. At any time, competitors from among her own species may appear, but it is much more likely that the remnants of the prey can be simply taken by a larger lover of free meal. The marsupial shrew cannot eat the whole shrimp alone even in half an hour – it needs to rest. Her cubs need milk, and there will be more of it once the female can rest. Therefore, she drags the remains of the prey into a large rosette of a water hyacinth and settles down next to it. She feels weariness together with satiety. Having sniffed air, the marsupial shrew made herself comfortable in the middle of the plant rosette and had fallen asleep with one eye open.
Meat juice from the remains of the prey drips into the water. The smell of the remains attracts fish, and they gather under the thickets of water hyacinth. Trying to get to the remains of the prawn, they pull the roots of the plant and squeeze between them to the surface of the water. The shocks of the fish disturb the sleeping marsupial shrew female, and she interrupts her sleep several times, looking around and sniffing. But she does not notice anything disturbing, and again falls asleep.
Not only water, but also the wind carries the smell of the prey of the marsupial shrew. To some of the inhabitants of the lake, one half-eaten prawn is not worth the attention, but someone else can try to obtain even such a small prey. Another marsupial shrew may try to take the carcass from the lawful owner. And this creature soon appears on the islet of water hyacinth, attracted by the smell of someone else’s bounty.
The intruder is a male. It is smaller and more aggressive than the female. Jumping over the leaves of water lilies, he easily reaches the thickets of water hyacinth, in which the female marsupial shrew hid her prey. Having jumped on the leaf, the male stretches his sensitive proboscis-like nose and catches the appetizing smell of prawn meat. Using his sense of smell, he quickly reaches a rosette of water hyacinth with the half-eaten prawn in it. However, the male either does not notice or pay attention to the smell of the female – who is resting after her hunt. Obviously, this male is used to solving the problems of dominance with force, so it can afford not pay attention to them.
This time, however, the male marsupial shrew makes a fatal mistake by underestimating his opponent. Before he can take a piece of the prey he pretended to, the female attacks, pouncing on the male. While she may not be as agile as the male, but she is well rested and full of energy. The female grabs his shoulder and begins to toss the male around like a dog. He cries in pain and gives a jerk in attempt to bite his enemy, who has appeared out of nowhere. But the only thing he manages to do is scratch the female with his hind paw. The female does not let go of his shoulder, moving her jaws, as if trying to chew off a piece. The two animals grapple in a ball and roll among the leaves of the water hyacinth. Eventually, both animals fall into the water. They do not drown, because the sarments of water hyacinth stretch and intertwine almost under the very surface of the water. But the female is more concerned with the fate of her joeys – she cannot afford to allow the water to get into the brood pouch. She feels the cubs stir from the water seeping into the pouch, unclenches her jaws and jumps out onto the leaf of the plant. The male does not realize that he was released, and for another second, he still flounders in the water. Jumping out onto the floats of the water hyacinth, he charges the female. His teeth only grab a flap of skin on the female’s thigh, leaving a shallow but long cut. In response, the female turns around and seizes him by the base of the tail. Squeaking in pain, the male escapes from her teeth and flees. The free treat was too expensive for him. The owner of the prey made some jumps following him, but didn’t begin to chase him for real. She displayed him her force, drove the stranger away from the prey and the only thing, she needs to do now is to finish her food. The sharp teeth of the marsupial shrew will easily bite through even the strong chitinous armor on the claws of the caught prawn, and after feeding, the remains of the prey are unlikely to interest anyone larger than microscopic crustaceans or worms.
In the ecosystem, every predator can easily become a prey, and this circumstance even saves partly the herbivorous inhabitants of Lake Carpentaria from destruction, maintaining a certain balance between predators and prey.
The shores of the lake are cut by shallow bays with swampy shores. This is a great place for shrimp and fish juveniles to live – large underwater predators rarely appear here. In addition, microscopic algae thrive in well-lit water, serving as food for shrimp and fish fry. Near the coast, the surface of such bays is usually covered with a dense carpet of duckweed, and this provides additional protection and food for small animals.
A school of young bristle-legged shrimp feeds in shallow water. They are smaller and more transparent than adults, so a predator hunting with the help of sight would hardly detect them. But among the inhabitants of the lake there are those who hunt in a different way, and they do not care what their food looks like.
A young barracuda prawn, barely a tenth of the size of an adult, is already an active predator. Hanging on the carpet of duckweed from below, it senses the presence of young bristle-legged shrimps. Its antennae, equipped with sensitive bristles, make it possible to detect the movement of the surrounding water, and the primitive brain of this predator distinguishes among the multitude of sensations those that indicate the presence of prey. It seems that the prey does not notice the hidden hunter: the prawn feels the movement of water next to it. It targets prey almost blindly, but there is still a chance of success.
A long beak, widened at the end, plunges into the water quickly, almost without a splash. With a lateral movement, it rakes a layer of duckweed from the surface of the water and rises up. This is followed by another movement of the beak along the surface of the water – now in the opposite direction. A school of bristle-legged shrimp breaks loose and throws itself all over the place. Part of the shrimp rushes into the silt and freezes, being lightly powdered with it. Other individuals hide in the thickets. The short-sighted shrimps hardly notice how long bird legs with thin toes passed by, but they feel the movement of the water. The young barracuda prawn, alas, did not have time to react to the danger that appeared so suddenly, and together with many other inhabitants of the duckweed thickets, was swallowed by the owner of the beak – a long-legged white bird with several black spots on its plumage.
This inhabitant of Lake Carpentaria is a scoopbeak, a strange bird, similar to a heron or spoonbill, but is in fact a close relative of geese. Scoopbeak has lost an ability to swim – its toes are not connected by a palama. But its legs have become similar to those of a heron and allow their owner to wander through the silt with ease. These birds are common in the tropics of the Old World and Meganesia and inhabits warm shallow bodies of water. In places with a seasonal climate, where bodies of water dry up for part of the year, the scoopbeaks are migratory birds. And where the climate remains humid all year round, scoopbeaks form large settled populations.
Scoopbeaks live and feed in flocks. They “mow” duckweed, often synchronizing their movements. This food is rich in protein and vitamins, and these birds do very well on such a diet. In addition, duckweed reproduces very quickly, and they are always provided with food. Scoopbeaks are distinguished by their aggressiveness towards ducks – their main competitors for food; they drive them out to deeper parts of lakes and rivers, where they cannot feed themselves.
The scoopbeak’s beak is a device for filtering small food particles from water. A feeding bird tilts its head to one side and makes an arc along the surface of the water with its beak, moving its head and neck from side to side. Bristles grow along the edges of the beak, forming a filtration apparatus. With their help, the bird captures duckweed and other small floating plants from the surface of the water. In addition to duckweed, scoopbeaks feed on a variety of floating plant inhabitants, including mosquito larvae, as well as cladocerans and other aquatic animals that accumulate in the upper layer of water. During the mass flight of mayflies, when thousands of these insects die on the surface of the water, scoopbeaks flock to the reservoirs, where this occurs, and feed in numerous flocks. Apart from the aggressiveness towards water birds, scoopbeaks are among the most peaceful lake inhabitants.
A scoopbeak flock wanders through shallow water. Duckweed thickets do not form a continuous carpet, and birds feed only when they are in close proximity to the plants. A small heron walks behind them, looking for invertebrates and fish fry, which have been frightened by the scoopbeaks. It is not afraid to come close to them, and sometimes snatches fish right from under their feet. Sometimes one scoopbeak or another “mows” the water – the bird found a school of shrimps or small fry near the surface of the water and catches them this way. During feeding, the scoopbeaks are careful – they can be attacked by aella eagles living in the forests around the lake. Therefore, the birds, taking duckweed from the surface of the water, look at the sky with one eye, trying to notice in time a black-and-white wide-winged bird, whose claws bring death to them. But the danger can appear also from the other side – from under the water.
A young eingana, born a week ago, has time to shed. At birth, it was already a two-meter creature, completely ready to withstand possible enemies. For a while, the newborn eingana lived off the supply of nutrients received in the mother’s womb. Now, after shedding, it is ready for the first independent lunch of its life. Reptiles almost do not need to learn – all the necessary behaviors are innate, and they just need to apply them correctly. The most important thing for a hunter is to choose the right prey. There are many animals around, and the snake can smell them in the water. In the distance, a herd of bovipotamuses, massive and stupid creatures, bask in the water. But for a young snake, even newborn bovipotamus calves are too large, and adults can easily squash it into jelly. The marsupial shrew, running along the leaves near the shore is too small a prey item for a reptile of this size. Fish swim faster than einganas, and they simply cannot be obtained. But a flock of scoopbeaks that have taken a liking to the coastal shallow water is an ideal opportunity to get a good lunch. These birds are just the right size and do not seem to be alarmed yet.
The eingana inhales a gulp of air and disappears under the water. It is not visible under the leaves of water lilies and aponogetons floating on the surface, and it is getting closer and closer to the bird flock. Scoopbeaks are busy feeding – they gather duckweed from the surface of the water. The glare of sunlight on the waves prevents the birds from seeing what the depth is hiding. And while they are calm, but it will not continue as such for long.
The young eingana slides along the bottom, trying not to approach the surface of the water. It keeps close to the thickets of the aquatic plants, and, in order to replenish its air supply, raises its head among their leaves creeping near the surface of the water. It manages to imperceptibly approach the feeding scoopbeaks at a sufficiently close distance, and the reptile only waits for a convenient moment to attack.
Scoopbeaks gather duckweed from the surface of the water, unaware that they are moving towards danger. A flock of about two dozen birds stretches out in a long line, gathering food from the surface of the pool. Raising their legs sedately, the birds walk closer and closer to the hidden eingana. The reptile senses the steps of birds, muffled by a layer of silt, and prepares to attack. It tensed its whole body, ready to put all its strength into one precise throw. And the birds are coming closer and closer to the snake...
Eingana’s throw was surprisingly accurate for its first hunt in its life. The reptile grabs the scoopbeak’s neck, pulls the bird into the water, wrapping its body around the bird. The caught scoopbeak had time to emit a short, alarming cry and flapped its wings in an unsuccessful attempt to escape from the death rings of the eingana. The rest of the birds, seeing what had happened, run to the sides, flapping their wings, and take off, sending alarming calls to each other. The panic of scoopbeaks spreads to the other inhabitants of the lake. Small birds that arrived at the watering place took off and headed towards the forest. A small kangaroo, lazily chewing on the leaves of marsh plants, jumps out of the water in one jump and hops away from the shore. A herd of bovipotamuses, resting nearby, reacted to the noise of the fleeing scoopbeaks with a lingering bellow. The pool turned to a place of the tragedy became deserted very fast.
Eingana continues to tighten the rings around the scoopbeack’s body. It feels the movements of the prey and whenever the bird tries to move, squeezes the rings even tighter. The reptile is much heavier than the bird, and the body of the caught scoopbeak gradually disappears under the water. Clouds of silt rise from the bottom, a torn stem of a water plant, a white feather on the surface of the water and several air bubbles escaped from the lungs of a strangled bird – these are all evidences of the successful hunt of the eingana.
After a few minutes, eingana loosened its rings and the body of the scoopbeak flutters in the water – the bird is dead. The snake is now ready to swallow its food. Holding the prey with the coils of its body, eingana sticks its head out of the water and takes a good breath of fresh air. Then it dives and begins to swallow the dead bird. Having clasped the body of the scoopbeak with its jaws, the snake begins to stretch itself onto its prey. Due to the elastic ligaments, the jaws of the reptile open very wide. And the buoyancy of the water helps the eingana swallow the bird quickly, without friction on the ground. Despite the fact that it was the first lunch in its life, eingana finishes it in fifteen minutes. After the prey takes its proper place in the stomach, the reptile gradually falls into a passive condition. Now the only things it needs are warmth and peace. The water in the gulf warms up well, and it makes no sense for the eingana to swim away somewhere. It simply finds a place in the shallows away from the coast and lays down at the bottom, exposing only the tip of its nose out of the water for breathing.
Eingana is not the only reptile kind in the lake. Lake Carpentaria became home to another kind of reptile, a representative of the archosaur clade that is dying out in the Neocene.
On the sandy shores of Lake Carpentaria, long-tailed creatures covered with armored hide bask in the sun. Their backs are covered with strong corneous scutes, and their tails are laterally compressed and deep. When one of the reptiles raises its head, one more feature of this species becomes noticeable – an elongated narrow snout. The upper jaw in adults is flattened, and the teeth are directed not from top to bottom, but to the sides. Because of this, the jaw of the animal is a bit like the rostrum of a sawfish. This is a saw-nosed crocodile, one of the specialized species of the crocodile order.
For 25 million before that time, people actively exterminated crocodiles for various reasons, and in most of the former range, they disappeared. In the early Neocene, other reptiles took advantage of the situation, becoming ecological analogs of crocodiles in most of the former range of these animals. To survive, the few remaining crocodile species specialized to avoid competition with their replacements. In particular, saw-nosed crocodiles have become almost exclusively fish-eating reptiles. In connection with the change in the diet, the behavior of these animals has changed: they are less bloodthirsty than their ancestors, who could, at an opportunity, eat their own smaller relative of smaller size. In contrast to them, saw-nosed crocodiles actually do not pay attention to the young of their own species, and young individuals roam freely among adult relatives. Sometimes these crocodiles, basking in the sun, lie on top of each other, and their resting places look more like a seal rookery.
A large saw-nosed crocodile rises to its feet and slowly walks towards the water, dragging its long tail along the ground. On land, it seems awkward because of the elongated hind legs, which is why its sacrum rises noticeably above the shoulders. But, when the saw-nosed crocodile enters the water, it transforms. Having pressed its front paws to the sides, it walks for some time in shallow water only on its hind legs, and then sharply flaps its tail and moves into the depths.
Saw-nosed crocodiles hunt only live prey and do not feed on carrion. They prefer to ambush from the bottom, holding their breath for half an hour or more. All this time the crocodile remains motionless, and the fish often lose caution, swimming almost point-blank to the waiting predator. Usually, the saw-nosed crocodile hides at the bottom near thickets of aquatic plants or among the snags, where fish like to hide.
Near the coast, at a depth of about a meter, leaves of aponogetons sway. Superb plants with thin decumbent rhizomes spread huge leaves, stretching in rosettes over the surface of the water. The surface of the leaves is covered with an elegant network of veins, between which the leaf tissues near the central vein are slightly corrugated. The sun gives young leaves a beautiful reddish hue, which changes to a deep green color as it grows. A little deeper from the surface of the water, dense thickets of hornwort and pondweed rise. These long-stemmed plants with small leaves provide shelter for numerous fish.
Among the leaves and stems, fish with deep bodies flicker. Their scales have a green metallic sheen, and bright red spots reflect from the operculums. These are disc rainbow fishes, representatives of a group of freshwater fish characteristic of Meganesia. Once upon a time in the human epoch, their ancestors displayed tremendous diversity, and among them there were many endemic species. But after the introduction of new species of fish into Australia and New Guinea, the numbers and diversity of native species began to decline. Rainbow fishes, capable of living not only in fresh, but also in brackish water, survived in estuaries and freshwater bays, as well as in isolated lakes. Some species of these fish proved to be competitive in the new conditions, and their descendants took a noteworthy place in the newly emerging ecosystems. The brackish waters of Lake Carpentaria are home to many species of rainbow fishes. Sympatric speciation led to the appearance of distinct differences in color in the different species of these fish, which made it possible to distinguish quickly congeners from representatives of other species. Some species of rainbow fishes in Lake Carpentaria are remarkable with their bright coloration, including contrasting spots and stripes, as well as “neon” spots that glow brightly in the rays of sun.
Ruby-red spot on the operculum of disc rainbow fish serves as a species-specific identification signal. These fishes keep in schools in the thickets of underwater grasses, and bright color spots help them find each other in the tangle of stems and leaves. These fish rarely appear in open areas of shallow water, but when they do, their school is a stunning sight to behold.
A flock of scoopbeaks flies over the lake, hurrying into shallow waters, where the surface of the water is covered with duckweed. A flock of birds flies low above the surface of the water, and shadows of flying scoopbeaks frightening the inhabitants of the thickets, including the disc rainbow fishes, which hide among the undergrowth. Flying over the water, scoopbeaks notice a saw-nosed crocodile swimming to the fishing and choosing a position for ambush. This reptile does not hunt scoopbeaks, so the birds avoid the saw-nosed crocodile only because of its size. The flock of birds flies on, and the saw-nosed crocodile continues its way, not paying attention to them. It is useless to hunt in the thickets: the fish frightened by the crocodile only hide deeper into the midst of the stalks. Therefore, the crocodile swims along the coast, looking for a more convenient place to feed. Having covered about two hundred meters, it seems to have found a good place for an ambush.
Here the plants no longer form continuous thickets in the shallow coastal waters. From time to time, a local herd of bovipotamuses appears at this part of the coast, bringing the confusion and ruin to the leisurely course of life in the thickets. These gluttonous animals pull out whole armfuls of aquatic plants and eat them, leaving cakes of manure in the water. After their grazing, continuous thickets of underwater plants disappear. In the aftermath, only single bushes remain, which for some reason were not eaten by these animals. But then the real flourishing of life begins: the surviving rhizomes and tubers quickly form new leaves, and the surviving shoots of long-stemmed grasses take root and grow. Bovipotamus herds plow the coastal sand with their hooves, and the waves carry away the silt that has accumulated among the thickets. Feeding of these herbivores literally rejuvenates the natural community of coastal thickets, minimizing decomposition and leaving areas free of vegetation, which prevents the appearing of stagnant water zones in which silt begins to accumulate. In addition, many species of aquatic animals prefer to live not in solid thickets, but on the border of the thickets and areas of the bottom, free from plants.
The saw-nosed crocodile has found such a place. Here the waves throw onto the shore a tree trunk, which was once carried by the river into the lake. The trunk lies on a sandy bottom with its roots turned to the shore, surrounded by thickets of pondweed, and on one side a vast sandy area adjoins it. Only in some places it is overgrown with small bushes of pondweed – these are the remnants of thickets eaten by bovipotamuses about two weeks ago. Inhaling a portion of air, the saw-nosed crocodile sinks to the bottom and waits.
A school of disc rainbow fishes has been living in pondweed thickets in this area for several months. Previously, the thickets were much more extensive and there was enough food for all the fish. But then the situation changed: a herd of bovipotamuses came here to feed, and the usual state of affairs was disrupted. Large animals roamed along the bottom, raising clouds of silt, and devoured the plants, tearing them up by the roots. The disk rainbow fishes that lived on the edge of the thickets were forced to move to other places when the hulking bovipotamuses destroyed their home. Gradually, the thickets of pondweed were reduced to a small area around the tree trunk, where it was not so convenient for bovipotamuses to feed. This area has accumulated a lot of fish that previously lived in an area ten times larger. The disk rainbow fishes, finding themselves in this captivity, immediately gathered in one common school.
These fish do not do well in these thickets. Once in there, they first eat everything that can be eaten – worms, shrimp and snails. Some fishes pick the tops of the pondweed shoots, but they were not to their taste. Of course, under such circumstances, food ran out very quickly and hunger sets in. Some of the fish of other species, forced to move here, left the thickets for several nights, crossing a vast area of the sandy bottom, which had recently been densely overgrown with plants. But disk rainbow fishes were not among them – they are too fearful and stressed when they find themselves outside the thickets.
When the saw-nosed crocodile sinks to the bottom, several disc rainbow fishes notice its movements and rush into the thickets. But then the reptile freezes, slightly opening its mouth, and the fish returned to their usual life, completely forgetting about its existence. The body of the hidden saw-nosed crocodile is motionless, and only the eyes discreetly turn, following the fish. Several times fishes swim out of the thickets one by one, but immediately hid, not giving the saw-nosed crocodile a chance to catch them.
A school of disc rainbow fishes, crowding together in a small area of thickets, attracts the attention of another predator. This creature is much smaller than a crocodile, but it is also a skilled fish hunter. Its territory also turns out to be a feeding place for bovipotamuses, and the animals destroyed a significant part of the vegetation, forcing the owner of this territory to huddle on a tiny patch of surviving vegetation that barely hides its body. This is a distant relative of disc rainbow fish, the wide-mouthed rainbow pike. The length of this fish is about 70 centimeters, it is an adult female.
After a significant part of the hiding places on the territory of the rainbow pike was destroyed by bovipotamuses, it became much harder for the fish to hunt: too few fish swim over the sandbank, and they do not always swim in range for a sure strike. Therefore, the predatory fish decides to take a bold step – to cross the area of the bottom with destroyed vegetation, and to hunt in the preserved thickets.
After making sure that there are no large predators around, the fish leaves its shelter. Wide-mouthed rainbow pike has the ability to change its coloration, adjusting it to the shades of the surrounding area. At the beginning of this risky journey, the color of the rainbow pike still retained its greenish tints, that help it to hide among the plants, but within a few minutes its coloration changed to sandy-yellow, corresponding to the background of the bottom. The body of the predatory fish is covered with a marble pattern, which is remarkably similar to the glare of sunlight falling to the bottom through the surface of the water. Now the rainbow pike is ready to resettle.
In an open place, the fish behaves very carefully: the rainbow pike moves with quick bursts from one shelter to another. It freezes near some driftwood, now among the remains of plants, gnawed by the lumbering bovipotamuses, in a depression at the bottom. The fish gradually approaches the trunk of a tree lying at the bottom, near which its prey, disk rainbow fishes, hide in the thickets. Several times the rainbow pike was frightened by the shadows of birds flying over the water, and it laid down on the bottom and pressed its fins against the body, trying to become invisible. But these were false alarms, and the fish reacted to them only because it lacks any good shelter. And it noticed once a saw-nosed crocodile swimming in the distance. This situation is extremely dangerous for the fish: the sharp teeth of this crocodile, which form a kind of double-sided saw in the upper jaw, can inflict terrible wounds on large fish, and small prey will simply be chopped in half. But the crocodile has swam away, and, it seems, does not notice the rainbow pike hiding at the bottom.
The goal of this risky march is getting closer. The broad-mouthed rainbow pike smells the fish hiding in the thickets and becomes more and more daring. Finally, it reaches the end of the trunk with broken branches sticking out above the bottom. This is much better – the predatory fish lays down on the bottom next to the tree trunk and immediately gains confidence in its movement and relieves the stress of being in the open..
The rainbow pike cautiously swims along the trunk. It smells the fish hiding among the plants and prepares to attack. Disc rainbow fishes flicker among the plants, and all the attention of the predator is concentrated on them. The rainbow pike is so busy hunting that it does not pay attention to something long lying on the sand next to the plants on the other side of the thicket. It swims forward a little more, and this object disappears from its field of vision, obscured by leaves and shoots. The coloration of the predatory fish again changed from sandy-yellow to greenish with vertical stripes of irregular shape, and it feels like itself in its usual habitat. Deep and rounded bodies of disc rainbow fishes flicker awfully close – the hunt looks to be successful.
The flock of disc rainbow fishes, suffering from starvation, hides in the thickets. Of course, these fishes are able to survive hunger, and, if necessary, could cross the dangerous area above the sandy bottom devoid of vegetation. But it is not safe to do so during the day: there are many predators around. And the biggest surprise for these fish is the appearance of a predator in their own shelter.
The rainbow pike attacks disc rainbow fishes in one strike. Its wide mouth opened, and one small fish is literally sucked in by the stream of water. In the next instant, the teeth of the predator sink into its body. School of disc rainbow fishes, smelling blood, is horrified. Fishes scurry about through the thickets and some of them begin to appear at the edge of the thickets, sparkling in the sun rays with bright spots on their gill covers.
Swallowing a shrimp or a long-bodied fish is easy – the rainbow pike has done this more than once. But the deep body of the disc rainbow fish makes certain difficulties for the predator, which is accustomed to swallowing prey whole. Therefore, the rainbow pike has to work hard to do this. It shakes its head and makes extra effort to swallow its prey. Thanks to elastic ligaments, its jaw bones part and let the prey down the throat. One more gulp follows, and the prey slips into the stomach.
A flock of frightened disk rainbow fish burst from the thicket, their colored markings flashing in the sun. The bright brilliance brings the saw-nosed crocodile, waiting in ambush, out of its stupor. The reptile reacts instantly: the saw-nosed crocodile tosses up its head and makes a sharp lateral movement with it. At the same time, its jaws are slightly open, and the terrible smashing teeth of the upper jaw are fully operational. The head of the saw-nosed crocodile crashes right into the school of rainbow fishes, and its teeth almost immediately find their target. Two fishes impaled on the teeth of the upper jaw at once. Jerking its head in the other direction, the saw-nosed crocodile drops them from its teeth and manages to hit one more fish. The fish managed to escape from croc’s teeth, but even so the fish’s life is rapidly coming to an end: the rainbow fish is wounded and helplessly twitching near the bottom, falling to one side and trying in vain to escape from the predator. It is bleeding, and even if it manages to get away from the crocodile, it is unlikely to live until the morning.
The school of disc rainbow fishes swims away, and the saw-nosed crocodile begins to pick up its prey. Tilting its head to one side, it picks up the killed fish with the teeth of the lower jaw and accurately moves the prey down the throat. The wounded fish try to escape when the crocodile turns head to it, but long jaws grab it, and croc’s teeth pierce its body. The hunt is over, and the crocodile can now emerge to the surface for air, before returning to shore to digest its lunch, basking in the sun.
Once in the open, disc rainbow fishes rush in search of shelter, sparkling with red spots on their gill covers. The nearest thickets are quite far away, and their color and spots attract the attention of one more saw-nosed crocodile. This crocodile has just gone fishing and was not ready to see a large school of frightened fish. But the reptile makes a decision quickly and rushes in pursuit with haste.
Having pressed its front paws to the body, the saw-nosed crocodile waves from side to side with its deep tail compressed from the sides, helping itself with wide hind feet and membranes between the toes. Gradually, the distance between it and the school of disc rainbow fishes is reduced, and in less than a minute of chase, the crocodile has already caught up with the last fishes in the school. Trying to injure them with the teeth of the upper jaw, directed to the sides, the saw-nosed crocodile begins to shake its head. Fishes, however, manage to avoid its attacks – in the water they move more freely than the crocodile. But the crocodile is more adapted for fast swimming than these inhabitants of the thickets, so the disc rainbow fishes are in real danger. But quite unexpectedly, the saw-nosed crocodile turns around and swims to the shore as fast as it can.
The school of disc rainbow fishes dives deeper. When it becomes calmer, fishes will be able to find thickets of underwater grasses suitable for life. In the meantime, something else scares them. They feel the waves generated by the movement of a huge wriggling body and rush to the bottom. And after a few seconds the school of fish is covered with an ominous writhing shadow of an adult eingana.
Wriggling gracefully, the monster swims at a shallow depth. From time to time, the huge snake sticks out its tongue, determining the presence of possible prey by smell. The saw-nosed crocodile noticed the snake at the right time, but could not hide its own presence – some of its droppings got into the water. And the specific smell, well known to eingana, became a reliable guide for the predator. An adult eingana can easily swallow a saw-nosed crocodile whole, and these reptiles often become prey for the giant snakes.
The snake has poor vision, but the silhouette of the saw-nosed crocodile, desperately rushing to the shore, is very noticeable on the surface of the water when viewed from below. The crocodile paddles with a deep tail and helps itself with its hind legs. In contrast, the snake’s movements appear to be slow and fluid, but it is a deceptive impression. Snake swims very quickly and the distance between them gradually decreases. At some point in time, the eingana’s muzzle appeared at the distance of less than two meters from the tail of the saw-nosed crocodile. The crocodile’s only salvation is to get to the shore: once on the shore, eingana becomes slow and prefers not to hunt. Adult einganas oftentimes simply do not leave the water once reaching a certain size.
The saw-nosed crocodile literally throws itself on the shore, selected by its relatives, and clumsily runs away from the water at a gallop, raising its snout up and looking behind itself with one eye. The rest of the crocodiles did not see what caused this behavior, so only a few small crocodiles jumped up and ran away, as if imitating this one. The frightened saw-nosed crocodile gallops, making long clumsy jumps on its hind legs and plopping down heavily on the weaker front legs. It runs away but does not take its eyes off the water.
Several ducks, swimming near the crocodile rookery, fly into the air with loud shrieking. One of the adult saw-nosed crocodiles, basking on the shore, raised its head and looked at them. But then a wave rushes to the shore, from which a huge eingana’s head with an open mouth with pointed long teeth pulls ahead. The giant snake is somewhat reminiscent of the killer whale of the human era, which hunted seals in almost the same way, beaching themselves into their rookery with the oncoming wave of the surf in order to grab the prey and leave together with the wave receding from the coast. But there is no surf on Lake Carpentaria, and eingana ran aground with most of its body. The front part of its body, however, has the ability to move freely.
At the moment the eingana appeared on the shore, the saw-nosed crocodiles understand what their relative was afraid of. They jump to their feet and run to the sides, hoping to avoid the teeth and the deadly “embrace” of the eingana. The hunt of the giant reptile clearly failed: the intended prey escaped, and now everyone who can become the prey of this snake knows about its presence. But the reptile is in no hurry to crawl away: keeping most of its body in the water, it crawls along the beach from side to side, tasting the air with its tongue. It smells the scent of saw-nosed crocodiles, mixing with the smells of forest animals carried by the breeze from the forest. But they are all out of reach, and the eingana returns to the hunt, sliding sideways into the water. But the giant snake does not go far from the shore – its back can be seen in the shallow water near the crocodile rookery.
Saw-nosed crocodiles follow the movements of the reptile. One of them, who almost became the prey of this snake, is still breathing heavily, with its mouth open. It can no longer stand the continuation of this chase – it needs some rest. But eingana also cannot continue hunting – the physiology of the reptile imposes restrictions on its capabilities. For some time, the giant snake crawls in the shallow water along the coast. Then it pokes its head out of the water and breathes; the hiss is clearly audible. Having renewed its air supply, the reptile sets off in a majestic movement into the depths of the lake. Now it is not lucky, but someday, when the underwater grasses will grow taller, it will return. And then the careless crocodile will not notice the snake until it is too late...
Other individuals may be more successful hunters. A young individual of Eingana, about eight meters long, chooses an area of the coast, overgrown with aquatic plants, for an ambush. Here, in the shade of floating leaves of water lilies, it is completely invisible to the animals that will come to the watering place. And the snake will be able to choose a suitable prey for itself: it is already large enough to cope with many of the inhabitants of the forests growing around Lake Carpentaria. The snake cautiously pokes the tip of its muzzle out of the water, prying the floating leaf of the water lily with it, and inhales a portion of air. Now it can lie at the bottom for about a quarter of an hour, without attracting attention to itself.
The eingana, hiding under water, does not see who exactly comes to the watering place. But the reptile lies at the bottom of the lake and feels the shaking of the ground under the feet of the animals walking along the shore. It may not feel the light steps of rodents or small marsupials, but the steps of animals weighing over fifty kilograms are felt by the snake very well, and the reptile is waiting for a convenient moment to attack only.
These steps are very strange. The strength of the shaking of the ground indicates that a large animal is walking. But it seems that it is in no hurry – the steps follow one after the other at large intervals. From time to time, the resounding shaking of the ground from heavy steps stops and is replaced by short rhythmic sounds, as if this creature is scraping the ground with its paws. And the rhythm of the shaking of the soil indicates that at this moment the animal is moving not on four legs, but on two.
The steps are getting closer and more distinct. Eingana carefully breathes in fresh air and continues to wait, hoping for success in the hunt.
In the Neocene, nature seemed to breathe deeply, freed from the heavy burden in the form of the human race. After the end of the era of human domination, the Earth’s biosphere as if healed its wounds and recovered from a serious illness. The species of living organisms that managed to survive in the era of anthropogenic pressure began to evolve rapidly, restoring biological balance and species diversity in ecosystems. In such conditions, even decaying groups of living beings were able to realize their evolutionary potential. And a representative of one such group slowly wanders to the watering place.
If you look at the footprints of this animal, then at first glance it might seem that it walked in the opposite direction. Its columnar hind legs are turned with the feet to the side and back a little bit – it is a legacy inherited from its ancestor. The front paws, armed with huge sharp claws, rest on the ground with knuckles. But the main load of the weight of the huge body is taken by the hind legs. The body of the animal looks like an artichoke, covered with bristly hair and reddish corneous plates on the back. The narrow, elongated head with tiny, half-blind eyes seems to be balanced by a rounded broadtail. This creature, which looks like a hedgehog, anteater and a dinosaur at the same time, is stegoechidna, the largest representative of the relic clade of primitive egg-laying mammals on the Earth in Neocene epoch.
A slow metabolism does not contribute to the speed of movement. Stegoechidna walks to the lake with its usual unhurried step, waddling awkwardly from side to side. Even with all its effort, it cannot not run, but this does not cause it any inconveniences – its food does not run.
A rotten tree trunk blocks the animal’s path. However, stegoechidna did not bypass it. Instead, the beast sniffs the trunk, sniffing loudly, and sharply hits it with the huge claws of its front paws. The rotting wood crumbles instantly, and among the fragments of the trunk its inhabitants begin to stir. Several large scorpions dart into the forest floor, but the sharp claw of the stegoechidna plows up the ground, and a long tongue licks up one of them. Thick larvae of capricorn beetles move helplessly among the dust, unsuccessfully trying to return to the usual tightness of the galleries they had gnawed through. But most of them only have a few minutes to live. The stegoechidna begins to rake the pieces of wood, sniffing at them. Sensing the larva, it sticks out its tongue, covered with sticky saliva, and licks it off. It swallows one by one all the large larvae; only somewhere deep among the dust one more fat larva left and several smaller larvae manage to avoid the sticky tongue of the animal. Finished with its food, the stegoechidna slowly walks towards the water.
The eingana, who was lying in ambush, tenses. The footsteps are getting clearer – someone walking along the shore is approaching the water. The reptile moves cautiously and positions its head closer to the shore.
The stegoechidna comes to the water’s edge. For several minutes it looks around and sniffs the air, trying to detect the presence of enemies in advance.
The eingana, hiding in the shadow of the water lily leaves, slowly creeps closer.
The stegoechidna sniffs the air in its nostrils and feels the aroma of flowers of water lily growing not far from the shore. This beast is short-sighted and cannot discern the flowers and leaves of the water lily. Therefore, stegoechidna does not notice how one leaf has swung to the side away from the wind.
The eingana carefully takes up position before the decisive blow. The entire body of the reptile is like a compressed spring. Snake is ready to attack.
Having made sure that it is safe, the stegoechidna lowers its head to the water and begins lapping noisily.
The head of the huge snake literally flies out of the water with tremendous force. The eingana strikes its head into the shoulder of the stegoechidna and immediately, right in the rush, wraps the front of its body around the neck and shoulders of the stegoechidna. In light of this sudden attack, the stegoechidna sways, falling into the water. Without releasing its deadly embrace, eingana begins to move out of the water, putting new loops on the body of the stegoechidna.
An animal like a kangaroo or a bovipotamus calf would hardly have been able to resist such an attack for more than a few minutes. The loops of the muscular body of the snake, squeezing the chest of the victim, deprive it of the opportunity to breathe. But this time the snake met a worthy opponent.
Due to its slow metabolism, stegoechidna is able to hold its breath for a long time, so it easily tolerates suffocation. Its body constitution is very dense, and its bones are strong. In addition, stegoechidna has extraordinarily strong muscles, so it even manages to inhale while being in the rings of the eingana’s body. With an inhalation the hope of liberation comes, and the stegoechidna begins to act. It squeezes strongly the body of the eingana with its front paws and deeply plunges its claws into the side of the reptile.
Feeling pain, eingana begin wriggling, literally rolling through the shallow water along with the stegoechidna, entwined with rings of snake’s body. It looks like this prey is not going to give up too quickly. Usually, marsupials or placental mammals die within a few minutes, having fallen into the “embrace” of the eingana, and the snake manages to deal with them without getting injured. But it looks like the reptile made a mistake this time. It attacked an animal that is not only too large, but also one that can fight back. Now it needs to get away from such a dangerous opponent, and it pulls the stegoechidna to the depths. The reptile’s grip gradually weakens, but the stegoechidna continues to hold the snake in its front paws. From time to time, the beast loosens its grip, but it is done only to squeeze then even tighter and to plunge its claws into the enemy once again. Several cut wounds inflicted by the long claws of the stegoechidna are already bleeding on the body of the giant snake. Now it is a snake’s turn to try to free itself from the beast holding. The loops of the reptile’s body loosen and release the stegoechidna. With a few strong body movements, eingana tries to escape from the claws of the stegoechidna. This animal thinks as slowly and unhurriedly as it breathes. It hardly gets the idea that the reptile no longer poses a danger to it. Finally, its mighty paws unclench and the eingana rapidly sneaks away out of its claws. Leaving a bloody trail, the reptile hides in a greenish murk.
Stegoechidna makes some efforts to stand on its feet. During the fight with the snake, it appeared quite far from the shore, and now the water reaches its shoulders. Raising its head, the stegoechidna takes a deep breath and trudges along the bottom towards the shore. Its head is lowered into the water, and the animal seems to be sniffing something under the water. But it is just an illusion – it is just the normal position of the animal’s body. As it approaches the shore, stegoechidna appears from the water more and more. However, shortly before reaching the shore, the animal stops. The water lily, the leaves of which helped eingana to hide, attracts the attention of the beast. With a few movements of its claws, the stegoechidna cuts off the leaves of the plant and digs out the tuber from the silt. With some effort, it went through the mouth of the stegochidna, and the huge animal begins to chew the tuber, rubbing it with corneous plates, which, in due course of evolution, appeared in the jaws of its immediate ancestors, instead of the reduced teeth. Such a large animal cannot live by feeding only on insects and other invertebrates. Perhaps it was the ability to consume available plant food that allowed stegoechidna to become a giant among monotremes.
Stegoechidna is one of the numerous guests of the lake. It does not live here permanently, but only comes to drink or feed for some time on the gifts of the lake – tubers of coastal plants or fish and shrimps captured in drying puddles along the shores of the lake. But the life of other species of mammals is much stronger associated with the lake. Bovipotamuses are the most numerous of the large inhabitants of Lake Carpentaria. These descendants of the water buffalo have perfectly adapted to the aquatic lifestyle and are, to some extent, analogous to the hippos of the human era. Each herd of these animals occupies a certain area of the coast, and the boundaries of the territory are marked with piles of manure, which are regularly refreshed. Clumsy bovipotamuses most often go out to graze at night, and at this time they can go far from the lake shore.
In the thicket of the rainforest, the darkness seems even more impenetrable due to the fact that the dense crowns of trees obscure the faint light of the moon and stars. Owls echo in the crowns of trees with hollow voices, and the background noise is created by numerous frogs and insects. Crickets chirp in every manner, and the voices of cicadas resemble whistles, metallic ringing or grinding. And frogs, claiming their rights to the territory, not only croak, but also bark like a small dog, or squeak abruptly. Bovipotamuses do not pay attention to these sounds, but if the night singers suddenly become quiet, these giants raise their heads and begin to sniff the air and listen, hoping to recognize in time the quiet rustling footsteps of a creeping predator among the sounds of the forest. If the alarm turns out to be false, insects and frogs continue their nightly concert, and bovipotamuses continue the interrupted grazing. In places, where these animals grazed at night, the growth of trees in the undergrowth is completely destroyed or gnawed.
The heavy smell of bovipotamus herd attracts thousands of blood-sucking insects – mosquitoes and midges. On the neck, back and sides, bovipotamus is protected by a thick skin, which is hardly bitten through by both a predator and a scavenger. But on the head and groin, the skin is much thinner, and these places are more intensely attacked by blood-sucking insects. Trying to escape from them, bovipotamuses wallow in the mud, but it does not help much – after a short time, the winged bloodsuckers return. But insects, in turn, attract bats, and these winged creatures save bovipotamuses from suffering, exterminating a significant number of blood-sucking dipterans.
When dawn begins, bovipotamuses leave the place of night grazing and move to their native habitat. These animals are quite conservative in their habits and follow the same paths for many generations. In some places along the coast, the rainforest is cut by wide “roads”, which have been trodden and extended by several successive generations of bovipotamuses. In these places, the plank-buttress roots of trees are broken by the hooves of bovipotamuses, the shoots are eaten or trampled into the ground, and even the ground itself is tightly compacted. The width of the trail is such that three adult bovipotamus pass freely along it shoulder to shoulder. Herbaceous plants grow abundantly along the edges of such a path – while bovipotamuses do not eat the greens during the movement, their manure serves as additional fertilizer for the plants.
Bovipotamus herd moves along the trail. A large male walks at the forefront – it is the leader of the herd. Behind him there are males of lower rank and females with calves. Old animals close the herd procession – they barely have enough strength to stay close to their relatives. The ground is rumbling with the beats of wide hooves, and small animals that find themselves in the path of the herd can be crushed into paste. Usually, a herd of bovipotamuses is accompanied by birds, which expect a free treat in the form of animals trampled by the herd.
The sun barely has time to rise above the horizon when the first members of the herd already enter the lake. Bovipotamuses will spend the next few hours sleeping lightly and chewing their cud.
A herd of bovipotamuses rests in shallow water after overnight feeding. They swim in the water, barely touching the bottom with their feet, ruminating and blowing from their mouths bubbles of methane, formed during the fermentation of plant matter in the stomach. Several animals that are not full during the night feeding do not sleep. They eat reeds in the coastal thickets, pulling it out in bunches from the silty soil. Birds feed next to the massive animals. Herons walk on the backs of bovipotamuses and sometimes peck on fish that inadvertently swim too close to the surface of the water. In shallow waters near the herd, the scoopbeaks walk, making steps pompously. From time to time the birds lower their heads into the water and with lateral movements “mow” the duckweed, simultaneously straining fry and small crustaceans out of the water. Scaring aquatic animals, bovipotamuses help the scoopbeaks and herons feed. In addition, it is safer around them. Saw-nosed crocodile, swimming to hunt, prefers not to approach bovipotamuses. There are females with calves in the herd, and they can easily pounce on this crocodile if they think it poses a danger to their offspring.
When the sun rises high enough in the sky, the herd begins feeding in the water. Bovipotamuses come to an area of their territory, where thickets of giant eel grass sway at a depth of about two meters. Its leaves reach a length of four meters and spread over the surface of the water in a continuous carpet. Breeding with the help of runners, eel grass quickly conquers living space and forms impenetrable thickets that are inhabited by fish, shrimps and other inhabitants of the lake, which love solitude and shelter.
Bovipotamuses walk along the lake bottom, raising clouds of silt. They are approaching the thickets of eel grass, and their presence will disrupt the usual life of many lake inhabitants very soon.
Having reached the thickets, the animals begin to pick off long leaves waving in the water. Calves stay on the surface of the water, eating only the tips of the leaves, while the adult bovipotamuses dive and uproot plants to engulf them slowly while floating on the surface of the water. Dozens of fish, disturbed by the appearance of the bovipotamuses, leave their hiding places. Some of them are in a hurry to hide in the still untouched thickets, while others, on the contrary, swim near the bovipotamuses and catch shrimps and small fish that have lost their shelters.
When bovipotamuses finish feeding, very few plants survive. But the survivors will have room to grow, and in a few months the thickets will be as dense as before. This is an absolutely natural course of events – the activity of bovipotamuses rejuvenates the biocenosis, preventing productive underwater “forests” from silting up and choking off young growth with dying leaves.
A herd of bovipotamuses grazes among aquatic plants, like ordinary cows in a forest. Calves swim next to the adults – they are just learning to dive for food. And the adult male, the head of the herd, is always on the alert: he must ensure the safety of the herd and recognize the approach of an enemy in time. And it is exceedingly difficult to do it, because sometimes the enemy appears from under the water, where the senses of bovipotamuses cannot recognize it in time.
An adult eingana is searching for food. The last time it ate was about a month ago and it has been hungry for some time. Due to its slow metabolism, the reptile may not go hunting very often, and the lake in general can supply with food a viable population of these predators. The reptile swims at a depth of about two meters. It is poorly visible from the surface; therefore waterfowl do not even notice this predator and continue to feed quietly. The eingana does not pay attention to them – a monster about eighteen meters long needs more substantial prey than a duck. The reptile senses the presence of possible prey – the smell of the bovipotamus’ manure and urine spreads far in the water, and the senses of the eingana are able to recognize even the smallest amounts of odorous substances dissolved in water.
The appearing of the giant snake comes as a surprise to bovipotamuses. When the long body of the reptile emerges from the depths, the leader roars in fear and the herd instantly panicked. Large males are not afraid of the eingana: they beat the water with their hooves and blow bubbles, emitting a threatening roar under the water. The snake does not hear their roar, but it senses waves from the movements of hooves and gurgling with its whole body. Youngsters caught off guard panic more than adults. The calves rush to the shore, and one of them climbs onto the body of his mother from fear. Adult animals swim to the shore and a stampede begins in the shallow water. One bovipotamus slips and falls, and the rest of the animals run straight over its body, and the trampled beast bellowing in pain. The herd’s momentary delay determined the success of the attack. One young bull was left in the back rows, and the snake caught it with one accurate rush.
Grabbing the prey by its hind leg, eingana clenches its jaws, and its pointed teeth sink deep into the bovipotamus’ flesh. To deprive the prey the opportunity to escape, eingana throws the bovipotamus down into the water and quickly wraps it with several rings around its body. Bovipotamus tries to break free, moaning pitifully in vain as it watches its relatives in such a rush to leave the water. But no one will come to help him. The muscles of an adult eingana are too strong to be unclenched, and the captured beast is doomed.
The eingana pulls its prey into the water, continuing to squeeze it with body coils. It responds to every movement of the prey by tightening its coils even tighter. After a few minutes, the reptile feels the final convulsive tremor of its prey, after which the body of bovipotamus goes limp and then stays motionless. Now eingana can relax its grip.
Einganas prefer not to hunt adult bovipotamus males. The horns of these animals are directed to the back and sides, and the animals themselves reach a weight of about 400 kilograms. It is quite difficult to swallow such a massive prey, and it is completely impossible to regurgitate it also – tips of the horns, directed backward, prevent the prey’s body from leaving the esophagus, and the carcass of bovipotamus can get stuck in the throat of the snake, killing it slowly. Therefore, young animals and females most often become prey of the giant eingana.
Swallowing a bovipotamus carcass is a difficult task. However, Eingana does this job perfectly. Feeling the prey with its tongue, the reptile finds its head and latches onto it. Moving alternately the upper and lower jaw forward, it begins literally to stretch its body onto the prey. The bull's head quickly disappears into the snake’s throat. When the jaws of the snake reach the shoulders of the prey, the elastic ligaments holding the jaw bones stretch, and the snake continues swallowing its prey. In order not to hold its breath, the reptile sticks the tip of the trachea out of its mouth, in the middle of the lower jaw. It turns to its side, and the trachea is now above the water. The reptile breathes freely again, continuing swallowing its prey.
In half an hour, only the hind legs and tail of the bovipotamus are sticking out of its mouth. The jaw bones gradually fall into place, the ligaments between them contract, and a huge swell forms right behind the head – it is the body of the swallowed prey. With a few smooth movements of the front part of the body, the eingana pushes the prey deeper along the esophagus, and soon it takes its place in the stomach. Now the eingana regains the ability to swim freely. It turns around and disappears in the depths of the lake.
Eingana does not swim too far from the coast – here it finds its habitual food and places for the rest. Far from the shores of Lake Carpentaria, there are completely different living creatures that rarely get in coastal waters. The main food source here is phytoplankton, which cladocerans feed on. These creatures are remarkable in their fast growth rate and rapid reproduction, which helps them to resist successfully the feeding activity of predators. Birds flying over the surface of the lake away from the shore can see that the water of the lake has different colors in different places. These are signs of the presence of zooplankton – crustaceans of various species. Most often, their swarms are reddish or grayish in color. But sometimes the congestions of crustaceans seem to be crossed by silvery strokes – it is the fish living in the water column that feed.
A shoal of crustaceans, when viewed from under the water, resembles fog. Numerous microscopic creatures move in the water column, continuously filtering unicellular algae. They perceive only their microscopic neighbors of the same size – fish fry, larvae of worms and mollusks. Large animals are something that is beyond their perception.
A large school of fish swims at a depth of about two meters. They are grayish in coloration with a metallic sheen and dark longitudinal stripes on their sides – it is branchiochromis, one of the most abundant fish species in Lake Carpentaria. Their appearance has an unusual feature – large head with a wide mouth. But the teeth of these fish are very small and serve more to “lock” the mouth rather than to hold the prey. After all, the food of these fish includes planktonic crustaceans only.
A school of branchiochromises scatters in a range over ten meters wide. As long as there are no predators nearby, it is safe. Branchiochromis fishes spend their entire life away from the coast and prefer not to approach floating objects. If they fall into coastal waters by mistake, they immediately try to go into open water, away from the numerous predators of the coastal thickets.
The first fishes in the school feel the approach of the congestion of planktonic crustaceans and begin to feed without slowing down. They simply open their mouths and filter the water through thick gill rakers. From time to time, fishes close their mouths and swallow the mass of crustaceans that have accumulated on their gills. This feeding method is highly effective for pelagic fishes, since it allows them to not slow down and does not make the fish more vulnerable to predators at the time of feeding.
Having heard the characteristic sounds made by feeding relatives, fishes from the back of the school, changed their position. They swim forward and to the sides of the front of the pack, and after a few minutes the pack stretches out, forming a broad front. Fishes line up in the way not to follow one another, and swim with their mouths wide open.
The array of branchochromises crosses the congestion of crustaceans, leaving behind patches of water where hardly more than half of the former number of these creatures remains. But this is not a problem for rapidly breeding cladocerans – due to their growth rate, abundance of food, and parthenogenetic reproduction, they easily repair damage from predators. In addition, fish that feed on branchiochromis turn out to be their allies to some extent.
A small school of fish, larger than branchiochromis, rushes at a depth of about three meters. These slender and strong fish, each about 70 cm long, are somewhat reminiscent of marine pelagic fish – horse mackerels, tunas and trevallies. They are called carangochromises and are also descendants of tilapia and distant relatives of the branchiochromis. In contrast to the planktivorous branchiochromis, the large carangochromis is an active predator. Branchiochromis is one of the basic kinds of prey of these giants. The wide mouth of carangochromis allows it to swallow easily fish as long as a third of its own length.
Carangochromises seek prey by smell. When they hear the characteristic sounds of a feeding school of branchiochromises, their excitement grows. The predators begin to move their tails faster and accelerate, as if afraid to be late for dinner. Their large eyes distinguish a cluster of branchiochromises feeding near the surface of the water, and predators unmistakably go in their direction.
It is hardly possible to understand which one of branchiochromis school was the first to notice the approach of predators. The frightened fish rushed to the only shelter available in the open water of the lake – to its own relatives. Its sudden movement was noticed by other branchochromises faster than the cause of the panic. The regular array of feeding fish was broken and disintegrated, like a drop of mercury, into several spherical schools. Several small flocks immediately merged into a larger one.
Carangochromises swim alongside the packs of branchiochromises. They expected on a surprise attack, allowing them to cut off several fish from the general school and eat them. But their plans were disrupted. The surface of each spherical school of branchiochromis literally boils from the bodies of fish trying to hide from predators among their relatives. Two large schools of branchiochromises are slowly moving towards each other, while carangochromises are circling at a distance, and then merge into one common school. Now it is more difficult for carangochromis to get food for themselves. However one of them has decided to take a desperate step and rushes straight into the cluster of branchochromises. School of frightened fish literally swallows the predator, and then releases it from the other side – without prey. But for some fractions of a second, several fish left the school, in order to rush then under the protection of their relatives. And a minute later another carangochromis attacks the pack. It does not rush into the middle of the accumulation of prey, but swims along a tangent. Branchiochromis, frightened by such a maneuver, rushes to the sides, and one of the fish for a second finds itself outside the school. Its fate was sealed: the mouth of the carangochromis opens like a pipe and sucks the prey into its gullet in a split second.
For several times carangochromises attacked branchiochromis school, and about half of their attacks were successful. Having filled their stomachs, the predators gather again in a pack and leave the battlefield. Branchochromises cannot calm down for a long time after the predators have disappeared in the blue haze: their school continues whirling in one place, retaining its spherical shape, but gradually spreads out and fishes continue feeding again.
Carangochromises almost never appear near the coast. These fish prefer the clean and oxygen-rich water of the central part of the lake, experiencing some stress in the silt-polluted water of the coastal areas. After a successful hunt, the predators swim guided by their sense of smell. In the central part of the lake, where there are almost no visual reference points, their sense of smell helps the animals feel at home. Carangochromises swim, feeling the scent trail left after their congeners. Soon they catch up with a more numerous carangochromis pack and unite with it.
Usually, carangochromises prefer the society of congeners, although they are predators. But the amount of prey in the lake is enough for these fish to feed together. But occasionally some fish have to leave the society of their relatives in pursuit of more important goals.
A pack of carangochromises enters the area of reddish water. Their sense of smell tells these fishes that they are surrounded by a huge congestion of crustaceans, which give the water such a color. Visibility decreases sharply and fishes swim slower. They notice several blurred silhouettes slowly swimming among the clouds of microscopic crustaceans at a fairly large distance from each other. When carangochromises swim closer, they distinguish their relatives in these silhouettes. But loners clearly do not seek to join the pack and go to an area of clear water. When several carangochromises of the pack swim up to one of these individuals, that fish takes a warning pose, turning to its relatives sideways and sharply waving its tail, sending a wave of water towards the strangers. By these actions, the loner makes it clear to the fish from the school that it is better for them to stay away from this one. Carangochromis pack continues its way and soon hides in the distance.
The lone caragochromis is a male. He has a large head with a swollen throat, and his body coloration is much paler than usual. Only the lips of this individual have a bright white color. These features of the fish’s appearance are associated with the important work that this male performs. When the carangochromis pack left, the single male made sure that everything around was calm again. He did not notice any single large living creature around – only myriads of crustaceans living their hectic life. Then the male opened his mouth.
Fry swim out of his mouth in a living stream – about four hundred of them. They look little like their father yet – they are translucent cross-striped creatures about half a centimeter long. They came into being about two weeks ago and have already grown a little, but so far, the male manages to contain his entire brood in his mouth. The ancestors of carangochromis, tilapias, raised their offspring in this way, but laid eggs in a hole at the bottom, and only then took them into their mouths. In the course of evolution, some of the descendants of tilapia adapted to the pelagic way of life, and the bottom stage of spawning in them gradually disappeared. Only the “breaking away” from the bottom did the descendants of tilapia real pelagic fish. Carangochromis belongs to just such species.
The white lips of the parenting male represent an important signal for his offspring: a sign of safety and protection. Feeding in open water, the fry constantly keep the lips of the male in the field of view, and in case of danger they return to him. The male carangochromis carried the entire brood to the cluster of crustaceans and releases, allowing the fry to feed. Already at the moment of hatching from eggs, the fry of carangochromis are quite large, and only the large size of the parent itself allows him to bear numerous offspring. The large size of the fry gives them a certain advantage: having learned to swim, the fry immediately begin feeding on young crustaceans, and later pass on to adults. Having got out of their father’s mouth, the fry feed on their own. Already at this time, predatory tendencies begin to appear. Lagging in growth fry become victims of their larger siblings. The father does not intervene in the conflicts that occur between the fry - he is too big for this. His parental responsibilities include providing the offspring with food and protection from large enemies. Therefore, incubating males of carangochromis go to where there is ample food for their offspring.
When the fry were full, they began to return to their parent’s mouth. To get into the father’s mouth, the fry simply nip his lips, and the male’s jaws open just enough so that they can swim into his mouth. The male of carangochromis rather senses the presence of his fry by the movement of water around them than sees them. A caring dad does not count his fry and the loss of several individuals from a brood of several hundred individuals only increases the chances of surviving of the remained ones. However, the male carangochromis is a caring parent.
A whole swarm of fry hovers around the head of an adult male carangochromis, which is motionlessly hanging in the water column at a depth of about a meter. Their father chose a good place for the offspring outing – right in the middle of the congestion of copepods. His fry feed – they need to do it as actively as possible, since in the first weeks of life they grow intensively. The male behaves calmly and confidently – he does everything according to his parental instinct. This large carangochromis has raised offspring many times and the parental instinct, supported by experience, did not let him down.
The male suddenly feels that the fry are frightened of something: their movements become sharper and more fussy, and at once several fry began to nip the edges of his lips. The male opens his mouth and moves his fins invitingly. The whole brood rushes into his mouth, and five seconds after the assembly signal all the fry were already safe in his throat pouch. The male wags his tail lazily and turns around.
The troublemaker turned out to be a young male carangochromis, also engaged in raising offspring. It is located about three meters from the adult male and does not hurry to move away when the adult male pays attention to him. Obviously, he was attracted by the mass of crustaceans and decided to pasture his brood right here. But an adult male cannot allow a stranger to do this – now he perceives the alien male and his offspring as a danger to his own brood.
The young male opens his mouth and releases his offspring to the “pasture”. He does not pay attention to the large male that is nearby, and thus has made a huge mistake. Usually, males with their offspring keep at a certain distance from each other in order to avoid competition between fry from their broods. But this male barely had time to hide his brood in his mouth when the large adult male swam up to him, displaying his side and spread fins. He chooses to confine himself to a demonstration of size and strength, since his mouth is full of his own brood, and a fight means a great danger of losing part of the offspring from an accidental snout hitting an opponent in the throat. The young male tries to defend his right to a part of this territory: he also turns to his opponent sideways and opens his fins, trembling with its whole body. But the older adult male confident in his superiority, waves his tail, and the young rival feels the force of the wave launched at him. He prefers to tighten his fins and to retreat to a safe distance. The winner opens his mouth again, releasing his brood for feeding.
Rearing offspring is an extremely dangerous stage in the life of a male carangochromis. As long as he takes care of the offspring (about six weeks), he will have to observe a strict fasting. At this time, the fat outgrowth on his forehead dissolves, which is used for demonstration during courtship rituals. Actually, the female estimates particularly the size of this outgrowth, when forming a pair with the male: “brainy” males enjoy special preference, since this is a sign that they ate well before pairing. A small outgrowth on the forehead means that the male is less prepared for raising offspring: such individuals, as a rule, are more worrisome during the period of bearing eggs and larvae, lose a lot of weight or try to part with the growing fry as soon as possible. Usually, the brood of such males quickly dies at various stages of development.
The incubating caragochromis is always on the alert. While the fry are small in size, even branchochromises, which usually themselves become the food of this species, are dangerous to them.
The male carangochromis monitors the world around him. He sees his fry, which feed on crustaceans, swimming around his head. Somewhere far from himself, he distinguishes the silhouettes of several relatives, the same large males. They are also engaged in raising offspring, but they keep at a fairly large distance from each other and from him. Therefore, the male carangochromis is calm. The time of raising the offspring is quite different from its usual way of life, when it is constantly busy looking for food and chasing prey. In the meantime, he has other concerns.
Somewhere to the side, a young male carangochromis is swimming. This youngster tried to feed his fry in this feeding area, but was expelled and is now looking for a suitable place to feed his offspring. However, the better parts of feeding area are occupied, and he will have to work hard to find a suitable place and at the same time not cause aggression from any of its stronger relatives. Therefore, he has to clench his jaws tighter and get out to the edge of the feeding area.
The young male of carangochromis swims cautiously – he has to stay away from the stronger owners of the plots, into which the crustacean accumulation is invisibly divided. Having caused the displeasure of several larger males, he manages to get to the edge of the feeding area. Here the competition is much less, but food for the fry is much scarcer – crustaceans form only separate flocks almost under the very surface of the water. It is not very favorable for feeding the fry – while they are small, near the surface of the water they may simply get motion sickness. But their parent has no other choice, and the male releases fry almost at the very surface of the lake, were small crustaceans scurry about. The fry have become very hungry while their father was looking for a place to feed them, so they literally pounce on the crustaceans and begin to fill their tiny stomachs. They quickly eat everything that could be eaten, but they are unlikely to be full. Therefore, the male simply gathers them all in his mouth and swims to the next flock of crustaceans. Of course, this is a more demanding tactic, but he will be able to feed his offspring at a time when the fry should have food all the time. And there is another advantage in its position on the border between the congestion of crustaceans and the area of clear water.
In the distance, among the greenish haze, the silhouette of another inhabitant of Lake Carpentaria appears. A wide flattened head, pointed fins, a large unequal-lobed tail and a characteristic triangular dorsal fin – perhaps it would be more appropriate for this creature to live in the sea. These animals represent a legacy of the maritime past of Lake Carpentaria, striking fear in those who cannot resist them. The creature approaches a flock of planktonic crustaceans in search of food, but the crustaceans themselves are of less interest to him than anything else. This is a shark – a representative of the genus to which in human epoch the bull shark belonged, the ancestor of this species. And the descendant of this predator retained the most characteristic features of its ancestor, including bloodlust. This species has two main differences from its ancestor – size and color. These sharks reach only one and a half meters in length, and more often they are even smaller. And the color of their body is not dull gray or brownish, but green, and even bluish green. This is a green shark, one more predatory species in the lake.
A lake for aquatic animals is somewhat like an island for terrestrial animals. There is a strictly limited food supply here, which can feed a smaller population than the open water of the sea or the basin of a large river. And from here it is difficult to settle anywhere else, except for directly accessible nearby places. Therefore, large animal species, “locked” in a relatively small lake, evolve like large land animals that appeared on a small island: in order to maintain a sufficiently large population, they decrease in size. Nevertheless, dwarf sharks are not inferior to their distant ancestors in terms of ferocity and voracity, adjusted only for size.
After one green shark, two more appear from the mist of the lake. A young male carangochromis notices them in time. He immediately gives a signal for danger, and the fry disappear into his mouth in just three seconds. Having tightly compressed his lips, the male freezes at the surface of the water, trying not to give himself out with unnecessary movements. The three sharks, each almost three times his length, swim under him at a depth of about five meters. He was not noticed, and thus has saved his offspring.
The males who occupied the feeding areas inside the crustacean aggregation do not immediately notice the approach of danger. Only one of them heard the alarm signal given by a young male from the edge of the feeding area and managed to gather his fry in his mouth unnoticed. The other males, who sensed the approach of sharks, took action to save themselves too late. They begin to gather fry together and hide. The only way to become less noticeable in open water away from the coast is to freeze in the hope that the danger will pass by. But it is too late to do this: while gathering the fry in their mouths, caragochromis males unwittingly gave themselves away with movements and sounds, and the sharks have noticed this.
A large carangochromis gathered hastily his brood in the mouth and did not immediately see that one of the sharks was approaching him. The parental instinct demanded of him, first of all, to protect the offspring, and the male did not rush into flight until the last fry swam into his mouth. And so, he let the shark get too close to him. Carangochromis is faster than the green shark, but the sharks are superior in numbers and have better maneuverability. And this carangochromis male has been starving for more than a week, brooding offspring in his mouth. Therefore, his chances of salvation are much less than in a school of congeners.
One of the sharks chases the carangochromis male, but the fish made a quick dash forward, escaping from its teeth. The second shark tried to grab the carangochromis from below, but it rushed to the surface of the lake and swam, churning the water with its tail. It managed to break away from the pursuit for a short while, but after a few seconds the shark caught up with it. Sharp teeth of the predator tore out a piece from the side of the carangochromis male, and the fish began to thrash in pain, and blood gushed from the wound. Now sharks do not need other prey - all their attention has turned to this individual. Along with the blood, the carangochromis male loses its vitality, and two sharks easily catch up with it. They seem to be playing cat and mouse with their prey, inflicting bite after bite on the fish. Finally, the game ends: the sharp teeth of the green shark cut off the tail of the caragochromis like a knife. The dying male did the last thing he could do for his offspring – he opened his mouth and released the fry. And then the jaws of one shark grabbed his torso and bit it in half. The second shark pounces on the rags of meat from the torn body, and begins to tear at it greedily. After the feast of two predators from the fish full of strength a few minutes ago, only a head with an open mouth and bulging eyes remained, which slowly plunges into the depths. Some of the fry raised by this male ended up in the jaws of sharks along with the body of their father, but a significant part of the fry survived the slaughter. They gathered in a flock in the depths, frightened and doomed to inevitable death. Without paternal protection, they will be quickly eaten by numerous predators: from planktonic crustaceans to branchiochromis.
The third shark turned out to be not so lucky: it was noticed in time, and carangochromises managed to gather their broods and flee. Green sharks, like their ancestors of the human epoch, are doomed to be eternal wanderers: they do not have a swim bladder and these fish drown if they stop. Therefore, their whole life is in constant motion. Regardless of the success of the hunt, they leave the congestion of crustaceans, in which the caragochromis offspring are raised, and swim further. Soon their silhouettes disappear into the distance, and there is almost nothing to remind the viewer of the drama that had just occurred moments ago. Only the gradually weakening smell of fish blood and a flock of orphaned fry were evidence of shark hunting.
After the predators left the battlefield, carangochromis males began to gather again to feed their offspring. One by one, they return to the congestion of crustaceans and take their places at a discreet distance from each other. Almost all of them returned – except one, torn to pieces by the sharks. The young male, first noticed the sharks, also returned here. He managed to keep his brood intact, and now there is a room in the shoal of crustaceans to feed his offspring. After making sure that the danger has passed, carangochromis males open their mouths and release their fry to feed. It happens that life circumstances equalize the probability of survival of the offspring both for an experienced strong male who knows how to take his rightful place in the cycle of life, and for a novice who raises his offspring for the first time.
Carangochromises feed only on live prey, which they catch themselves. In this regard, green sharks are less picky, and with the equal pleasure they eat both live fish and other animals, and carrion at the wide range of stages of decomposition.
Several days have passed since the drama enacted among the carangochromis males. Some males have already fulfilled their parental duties and left their offspring, giving it the opportunity to live independently. And other fishes took their place, competing among themselves for living space. Their life goes on.
But for some of the inhabitants of the lake, life has come to an end. Heavy rains fell, and the rivers that overflowed the banks carried into the lake many corpses of animals that were taken by surprise by the flood and could not escape. Among them there was an old bovipotamus. It was a large female, one of the main ones in the herd. Her body could not withstand the parasitic infection, and within a few weeks, she weakened quickly and even gave up her place in the hierarchy of the herd to stronger competitors. Due to the help of the herd, eingana did not have time to attack her, but the life of this beast was already coming to an end. And then one afternoon, when a heavy tropical downpour rushed over the lake, the heart of a huge beast stopped. The surrounding animals felt the death of their relative: mooing anxiously, they sniffed the air and snorted, glancing sideways at the dead body of the old female. They left the place of death of a relative as quickly as possible, feeling instinctively that the smell of carrion could attract dangerous animals. The river, at the mouth of which the animal died, did the rest.
The carcass of a dead bovipotamus female sways on the surface of the water. The wind and current carried it far from the coast, and now it is inaccessible to coastal scavengers. The smell of meat, which has already begun to decompose, attracts the attention of the inhabitants of the lake, who do not care how fresh the meat is. Triangular back fins cut the surface of the water near the carcass of bovipotamus – green sharks have come to the smell. Their backs are poorly seen against the background of lake water, but from time to time in the depths the white belly of the fish “sparkles”, when it makes a bend around the carcass. Sharks behave very carefully – they as if convince once again that their prey is really dead. Gradually, about three dozen sharks of various sizes gather around the carcass of bovipotamus: from half-meter “adolescents” to “giants” one and a half meters long. One fish reaches the length of one meter and seventy five centimeters – it is exceptionally large in measurements of this dwarf species.
Green sharks seem as if being in indecision: who will take the first bite? They swim closer and closer to the carcass as their number grows. Finally, the excitement of the predators overcame some critical point and one of the fish clung to the bovipotamus’ hide. Sharp teeth tear the skin and this was the signal for the beginning of the feast. Dozens of fishes almost simultaneously pounced on the carcass and begin to tear it up. The pressure of the predators is so strong that the carcass of the bovipotamus literally spins in the water. Guts fall out of its torn belly and several sharks immediately begin to pull at them, greedily swallowing pieces. In an attempt to get its own piece of meat, one of the sharks accelerated and literally slipped on its belly along the backs of its congeners, slapping its tail from side to side. Once on top of the carcass, it pulled out a piece of meat with its teeth and rolled back into the water.
Gradually, the soft tissues were eaten, and the carcass of bovipotamus began to sink. There is still enough meat on the bones, so the sharks continue to feast. They even crawl into the chest of bovipotamus, nibbling the soft tissues on the inside of the ribs. The sharp teeth of predators easily tear the ligaments, cut the cartilage and leave deep scratches on the bones.
Sharks are creatures ideally adapted to devouring carrion. But even they do not have the opportunity to eat absolutely everything on the bones of a dead bovipotamus. Therefore, they leave the carcass when there is too little soft tissue left on it to bite off. The remains of the bovipotamus sinks down into the depths of the lake, where bottom dwellers – small fish, crustaceans and mollusks – will eat them. Even the bones of bovipotamus will be eaten away by radulae of the mollusks and will gradually crumble to dust.
The shores of Lake Carpentaria have numerous many bays, where water is warmed by scorching sun. In some bays flocks of birds roam, gathering duckweed from the surface, or bovipotamuses graze, devouring floating plants. But there are bays also, where it is dangerous to appear not only for small animals, but even for adult bovipotamuses. Plants in such bays are broken and uprooted from the bottom by animals that feel like masters of the situation in the ecosystem of the lake. In such bays, real “rookeries” of einganas are formed. Well-fed snakes come here to warm up properly and digest their prey in peace and under the protection of their own kind.
In one of these bays, several dozen einganas have gathered. There are very few young reptiles here, and most of the reptiles are real monsters having a length of 7 to 15 meters. Well-fed, digesting their prey, they do not pay attention to each other. In this condition, einganas are not aggressive towards their relatives. The massive reptiles lie with only their backs out of the water, and the sun warms their bodies. Such a cluster of einganas would frighten almost everyone, but there is one creature that is not at all afraid of the tyrants of the lake.
On the back of one of these snakes, as if along a living road, a tiny marsupial shrew runs. It jumps over the strip of water where the rings of the reptile’s body go into the depths. The snake’s body is a set table for it. The marsupial shrew is looking for leeches that stick to the bodies of the giant reptiles. Parasitic fish lice like to attach near the abrasions left by resisting prey. All these creatures are delicacies for the marsupial shrew. Due to the speed of its movements, the animal manages to grab them before they take flight. While traveling along the back of an adult eingana, which has grown to a truly gigantic size, the marsupial shrew has found a large leech. The worm has bitten through the skin of the snake with its three jaws and is sated with its blood without restriction. The marsupial shrew is a creature that shoots first and asks questions later. Trigger happy and in a frenzy, it instantly grabs the body of the leech with its sharp teeth and pulls the leech out of the skin of the eingana. The leech, almost twice as long as the marsupial shrew, is in no hurry to detach from the snake’s skin. Undaunted however, the marsupial shrew begins to bite the leech’s body repeatedly causing the worm to twitch in agony. From the wounds inflicted by the beast, the blood of eingana oozes, which the leech had managed to consume. Finally, the marsupial shew closes its jaws right next to the leech’s mouth sucker and decapitate the parasitic blood sucker. Blood spurts from the inside of the leech, and the marsupial shrew begins to lick it greedily. Despite its size, the marsupial shrew is a bloodthirsty predator. Having finished with the drops of blood, the animal greedily grabs at the still wriggling leech, and proceeds to devour it.
The lake provides food for all living things – from a tiny marsupial shrew to a giant eingana. And all of these creatures are links in the food chain, equally important for the balance of the ecosystem.


Bristle-legged shrimp (Planctoatyopsis setipes)
Order: Decapods (Decapoda)
Family: Atyids (Atyidae)

Reservoirs of Australia and New Guinea of Holocene epoch were rather poor in true freshwater fishes. Their population developed basically from sea species, adapted to life in fresh water, and from migratory species of fishes. Because Australia at the moment of origin of orders and families of freshwater fishes was separated from other continents by sea passages, it has had an effect on its ichthyofauna which appreciably differs from ichthyofauna of near islands and Asia.
In Neocene the fauna of seas has changed strongly: it is connected to fluctuations of biomass of plankton and extinction of coral reeves. The fauna of fresh waters has suffered less though species of fishes connected to sea biotopes, mostly have died out. Therefore in Australia the nature had organized interesting experiment: ecological niches of fishes were partly occupied with other animals, swimming crustaceans.
Bristle-legged shrimp is one of such species occupying free ecological niches. Absence of fishes filtering microscopic algae in reservoirs of the Australian region has permitted this species of shrimps to reach this success. This pelagic crustacean up to 5 cm long meets in big shoals in lakes at small depth. The bristle-legged shrimp gathers food for itself with the help of filtering device developed on forward legs. At shrimps of family Atyidae, known to humans, at two forward pairs of walking legs the special adaptation for getting food was developed: brushes of hairs sticking up in sides. With their help shrimp digs out tiny edible animals, sifting through them sand, as through a sieve. At the bristle-legged shrimp this filtering device is transformed for filtration of plankton organisms and large algal cells from water. At the internal side of legs brushes are especially strongly advanced.
Swimming in thickness of water, shrimp makes paddling movements by forward pairs of legs. At the stroke brush gathers plankton from water and when the leg makes return movement, feeding arms scrape from bristles paste of algal cells and plankton, and push it into mouth. The basic swimming organ of this shrimp is third pair of legs with wide blades (as in water beetles). In the representatives of this family known in Holocene (for example, at Malayan wood shrimp Atyopsis moluccensis) these legs served for keeping at the bottom in stream. In connection with the passing to pelagic way of life function of these legs had changed. Fifth pair of walking legs is thin and adapted to accurate movements. They serve for clearing of gills of silt and suspension.
Body of the bristle-legged shrimp is sharp-nosed and streamline-shaped. This crustacean constantly keeps in thickness of water, occasionally sitting on stalks of floating plants for rest.
Short moments of pairing at these shrimps pass in thickness of water. The female is little bit larger than the male, but in him the claw at the tip of rowing leg is better advanced. Male swims up to the female from below, overturning upside down, and clasps her body by rowing legs. He injects sperm in oviducts of the female with the help of first pair of abdominal legs, and then swims away. Female lays about hundred large eggs and bear them on abdominal legs during some days. Development of this species includes the planktonic larva stage, which transforms into tiny copy of adult animal after two month of life.
Young shrimps do not compete to adults for food: they live near coast in thickets of plants. Their forage is large infusorians and rotifers; growing up, they pass to feeding by small crustaceans and algae. Shrimps had reached length about 2 - 3 cm gather in schools and swim in thickness of water, and pass to adult food. Having reached such length, they can have posterity.
Bristle-legged shrimp lives up to two-year-old age seldom.
In the rivers and lakes of Meganesia there are also close species of shrimps:
Bearded shrimp (Pl. barbatus) is considerably more specialized species: it eats almost exclusively algae, competing with plankton cladoceran crustaceans. At its forward legs there are brushes of very rich thin bristles, permitting to filter only rather tiny cells of algae, and only smallest plankton animals - rotifers. This shrimp is rather small – length of its body is up to 3 cm. Body of this crustacean is practically transparent with light greenish shade: it helps to mask from possible predators among plankton algae. Because the food source, used by this species, differs in big efficiency, bearded shrimp makes big congestions. But its number strongly changes in various seasons proportionally to amount of phytoplankton. Life expectancy of this species exceeds one year seldom, but the young shrimp can breed already at the fifth week of life.
Needle-legged shrimp (Pl. spinosus) as against to relatives is active predator eating large plankton crustaceans (including larvae of other shrimps) and even small fishes. Bristles on legs are hooked, large and thin – they are adapted to hooking and keeping small catch, instead of algae filtering. Length of this shrimp is up to 6 cm. The body is colored green with reddish-brown and black vertical strips; on pair of swimming legs there are white longitudinal strips. It keeps solitarily or in small changeable congestions in thickets of floating plants, immediately attacking shrimps and small fishes. At times shrimps of this species can have fights for catch, and as a result of which crustaceans can lose not only catch, but also pair of legs moreover. Larvae of this species at first eat microalgae, than catch in the beginning small plankton crustaceans, and later small shrimps and fish fry.

Barracuda prawn (Sphyraenolemon serripes)
Order: Decapods (Decapoda)
Family: Palaemonids (Palaemonidae)

Habitat: rivers and lakes of Northern Meganesia.
In seas of Neocene crustaceans compete to predatory fishes, have got good chance during mass extinction when the global cataclysm had carried away to non-existence the majority of predator species and has laid down survived species in rather equal conditions. So, at the reeves of Pacific ocean formed by large bivalve mollusks and algae, there are large predatory mantis shrimps. In freshwater reservoirs of Meganesia the similar situation had taken place: the ichthyofauna of this continent was considerably depleted during mass extinction, than decapods have taken advantage. And here evolution showed to the world the new kind of predator – the barracuda prawn.
It is rather large prawn – length of its flexible body is up to 30 cm. Its cephalothorax is rather short: about a quarter of general length of animal, but pleon is very large and muscled. In it there is plenty of muscles providing intense work of swimming legs (pleopods). Swimming abdominal legs of this prawn are covered with numerous hairs. During forward movement of leg hairs press to it and do not interfere with movement, but in rowing time they form extensive rowing surface.
Pincers of barracuda prawn are well advanced: with their help this crustacean seizes and kills catch: smaller shrimps and fishes. Pincers of this prawn are rather large (their size is about half of body length), serrated at the cutting edge. Seizing fish, the barracuda prawn pierces by teeth of pincers its spinal cord, and at the caught shrimps breaks off abdominal nerve chain. It instantly paralyses catch and deprives it of opportunity to resist. Walking legs and sharp serrated mouth feet help predator to kill catch.
Eyes of barracuda prawn are very large, spherical, located on long stems. Facets making these eyes are numerous, therefore prawn can distinguish even tiny details of environmental district. In water inhabitancy the chemical feeling has not less important role. Organs of chemical feeling (chemoreceptors) are placed at the barracuda prawn on antennae. antennae of this prawn are as long, as body, feather-like due to set of hairs (it considerably increases their sensitive surface).
Barracuda prawn spends the most part of time in ambush – among thickets of floating plants. As well as all crustaceans, it is not able to chase prey for a long time, therefore it has selected optimal for crustacean physiology tactics of ambuscader. In this connection at it cryptic colouring was developed: the basic background color of body is yellowish-green with faltering longitudinal dark green strips at the top side of body. The barracuda prawn clings to floating plants upside down: thus it has practically full circular field of view.
Having noticed possible catch, barracuda prawn cautiously creeps to it, having turned pincers together: probability of their hooking for plants during solving throw is less so. When the planned prey appears close, prawn makes throw. Having pushed by walking legs from plants, it starts to work intensively by swimming legs, at once developing the big speed. Usually the chase lasts no more than ten seconds – physiological opportunities of organism of crustacean do not permit longer chase. If the first throw was unsuccessful, the prawn stops chase and again hides in thickets. Usually only one throw from five ones is successful.
Having caught fish or shrimp, the barracuda prawn kills it by strong compression of pincers and starts to eat. But it is not safe occupation: involved by smell of blood, hungry neighbours gather, and at times fairly preyed food becomes the property of the neighbour which simply had appeared in necessary place in necessary time. Therefore the prawn tries to drag prey off in place, where it will not be to found at once by competitors. Usually it hides in thicket of plants and starts to eat catch hasty, beginning to eat softest parts. Barracuda prawn simply throws out rests of catch, and they fall on bottom, becoming food for other lake inhabitants.
Usually barracuda prawns live solitarily, banishing neighbours from territory which they occupy. But from time to time under influence of breeding instinct they become much more tolerant to some neighbours.
Males of this prawn species differ from females in smaller size. But at them pincers and very long antennae are appreciably larger. It gives them certain advantages to larger and strong female: in time of “acquaintance” it looks more impressive, suppressing a little by demonstrations aggression of the female.
The female lays rather small amount of eggs: about hundred ones. But each egg is rather large: its diameter is about 4 mm. After a fortnight incubating on abdominal legs of the female from it not helpless plankton larva, but well advanced young prawn hatch. It differs from adult representatives of species only in underdeveloped pincers and very small size of body. Young prawns are predators of their weight category: they eat plankton crustaceans and fry, gradually passing to larger prey.
Sexual maturity at barracuda prawn comes at the age of half-year at length about 20 cm. After that growth rate of crustacean decreases, but time of intensive breeding comes there. Each two months during almost three years the female bears the next portion of eggs.
But barracuda prawns will never become most numerous inhabitants of Meganesian lakes, and partly they are the reason of it. Among barracuda prawns at any age the cannibalism is usual phenomenon, and because of it only rather few from young prawns can live up to mature age.

Green shark (Carcharhinus viridis)
Order: Carchariniform sharks (Carcharhiniformes)
Family: Requiem sharks (Carcharhinidae)

Habitat: Lake Carpentaria, waters off the coast.

Drawing by Sauron from FurNation

Several representatives of the fauna of Lake Carpentaria serve as reminders of the marine past of lake. One of the inhabitants of Lake Carpentaria, by its appearance, gives the impression that this lake is still a part of the sea. The pointed fin appearing on the surface of the lake belongs to a shark.
The shark of Lake Carpentaria is a descendant of the bull shark (Carcharhinus leucas), which lived in the seas surrounding Australia and New Guinea in human epoch. Following the change of the habitat, the appearance of the descendants of this shark changed, although it remains recognizable. This species of shark is a real dwarf compared to its ancestors and relatives: the length of an adult does not exceed one and a half meters. Dwarfism is associated with the limited habitat – these sharks inhabit a closed reservoir and cannot go far into the swamps surrounding the lake: this shark can hardly tolerate oxygen-poor water, and in dirty water begins to “cough”, attempting to clear its gills from silt and plant debris.
The color of the shark’s body gives this species its name – green shark. Typically, the coloration of the fins and upper body is off-green with lighter areas while the belly is white. The individual variability in the color of this species is quite large – there are some individuals that are pure bluish green in coloration, while other individuals vary wildly in coloration, from sporting piebald patterns to almost completely black. The presence of greenish tints in the color is associated with the peculiarities of their habitat: microscopic algae develop in the water of the lake, giving it a characteristic greenish tint. Due to this specific coloration, the green shark is less visible from afar.
In proportions, the green shark resembles its ancestor. It has a flattened head, pointed fins, and heterocercal tail. The eyes of this shark are small and its vision is not exceptionally good. In the waters of Lake Carpentaria, where microsopic algae proliferate abundantly, vision plays a lesser role than in the open ocean. The sense of smell in this species is very acute. Also, the green shark has developed lateral line organs.
This species lives in the water column, diving to a depth of 30-40 meters. Most often, green sharks live in the interior of the lake, but juveniles are often found near the coast, where there is less danger of attack by adults of their own species. In the search for food, adults occasionally approach the shores.
Like its ancestors, the green shark feeds on fish. In addition, this shark eats dead animals, whose bodies are carried by rivers far into the lake. The green shark often attacks juveniles of the large local eingana snake. Several adult sharks are able to attack even a five-meter “adolescent” of this reptile, but adult eingana individuals pose a direct threat to them – large eingana can easily swallow an adult green shark whole. Therefore, the relationship of the green shark and the eingana resembles a low-intensity war.
Green sharks live alone or in groups of up to five adults.
This species is viviparous, like its ancestor: the female gives birth to up to four juveniles at a time. From the first minutes of life, they are already fully independent and have relatively few enemies. One of the factors regulating the number of this species is adult cannibalism.

Disk 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.

Wide-mouthed rainbow pike (Esocitaenia angustistoma)
Order: Aterinoid fishes (Ateriniformes)
Family: Rainbow fishes (Melanotaeniidae)

Habitat: freshwater reservoirs of Northern Meganesia (Carpentaria Lake), 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.

Largemouth carangochromis (Carangochromis macropomum)
Order: Perciformes (Perciformes), suborder Labroidei
Family: Cichlids (Cichlidae)

Habitat: Northern Meganesia, Lake Carpentaria, areas away from the coast.
In the human era, numerous fish species were introduced to New Guinea, which were planned to be used as commercial fish. After the extinction of mankind, some of the introduced species became extinct without any descendants, but other species managed to survive and evolve. Their descendants occupied various ecological niches in the ecosystems of the Neocene.
In the early stages of the lake formation, the descendants of marine fish dominated Lake Carpentaria, but later the waters of the lake desalinated, causing their replacing by descendants of freshwater species. Among the fish that inhabit the lake, fish of the cichlid family have achieved some success. Due to their peculiar way of breeding, some of them managed to leave the coastal zone and came to inhabit open waters. The ancestor of various cichlids of Lake Carpentaria is the Mozambican tilapia (Oreochromis mossambicus (Tilapia mossambica)), introduced to New Guinea. This unpretentious species quickly settled in all available habitats, and as a result of evolution gave rise to a whole group of species differing from each other in behavior and ecology.
Avoiding competition in coastal habitats, one of the tilapia descendants adopted a pelagic lifestyle far from the shores of the lake. It acquired a streamlined body and developed into an excellent swimmer. This is how the large-mouthed carangochromis appeared, one of the characteristic inhabitants of Lake Carpentaria.
This species of fish only accidentally enters the coastal areas, preferring the vast, open waters of the lake’s center. The appearance of the carangochromis shows that it is a fish capable of great bursts of speed. The head of the fish is relatively large and flattened, with a wide mouth that can be extended into a tube due to elastic membranes connecting the jaw bones. The body is torpedo-shaped and muscular, with a strong caudal peduncle; caudal fin has a crescent shape. It gives Caranochromis a resemblance to fast-swimming trevallies (Caranx) – marine fish of the human epoch. The length of an adult fish is up to 60 cm, males are larger and more massive than females.
The dorsal and anal fins of the fish are shifted back and have rigid fin rays. The spiny part of the dorsal fin is reduced to some separate spines with a rudimentary membrane stretched between the back and the posterior edge of such spine. On the back of the fish, there are up to ten such spines. The pectoral fins are narrow and pointed. The pelvic fins are shifted forward almost under the base of the pectorals; they are narrow and resilient. During swimming, the pelvic fins fold along the body, forming a kind of keel on the abdomen.
The body color of this fish is bluish green, with a lighter belly; there is a dark spot on the head between the eyes. During the mating season in the male, this spot increases in size, stretching from almost the tip of the snout to the back of the head. Male also differs from female by a characteristic fatty build-up on the head. In order not to interfere with the movement of the fish, this outgrowth has the shape of a ridge compressed from the sides and stretched from the bridge of the nose to the middle of the back (to the first spines of the dorsal fin); there is a weakly pronounced keel on the upper part of the ridge.
This type of fish is an active predator. The teeth of the carangochromis are exceedingly small, and the fish captures its prey by sucking it in with its mouth, which opens in the form of a tube. Fish and pelagic shrimps are the carangochromis’s primary food sources. Carangochromis live in schools of up to twenty individuals.
It is the flexibility of their reproductive behavior that has allowed this species to leave the coastal zone, stopping spawning eggs in the nesting hole at the bottom. These fish incubate their eggs in their mouths. This is done by the male, for whom the fat build-up on the head serves, among other things, as a supply of nutrients, allowing the male to save energy while he raises his young. During the breeding season, the scales of the male become an intense shade of blue, while the dark spot on his head expands a lot. At the same time, the lips of the male thicken and become white. The male, ready for spawning, displays himself to the females, spreading his fins and shaking with his whole body in front of the chosen female. The formed pair gradually begins to keep apart from other fishes of the school. Spawning in this species occurs quickly and without long courtship rituals. The female spawns a portion of eggs into the water, and the male immediately fertilizes them and catches them with his mouth. In total, the female spawns up to 500 eggs in 3-4 batches. Having gathered the clutch, the male leaves the school. At this time his behavior changes: he stops feeding and stays in the upper layers of water, at a depth of up to a meter from the surface. Sometimes several males incubating eggs unite into the school. Incubation takes up to 5 days, and larvae spend the same time in male’s mouth, while turning into fry. During the first month of their life, the male takes care of the juveniles: he hides them in his mouth in case of danger and transfers them to places rich in food. Small cladocerans living in the upper layers of water serve as food for the young. Fry of this species have a characteristic cross-striped color – gray with black stripes. These stripes fade with age. Young fish reach maturity in the second year of life.

Branchiochromis (Branchiochromis pelagicus)
Order: Percoid fishes (Perciformes), suborder Labroidei
Family: Cichlids (Cichlidae)

Habitat: Northern Meganesia, Lake Carpentaria, areas far from the coast.
The descendants of the Mozambican tilapia (Oreochromis mossambicus), introduced by humans to New Guinea, have mastered various ecological niches, differing wildly from one another in terms of lifestyle. Lake Carpentaria is inhabited by several cichlid species descended from a common ancestor. One of them is a large carangochromis, an active predator. Another type of pelagic lake cichlid is the small and numerous branchiochromis.
Unlike its predatory neighbor, branchiochromis feeds on small crustaceans and fish fry that live in the water column. This type of cichlid is remarkable in its large mouth and dense gill rakers – these are the adaptations for filtering planktonic organisms while in motion. Schools of branchiochromis swim far from the coast. Having found an untapped food source, these cichlids are one of the most abundant fish species in Lake Carpentaria.
Branchiochromis is a relatively small species; the length of an adult is no more than 15 cm. Due to the development of the filtration apparatus the head of this fish is large – about one fifth of its total length, excluding the fins. The body is elongated and torpedo-shaped. The spiny part of the dorsal fin is low, with shortened rays. The anal fin and the soft part of the dorsal fin are large and pointed. In males, the tip of the dorsal fin is extended. The caudal peduncle is short and deep while the caudal fin is rigid and crescent. Branchiochromis is a good swimmer, capable of reaching speeds up to 40 km/h.
The color of the branchiochromis body is typical for schooling fish – silvery-gray with metallic sheen and numerous longitudinal dark blue stripes. The eyes are large and silvery; the lips are white. The fins are transparent with a grayish tint; the extended tip of the dorsal fin of the male is bluish in coloration, which becomes much brighter during courtship.
Branchiochromis fishes gather in large schools numbering several thousand individuals of approximately the same size and age. Feeding fish form a crescent-shaped line and surround the congestion of planktonic crustaceans, gradually closing the edges of the school and driving their prey into a dense ball. Being under attack, these fishes gather in a spherical school.
Branchiochromis feeds mainly on zooplankton. In the dense accumulation of crustaceans, they swim slowly, gulping and filtering separate portions of water through their gills. In sparse but extended congestions of crustaceans, fish swim with open mouths and gill covers, filtering the prey while in motion. The open mouth of branchiochromis expands into a tube. In addition to crustaceans, branchiochromis fishes also feed on planktonic algae, which they filter out together with the crustaceans or simply during the movement.
Reproduction of these fish takes place in a school. Males and females form pairs and stay together for some time inside the flock. If a school has to spread out to the sides, fleeing large predators, both fish from a pair will spend a great deal of time searching for each other when the school reunites. The presence of pairs in the flock is an incentive for spawning. As pairs form in the school the overall excitement grows – fishes exchange signals, synchronizing their physiological state, and some days later the spawning begins. Males get brighter, while their heads turs black, and against this background, their white lips stand out well. In contrast, the female’s head turns into a shade of gray. The stripes on the body of fish of both sexes become wider and darker. As the male and female in the pair circle around each other, the male displays to the female a brightly colored tip of his dorsal fin. The eggs are spawned directly into the water. Female fertility is up to 200 eggs.
The fertilized eggs are gathered by fishes of both sexes; the clutch is then incubated in the mouth. Male and female evenly distribute the clutch, and after that the pair breaks up. Each fish independently takes care of its part of the clutch. Incubating fish leave the general school and form small schools in areas where planktonic invertebrates form congestions. Egg incubation lasts 3 days and the offspring leave the parent’s mouth at the age of one week. For about two weeks, an adult fish takes care of the offspring, after which the fry move on to an independent life. At this time, there is a high probability that adult relatives can eat the juveniles themselves.
Branchiochromis reaches maturity at the age of 14-15 months.


Saw-nosed crocodile (Pristisuchus serratorostris)
Order: Crocodiles (Crocodilia)
Family: Saw-nosed crocodiles (Pristisuchidae)
Habitat: brackish sea gulfs, mouths of rivers of South-Eastern Asia, Indonesia, Meganesia (it is especially numerous in Arafura Lake).

In warmed up extensive shallow freshened coastal lagoons of coast of South-Eastern Asia life boils over. Here it is a lot of forage, algae, plankton; it ideal place for feeding and fatting. Besides water has the lowered salinity that reduces expenses of forces to osmotic regulation. Here numerous oceanic fishes come to food up. They frequently swim in big dense shoals, relying to the best passive protection by the large number. It is meaningful frequently, but not always. Suddenly narrow long shadow runs into such dense shoal. Narrow long flat “saber”, armed at edges by big sharp thorns, starts operate barbarously here and there, harming strongly incautious fishes. In shoal the panic begins. The density of the fish shoal plays not on a hand to its members; they rush, come across against each other, are thrown here and there and in larger number get under ruthless impact of terrible weapon. Eventually the shoal blurs in sides, leaving about ten twitching, bleeding profusely, and crippled fishes. Predator quietly begins meal.
It is the saw-nosed crocodile growing up to length up to 3 m. It is one of few species of crocodiles had survived up to this time. It is very much specialized one and it seems similar to gavial. But gavial had died out, not having left descendants: its number was decreased by people, and specialization did not promote a survival in epoch of mass extinction. The saw-nosed crocodile descends from any Asian species of crocodiles had survived in epoch of global cataclysms. Other species of crocodiles, the furious sharkodile, lives in tropics of Pacific Ocean. In the majority of tropical rivers the place of water predator was occupied by fishes (up to sharks!) and lizards. Therefore the saw-nosed crocodile lives any more not in rivers, but at the coast of sea lagoons where there are more fish frequently keeping in dense shoals.
It is perfectly adapted to feeding by fishes. At this reptile there are narrow graceful body, wide tail and extended narrow jaws. Long teeth at its long and sword-shaped top jaw grow originally: they are directed perpendicularly sideways. As a result the “saw” is formed like existing at Holocene saw-fishes one. It also operates by this saw in shoal of fishes, having rushed into its thicket and making sharp jerks by head here and there, horizontally and aslantly. The small part of teeth of usual shape and smaller by size, is visible in intervals between “saws jags” and serves for capture of catch. On the bottom jaw all teeth are small and “standard”. During hunting jaws are closed, and resistance of water is minimal. The body of this crocodile is not covered any more by heavy osseous armour as at its far ancestors, it is not necessary any more to this species to protect intensively, it is more necessary to have speed and maneuverability. This reptile is covered with strong elastic skin. Rudiments of armour are submitted partly by back and occipital scutes. The skin has greenish-grey color with fuzzy cross-striped pattern and lighter belly, masking it in a thickness of water have been lit up by solar patches of light in shallow water. Its paws are weaker, than at ancestors, and it never leaves far from water. But a lot of time it spends in water, but quite often it can be seen at the coast where it is basking at sunny place. Especially numerous groups of crocodiles of this species gather at sandy shallows in river estuaries.
Having got warm, crocodile starts to hunt, making the way to water along fenny marshy coast. Its paws are weak, and frequently the animal simply slides on dirt on stomach, pushing by them. It quickly and dexterously swims, using rather wide powerful tail. In the beginning, having noticed suitable fish shoal, it imperceptibly creeps to fishes, then as the knife, promptly runs into it and swings the weapon. Having sated, the reptile creeps out to the coast and has solar baths. The terrible blow of jaws armed with sharp teeth and a powerful tail waits predator dared to interrupt its rest. However large or pack predators occasionally nevertheless manage to win it, because paws of the crocodile are not such powerful, and skin is not so is strong as at crocodiles of Holocene.
It breeds like all crocodiles: the female lays eggs in nest dug on coast in silt and grass, and protects posterity. Young ones feed in shallow water in thickets, mainly with medium-sized fishes, and eat as usual crocodiles; they start to master the characteristic habit of hunting at the age of three years. In early age they can become chase of predators.
Adult individuals are territorial; they supervise sites at the coast do not supposing contenders. However this division is indistinct as at the seal rookery, and each time it is made anew in process of returning animals from fishing. Sorting out of relationships is usually strictly ritualized, and is limited to that contenders raise upwards the top jaw, looking who is larger.
During courtship fights males are not so ceremonious, and easily can put to each other an injury by “saws” armed with teeth, when swing them before the contender, and quite often impacts strikes.
The life duration may account about 70 years.

This reptile species was discovered by Arseny Zolotnikov, a forum member.

Eingana (Eingana archonta)
Order: Squamates (Squamata), suborder Snakes (Serpentes)
Family: Pythons (Pythonidae)

Habitat: Meganesia, Lake Carpentaria and nearby swamps and lakes.
In the prehistoric era, a python of the genus Liasis reached a length of 11 meters and lived in Australia. In human epoch, its relatives reached more modest sizes – a maximum of only 6 meters. After the disappearance of man, one species of Australian python repeated the evolutionary path of this extinct species and turned into an even larger giant, simultaneously becoming the largest snake of Neocene Earth.
Eingana is a reptile species that is much larger than anaconda of the human era. Adult eingana reaches 20 meters in length with a body width of up to a meter. These reptiles can hunt exceptionally large prey and can easily swallow animals weighing up to 150 kgs. Its large size limits this snake’s ability to move on land, but eingana has got rid of this difficulty by turning into an aquatic animal. Due to its large size, this reptile rarely appears on land – those found on dry land are usually juveniles looking to settle in other bodies of water.
Despite the thickness of its body, the Eingana looks like a harmoniously built animal due to its great length. It moves easily in the water thanks to its tail, which is slightly compressed from the sides. The head of the reptile is short and wide, its small eyes shifted upward. The reptile’s nostrils, equipped with leathery valves, are also shifted upward. Thanks to this, eingana can hide in ambush underwater, exposing only a small part of its head above the water surface.
The body of this reptile is an olive-green color with darker irregular spots forming a pattern similar to the glare of sunlight on the bottom. Due to this color, the eingana can disguise itself on the bottom near the coast, waiting for suitable prey to appear.
This species is able to cope with almost any inhabitant of Lake Carpentaria and the surrounding forests that comes to the water. Eingana hunts bovipotamuses in the water, and also ambushes near watering holes and drowns land animals in the water. Eingana bites the caught prey and holds it with its long, backward curving teeth. Wrapping its body around its prey, the reptile makes it difficult for it to breathe. If the prey is caught in deep enough water, eingana will simply drown the prey, keeping it under water with its powerful coils.
In terms of reproduction, eingana is quite different from its python ancestors and is more similar to boas: it is a viviparous species. Such an adaptation developed during the transition of the animal to a fully aquatic lifestyle and allows the female not to undertake dangerous trips on land. Eingana’s pregnancy lasts about 8 months; pregnant females spend most of their time in shallow waters, and during this time they hunt much less often than usual, especially in the second half of pregnancy. In the process of development, the embryos receive nutrition from the mother’s body through a kind of placenta, so young snakes at birth are about 2 meters long. The female gives birth to up to 15-20 juveniles at the same time. The juveniles are born in the water, and the young snakes break the embryonic membranes and rise to the surface to breathe on their own. The first prey of young snakes is water birds. As einganas grow, they begin to hunt large mammals.

The idea of the existence of this species of snake was proposed by Tim Morris, Adelaide, Australia.

Scoopbeak (Anserostrum bicolor)
Order: Anserine birds (Anseriformes)
Family: Spoonbill geese (Anserostridae)

Habitat: shallow waters of lakes of Southern and Eastern Asia, Northern Africa, Indonesia and Northern Meganesia.
Humid and warm climate of Neocene had caused special habitats: shallow-water reservoirs with well warmed water. Such reservoirs are especially numerous in Northern Africa where Nile, having turned to the west, had humidified Sahara Desert and had transformed it to savanna rich in life. In such shallow streams and ponds seaweed and flowering aquatic plants plentifully grow, and the surface of such reservoirs is richly overgrown with duckweed (Lemna). Abundance of forage creates favorable conditions for ones managed its gathering. Small fishes and crustaceans basically inhabit such reservoirs. Carpet of seaweed at the bottom involves some large herbivorous fishes but in such reservoirs it is possible to meet other larger animals.
On such spread stream with slow current the bird with long neck and thin legs wanders. Lowering bi-colored beak in water this bird drives it to sides gathering from surface duckweed the live creatures have clung to it. When the bird lifts head, it is visible, as the skinny pouch under beak is full of water. Slightly having stirred by head bird pours water out from mouth and swallows something. Then it again lowers beak in water and repeats its movements. It is the scoopbeak, the descendant of any geese among species inhabited Northern Africa. Bird is not solitary one: beside in shallow water its neighbours wander highly lifting legs up at each step.
By constitution scoopbeak is similar to some storks. Height of bird from toes up to crown is about 120 cm; weight is up to 5 kgs. Body feathering is white, only on wing flexion there are black feathers forming original “epaulets”. Head is covered from above with black feathers. The bottom part of head (from eye level) and throat are featherless and covered with smooth gray-blue skin. The long beak of bird is colored two colors: top jaw is carrot-orange-colored with yellowish tip, bottom one is dark-grey. At males in the basis of beak there is “knob” characteristic for anserine birds.
Wings of bird are wide and rounded: scoopbeak is excellent flyer and also can make long migrations choosing for reservoirs plentiful in food. Tail of bird is short and fan-shaped. Legs are long and covered with black skin. Between toes there is rudimentary palama getting to scoopbeaks from geese, their ancestors. This bird has also inherited from them characteristic voice: resonant honk.
Scoopbeak eats algae, plankton crustaceans and fry gathering it from water surface with the help of characteristic lateral movements of head. The beak of bird is specialized for such feeding by tiny organisms forming congestions: it is long, bottom jaw is grooved, and muscled tongue is located in it. The end of beak is flattened and wide. Along edge of corneous cover of beak there is filtering device of numerous bristles arranged by slanting lines. Long tongue is attached to mouth bottom. At its edges also lines of corneous bristles pass. The top part of gullet of bird has great number of elastic ring muscles which can strongly stretch and retract fast.
For feeding bird lowers head and moves it from side to another in parallel to water surface (the bottom jaw is submerged in water). During head movements water is gathering in throat pouch; then scoopbeak lifts head above water and by retraction of ring muscles pours out water of throat. Thus it flows through filtering device of beak, and all eatable organisms stay in bird’s mouth. During feeding process bird line stretch by a half moon and birds move to the coast driving fishes and crustaceans to shallow water. After that they simply scoop a congestion of food.
These birds live at freshwater reservoirs and migrate within limits of tropical zone of Old World and Australia. They stay for a long time only at large reservoirs nestind there in the beginning of dry season. They do it not casually: abundance of sunlight and plenty of organic substance in water results in mass development of plankton – the main food source of these birds. Reservoirs do not dry up completely: in dry season rather frequently there are rains filling up stocks of water.
Scoopbeak nests on the ground among reed-beds or on river islands in colonies numbering up to 50 - 100 birds. Pairs formed to some seasons and sometimes keep to all life as at geese. Birds formed pair prefer to feed together and spend a lot of time making to each other signs of attention. In nesting season pair builds nest of grass and thin rods in common.
In clutch of scoopbeaks there are 4 – 5 large eggs with spotty shell. Nestlings hatch after 28 days of incubating. They hath with opened eyes, covered with yellowish-grey down with brown longitudinal strips on cheeks, nape, sides and back. Their beaks are already rather wide and they can eat small organisms. As against to adult birds nestlings swim good: they have palamas between toes. As soon as nestlings hatch and dry, they abandon nest for ever.
The young growth feeds on surface of water filtering by beak the uppermost layer where plankton organisms concentrate. Both parents preserve hatch self-denyingly protecting chicks from enemies. But all the same the significant part of young birds perishes in teeth of large predatory fishes and reptiles inhabiting rivers and ponds. When young birds will grow up and start to fledge adult members of colony arrange collective feeding: having stretched to line adult birds drive fry and larvae of freshwater shrimps to coast and towards to them from land young birds walk. First time young birds can swim but later it is more and mare difficult to do it for them: legs increase and palama decreases. At last young birds in grey feathering with black beaks cease to swim and join adults starting to wander in shallow water together. But sooner or later parents will banish young growth, and juvenile scoopbeaks will have to live independent life in barchelor flights. At the third year of life they will cast the coat and will get the characteristic feathering of adult birds; and the top part of beak will color orange. Then young birds can form pairs which will be kept at them, probably, for all life.

Stegoechidna (Stegotachyglossus armatus)
Order: Monotremes (Monotremata)
Family: Echidnas (Tachyglossidae)

Habitat: forests and scrub of Northern and Eastern Meganesia.

Picture by Alexander Smyslov

Picture by Eugeny Hontor, tat shows the overall idea of the animal's appearance more exact,
but having mistakes in depiction of its hind legs and tail

During the Cenozoic era the branch of monotreme mammals gradually declined. Their variety gradually became lesser, and the habitat area narrowed steadily. In human epoch the area of monotremes included only Australia and New Guinea. But in these districts monotremes were competitive enough, and strongly kept their place in ecosystems. Before the occurrence of people in Australia the sheep-sized giant echidna existed in this continent. But human activity had quickly resulted in extinction of these animals.
Having survived in human epoch, monotremes had proved their viability. In Neocene representatives of this group of animals had formed a number of new species. The apopheosis of evolution of this order of mammals is the largest species of ever living monotremes, the inhabitant of rainforests at the north and east of Meganesia. This animal is named stegoechidna.
The appearance of stegoechidna causes memoirs on epoch of dinosaurs. This is a large four-footed animal, growing to about one and a half meters high at a shoulder and weighting up to 200 kgs. It has a massive constitution and thick short tail. Back and tail of this animal bristle up with corneous prickles and scales, providing reliable protection against an attack of predator. Along the back of animal pointed and long corneous spikes of reddish color grow, gradually transforming to reddish plates on tail and hips. The skin of this animal about 2 sm thick is covered with short and rough black wool. The top layer of skin cornificates, forming additional protection.
Head of stegoechidna is narrow and long, with slightly curved “Roman” snout and small mouth. The bottom jaw is mostly long and thin, and only in its basis bones extend. In these places on bottom jaw thick corneous plates, with which help the animal crushes forage, develop. At this animal there are small eyes, and also external auricles are not present. Sight and hearing at stegoechidna are weak, but sense of smell is very keen.
This animal lives in underbrush and moves, supporting on external part of hand and having turned up huge forepaw claws. With their help animal digs ground in searches of forage. As against to its smaller relatives, this animal is omnivorous, and the significant part of ration of stegoechidna is made of vegetative food – tubers and roots of plants. Animal digs them out by monstrous claws of forepaws, takes by small mouth and pounds between ridge corneous plates growing on jaws and tongue basement. Also it willingly eats earthworms, grubs and fruits fallen from trees.
Stegoechidna has very small brain, and its behaviour differs in primitiveness. It leads a solitary way of life, and shows interest to relatives only during the breeding time.
These animals breed at presence of enough of food, usually in late spring or in the beginning of summer. The female lays three large eggs with dense shell into the brooding pouch forming at this time. The incubation lasts about two months. Newborn cubs eat milky secretions of skin within three months, and leave a pouch rather well developed. Having left the pouch, they follow the mother and eat larvae of insects and other invertebrates, yet become advanced enough to digest vegetative food. Young animals abandon mother at the age of about 5 months. They reach sexual maturity at the 6-th year of life.
Life expectancy of stegoechidna reaches 60 – 70 years. The adult animal does not have enemies – only few predators can bite through its thick skin. However, the young animals have recently left the pouch are protected much more poorly, than adult individuals – corneous scales and spikes at them develop within approximately one month after they leave a parental pouch. At this age the greatest number of animals of this species perishes.

This species of animals was discovered by Tim Morris, Adelaide, Australia.

Marsupial shrew (Nanantechinus aquadromeus)
Order: Dasyuromorphia (Dasyuromorphia)
Family: Dasyurids (Dasyuridae)

Habitat: Northern and Eastern Meganesia, river walleys, lakes and bogs.

Picture by Eugeny Hontor

Till the Cenozoic, before the appearing of man and his satellites from among placentary mammals, marsupial mammals of Australia had developed practically all accessible ecological niches, having formed a plenty of various species. But one environment had remained completely inaccessible for them – water habitats were those ones. Among Australian marsupials there are no analogues of otters, seals or beavers. The brooding pouch, the refuge for young growth for long weeks, had made development of water inhabitancy impossible for marsupials. Therefore in Cenozoic in Australia the vacant place of large water vertebrates was shared by birds, turtles, platypuses and rodents.
In Neocene marsupials had made one original attempt to develop water habitats. Floating plants covering with leaves and stalks a surface of reservoirs, became the house for one such creature. At the end of day and at the early morning on the surface of carpet of floating plants it is possible to notice this creature, managed to find the compromise between presence of brooding pouch and semi-aquatic habit of life. It is tiny marsupial shrew - one of tiniest mammals of Neocene. Length of body of this creature may be about 4 cm; tail is about 2 cm long. The body constitution of marsupial shrew is very graceful; these small mammals are similar to shrews with long legs. Back legs of this animal are little bit longer than front ones. Head is rather large, with wide rounded ears. The muzzle is long, extended to mobile proboscis, on each side of which thin whiskers stick up. The marsupial shrew is the descendant of one of small species of marsupial mice (Antechinus).
As this animal lives in areas with a warm climate, its wool is short and rigid. It is colored light yellow, almost white color – it protects small mammal from overheat. The body temperature at the marsupial shrew is changeable: at night the animal is hidden among plants and runs into original catalepsy during which the body temperature lowers down to ambient temperature. At this time the marsupial shrew is rather languid, therefore it tries to find a reliable place where it will be not found by predator. Sometimes for spending the night the animal even gets into buds of water lilies which are closed for night, but do not immerse into the water. In hottest time of day marsupial shrew is also hidden in shadow to avoid overheat, but thus its temperature does not fall.
Fingers and toes of animal are bordered by “brushes” of hairs, and marsupial shrew greases them with fat secretions of anal glands. Due to it hairs on paws become not moistened, that permits this tiny creature to live on the surface of reservoirs. It quickly runs on floating water plants, and even can run small distances on the surface of water, quickly splashing on it by paws like the basilisk lizard (Basiliscus) known in Holocene epoch. Basically, young animals and adult males which are smaller, rather than females approximately to 30 – 40% are able to do it. Males and females without cubs can even dive for some seconds. The female, especially one with cubs, does not risk to run on water and to dive. It keeps on floating plants where it is easier to find forage and to hide from enemies.
At this creature there are very sharp teeth: marsupial shrew is a gluttonous predator, and devours for day twice more food, than it weighs itself. It eats insects and their larvae, and also small shrimps. The animal catches them, immersing head and forward part of body under water. Due to small size marsupial shrew catches larvae of mosquitoes in leaf axils of floating plants – this animal alongside with fishes and predatory insects controls the amount of mosquitoes in damp districts. Also it can catch fish fry hiding among plants, and even attacks small crabs.
Marsupial shrew lives in conditions where seasonal prevalence of climate rather feebly marked; therefore it breeds the year round. The brooding pouch at it is reduced up to two longitudinal plicas in groin area, bordering nipples from sides. In litter it may be only 3 – 5 cubs developing very quickly. At monthly age they already creep on back of the female, and in two months abandon mother. One – two weeks later the female is ready to reproduction again. Sexual maturity at young animals becomes at the age of three months. Life expectancy of the marsupial shrew is more, rather than at placentary mammals of similar size with constant body temperature: it may amount about two years. It is the result of night catalepsy which is slowing down the “combustion” of its organism.

The idea about the existence of this animal is stated by Tim Morris,
Adelaide, Australia, at the basis of idea of Dougal Dixon.

Bovipotamus (Neobubalis lacustris)
Order: Artiodactyls (Artiodactyla)
Family: Bovids (Bovidae)

Habitat: Carpentaria Lake and swamp forest of northern Meganesia.
The Pleistocene saw Australia populated by giant herbivores of the marsupial kind, now extinct, such as Zygomaturus and Palorchestes; such animals may have spent some time in water, but could not pass fully to an amphibious lifestyle due to rearing cubs in a pouch. The Holocene saw these large animals replaced by introduced ungulates brought by white settlers, among them was the Asian Buffalo (Bubalis bubalis), an animal with a preference for swampy habitats.
Its descendant in the Neocene has realized what the ancient marsupials could not, a completely amphibious mammal, analogous to the hippopotamus. This animal is the Bovipotamus. This animal is relatively small compared to its ancestor; the male reaches 400 kilograms while the female attains only 250 kilograms. Its small stature allows it to live in large groups and walk through forested areas with less difficulty. Its body is bulky and short-legged, with a larger head in proportion to its body than its ancestors, in this sense it resembles a pig at first glance more than a bull. The hooves are able to spread apart, allowing it to walk on swampy ground, and between the hooves there is a web of skin to aid in swimming. Nostrils, ears and eyes are all positioned on the top of the head, as with the hippopotamus. Its skin is dark grey and almost bald with hair only on the tip of the tail and along the neck. The hide is thick to deter biting insects and to protect against scratching vegetation. Its horns are broad at the base, forming a helmet like that of a musk-ox, this allows not only for combat but also to pass through rough vegetation even at a gallop. The points are small and swept to the side; males have larger horn points, while females simply possess the "helmet" with small points facing downward.
This animal is vegetarian, feeding on reeds and water plants. It forms large herds of up to 30, whose feeding prevents the Carpentaria Lake from becoming choked with vegetation. They spend most of the day in the water, and can dive to 2-3 meters deep to feed on aquatic vegetation such as the tubers of water-lilies. They also feed at the surface on water-hyacinth and the leaves of water lilies. During the night they disperse onto land to feed on reeds, and will sometimes eat softer vegetation in the swamp forest. During the day they stay in the water to prevent overheating. They are preyed upon by the Yagil and the Marsupial Panther when it is on land, and large aquatic pythons prey on their young in the lake.
The breeding time occurs in the dry season, when there is enough dry ground to run about. The males will display by throwing vegetation up with their heads and horns. When in combat, the males shove one another with their horn-helmets, head on. The males form leks of several individuals. The female gives birth to one large calf, which can swim immediately. Calves have light grey skin which sometimes has lighter patches that disappear with age. This animal has a lifespan of up to 30 years.

This species of mammals was discovered by Tim Morris, Adelaide, Australia.


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