Edited by Timothy Donald Morris

There are places on Earth, where sunlight has not penetrated for several billion years. This gift of the parent star is quickly absorbed and dispersed in the upper layers of the water, ensuring the reproduction of a great amount of phytoplankton – the basis of most of the food chains of the ocean. To the depths of the ocean, the energy of the Sun gets in a “preserved” form in the bodies of numerous live beings. Some of them sink into the depths already dead, and others make vertical migrations, feeding at certain times of the day in the upper layers of the water. So a small part of the biomass produced by microscopic algae reaches even the bottom of the deepest underwater trenches of the ocean. And due to it, the ocean is inhabited from the surface to the very bottom.
A significant part of the Pacific Ocean floor lies at depths of about five kilometers. Here is the realm of colossal water pressure, low temperatures and eternal darkness. The only food source present in this place is the bodies of other animals, as well as numerous microorganisms. But in the water, bacteria, which various invertebrates feed on, are rather rare. However, a thick layer of finest silt is literally stuffed with them; so many animals have turned into living conveyors, continuously passing literally kilograms of silt through their bodies.
Paradoxical as it sounds, but in the darkness of the ocean floor, it is possible literally to see its inhabitants. In some places, among the silt, short flashes and a flicker of yellow light may be noticed. This is a manifestation of the daily life of the most numerous (of course, except for bacteria) inhabitants of the ocean bottom – abyssal glowworms. Thin flattened worms eat long burrows through the silt layer, digesting the bacteria living in it. The weight of the intestines stuffed with such silt is about two-thirds of the weight of the animal itself. Each worm has its own feeding territory, jealously guarded from neighbors: food resources are too scarce to share them with others. From time to time, the worm exposes the back end of the body with a luminescent organ to the surface of the silt, and gives one or more short flashes. Neighbors notice them even if their heads are submerged in mud. However, if they stuck their heads out, they would not see anything: abyssal glowworms are blind. But there are numerous light-sensitive cells on the body of the worm of this species, so worms easily feel flashes of light.
But to glow in such conditions means to attract the attention of predators once again. Most of the inhabitants of this world of darkness, of course, are blind, but there are also sighted animals among them. Therefore, worms use a different method for marking of their territories: they leave lumps of droppings stuck together with odorous mucus in the thickness of the silt. Like signal buoys, they fence off the worm’s territory from outsiders. If some impudent worm enters the territory, the rightful owner will drive it away with the help of strong bites and head pushes. After the conflict, the host worm marks the territory with a vengeance.
However, these marks can give information not only to relatives. Sometimes they put completely undesirable aliens on the trail.
A strange creature, which resembles some kind of mechanism rather than something alive, walks along the bottom. Long jointed legs move one after another with the precision and regularity of a machine, and a small rounded body armed with a pair of double-folded “grippers” is dangling under them. Long antennae stick forward, groping the animal’s way. It is an abyssal harvester, a crustacean, one of the local predators, which went to find some food.
Unlike many inhabitants of the bottom, it has eyes, and when searching for prey, it is guided by sight. And its prey includes mainly abyssal glowworms. The eyes elongated into a narrow strip have a very wide field of view, and the crustacean quickly determines from which side the tempting light of the worm has blinked. Having turned in the right direction, the crustacean begins its hunt.
The tips of the legs of the abyssal harvester have tufts of hairs, so that it does not sink into the silt when moving. The legs move in a strictly defined order, so the abyssal harvester does not stumble, moving towards the colony of worms. Vision has almost completely played its role: when an animal moves, from under its feet in the thick mud, waves spread, warning worms of danger. Now the worms will not risk getting to the surface for a very long time: they rapidly burrow deep into the silt. But the abyssal harvester is not going to miss its prey: it locates the worms by probing the silt with its long antennae. So, when the sensory cells of its antennae detect one worm, an instant thrust of the claw-like maxillipedes, which had previously been folded under the stomach of the crustacean, follows.
The hunt turned out to be successful: one of the maxillipedes reached the target and took a writhing worm away from the silt. With the help of three pairs of mandibles, the abyssal harvester began to eat the caught worm slowly, while other abyssal glowworms hurriedly dug into the silt. Now they are relatively safe from the abyssal harvester, and soon the worms feel the tremors caused by the crustacean’s legs on the surface of the silt gradually weaken: it moves away in search of new prey. But the worms will not come out of their hiding soon – the instinct of self-preservation is strong, and in this world of predators, caution does not hurt.
The abyssal harvester is moving along the oceanic bottom. Long legs allow it to cross large areas effortlessly in search of food, and the animal does not stay anywhere for long. But this is not the only feeding strategy used by local predators.
The abyssal harvester covers quite a long distance from the colony of abyss glowworms – several tens of meters. Soon it finds something that looks like prey: a worm sticks out of the silt, and there are some more ones next to it. Waving its antennae, the crustacean checks what kind of prey it is. But there is no suspicious smell here, and the crustacean decides to attack. However, the abyssal harvester did not have time to take even two steps to the intended prey, as the silt as if exploded from the inside: something flat bent in half, and the crustacean appeared caught between these semicircular halves – as if a kind of steel trap had sprung.
The abyssal harvester fell prey of a kind of passive predator, the snare starfish. This echinoderm lies most of the time, sprinkled with a thin layer of silt, and waits for the new prey, without making unnecessary movements. The rays of this starfish are connected by a membrane forming a trap chamber for the prey who inadvertently stepped on an animal. In this case, the starfish simply bends in half, covering the prey with a membrane and tightly connecting its edges. The animal lies with its mouth up, so small prey is swallowed almost immediately.
The caught abyssal harvester twitches for a while inside the membrane of the snare starfish. At the moment of the attack, it instinctively self-amputated one of its long legs, but this action did not save it. The usual fate of the prey items of this predator awaits it: it gradually suffocates, and the starfish turns its stomach out and envelops the prey with it, digesting it without even swallowing.
The self-amputated leg of the caught abyssal harvester is rhythmically contracting for some time, distracting the attention of the starfish in vain. But this trick is designed more for fishes, predatory crustaceans and cephalopods, and in this case, it is simply useless. Sooner or later, the musculature of the leg stops contracting, and the limb begins to decay slowly.
A trail of the smell of dead meat, irresistible to local inhabitants, spreads over the bottom, attracting various animals. The closest one to the source of the fragrance was a strange creature with a downright implausible appearance. Up to this point, it was peacefully “grazing” on the oceanic bottom, eating silt along with its inhabitants. The elongated body of this creature rests on a dozen soft legs with wide “feet” that protect it from immersion in silt. From time to time, the creature turns the front end of its body to the sides, gathering another portion of silt with its short tentacles surrounding the mouth. This amazing creature is an echinoderm, scavenging sea pig. On the upper side of the animal’s body, three rows of dense tubercles stick out: along the “back” and on the border of the “back” and “sides”. But when the chemoreceptors of this animal caught the smell of food, it transformed and became looking like a porcupine: the tubercles stretched into very long tentacles that began to sway in the water, clarifying the direction to the source of the smell. These tentacles are covered with a large number of receptor cells, due to which the animal catches the smell, using them like antennae. The legs of the animal stretched out, lifting the holothuria above the silt layer – so the smell is felt more clearly.
Having found out where such an attractive smell comes from, the scavenging sea pig hurries to profit before other ocean inhabitants snatch the prey away. Like a ghost, it swims over the bottom of the ocean, waving its long tentacles and moving its legs in a fantastic slow-motion gallop. Its receptors sense the source of the smell more and more accurately. It does not matter that the leg of the abyssal harvester is covered with a hard shell: for this case, the holothuria has five sharp corneous jaws and corneous hooks on its tentacles.
Finally, the chemoreceptors of the scavenging sea pig accurately detect the source of the smell; the echinoderm slowly sinks to the bottom... and immediately gets ambushed. A large snare starfish, lying next to the first one, “slams", clamping the rear end of the holothuria’s body. The body of the captured holothuria jerks convulsively from side to side, and, needless to say, it is relatively lucky: the first starfish has not yet digested the body of the abyssal harvester; therefore it does not react to the accidental touch of the struggling holothuria. Otherwise, holothuria would not have had the slightest chance to escape. However, here it has an opportunity to escape: by a powerful contraction of its muscles, the scavenging sea pig tears itself in half. The voracious starfish gets its back part, but the front part easily swims away from a dangerous place. After a while, the lost part of the body will regenerate.
Holothurias easily restore lost body parts, and sometimes even resort to autotomy – self-amputation for the sake of preserving their own lives. But if there are no such abilities, then the most optimal way out is the ability to feel the dangers hidden in the mud in advance and avoid them in time. Vision is useless for this purpose – there is eternal night in the depths of the ocean. The sense of smell can easily deceive: some predators lure prey with chemicals that mimic attractive smells. However, some inhabitants of the abyss have acquired a “secret weapon” that makes it easy for them to recognize the presence of other living beings.
One of such inhabitants of the ocean lazily swims over the bottom, although in this case it is difficult to say for sure whether it is swimming or else it is walking. The long slippery body of a strange fish, covered with scaleless skin, moves over the mud on two long thin springy fins, stepping like legs. A long wattle sticks out on the chin of the fish; its tip looks like a small shovel. Because of it, the fish got the name eel-like threadbeard. Tiny eyes are barely visible on the head of this fish – the threadbeard is completely blind. But this feature does not prevent it from eating well and avoiding encounters with predators in time. Its secret weapon is a well-developed electric sense. The weak electric field generated by the fish replaces its field of vision. Any living creature with even the weakest electric field of its own will be immediately recognized by this fish by changes in the shape of its own field.
The eel-like threadbeard feeds on invertebrates burrowing into the ground, mainly worms and young holothurias. Due to the fact that any living being has an electric field, the seemingly lifeless ocean silt is an open book for the threadbeard. No living creature buried in it will appear unnoticed. And due to the electric sense, the threadbeard avoids the danger that caught up the abyssal harvester and the scavenging sea pig: the fish feels the presence of the snare starfish buried in the silt in time. It is hungry: its rays are spread wide to the side, and the trap is ready to get the next prey item. Being lucky enough, a snare starfish can overcome even prey the size of a threadbeard. But now it clearly won’t have to show its deadly hunting skills. The sensitive wattle of the threadbeard has recognized the weak electrical activity of the nervous system of the starfish, and the fish abruptly flaps its wing-shaped pectoral fins, gaining altitude. A few centimeters from the tip of its tail, the trap of the starfish closes: the echinoderm took the wave produced by the fins of the fish as a sign of close prey. Some minutes later, the snare starfish will realize the mistake and set the trap again, but the threadbeard will already be far away at this moment.
Having passed by a dangerous trap, the eel-shaped threadbeard continues to search for food. Occasionally it stops, bends over the bottom, and with some sharp movements of the wattle digs out of the silt one of the small edible inhabitants. Ironically, one of its prey items turned out to be a young snare starfish. Thrown out of the silt layer, it swims away, waving its rays. But by doing this, it reveals itself even more to the threadbeard: the amplified electrical impulses of the nervous system of the starfish make it clearly perceptible to the electroreceptors of the fish. The threadbeard turns its head towards the prey trying to escape and opens its mouth. The jaws of the fish are arranged so that the mouth can stretch into a long tube, easily sucking prey in. A strong current of water draws the snare starfish into the mouth of the threadbeard, and the fish swallows its prey.
Soon, the threadbeard finds another source of food – a colony of abyssal glowworms. And they are not given out by the light emitted from time to time, but again by an electric field. Frightened by the appearance of this fish, worms try to burrow deeper into the silt, but this does not save them: the threadbeard “stands on its head” and shakes its whole body sharply, scattering the silt to the sides. Clouds of the finest silt do not worsen hunting conditions for it, and buried worms become more accessible. Moving its head, the threadbeard draws them in with its mouth one by one. But it will not be able to exterminate the entire colony: some of the worms will have time to dig deep enough so that the fish could not dig them out. In addition, the threadbeard does not stay in one place for a long time: its movements can easily attract predators.
Moving along the ocean floor, the threadbeard feeds in various places little by little, so it does not deplete the already scarce local food resources. In addition, places rich in food are too far from each other, so the carnivorous inhabitants of the oceanic bottom inevitably have to become nomads. But not everyone – there are those among them who wait until the prey itself gets close enough to catch it.
The threadbeard continues to “walk” over the bottom on its fins, occasionally helping itself with a lazy push of the tail. This method of movement is advantageous because the waves almost do not spread from the body of the fish: it does not attract large predators that occasionally move here from the upper layers of the water, and does not scare off animals that represent a suitable food to the thereadbeard. It seems that fish is lucky again: its electroreceptors detect weak electrical activity under the surface of the silt. There’s clearly someone moving here. If the threadbeard had vision, it would have easily noticed a faint yellowish light among the silt. Another one is moving near it, and a third one is blinking nearby. But at the same time, the electroreceptors tell the fish that these are not worms: the electric field is too strong for them, and its center is somewhere nearby. And “worms” are just a part of something much bigger. At the last moment, the threadbeard makes a sharp rush to the side. It was frightened by an impulse of electrical activity, and caution saved the fish’s life. A tentacle shot out of the silt like an arrow, made a semicircle, and then disappeared in the sediment. Everything took literally a second, and if the threadbeard had hesitated for even a moment, another inhabitant of the ocean depths would have received a luxurious dinner. The threadbeard almost became the prey of a large mollusk, the floundersquid. Breaking with the “tradition” of its ancestors, this cephalopod changed the expanse of water to the stinking silt of the ocean “basement”. But nothing happens in nature just like that: such a passive lifestyle gives the floundersquid advantages – low energy costs for catching prey. The body of this mollusk has noticeably changed compared to its ancestors – it has become flat, and the fins have increased and began to border the whole body, like at the cuttlefish. The animal spends almost all its life buried in mud. Only sometimes the floundersquid changes the hunting place.
Buried in the silt, the mollusk becomes almost invisible to its prey. Only two very sensitive bulging eyes remain on the surface, looking up and to the sides, and a breathing tube opening into the mantle cavity of the mollusk, that sticks out above them. At times, the squid carefully “exhales” the waste water and sucks in the portion of fresh one. It tries to do it slowly so as not to scare off possible prey. But the flounder squid is not just a passive hunter waiting for the prey to stumble upon it. It actively lures the benthic inhabitants with the help of its thin arms, at the tips of which there are luminescent organs. Such arms represent an excellent imitation of abyssal glowworms, a favorite delicacy of numerous local predators. And they, in turn, make up the favorite delicacy of the amazing flat squid.
Failure in hunting forces the floundersquid to change the hunting place: here prey seems to be very rare for it. The surface of the silt is moving, and the squid begins to get out slowly. Thin arms, a head with “frog” eyes, and a flat body appear from the silt layer. The squid comes out of hiding with the help of undulating movements of its fins, whirling clouds of light suspension in the water. After circling a little in one place, the animal begins to search for a new place for an ambush. The most desirable place is near a colony of abyssal glowworms, so the floundersquid diligently searches for a specific very subtle smell of these animals in the water. The mollusk swims over the oceanic bottom in zigzags, holding a pair of tentacles ready. Unlike most cephalopods, it swims headfirst: the main means of movement in this species is its fins, not the jet propulsion. The thin tentacles of the animal hang down listlessly during swimming: they have practically lost the function of capturing prey, and the remnants of muscles in them are only enough to simulate the movements of worms.
After several hours of searching, the squid manages to catch the desired smell in the water: there is a colony of worms not far from it. It seems that many weeks ago, the inhabitants of this corner of the ocean floor were incredibly lucky: a huge carcass of some dead marine animal, most likely a large shark, sank here. Of course, the inhabitants of the upper layers of the water “worked hard” on it pretty much, but the carcass was sinking too fast for them to have time to eat everything. And a significant amount of meat and bones remained for the inhabitants of the oceanic bottom. Such “wealth” does not remain unnoticed, even though the bottom is very rarely inhabited. A large number of various animals gathered to the attractive smell of carrion, and they destroyed the remains of a dead animal in a few days. Even the bones were gnawed and eaten almost without a trace. Only a colony of abyssal glowworms, feeding on organic-rich silt, reminds of a former feast.
Separate flashes of yellowish lights indicate the location of a colony of worms, and the floundersquid is preparing to ambush somewhere in its vicinity. It swims along the edge of the colony, choosing a suitable place, but quite unexpectedly, it meets fierce resistance. The lights of the worm colony die, like candles blown out by the wind, when a flat body bursts out of the mud, stretching two tentacles forward. This colony is already occupied by another squid, and it will not allow a competitor to hunt on its territory. Both rivals violently flash lights and circle around each other, displaying strength and determination. And the newcomer is forced to retreat: its congener, who occupied this colony earlier, is much larger and stronger.
The floundersquid is forced to continue searching for a place to ambush. It leaves the territory occupied by its congener, and again swims in zigzags over the monotonous silty plain. And after a while, luck smiles on it: right on the course it notices flashes of lights of a colony of abyssal glowworms. It seems that the colony has no defenders – no one is in a hurry to defend the feeding area from the newcomer. But still the lights of the worms go out for a few seconds, and the squid feels the movement of the water. Apparently, some of its congeners hastily left this colony. But all the better – a stronger animal will have no competitors.
The floundersquid examines the colony of worms, and then, having chosen the most successful place for an ambush, turns head up and literally plunges into the silt layer. Clouds of silt cover the colony of worms, but it is one of the few inconveniences that such a neighborhood causes them. The presence of squid provides worms with protection, and the predator’s feces serve as additional feeding for the colony.
When the clouds of silt settled to the bottom, and the colony of worms continued its fussy life, on its outskirts, a “decoration” appeared, that represents a squid’s breathing tube, near which two shiny eyes protrude from under the silt. And among the many worm lights, eight fake ones appeared. Perhaps, somewhere in shallow water, such deception would be easily exposed, but in the dark, not all the inhabitants of the oceanic bottom can recognize it. And one creature moves straight into the trap, moving one by one its long jointed legs. The abyssal harvester makes the usual rounds of its possessions, not noticing that an unwanted guest has appeared here.
Having sensed the approach of the enemy, the worms extinguish their lights and bury themselves in the silt one by one. But several lights in the colony clearly do not want to go out, and their light attracts a lanky crustacean. Aiming at the nearest one, the abyssal harvester holds its long maxillipedes at the ready, being ready to attack at any moment. But today it is not a hunter, but the prey. Under the thickness of the silt, the tentacle of the floundersquid had already crawled up to it, and when the crustacean was about to grab the bait, the flat tip of the tentacle burst from the silt and literally swatted it like a fly.
Not caring at all about its disguise, the floundersquid dragged the escaping abyssal harvester to its mouth and put a deadly bite on it, after which the squid began to eat its prey calmly, ignoring its convulsions. After a while, the worms will receive a portion of feces of the mollusk with the remains of one of their enemies.
Not only worms eat silt rich in bacteria and containing organic particles. Many animals, which are predators in adulthood, feed on silt at their larval stages. Among the inhabitants of the silt, it is possible to find a variety of creatures: worm-like threadbeard fry and strange rounded crustaceans with lobe-shaped legs. Being disturbed, they swim above the silt and circle over it for a while, resembling certain water beetles, after which they dive back into the silt layer, leaving behind a cloud of turbidity. These are young animals; while growing up, they will lose the ability to swim, but they will grow long legs and become tireless walkers. This is how young abyssal harvesters look. The ability to swim saves them when other animals interfere in their lives.
Moving soft feet, as if dressed in slippers, one by one, the scavenging sea pig moves on the surface of the silt. In its manner of movement and the front end of the body, capable of stretching into the proboscis, this creature resembles an elephant a little bit (unless, of course, there is an elephant having a dozen legs and a bunch of tentacles on its back). The tip of its extensible proboscis is surrounded by short tentacles with corneous hooks. Usually it serves to scoop up silt, but sometimes, if the holothuria manages to find carrion, corneous hooks help to tear pieces of meat. However, they can be useful even while feeding on silt: holothuria, for all its apparent slowness, is able to grab a small animal living in silt. Most often, abyssal glowworms fall its prey, but sometimes the animal manages to grab something more substantial.
In the first months of life, threadbeard fry differ little from worms in their lifestyle. They also tirelessly pass a large amount of silt through their intestines, but with age they begin to hunt the worms, as well as other animals with which they used to get along peacefully. The invasion of their world by holothuria, which devours silt, is an event comparable only to the attack of a tiger on a deer herd. Caught by this “attack”, the inhabitants of the silt hurry to hide from the holothuria, crawl or swim away. But not everyone succeeds in it: the translucent fry of the eel-like threadbeard stuffed its intestines with silt too much and turned out to be not agile enough. The corneous hook of the holothuria caught its delicate skin and stuck deep into its body. From the sharp pain that pierced its body, the fry began thrashing convulsively. Sensing that there was some kind of living creature in the tentacles, the holothuria instantly squeezed all its oral tentacles together. A lot of corneous hooks immediately pierced into the body of the threadbeard fry, and it died almost instantly. Having slowly rotated the prey’s body, the holothuria swallowed it phlegmatically, after which it continued to swallow the silt. Startled by it, a young abyssal harvester rushed out of its hiding place, but did not orient itself, and slammed into the side of the holothuria, which was like an elephant next to a turtle compared to it. From surprise, the holothuria shrank sharply into a wrinkled, shapeless lump. But some seconds later, convinced that it was just an accident, it slowly spread its tentacles, stretched out its legs and continued its way along the oceanic bottom.
After some molts, the abyssal harvester will turn from a swimmer into a walker, and its former neighbors will turn just to its prey. And the threadbeard fry, who will manage to avoid encounters with predators, will become successful hunters. But any food chain here begins in the layer of silt, where glowworms eat a lot of bacteria. And the well-being of many animal species depends on how intensively these worms breed.
Glowworms reproduce like their very distant relative, the palolo worm, which lived during the Holocene at the reefs of the Pacific Ocean. However, although this method was developed by this species completely independently of palolo, the essence of this process is exactly the same in both species: in worms of both sexes, only the segments of the posterior part of the body, in which reproductive products develop, begin to reproduce directly. When the time of reproduction comes, the half of the worm filled with eggs or sperm simply breaks away from the rest of the body and solves the problem of reproduction itself, searching for representatives of its own kind in the depths of the ocean. This is quite difficult to do: worms live in scattered colonies, and there is not always a mature half of a worm of the opposite sex in its colony. Then the detached half, ready for reproduction, can search for a mate for many days. A large number of sensitive cells develop on the integuments of its body, which analyze substances dissolved in water. On each segment, a pair of paddle-shaped legs bordered with thick bristles develops – it helps to swim better. Wriggling in water, such a half of the worm can swim quite quickly, escaping from predators.
One of these halves – a male one, according to its small thickness – confidently makes its way in eternal darkness. Squirming, this half of the worm is searching for a special smell – the smell that a mature female half full of eggs emits. Where there are no undercurrents, it is very easy to do it – the smell “tracks” remain distinguishable for many hours. And several hours of fruitless efforts of the half-worm are finally more than rewarded: the coveted scent of the female is found! Moving rhythmically its paddle-like legs, the male half of the worm rushes along an invisible trail. But it seems that this headless cavalier is not alone here: the smell of the female half of the abyssal glowworm is mixed with a completely undesirable smell of another male. After a short chase, there is a meeting with the coveted “female”, and... with its “groom”. The appearance of a competitor did not go unnoticed: the male worm half, the first to reach the female, is preparing for defense. Opponents collide (is it possible to say “face to face” here if they don’t have any heads at all?) with each other, and a fierce battle ensues between them. They curl into a tight ball, trying to overcome the opponent, squishing it with sides and body rings. At this time, the female half swims indifferently at a distance. It is not interested at all in the quarrels of males – it is intended only to scatter eggs in the water and then die quickly. And the fight between the two male halves ends very unexpectedly: the challenger half literally tears the opponent in half, having captured it in a tight body loop. The knot immediately crumbles: the lucky half is in a hurry to fulfill its duty for the sake of future generations, and the pieces of the loser sink to the bottom. However, they are still alive, and they have a second chance: the seminal fluid will simply resorb, and the substances spent on its production will be spent for regeneration. And soon, having grown a new head, the pieces of the worm will literally get a “second youth”. If they are not dug up and eaten by a voracious threadbeared or an abyssal harvester, in a few months each of these worms will try to reproduce again, and, perhaps, will be lucky in this.
But the winning half of the worm will no longer have a second chance: the female half of the worm secretes hormones that cause irreversible biochemical reactions in the male half. The rapid development of reproductive cells begins, and the segments of both halves swell and burst – their life is over. A cloud of tiny eggs spreads out in the water, and they are immediately fertilized by the seminal fluid produced by the male half of the worm. Fertilized eggs are carried by a weak current. Some hours later, the larvae will hatch from them, and they will spend about a week swimming in the water column. Then they will settle on the oceanic bottom and turn into young worms. Regularly fissioning into two or more parts, each worm can become the ancestor of a large colony, in which after some time new individuals will appear, ready to sacrifice parts of themselves for the sake of procreation.
And many lives, many destinies of living beings, intertwining and fitting together, create a single biosphere of planet Earth, the third planet from the Sun.

Abyssal glowworm (Bathypalolo lucens)
Order: Phyllodocida (Phyllodocida)
Family: Phyllodocidae (Phyllodocidae)
Habitat: Pacific Ocean bottom, depth of 3-5 km.

Picture by Biolog

If there are relatively few bacteria in the ocean water column, then their number increases thousands of times on the ocean floor, which makes it possible for a particular ecosystem to develop. Swallowing silt, benthic animals of the ocean digest organic substances that accumulate in it, including bacteria.
Abyssal glowworm is a polychaete worm that uses this food resource for life. It is a small animal – its body length is about 5 cm. The worm’s body is flattened: it spends a significant part of its time buried in a thin upper layer of silt, which is the richest in organic substances settling from the water and is more abundantly populated with bacteria. Since the food of this worm is spread at a great distance, it is forced to guard its feeding area from its congeners, making odorous marks. The worm can glow, and it uses this ability to protect its feeding territory: exposing the back of the body from the mud, it emits short flashes of yellow light, claiming the right to the territory. The worm is eyeless, but there are separate light-sensitive cells on the covers of the head, so it can distinguish the light of its relatives. In case of danger, the worm also uses light for protection: it shoots at the enemy with a jet of acrid glowing liquid, flashing brightly in the darkness of the depths, and escapes by burying itself in the thickness of the silt. Like most worms, this species is capable of regeneration by regenerating torn away body parts: the body can easily regenerate an amputated head. The worm uses this ability not only for protection, but also for reproduction.
Abyssal glowworm is diecious species; its reproductive organs are located in the back part of its body. When the animal is ready to breed, the rear half of its body with gonads ready for reproduction simply breaks away from the body, and searches independently for the opposite sex half by smell. In this way, worms avoid degeneration due to inbreeding. The larva develops in the water column, absorbing dissolved organic substances through the body surface and eating bacteria and protozoans.

Floundersquid (Glossotheutis latisomus)
Order: Squids (Teuthida)
Family: Hooked squids (Onychoteuthidae)
Habitat: Pacific Ocean bottom, depth of 4-5 km.

Picture by Timothy Morris, colorization by Biolog

Cephalopods have achieved evolutionary success as actively swimming (nectonic) animals. Throughout geological history, they have actively competed with fish in the World Ocean. And most likely, they “allowed” fishes to appear on Earth only because the early evolution of fish took place in coastal waters of lowered salinity, forever “closed” to cephalopods.
From time to time, among the cephalopods, the species that lost the active lifestyle of their ancestors evolved. Such species also exists in the Neocene ocean – this is an abyssal floundersquid.
This cephalopod species is quite large (body length without arms is up to 70-80 cm). It has a remarkable lifestyle, in sharp contrast to most cephalopods: it is a passive predator that waits for prey, being burrowed into the ocean silt. Its body is very flat and wide, having muscular fins – although the animal is passive, it can make rapid rushes if the prey does not swim close to it. The lifestyle has affected its appearance: the eyes of the mollusk are turned upwards; the tube-shaped hyponome is long and can stretch greatly. When the mollusk lies motionless in ambush, it rises above the ground, allowing it to breathe. The tentacles of the floundersquid are thin and weak – they have long lost the function of swimming and capturing prey, but, nevertheless, they are very useful to their owner: bioluminescent organs are located at the tips of the arms. With their help, the animal mimics the movements of abyssal glowworms, luring its prey – fish and crustaceans. To catch its prey, the squid uses a pair of tentacles that can stretch to almost two meters and are equipped with corneous hooks and strong suckers at their ends.
Floundersquid spends almost all its life buried in silt, except for the early stage of development. For reproduction, females release an odorous substance into the water, according to which they are found by a smaller and actively swimming male. One male can fertilize up to a dozen females in a lifetime. The eggs are spawned into the water, where pelagic larvae hatch from them almost immediately. Having used up the supply of nutrients from the yolk sac, they settle to the bottom and turn into a small semblance of an adult animal.

Abyssal harvester (Crustopilio exiguus)
Order: Isopods (Isopoda)
Family: Chaetiliids (Chaetiliidae)
Habitat: Pacific Ocean; oceanic bottom at a depth of 5-6 km.
Among the inhabitants of the ocean floor there are crustaceans; one of their representatives is the abyssal harvester. This crustacean got its name for its resemblance to land-dwelling arachnids: it has a short rounded body with long thin legs. The antennae and maxillipedes of the animal are very long and thin – with their help, abyssal harvester catches its prey without lowering its body to the bottom. The tips of its long jointed legs are equipped with horizontally arranged fans of long hairs; with their help, the crustacean keeps on the surface of the silt and does not sink into it. In case of danger, the animal can self-amputate the leg, which grows back completely after 2 molts, without harm to itself. The animal’s body has wine red color, including its antennae and legs.
Like most animals of the oceanic bottom, this crustacean is a predator; it feeds on worms and carrion. Its eyes are large, stretched into a wide band bordering the front edge of its head: in search of prey, abyssal harvester relies on vision, which allows it to distinguish the glow of the worm at a great distance. If necessary, this crustacean can swim, swinging its legs sharply, and attack its prey from above.
This crustacean is one of the few hermaphrodite species in the order it belongs to. Usually, when two sexually mature animals meet, they mutually fertilize each other, but if necessary, self-fertilization is possible. Young abyssal harvesters live on the bottom and eat silt. They have short legs, dig in the mud and are able to swim. After the second molt, they begin to hunt small animals, gradually becoming similar to adult animals.

Snare starfish (Droseraster trapa)
Order: Valvatida (Valvatida)
Family: Goniasterids (Goniasteridae)
Habitat: Pacific Ocean bottom at a depth of 5-6 km.
The mass extinction of species of living creatures affected representatives of all phyla, including echinoderms: many species of these animals that lived at coral reefs and in the depths of the ocean died out. But the remaining species, evolving rapidly, filled the vacated ecological niches again, and the diversity of species in the biosphere was restored. Passing to a new habit of life, living beings do not always part with their old habits, although their modification is sometimes just amazing.
Snare starfish is still a predator, like all starfish species. But the way it hunts became truly amazing. This animal buries itself in fine oceanic silt, after which it patiently waits for the prey of appropriate size. But if most starfish crawl so that their mouths are directed down (in them, mouth is located in the center of the lower side of the animal), then this species is waiting for prey, lying with its mouth up. At this time, only rows of ambulacral legs stick out from the surface of the silt.
The ambulacral legs of this star have turned into sensitive and grasping organs, signaling the approach of prey and firmly grasping it when it steps on the body of the star. When the prey is captured, the star folds in half and covers it with half of its body to protect itself from attacks by other predators attracted by its prey.
The body of this species is very flattened, with a diameter of about half a meter. A thin membrane is stretched between the rays, increasing the trapping surface. The rays are muscular, flat and wide; on the oral side of each of them there is a double row of legs equipped with chemoreceptors. At the tip of each leg, three corneous hooks have developed, which cling to the prey when it touches them. The skeleton is greatly reduced: the bone tissue is replaced by cartilage, and the shell plates – by corneous shields.
This echinoderm species is a viviparous hermaphrodite. After mating, up to 15-20 large (up to 5 cm in diameter) young individuals develop in its ovaries. They are able to move quickly with the help of legs, and can even swim some distance, like jellyfish. In this way, they settle down, searching for a place to live. Some weeks later, they turn into sedentary ambush predators, like an adult animal.

Scavenging sea pig (Elephanthuria elephantipes)
Order: Elasipodida (Elasipodida)
Family: Elpidiids (Elpidiidae)
Habitat: Pacific Ocean bottom at a depth of 4-6 km.
Echinoderms are among the characteristic inhabitants of the ocean depths. In Holocene, there were many species of them, of the most bizarre appearances. The mass extinction at the turn of Holocene and Neocene adversely affected their numbers and species diversity. However, after the stabilization of natural conditions, the survived species repopulated the ocean, giving no less bizarre descendants than before.
Scavenging sea pig is a creature about which it is impossible to say definitely whether it is bizarre or ugly. But all the same, it is a wonderful example of adaptation to life in the cold world of the ocean floor. This echinoderm has a long body (length up to 30-40 cm with a thickness of about 10 cm); the shell is reduced, like in all representatives of the class. The animal’s skin is translucent and grayish; the insides are visible through it. On the underside of the body, there are two rows of large, well-developed ambulacral legs with wide “feet” that prevent sinking in silt. Along the middle line of the upper side and on the sides there are three rows of sensitive tentacles capable of stretching strongly (up to half a meter) and moving. The tentacles are covered with chemoreceptors, which make it possible to detect the presence of even the faintest smell of possible and most desirable prey – dead animals – in the water. But such food is very rare on the ocean floor, so most often the scavenging sea pig feeds on organic residues, simply swallowing silt. The mouth of this animal is surrounded by ten short tentacles bearing corneous hooks on the inside, with which this species tears carrion and catches slow-moving animals in the mud.
The animal walks quickly on the bottom, alternately moving forward pairs of its legs – from the first to the last pair. Most of the time, this holothuria is slow, but, having sensed the smell of carrion, it quickly moves (“gallops”) towards it, sometimes correcting the direction of its movement with the help of chemoreceptors.

Eel-like threadbeard (Bathygymnotops longibarbus)
Order: Codfish (Gadiformes)
Family: Bathygymnotopids (Bathygymnotopidae)
Habitat: Pacific Ocean, bathybental zone.

Picture by Timothy Morris, colorization by Alexander Smyslov

As shown by observations from deep-sea research vessels conducted by humans – the only intelligent species on the planet – the ocean appeared densely populated from the uppermost layers of water to the bottom of the deepest depressions. Low water temperature, poor nutrition, low level of oxygen and enormous water pressure – all these conditions did not stop the conquering of the depths of the World Ocean by living beings. Fishes are found, obviously, at all depths of the ocean, and some of them have mastered life near the craters of active underwater volcanoes.
Eel-like threadbeard is one of the few fish species living on the ocean floor. It is a fish similar to an electric eel – its body is very long (the total length of the fish is about 1 meter at a depth of up to 8 cm), although this species belongs to the codfish order (Gadiformes). The anal fin of this fish stretches along the entire underside of the body, so the reduced abdominal fins and anal opening are shifted forward and are located between the bases of the pectoral fins. Due to the undulating movements of the anal fin, the fish can slowly swim over the bottom, searching for food. For faster movement (for example, to escape from enemies), strong pectoral fins, similar to wings, serve. The fish lacks dorsal fins, and the tail fin is reduced to several long rays. The pelvic fins also play almost no role in its swimming: they have turned into long appendages that allow the fish to “step” on the bottom, as if on feet. The skin of the fish is scaleless, translucent and whitish, covered with a slime layer.
Eel-like threadbeard feeds on benthic invertebrates burrowing into the ground – worms, young holothurians and starfish. Its head is equipped with a retractable mouth and a sensitive outgrowth up to 20 cm long on its lower lip; when the fish “walks” over the bottom on its thread-like fins, this wattle probes the silt and helps to take prey from it – its tip is flat and works like a shovel. The prey dug out of the ground is sucked in by a toothless mouth stretching into a long tube. The eyes of eel-like threadbeard are tiny, barely visible under the skin as two small dots; vision, useless at great depths, is lost. The fish is guided by a highly developed sense of smell (it has wide slit-like nostrils that can turn slightly to the sides, catching the direction of the source of the smell) and an electric sense. The body of the fish is equipped with electroreceptors that allow it to detect the slightest extraneous electrical activity indicating the presence and size of living beings around the fish. The finger-like process on the lower lip is especially sensitive.
This fish spawns small eggs, which the male bears in its branchial cavity for several days without eating. To place them there and fertilize them, fishes of both sexes have developed flexible tubular outgrowth of the cloaca, so the female lays eggs directly into the “incubator”, pushing its ovipositor under the male’s gill cover. Fertilization also takes place there.
The juveniles of this species are worm-like; they inhabit the mud, feeding on bacteria, and with age they switch to feeding on worms.

“There are many roads in the world, but the best of them is the on leading to the home” – popular proverb says so. It is just a proper time* to return from remote warm Neocene to present day, to rigorous Holocene. Those accidents, which can result in change of epochs, may have not come yet, or they may happen even next day or week – it is kept from our mind by the Allmighty Time. And that facts about the world of the future, which the author of these lines have told about, as people in Russia say, are “written by pitchfork on the water”. While it is impossible to check up it at the present level of development of engineering, hence to prove or to deny conceptions and ideas, stated by author of these lines, by anything material is impossible. Therefore everything, that had been written about the inhabitants of has not come yet Neocene, the author of these lines considers simply “the science-fiction fairy tale”.
At this place in each more or less known fairy tale, there is the phrase: “... and they lived happily ever after... ”. To tell the truth, in some fairy tales, the following phrase is added: “... and died in the same day”. However, the great Russian poet A. S. Pushkin in the famous “Tale of the Golden Cockerel” warns:

“Tale of sense, if not of truth!
Food for thought to honest youth.”

Therefore, when parting, it is necessary to look once more at the world of non-existent inhabitants of the future Earth and to remember the following things:

— Live beings, which had been met by readers at the pages of this book, should absolutely not necessarily appear on the Earth at the appointed time. Probably, some of them also will never appear on the Earth;

— Evolution of live beings at the Earth had not terminated with occurrence of the human. “Absence of evolution” now is only an illusory phenomenon. Actually, the world is changing slowly, and live beings also constantly change. Therefore in the future the living world of the planet will differ considerably from modern one;

— Evolution of live beings is not simply certain casual sorting of various combinations of genes. It occurs according certain laws and principles resulting from properties of live beings and direction of biological processes which they are involved into. These laws have been realized in the past and will be realized in the future;

— Historical development of live beings is not predetermined by a certain purpose. This process is determined by combination of changes of environment and internal, genetically caused opportunities of the organism of changing when adapting to changes of the environment. Interaction of these factors also determines the destiny of any species – its survival, change or extinction;

— The evolution of species on the planet will proceed until there will exist conditions on the Earth favorable for existence of carbon-based protein life.

And each dweller of the Earth should remember one more thing: the future is not predetermined. It depends on the present, and our daily actions, put together, already today, even right now, this minute, have the influence to the future. In many respects, the appearance of the future, which expects the Earth, depends on us, the people.

* Ha-ha, what a naive guy I had been at that time, many years ago! The journey goes on! - P. V.