«Hanging gardens» of the ocean

 

Tour to Neocene

 

8. «Hanging gardens» of the ocean

 

 

 

In historical time it was known, that in the centre of Pacific ocean there is a huge desert - the area poor in plancton reaching from coast of Northern America (California) up to Hawaiian islands. This sea desert does not concede to Sahara desert in size. It is deserted because of extremely small quantity of plancton in this area. But after 25 million years, in a warm Neocene currents have changed their directions, and new groups of live beings had made desert a garden, original “hanging gardens” of the ocean.
Majestic sailerfish schools leave waters of Antarctic Region and go to the north, to equator with oceanic current. Here females of these species search for waters, a stream going on northwest from Atlantic, and with this current leave in the centre of northern Pacific. Current itself leads them to needed place - to “hanging gardens” of Pacific Ocean. It is the true island of life - in the huge ring of currents formed by an underwater relief, the unique community of live organisms was stretched.
The basis of this community is made by the special animals developed a new way of life. These are invertebrate representatives of chordate phylum - salpas. Salpas known to people are colonial or solitary creatures living in a thickness of ocean water and filtering tons of water in searches of a plancton which is their food. “Plancton accident” at the boundary of Holocene and Neocene, shaken food chains of ocean, had forced the single survived species to evolve, finding new forms of existence. Salpas had evolved the special mode of life which had helped them to become independent of plancton quantity in water. They had constructed symbiosis with algae, and began to rear them in vast guillet, having transformed the body to a greenhouse. And this alive greenhouse can emerge or be immersed, saving itself and "crop" from storm and rains of pernicious for sea inhabitants fresh water. Colonies of gardnersalpas had settle water desert in the centre of Pacific ocean, having transformed it to magnificent garden. The only two things, necessary for them are sun light and quiet water. And at the ocean it is enough of it.
Salpas form long double chains at the surface of ocean, breeding by budding. By the channels, connecting individuals, cells of sea symbiotic algae find a body of young animal. Energy of growth of salpas is amazing: for day the animal had been to have eaten on 2/3, is completely restored. And one salpa for one week can form up to twenty new individuals.
Such speed of increase of a biomass has not remained unnoticed by sea inhabitants, and they lodge in salpa colonies in mass amounts, finding to themselves shelter and food. On a jellylike surface of salpa colony the crustacean “salpa louse” creeps. It has a long thin proboscis which helps to exhausts tissues of salpa branchial pockets in which algae grow. It would seem, it can breed in colonies of salpas in huge quantities, destroying all jellylike sea gardeners, but the salpa’s habit of life partly imposes restrictions to its number. Therefore its harm is not so great, and salpas are quickly restored/ It is not so difficult because they more, than on 95 % consist of sea water.
Floating near surface, colonies of a salpa make the sea as though "viscous", extinguishing little waves. In the centre of colonies of salpa water moves slowly, and there are good conditions for growth of algae, including undesirable ones. Such weeds grow on an external surface of a colony, blocking a sunlight to "beds" in a branchial cavity of a salpa. But here the salpa has ally. The flat translucent worm slides on a surface of colonies, scraping by sharp jaws algal cover from a surface of a salpa. Except for them it swallows the rests of dying off members of a colony, playing the hospital attendant. A salpa is not only a table, but also the house for it: it lives in the branchial cavity of salpas, leaving it for a feed in the afternoon.
From time to time new settlers arrive to colonies of salpas. They live here not constantly, in due course leaving sea “hanging gardens”. The giant sailerfish in school of neighbours comes nearer to colonies of salpas. But it will not to have eaten any animal here.
This fish is the female, and in general all this school consists of females. Their purpose is to not have a meal but to bear posterity. The body of fishes turns pale, the tail convulsively pulls here and there - at a fish real “birth pangs” begin. At last one for one sailerfishes start to give rise to posterity, throwing up in water hundreds of tiny fries in length up to 2 cm. Fries almost at once start to move and dexterously direct in shelter among ribbon-like colonies of salpas. They still glass-transparent, only black eyes and iridescent patches of light give out presence of small fishes at water. Schools of sailerfishes give rise fries almost simultaneously, and right away swim to an open ocean, to place rich in plancton. And their fries begin independent life in colonies of the gardnersalpa. But this life is very uneasy. It will not suffice food to all – cleaning worms are able to be hidden, and the shell of “salpa louse” not any fry can crush. Nothing else is left, but to catch rests of salpas when larger animal will have eaten this alive meat jelly, or to hunt dexterously worms and larvae of small organisms. A pharyngeal cavity of a salpa is a fine shelter for a fry, therefore soon almost all free zooids of salpas appear occupied by them. To fries of the sailerfish it is a big luck: they are large enough, that rescues them from set of invertebrate predators. However they are fine food for other ocean creatures. Few fries will survive and will turn to huge ocean beauties.
The salpa can not protect itself from hordes of commensals and parasites, it only can filter water and protect by the own body a colony of algae. And then the salpa is able to swim. And by evening colonies of salpas start to be immersed in sea depths. There, on 100-meter depth, salpas fill up from environmental water stocks of mineral substances, phosphates and the nitrates necessary for growth of symbiotic algae, absorbing it by special protein complexes. To surfaces under beams of the sun this complexes will disintegrate, giving to the symbiotic algae substances necessary for growth.
And on this depth, in a night cool and silence in colonies of salpas inhabitants of depths start to appear. As if a phantom, from depths the strange soft luminous creature appears, flaping by pair of fins. It is the long-tentacled slimesquid having gone to night harvesting. After the first alive phantom there is the second, the third, and soon in many colonies of salpas already one - two squids sit. Keeping by pair of tentacles for a colony, the animal surveys pharyngeal cavities of salpas by other tentacles. Occasionally that one other tentacle sends a small animal in a mouth of the squid. More often it happens a fry of the sailerfish. Usually for the first month of life up to half of all fries perishes. But the survivors will receive more food and will grow faster. Sometimes the squid sharply draws aside a tentacle: in some small houses the “salpa louse” is hidden, and this crustacean can protect itself with the help of picks of a sharp proboscis. Squid having soft mucous tentacles can not cope with the armored opponent. And other visitor from depths makes it easy. The big-eyed needlefish with a short body and the long toothless snout similar to a tweezers, hunts any catch, but it prefers crustaceans. Inspecting zooids of salpa, it pierces and breaks off by a long snout their soft bodies, pulling out from them crustaceans and worms. Some worms prefer "to pay off" from a predator with a half of a body - for some weeks they easily will regenerate it. The main question is to not lose a head, and other losses can be gone through.
The needlefish quickly swims among colonies of salpa, and its sensitive large eyes catch the slightest movement. It does not miss a case to regale itself with the squid. Having noticed it, slimesquids extinguish lights and become practically invisible. The thick layer of slime absorbs their smell, making sharp sense of smell of a needlefish useless. But the fish reacts to the movement of water made by hidden squids, and attacks. However the squid has two reliable means of protection. When the needlefish snatches one squid, that one simply slips out from jaws of the fish. The layer of slime environmental a body of the squid, in case of need is easily shed: on the bottom side of a body there is "seam" from the thin crosspiece of slime. The squid frees itself from a slime cover by jerk, leaving "clothes" in a mouth of a predator. Then it applies the second means of defense – animal throws in water from special glands two jets of colorless liquids. Mixing up in water, they give sharp flash of light, blinding a predator. Under covering of a veil of luminous clouds the squid slips away in depth. There, hanging in a thickness of water, it easily will restore a mucous cover on a body during some hours.
In the morning the feast of inhabitants of depths comes to an end, and they go away to the gloomy world. And salpas rise at the surface of water. Rhythmically and synchronously pushing out water, colonies gradually rise to a surface of water by short jerks. And only at the surface zooids disperse as much as possible, increasing a surface of a colony and this way slowing down its immersing. From time to time salpas push out portions of water, supporting a colony at the surface. At night they had a lot: the part of zooids is torn, the part was lost in jaws of underwater inhabitants, some individuals are torn off a colony and swim at the surface of water, convulsively throwing out water. But they are not doomed at all: in some hours at such single individual it will start to be formed the runner on which primordiums of new salpas will appear. They will grow, and some weeks later, if it will be a luck, from one individual the new colony is formed.
Among colonies algae-eating worms creep - the loss by night visitors also is put to them. Some worms are actively fed, grew restored segments, other ones eat algae or cross between colonies of salpas. They should be especially cautious - fries of the sailerfish are very hungry. First time they can eat large (in comparison with their own size) animals, but further they gradually pass to smaller food and become filtrating organisms from predators. Thus, young growth and adult fishes do not compete with each other for food.
From time to time in colonies for dinner there is something more essential, than watery bodies of salpas. Ill and dead deep-water fishes emerge to a surface of water, relieving the monotony in almost vegetarian diet of inhabitants of salpa colonies. Around of the fish body tens of worms and crustaceans gather. They tear meat of the dead animal, trying to eat plenty for future use. Thus crumbs of meat little came salpa’s way - they can digest the food acting from the outside though they mostly feed due to symbiotic algae. On such food salpas grow and develop more faster.
When the body of a fish will be regularly distributed to hundreds of small stomaches, it will not be gone completely - the dung of predators will be digested by salpas and becomes fertilizer for algae. Granting of a shelter for set of tiny creatures gives a salpa benefit - almost all their dung is used as fertilizer of algae, and additional portions of carbonic gas get to a salpa formed to sugars and proteins. Colonies of algae in branchial pockets of salpa produce a lot of oxygen which provides huge energy of growth of this animal.
After some weeks young growth of sailerfishes will spend a lot of time outside of colonies. Small fishes have very much grown up: now they are about 10 cm long. Many of their small neighbours from possible predators have turned to food for them. But small fishes gradually pass to a new diet - all of them swim with opened mouth in congestions of larvae and small plancton organisms more often than before this time. Sometimes they "by force of habit" can have eaten the crustacean or the algae-eating worm, but every day these bents are shown more and more poorly. At last small schools of young sailerfishes leave a colony of salpas and go to depths of ocean. There current passes which will carry them away further to the west - to coast of Asia and Australia where it will take them to the surface together with set of deep-water creatures. It will be the first wandering of these amazing fishes. There, near the coast, the enormous quantity of plancton grows on organic substances, phosphates and nitrates in which deep waters are rich: young sailerfishes will eat it. And then they will go to southern sea pastures to coast of Antarctica with adult neighbours together. And some of them will return to “hanging gardens” if they will survive at the ocean full of dangers.
Without larvas of sailerfishes the community gradually starts to come to a normal condition - injured zooids regenerate, form new colonies and grow. Their commensals start to breed actively: worms lay clots of eggs in branchial cavities of salpas, “salpa lice” crustaceans carry tens of young crayfishes on a back side of body. The ocean is filled with the larvae forming the real clouds among salpa colonies. The part of them will be eaten by salpas, another part will be lost in the ocean and die, but some ones will settle in colonies on places, rich in food, and will give the following generation of underwater garden inhabitants.
But the plenty of alive creatures does not remain unnoticed, and once at night slimesquids and a big-eyed needlefish will not come to hunt in the plunged colonies of a salpa. They were fed here long time, but one more applicant for food has appeared with whom they will not cope. Therefore, rescuing their own lives, these inhabitants of gloomy depths will hunt in the other place at this night.
In depths of night ocean pairs of lights appear. They rise closer to a surface, and soon owners of these lights become visible. These are strange creatures - it seems, that the jellyfish have pierced through by a fish. But this is self-dependent alive creature - the jellyfish blenny. Fishes 35 - 40 cm long rise from depths of ocean a head upwards. The most part of time they swim in this vertical position. Strange "collar" behind their head is formed by pectoral fins. Sometimes the fish stops and opens these fins, braking immersing.
These fishes are woracious predators, and they are ready to eat. Squids and needlefishes also are afraid of them - blennies have sharp cutting teeth and are capable to tear to pieces any catch. But now they are swimming to a colony of salpas. Sharp teeth of numerous fishes pierce in a colony, and blennies start to devour salpas together with their symbionts and parasites. In general salpas have doubtful food value because they are too watery and rich in cellulose. But the great number of tasty fleshy inhabitants live in them. This feast lasts all night. And only morning stops it when the rising sun frightens of its light predators adapted to depth darkness. Blennies swim downwards and open "umbrellas". Slowly moving with their edges, they are immersed to depth. Their lights become smaller, and the peace comes to underwater garden again.
After a feast of jellyfish blennies the colony looks very pitiful: there is a big number of injured zooids, and the significant part of adult population of symbionts is lost. But it repeats seldom; for night current will carry school of blennies to other place, and the following predatory attack will pass far from here. And the colony will have time to be restored due to indefatigable work of a remarkable organism - gardnersalpa.
Productivity of the ocean is huge, and it feeds not only underwater inhabitants. Flights of sea birds feed exclusively on sea food, and among them there is one of the largest flying birds in the world, “the sea lord” - the nomade albatross. These giants travel above oceans alone or in pairs, returning every year to native islands near Antarctic coast.

Bestiary

Algae-eating worm (Nectonereis reptans)
Order: Phyllodocida
Family: Nereididae


The bristle worm (Polychaeta), living on a surface of salpa colonies. The size of the body is up to 4 cm at width up to 5 mm. A body is flattish, segmented and translucent; on each segment there is a pair of swimming structures with bunches of bristles and hooks on the bottom side. The worm is a good swimmer, but the most part of time it spends on a surface of salpa colonies, playing a role of refuse collector: animal eats dying off parts of tissues, settling particles, algae growing on a surface of salpa body. At danger it is hidden in a branchial cavity of a salpa.
Breeds, laying eggs in an exhalant siphon of salpa; the clutch covered by mucous capsule is pasted on a surface of a siphon. The current of water takes larvae out in water. Larvae live in a plancton about 1 month, further they settle on a colony of salpas and have metamorphosis to young worms.

Slimesquid (Crystallophlegma phantom)
Order: Teuthida
Family: Crystallotheutidae



Picture by Timothy Morris

Initial image - picture by Pavel Volkov

The deep-water squid up to 80 cm in length (50 cm accounts for tentacles) with very soft, translucent body covered by a slime layer. Through a body internal organs are visible. Fins are heart-shaped, body is wide. Eyes are big, silvery and dark blue shining. On a body there are tiny luminous organs as numerous dots. Around of eyes larger organs of a luminescence are disposed, along tentacles a line of small reflecting light lenses with crystals of guanine passes. Mollusc lives at depths up to 300 meters, rises on depth 80 - 100 meters for a feed at night.

“Salpa louse” (Salpophthirus parasiticus)
Order: Isopoda
Family: Cirolanidae


Large (length of the body is up to 2 - 3 cm) crustacean of isopod group (Isopoda), parasitizing on colonies of a salpa. A body is flat, oval-shaped, translucent with a greenish shade; antennas are long, covered with hairs, at danger they can be turned under the carapace; legs are short and prehensile. Crustacean eats bodies of salpas, eating them away from tunic, and also eats tiny plancton organisms which are picked up from water by long antennas. At danger animal hugs the cover of salpa or penetrates to its branchial cavity or an exhalant siphon.

Gardnersalpa (Viridisalpa hortensis)
Order: Salps (Salpida)
Family: Viridisalpidae


The plancton animal of tunica group (Tunicata). It formed symbiosis with green unicellular algae which settle down in special sections of branchial cavity of a body, supplying salpa oxygen, cellulose and sugars. Gardnersalpa lives at the surface of ocean by large colonies formed as a long double chain of individuals (includes up to 200 - 250 zooids up to 30 cm in length everyone). At night it dives to depth up to 100 meters for updating stocks of phosphates and the nitrates necessary for a feed of symbiotic algae. Also on depth the colony waits strong storms. Actually the salpa lives mostly due to algae colony in the body and serves as alive "greenhouse" for them, supplying algae by organic and mineral substances, and also protecting them from external influences. A body of a separate salpa is cylindrical, very soft, translucent, algae pockets are allocated as cross green half rings. The body is covered by tunic contents big per cent of cellulose which makes an animal by less edible. Separate zooids are connected with each other ones by ducts, but these connections are very fragile, therefore the colony tears easily. Each individual of a colony has special gemma in the place of duct attachment. In case of damage of connection with the next zooid the gemma starts to grow and turns to a new chain of individuals, forming approximately during the week about 20 new individuals of the normal size. New individuals receive cells of symbiotic seaweed through the ducts, connecting individuals, or from the water environmental a colony. Cells get in water at break of a body of any zooid (for example, at an attack of the parasite or a predator). From time to time separate individuals of a colony start to lay eggs, bearing them in a cavity of a body. Larvae left eggs, grasp cells of the symbiotic algae, go outside through break of a parent body and swim away. A bit later the single individual forms an independent colony.
After the attack of predators the colony regenerates quickly. Partly attacks even do good for colonies because it raises probability of a meeting of a young animal with cells of algae.
Colonies of the gardnersalpa have occupied desert areas of ocean, having formed high-capacity communities with the large biomass. In colonies of salpas numerous ocean fishes spawn. Fries of fishes are frequently hidden in wide branchial cavity of salpa.

Big-eyed needlefish (Bathybelone brachysoma)
Order: Needlefishes (Beloniformes)
Family: Xenoxiphiidae



The descendant of sea needlefishes (Belone), developed life in depths of open ocean. It differs from ancestors by a short body (length of body is only 3 times more than height). The head is large: taken together with a snout it mounts to 40 % of fish length. Snout is thin, long, without teeth. Eyes are very big. Fins are crescent, a tail stalk is short, tail fin is half-moon formed: the fish can quickly swim on long distance. Colouring of a body is silvery, back is bluish. Fish lives on depths up to 200 meters, at night frequently meets at the surface. In colonies of gardnersalpas fish feeds (it eats parasitic crustaceans, fries of fishes) and spawns sticky eggs (up to 500 ones).

Jellyfish blenny (Medusoblennius holopelagicus)
Order: Percoid fishes (Perciformes)
Family: Blenniidae



Species of the coastal fishes have adapted for inhabiting in thickness of oceanic water. Such way of evolution is quite possible: in lake Baikal there are representatives of an endemic genera of Baikal cod (Comephorus), descended undoubtedly from coastal fishes. Baikal cods live in a thickness of water and make vertical migrations. It is considered, that the ichthyofauna of open ocean is formed of representatives of the coastal waters migrating to a thickness of water.
The jellyfish blenny is named so for the special adaptation for soaring in a thickness of water: its pectoral fins are very long (more than 2/3 lengths of a body) and wide. On a throat they grow together as "collar". Normal position of the jellyfish blenny in a thickness of water is head upwards tail-standing one. Thus pectoral fins are opened completely; behind a back of a fish they are overlapped, creating this way the original "parachute" facilitating soaring in water. The fish soaring in a thickness of water, reminds the jellyfish. A liver of the blenny is very large, plenty of fat. It helps as similarity to float, replacing the reduced swimming bubble. A body of a fish is high, a head is wide and short, jaws have sharp cutting teeth. Eyes are directed to sides and forward. Males have outgrowths of skin as shrubs above eyes, for females - simple "hornets". Behind an eye of a fish there is located a luminous organ (photophore), at the male its light is bright white, at the female - dim, greenish-white. The body of fishes is silvery, the female is more stout, the male is more harmonous and larger (length of the body is up to 40 cm). Spawn large eggs (up to 50 ones) to thickness of water, the male takes and incubates eggs in a mouth.
This fish is a predator, eats invertebrates and small fishes. Lives on depth 250 - 300 m, makes rise on depth up to 100 m for feeding in salpa colonies at night.

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