Echinoderms are an ancient group of invertebrates that consists exclusively of marine organisms living in water with high salinity. In some respects they are close to the phylum chordates. For example, echinoderms are typical deuterostome animals, they have a secondary body cavity - a whole, and the structure of the skin is similar to that of chordates. The evolution of echinoderms was very complex and was accompanied by a change of forms, the extinction of some groups, and the transformation of others. Paleontological materials indicate that echinoderms obviously existed already in the Precambrian, since in subsequent geological periods they were quite widely represented. Based on the totality of scientific data on the origin of echinoderms, there is reason to assume that the ancestors of echinoderms were free-living, bilaterally symmetrical animals, which in the process of evolution acquired radial symmetry in connection with the transition to an attached lifestyle. Subsequently, echinoderms returned to free movement, maintaining a symmetrical radial structure, and only crinoids partially continue to lead an attached lifestyle.

Thus, radial symmetry in echinoderms is a secondary phenomenon. This is confirmed by their progress individual development: in ontogenesis they go through the larval stage (dipleuroles) with bilateral symmetry, and not with radial symmetry, which is characteristic of adult individuals. Here there is a connection between ontogenesis and phylogeny.

In their structure, echinoderms represent a very unique specialized group of animals. Unlike all other invertebrates, they have a special water-vascular system - ambulacral. None of the other types of animals have such a system. Its structure and functions are set out in a school zoology textbook, and there is no need to repeat it here. It is easy to see that the structure of this system and the arrangement of other organ systems of echinoderms bears the stamp of radial symmetry. The nervous system, for example, consists of three tiers, consisting of rings and radial trunks extending from them, of which the ring and trunks of the outer (superficial) tier are associated with sensory organs, which in echinoderms are generally poorly developed. For example, they have no phonoreceptors at all; the organs of touch, smell and taste are sensory cells on the ambulacral legs, on the oral tentacles and other parts of the body; the organs of vision are presented in the form of eye pits (in sea stars), light-sensitive organs (in holothurians), pigment spots (in sea urchins); stator receptors in the form of otocysts are present only in some species of holothurians. Despite their modest receptor apparatus, echinoderms react quite strongly to changes in illumination and perceive taste stimulation well.

Assessing the behavior of echinoderms, it should be noted that it has reached significant diversity, which is associated with a more developed nervous system compared to other animals that have a radial type of body structure. In echinoderms, the number of interneurons increased, which improved and refined the connections between the sensory and musculoskeletal system, and this was of great importance in the conditions of the disappearance of direct contacts between their sense organs and working tissues, since the nervous network of echinoderms moved from the surface to deeper parts of the body and turned into radial nerve cords without the formation of a compact nerve center.

Echinoderms live in seas and oceans of all latitudes on a wide variety of soils and at various depths (from the littoral zone to the deepest depressions). Their free-swimming larvae play a role in the settlement of echinoderms. However, the penetration of these animals into certain parts of the World Ocean depends primarily on salinity and salt composition water. Echinoderms are especially abundant in the Red Sea with high salinity. There are also many of them in the salty seas Arctic Ocean- Okhotsk, Chukotka, Kara, Barents. Only 8 species live in the less saline Black Sea, and 1 species in the Baltic Sea.

Echinoderms reproduce both sexually and asexually. Caring for their offspring manifests itself in the form of the mother carrying eggs or young in certain areas of her body. Echinoderms living in the polar seas are characterized by viviparity (bypassing the larval stage). Under unfavorable conditions or when attacked by enemies, echinoderms resort to autotomy with subsequent regeneration of lost parts.

Large sea urchins can live up to 35 years, starfish - more than 14 years, brittle stars - up to 5 years.

Currently, there are about 6,000 species of echinoderms, which play a significant role in the cycle of substances in the seas and oceans, in changes in their salt composition and in the food chains of aquatic organisms. Ground-eating echinoderms use small animals living in bottom sediments as food, sea urchins eat algae, predatory starfish feed on fish, mollusks, sea urchins, coral polyps, etc. In turn, echinoderms are part of the food supply of some fish (for example , motley catfish, cod, etc.), and in tropical seas - stingrays. A prominent place among the enemies of echinoderms is occupied by spiny lobsters, which are especially willing to eat brittle stars and sea lilies, but they also attack other echinoderms - sea urchins, sea stars and sea cucumbers.

Echinoderms have a certain practical significance. For example, sea cucumbers and sea urchin caviar are eaten; fossil echinoderms (their skeletal remains) form limestones and marble, used as construction material, and sea urchins are the subject of various biological studies.

This book completes a four-volume series of stories about animals. The first part is invertebrates. They live everywhere: they permeate the air, the earth, and the waters of the earth from the surface to the greatest depths. How does an octopus work and what are its habits? Can an octopus sink a ship? Is it myth or fact that a scorpion, surrounded by a ring of hot coals, kills itself? The book will tell you about this. Fossil Animals tells the story of the evolution of some members of the animal kingdom, including humans. How to explain that the Devonian fish coelacanth has survived to this day, while the giant dinosaurs of the Mesozoic became extinct? The complex and mysterious path of animal evolution is examined in the context of the origin and development of life on Earth.

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This is a unique group of animals, unlike any other, of ancient origin (they appeared in the Precambrian) and unclear. The Russian scientist I.I. Mechnikov, studying the development of echinoderms, however, has long provided evidence that the evolutionary paths of echinoderms are close to chordates. For this reason, some researchers even produce chordates, and from them vertebrates from echinoderms. But their voices do not sound convincing to all specialists.

More than six thousand species of echinoderms have already been described (and twice as many extinct ones). Echinoderms have been and are classified in different ways. We will take as a basis the system adopted by Soviet scientists, which includes five classes in the phylum of echinoderms: sea lilies, sea capsules, or sea cucumbers, sea urchins, starfish, and brittle stars that look similar to them, or snaketails.

general review

Representatives of all five named classes differ quite significantly from each other. But they also have a lot common features.

The first and most amazing thing that nature has endowed echinoderms with is the so-called ambulacral system, which no other animal has.

The main purpose of the ambulacral system is movement. However, in some echinoderms it also has other functions, for example tactile, and in crinoids, brittle stars and some urchins also respiratory. This system consists of a ring canal surrounding the mouth and five radial canals extending from it and is filled with a liquid that is almost indistinguishable from sea water. From the radial canals, smaller tubules bring this fluid to the ambulacral legs of animals, at the end of which, as a rule, suction cups are located.

Further, a feature inherent in all echinoderms is a radial plan of structure, usually a multiple of five. The ambulacral system, the nervous system, the circulatory system, and some other organs have a multiple of five ray structure.

Finally, the skeleton. Unlike all other invertebrates, it is internal (calcareous) in origin and arises from a tiny, “barely noticeable grain of calcium carbonate under a microscope,” which lies inside the skin cell. This grain grows over time, leaves the cell that gave birth to it and now lies in the intercellular space in the form of a three-ray plate. Its rays branch, connect with other similar branches, the edges of the overgrown plates merge and form a fairly strong shell or “a more or less loose or dense network, or connect to each other like vertebrae” (Z. I. Baranova). However, holothurians have a different skeleton: individual small plates scattered in the skin.

As the name indicates, the skin of echinoderms is armed with needles and tubercles of varying lengths. And sea stars and urchins have on their surface something that no other animal has either - pedicellariae formed from needles. These are a kind of small pincers or tweezers driven by special muscles. They sit on movable legs (in sea urchins) and are capable of grabbing some small creature, alternately bending towards each other, passing it from one pedicellaria to another located closer to the mouth, and thus, like a relay race, delivering the caught prey directly into the hedgehog's mouth. For some hedgehogs, they also work for defense: they are endowed with a poisonous gland, and then the “bite” of these tweezers is unsafe for not very large enemies. These “pincers” of some starfish are so strong that, having grabbed onto the crab or worm that attacked them, they hold it and do not let go for several days until it stops moving. However, the main purpose of pedicellaria is believed to be to clean the skin of any debris stuck between the needles.

Brittle stars of normal appearance

Ophiura "head of the gorgon Medusa"

Lancetine sea urchin

To protect themselves from enemies, echinoderms, in particular starfish, have more effective weapons. This is mainly toxic substances, which are found in various tissues and cause pain and even death to many animals. From such poisonous substances of sea stars, for example, saponin has been isolated. It is dangerous because it dissolves red blood cells. Fish placed in water in which the “juices” of starfish tissues are dissolved quickly dies, showing obvious signs of poisoning.

“Harmful effects on humans have been observed so far only in Acanthaster planci. This multi-armed starfish, completely covered with long spines, lives along almost all the coasts of the Indian and western Pacific Oceans, from the Red Sea to the Great Sea. barrier reef in Australia. If a person pricks himself on its needle, he will immediately feel very severe pain that lasts for hours. The injection site swells, loses sensitivity and exhibits paralytic symptoms. Sometimes nausea comes to the throat and vomiting begins. Apparently, the cells of the skin covering the needles contain poisonous glands, the contents of which are released when injected into the wound" ( Hubert Fechter).

It has been established that some other species of starfish have poisonous spines. It has long been known that sea urchins (for example, the genera Echinothrix and Diadem) are endowed with them. Their needles are up to 30 centimeters long!

“Some hedgehogs with poisonous needles, with the help of... numerous eyes, direct their needles in the direction from which danger threatens... Other types of hedgehogs do not aim their needles, but “just in case” constantly sway them back and forth in waves. When a poisonous sea urchin with large spines is stepped on... the needles not only pierce the human body, but also break off, causing, along with poisoning, suppuration. This poison... causes dizziness, muteness, relaxation of the muscles of the limbs and facial muscles, and suffocation in a person" ( N. I. Tarasov).

“A shadow falls on the hedgehog-diadem - he immediately jerks all the needles on the shadowed surface of the body towards it. The locking muscle at the joint connecting the needles to the shell holds them firmly, like attached bayonets. If a shadow moves or a person touches the hedgehog, a frightening manipulation of long needles immediately begins, which are often tightly connected to one another in peak-shaped bundles - under water you can hear the clanging of knitting needles. The thinnest needle points penetrate deep into the skin and break off there. The injection site becomes inflamed and hurts for some time, but serious consequences after that it usually doesn’t happen" ( Hubert Fechter).

It is interesting to note here how deftly the Balistes fish deals with the diadem hedgehog. Carefully grabbing it by one or more needles, lifts it up from the bottom and throws it to the bottom again. She repeats this clever maneuver over and over again until the hedgehog falls with its mouth up. There are no spines around its mouth, and the fish boldly bites into this unprotected place.

Purple sea urchin

Blue starfish

Substances released starfish into water, have a specific smell that causes many animals to immediately flee. It especially frightens many snails, shells, sea urchins and brittle stars.

Most echinoderms reproduce only sexually. Those who do not care about their offspring lay their eggs directly in the water, where their fertilization and development occur (there are viviparous echinoderms, especially in cold waters). Tiny larvae emerge from the eggs (usually no more than a millimeter, although one starfish has a very large larva - 1.5 centimeters). Depending on the type of animal, breeding season and other conditions, echinoderm larvae swim in the mass of plankton scattered in surface layers sea, from several days to two to three months. Then they settle to the bottom and turn into the type of echinoderm intended for them by nature.

Some starfish, brittle stars and sea cucumbers also reproduce asexually: one animal is divided into two or more parts. Then each “piece” thus obtained, growing tissues and organs, turns into a full-fledged, fully “complete” creature of its previous species.

It is not surprising, therefore, that echinoderms are capable of autotomy and subsequent regeneration. Grabbed by an enemy, say, by a ray, a starfish itself, by contracting its muscles, “cuts off” it from itself, like a lizard in such cases, its tail. The sea cucumber, without hesitation, without regret, throws out its insides and entrails directly towards the mouth ready to devour it and, while the predator devours them, hurries to quickly hide, hide in silt or sand. And some echinoderms, when in serious danger, “sometimes even fall apart”!

"Company" of tiara hedgehogs

Various sea urchins. No. 2 depicts a hedgehog tiara

Sea urchins, covered with strong armor, do not particularly need such extreme self-mutilation. But they, too, give the enemy their hydraulic legs, needles and pedicellaria as payment for life.

Later, all body parts lost in dangerous situations will be restored more or less short term: in a holothurian that has sacrificed its entrails to a predator, they will grow again in nine to twelve days. The discarded hand of a starfish, if not eaten by an enemy, usually dies, but the linkia continues to live and after a while a new whole starfish grows from it, from one severed hand!

Caring for offspring is one of the highest forms of animal behavior. So what do you think? These thoughtless, seemingly completely primitive creatures - sea cucumbers, starfish and urchins - show this maternal care. Not all, but many. For example, some sea cucumbers carry their small babies everywhere on their backs. For others, the matter is even more serious: the juveniles also sit on their backs, but in special brood chambers, covered on top with calcareous plates (just like the pee-pee toad!). Some starfish and urchins, like tarantula spiders, also provide their backs to children in the form of vehicle or, on the contrary, they cover them from above with their body, and one sea urchin had its young near its mouth. In one species of starfish, the young fill special outgrowths of the stomach to capacity. There are also sea stars in which, by the time the eggs mature, a special brood chamber is formed on its back, covered on top with a film with holes through which water circulates. The eggs and then the young develop under this kind of tent. Only when they grow up to one and a half centimeters do the young stars leave their orphanage.

Sea lilies are creatures that almost all are completely deprived of freedom of movement. They sit their entire adult lives on the bottom, attached to it by long, flexible stems, with their arms folded in a loose bun, really similar to a lily flower. All other echinoderms crawl serenely along the bottom. However, they can move not only on horizontal surfaces. Almost all starfish and many urchins crawl onto steep cliffs, and some stars can even climb the smooth glass wall of an aquarium. Only some holothurians swim in the water column - they lead, as they say, a pelagic lifestyle. There are also commensals (cohabitants) among echinoderms. For example, the spines of living sea urchins often provide protection, shelter and food for various brittle stars (as well as cardinal fish and some shrimp). They, that is, brittle stars, settle close to the mouth of sea lilies, taking away some of the food they catch, but “without causing noticeable harm to the owners.”

Various sea cucumbers

Various sea lilies

All echinoderms (except for immobile crinoids) sometimes bury themselves in mud. Many holothurians, sea urchins, and stars feed on silt.

“Most echinoderms feed on animal food, but some of them consume exclusively coastal algae or even the remains of terrestrial vegetation” ( Z. I. Baranova).

Sea urchins, as shown by observations of them in aquariums, are omnivores. They devour dead fish and other carrion, living daphnia, small starfish and snails, shells, their own relatives, as well as algae of all kinds, lettuce, even wood and... groundnut oil.

On the other hand, echinoderms can starve for a long time. Some starfish, for example, did not eat anything for 18 months and remained alive.

“Rocks, even granite or basalt, are sometimes drilled by sea urchins, where the water is shallow and the surf is strong. Sometimes these caves are designed for only one inhabitant - a hedgehog, sometimes they are entire cauldrons half a meter deep and a third of a meter in diameter, where several dozen hedgehogs the size of an apple or a fist sit. This way of life saves sea urchins from drying out at low tide or other drop in water, and from predators, and from the blows of the surf" ( N. I. Tarasov).

“It is quite clear that in order to drill into such hard rocks as granite, hedgehogs must have a very durable drilling apparatus. Indeed, their jaws and teeth are something amazing. The very appearance of the chewing apparatus, called by former scientists “Aristotle’s Lantern,” clearly proves its purpose. This is a real drill, like those used in metal workshops" ( P. E. Vasilkovsky).

But with this drill, the sea urchin only gnaws granite. The work is progressing quickly, and soon the cave drilled in the stone is ready. Then the hedgehog begins to finish it more thoroughly. He twirls and twirls inside her, his needles scrape along her roughly hewn walls, scraping them out and polishing them to a shine.

A sea urchin, and below “Aristotle’s lantern”, armed with gnawing, drilling, chewing and other “teeth” oral apparatus

Echinoderms are found only in seas and oceans at all latitudes and at all depths - from the littoral to the abyssal (10 thousand meters from the surface).

“All echinoderms... are very sensitive to the slightest desalination of water. They are absent in the Caspian Sea, in the Baltic Sea they are represented by only three species, and in the Black Sea by only eight species, but in the Barents, Kara, Chukchi and Okhotsk seas they make up the bulk of bottom animals" ( Z. I. Baranova).

But the minimum and maximum limits of their growth are very far from each other: the smallest echinoderm can be several millimeters long, and the largest (giant holothurian) can be five meters long!

Longevity is decent: sea urchins have an average of 10–15 years, perhaps 35, sea stars have 20 years or more. The life of sea cucumbers is shorter - five years, maybe more.

Starfish

Not all starfish have only five arms, but some have six, seven, eight, sixteen... and even fifty! At the end of each beam sits a tiny eye. He sees very poorly: he can only distinguish light from darkness. The rays of some starfish are very short: they barely protrude beyond the edges of the central disk-body. Such stars look like pentagons.

Starfish are usually very brightly colored: yellow, orange, red of all shades, less often gray, green, blue or purple. They live from coastal areas to the deepest depths of the ocean. One starfish was caught in the Philippine Trench - 9990 meters from the surface!

Some starfish are very large: up to a meter across.

Not a single animal has such interesting legs as echinoderms: they, as we already know, are “hydraulic”. Tiny, thin and stretchy like rubber. The legs sit on the beams, on the underside. When a starfish crawls, its legs swell. Water is pumped into them from the ambulacral organs under pressure. Water stretches the leg, it stretches forward, sticks to the stones, and water is pumped into the other legs. And they crawl on. The sucked legs compress and pull the starfish forward.

Of course, the starfish crawls slowly - 15–20 centimeters per minute (9–12 meters per hour)! But when he runs away or attacks, he crawls twice as fast. Usually, in search of food, it crawls only about six meters per day. However, the prey that starfish hunt moves even more slowly. Many stars eat silt and algae, others eat shells and snails. Small ones are swallowed whole, and if a large shell comes across, the starfish embraces it with its rays and begins to pull the valve away from the valve (while developing a traction force of up to 5.5 kilograms). The shell is tightly closed, the starfish cannot always open it right away, but it is in no hurry - it takes an hour or two. The shell muscles that hold the valves get tired, and the mother-of-pearl house opens slightly. Then the starfish sticks its stomach out through its mouth and stuffs it into the shell. There the stomach - right inside the shell - digests the mollusk. It is very extensible, this stomach can squeeze through even a small gap in the shell (when the valves move apart by only 0.2 millimeters!) and penetrates into the snail’s house almost to its very top.

Many-armed starfish

An unprecedented thing: a starfish, it turns out, can digest food not only inside its body, but also outside - right in sea water!

Starfish somehow manage to attach their stomachs even to living fish. The fish swims and carries the starfish with it everywhere. And she sits on her back, sucks on her legs and slowly digests more live fish. Truly, the miracles that nature creates are more wonderful than fairy tale miracles!

They didn’t believe in this for a long time, they thought that starfish only eat dead fish: where can they catch up with living fish! But Dr. Gudger of the American Museum of Natural History collected very strong evidence that convinced the skeptics. Now few people doubt this. A starfish grabs a fish that accidentally stumbles upon it by its fins. What is enough? Pedicillary forceps, with which her back was thickly covered. Then the beam with the fish caught in its traps bends and brings the prey to its mouth, tail first. Then the stomach jumps out and covers her.

Starfish are quiet, toothless, and barely crawl. And what predators! They cause great harm in the sea: all the lions and tigers on Earth will not eat as much meat as starfish eat. They eat oysters, pearl mussels, fish, brittle stars, sea urchins, their own relatives, crabs... But the stars are of no use. What can they be used for? Maybe for fertilizer. But sea urchins have some benefits for people.

Echinoderms and cooking

Sea urchin milt and caviar are the objects of culinary desire. Both are very nutritious foods. Sea urchin caviar contains up to 34.9 percent fat and 19.2–20.3 percent protein. They eat it raw, salted, fried and pickled.

Edible sea urchins are harvested mainly by coastal residents Mediterranean Sea, Northern and South America, New Zealand and Japan.

« Collected hedgehogs on the shore they open it, take the caviar out of the shell and cook it in a cauldron over low heat until it looks like a thick mass of color beeswax, after which it is again placed in the cleaned shells of the hedgehogs. Hedgehog shells with boiled caviar are sold by peddlers individually. Every year the Creole population consumes so much a large number of hedgehogs, that in some places on the island their shells form entire mountains" ( Z. I. Baranova).

The shells of sea urchins themselves are also good for something: the paint contained in them is very durable, does not fade, and does not wash off. Therefore, sea urchin shells are not thrown away everywhere as unnecessary garbage, but are boiled in boilers to prepare a dye for leather and nets.

The same shell, containing a lot of calcium and phosphorus, is a good fertilizer for marginal lands.

Trepang is a famous delicacy of the coastal countries of the East. This is a sea cucumber (about forty of their species are eaten). And, like a typical holothurian, the sea cucumber has a body outline similar to a cucumber, which is why these animals are often called sea cucumbers or egg capsules. The sea cucumber resembles a cucumber when it lies quietly, but as soon as it begins to crawl, something worm-like is noticed in its movements. If you touch it, it can shrink so much that it turns into a ball. The skin on its back has spines (and the longer they are, the higher the price of sea cucumber on the food market). And on its ventral side there are many small ambulacral legs. It is usually dark green or dark brown in color. Lives on rocky outcrops or sandy bottoms of shallow waters or in thickets seaweed(usually no deeper than 50 meters).

A young, one-year-old sea cucumber weighs about fifty grams, and when it grows up - at about four or five years old - it will increase its weight sevenfold (such a sea cucumber is about 30–40 centimeters long).

Sea cucumber meat contains a lot of proteins and valuable mineral salts. Iodine, for example, is 100 times more than in any invertebrate animal of the sea and land (and 10 thousand times more than in beef!). There is a thousand times more iron in sea cucumber than in fish. In general, sea cucumber meat is rich in chlorine, sulfur, phosphorus, calcium, manganese, magnesium, cobalt, copper, iron, iodine and many other elements that sea water is so rich in and land soil is poor in. How does this holothurian manage to accumulate so many valuable substances? After all, it feeds only on all kinds of small living creatures and detritus (in other words, silt)…

“Japanese doctors prescribe sea cucumbers to overworked and weakened people, which in the Far Eastern countries are called “sea ginseng”... The meat of sea cucumbers has a dense consistency, it is transparent and resembles boiled sturgeon cartilage” ( Seafood).

Sea cucumbers are caught by trawls, dredges, spears, or they are collected by divers. They are hunted mainly off the coasts of Japan, China, Malaya, Indonesia, Polynesia and the Philippines, and also in smaller quantities along the coasts of Africa, America, Australia, Italy and in the Red Sea.

World production of just one type of sea cucumber - the Japanese stichopus - exceeded 8 million tons in 1981! Unless it's a typo, that's a lot. This is what is said, in any case, in the chapter on echinoderms in the second volume of “The Life of Animals” (2nd ed. M.: “Prosveshcheniye”, 1988).

China, in addition to those caught by its own population, annually imports 3 thousand tons of sea cucumbers worth 5-6 million dollars.

Sea cucumbers are sold dried, boiled, salted, smoked, and also canned: in own juice, in oil, tomato, in saline solution. All this is filled with broth obtained from sea cucumber meat, “which improves the taste and appearance of the canned food.”

In Samoa, sea cucumbers are eaten raw, in the Philippines they are fried.

In our stores, if you find sea cucumbers for sale, it will most likely be in dried form. (This is a real protein concentrate: it contains 81.8 percent proteins!) To prepare all the dishes described below, the following processing of dried sea cucumbers is required: they must be thoroughly washed in warm water from coal powder, which is used for drying. Then pour cold water and, changing it two or three times, keep the sea cucumbers in it for 24–30 hours, until they swell properly. Then the sea cucumber is “cut along the belly”, cleaned of any remaining entrails and cooked for another two to three hours until the meat becomes soft.

Now I will give a couple of recipes for cooking sea cucumbers, selected from many recommendations in the book “Seafood”.

Far Eastern sea cucumbers. Cut the boiled sea cucumbers into cubes. Chop the pork the same way. Fry it in a frying pan with onions and peppers, then mix with sea cucumbers, add tomato paste, flour, sour cream and simmer for fifty minutes. It is recommended to serve potatoes as a side dish; fresh vegetables are also suitable, say, tomatoes, cucumbers, etc. (for 70 grams of dried sea cucumbers - 250–300 grams of pork, two or three onions, two tablespoons of melted butter, one teaspoon of flour, 100– 150 grams of sour cream, one tablespoon of tomato paste, salt, spices).

Sea cucumber pate. Pass the sea cucumbers through a meat grinder. To the resulting minced meat, “add finely chopped onion, fried in vegetable oil, melted butter, salt and pepper... When serving, sprinkle the pate with finely chopped hard-boiled eggs” (for 50–60 grams of dried sea cucumbers - two or three onions, one egg, one or two tablespoons of vegetable oil, the same amount of butter, herbs, salt, spices taste).

As in the case of squid and other shellfish, they prepare various salads with sea cucumbers, casseroles, omelettes, vinaigrettes, soups, borscht, solyanka, cabbage soup... I think that, based on the little that I have said about culinary products from shellfish and sea cucumbers , a skilled housewife will quickly master the preparation of these dishes and even invent her own. We eat little seafood, but the need for it human body very urgent. Therefore, do not neglect “seafood”, but buy them whenever the opportunity presents itself.

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Municipal budget educational institution

Secondary school No. 8, Ussuriysk

PROJECT

Topic: “Far Eastern Echinoderms”

Completed by: student of class 7A

Zhovty Timofey

Head biology teacher

Pereverzeva Natalya Gennadievna

Ussuriysk

2015

Plan

Introduction 3

1. Classification of echinoderms and their habitat 4

2. General Features echinoderms 5

3. Diversity of echinoderms 7

List of sources used 11

Introduction

Animals belonging to the phylum Echinodermata are among the most ancient. Five hundred millions of years ago, when fish had not yet appeared, the bottom of the World Ocean was inhabited by numerous amazing animals, sometimes looking like unprecedented huge flowers or buds, sometimes like balls dotted with long needles, sometimes like multi-pointed stars. This was the heyday of echinoderms. Currently, there are no more than seven thousand species left, living in the seas and oceans on the most different latitudes. Some representatives of the type are also found in the waters of bays Sea of ​​Japan. These animals struck me with their extraordinary beauty, so I decided to study them in more detail.

Target: acquainted with characteristic features structures of representatives of the echinoderm type.

Tasks: study the features of external and internal structure echinoderms, consider their diversity, identify their role in nature and human life.

1. Classification of echinoderms and their habitat

Currently, science knows more than 6,500 species of echinoderms. All of them belong to the kingdom Animals , phylum Echinodermata. Modern echinoderms are classified into five classes: starfish; sea ​​urchins; brittle stars (snaketails), holothurians (sea cucumbers) and sea lilies.

Echinoderms are exclusively marine animals , very sensitive to water desalination. A decrease in the salinity of the water in their habitats can cause the death of animals. Echinoderms are especially abundant in the Red Sea with high salinity. There are also many of them in the salty seas of the Arctic Ocean - Okhotsk, Chukotka, Kara, Barents. Only 8 species live in the less saline Black Sea, and 1 species in the Baltic Sea.Meet on a variety ofdepthsWorld Ocean. Some species live only off the coast in shallow waters, while others inhabit the dark abysses of ocean depressions. Typically, echinoderms crawl along the ground, both on horizontal and vertical surfaces, less often burrow into the ground, and only stalked crinoids are motionlessly attached to the substrate.

Salinity of water The bays of the Sea of ​​Japan make its waters suitable for animals from the echinoderm group. A variety of starfish, urchins, sea ​​cucumbers, ophiur is possible watch everywhere. INwaters of Southern Primorye,According to scientists, they live25 types of stars.N most often Patiria crest and common Amur star are found. Of the 8 species of urchins, the most common in our country is considered to be the unarmed spherical sea urchin. Most often it is adjacent to the starfish Patiria. On great depths Peter the Great Bay (from 200 to 1500m), where very low temperature, lives a large, up to 20 cm long, yellowish-white heliometa sea lily. At shallow depths you can find brittle stars, including one of the most beautiful and largest brittle stars from the Far East - the head of the Gorgon. MostA well-known and large sea cucumber is the Far Eastern sea cucumber.

2. General features of echinoderms

Echinoderms are a group of invertebrate animals with a surprisingly diverse body shape: spherical, disc-shaped, radiant, in the form of blossoming flowers or buds.There is no division of the body into sections. Dimensions most echinodermsranges from 5 cm to 50 cm.

Echinoderms are characterized by three main characteristics:

Radiation symmetry, that is, their body can be conditionally divided into several ray-sectors diverging from one center point;

The skeleton is located in the inner layer of the skin and consists of numerous calcareous needles, spines, and outgrowths. For this feature of animals, the ancient Greeks gave them the name Echinoderms.

The ambulacral (water-vascular) system is a network of vessels filled with liquid, similar in composition to sea water. Numerous short outgrowths extend from the vessels, often with suction cups at the ends - ambulacral legs. These are peculiar organs of movement. Sea lilies, leading a sessile lifestyle, use their ambulacral legs not for movement, but for capturing food. In addition to movement, in some species the water-vascular system serves for respiration, excretion and touch.

Musculature developed to varying degrees depending on the mobility and nature of the skin skeleton. It is composed of individual muscles and muscle bands.

The nervous system of echinoderms has a primitive structure. Sense organs are poorly developed. Primitive ocelli are located at the ends of the rays of sea stars, and on the upper part of the body in sea urchins. There are also organs of touch.

The circulatory system consists of annular and radial vessels.

The respiratory organs are represented by cutaneous gills; some species of echinoderms breathe using the ambulacral system.

There is no excretory system. The release of waste products occurs through the walls of the channels of the water-vascular system and with the help of special amoeboid blood cells migrating inside the body.

Echinoderms differ in their feeding method. Some feed on the remains of dead animals and silt, others on algae and their remains, and still others are predators. The mouth of most species is located on the underside of the body. The digestive system begins with the mouth opening leading to a short esophagus, behind which is the intestine, which looks like a long tube or voluminous sac. Sea urchins have a special chewing apparatus in the depths of the mouth - “Aristotle's lantern”, on top of which there are five strong jaws that can protrude from the mouth. With their help, hedgehogs scrape food from stones.

Most echinoderms are dioecious animals, but hermaphrodites are also found. Development occurs with transformation (metamorphosis). The free-swimming larva has bilateral symmetry of the body and contributes to the dispersal of the species.

Many echinoderms have high ability to regeneration, i.e. capable of restoring lost body parts. So, for example, a whole animal can be restored from one ray of a starfish.

Echinoderms, despite their slowness, are not defenseless. They protect their lives in different ways. A starfish sacrifices one or more rays to escape. The threat of coral reefs, the crown of thorns starfish, is protected by sharp spines covered with poisonous mucus. Her injections are very painful and the wounds do not heal for a long time.

Many sea cucumbers, such as sea cucumbers, release a stream of sticky threads. Sometimes they throw their entrails at the enemy. In nine days internal organs are being restored. Sea urchins, studded with long and very brittle sharp spines, are also considered dangerous. When an injection occurs, poison and germs enter the wound. Hedgehogs from the diadem genus have the longest - over 30 cm - needles.

3 . Diversity of echinoderms

More often sea ​​stars resemble a five-pointed star. But there are also species with a large number of rays. Common in the Sea of ​​Japan, Patiriya comb has very short rays and more closely resembles a pentagon. And the unusual starfish Podosferaster from the South China Sea is shaped like a small ball with a diameter of just over 1 cm and looks more like a sea urchin. Starfish also display a rich variety of colors: red, orange, purple, bright blue, violet, etc.

All stars are mobile organisms, slowly moving along the substrate using ambulacral legs.Most stars are predators and corpse eaters; filter feeders are also known.The favorite foods of predators are worms, sponges, sea corals, mollusks, and sea urchins. The most aggressive and voracious starfish, the crossaster, even attacks its own relatives. The star simply swallows small animals whole.

In some places, starfish cause great harm to mussel and oyster farms. Corals also suffer from stars. crown of thorns starfish,Having climbed onto the coral, it turns its stomach out of its mouth and tightly covers a certain area of ​​the polyp with it.Then it releases digestive enzymes from the stomach. They penetrate through the pores of the calcareous skeleton of the polyps and turn all its contents into pulp, which the star then sucks back.These echinoderms caused great damage to the central part of the Great Barrier Reef.

Close relatives of starfish are brittle stars, or snaketails. They are the most mobile among echinoderms. Brittle stars move with the help of serpentine movements of long and flexible rays. By feeding method, the majority are filter feeders.

sea ​​lilies No wonder they got their name from appearance really resemble a flower. Their body consists of a long stalk and a calyx with a corolla of five rays. Often the rays of crinoids are highly branched and the number of such additional processes can range from ten to 200. Stem-shaped crinoids are the most ancient animals among echinoderms. They spend their entire lives in one place. Swaying slightly on its stem and spreading a corolla of feathery rays against the current, similar to a complex trapping net, the sea lily filters the water, catching small prey from it. Among sea lilies there are also stemless species. These are inhabitants of tropical shallow waters. They attach to the ground with tenacious shoots.

Sea urchins- bottom crawling or burrowing animals. There are 800 species living in algae thickets, on stones, and corals. Omnivorous - they feed on algae, sponges, mollusks, and various carrion. Sea urchins are the record holders among animals for the number of legs. The number of their legs can exceed 1000. Thanks to this, they deftly climb steep rocks and confidently hold on to the bottom even in strong surf.

Holothurians, or sea cucumbers, outwardly they look more like large and clumsy caterpillars. Their worm-like soft body can be smooth, rough, or covered with various outgrowths. Holothurians have incredible colors, ranging from speckled brown to bright yellow with orange and blue stripes.

These are bottom-dwelling, sedentary or crawling animals. They move slowly, contracting and stretching their body. Some species are able to swim using worm-like movements. Holothuria almost always lies on one side of the body. If you turn it over, it will definitely return to its original position.

They feed on plankton and organic debris; some species are filter feeders. The class of holothurians includes the largest and smallest echinoderms. For example, the spotted synapta living in the tropics reaches 2 m. Seeing its long body wrapped around coral protrusions, it is difficult to believe that this is not a dangerous starfish, but just an echinoderm that is harmless to humans. And in the North Sea there is a very tiny sea cucumber, its length does not exceed 0.5 cm.

Practical significance There are not many echinoderms for humans. Some echinoderms have been valued as nutritious food since ancient times. and healing food. The caviar and milt of some sea urchins are considered a delicacy by residents of the coasts of Asia and Europe. They are eaten raw, fried, or salted. In China and Japan, some sea cucumbers called sea cucumbers are used as food. On the Pacific Islands they are prepared for future use. Dried sea cucumbers contain little fat, but a lot of protein and minerals. IN Lately Preparations consisting of marine echinoderms have become widely used as life stimulants.

In nature, echinoderms are links in food chains, cleaning the water and seabed from dead organic matter.

Conclusion

Echinoderms are ancient invertebrate animals, bottom dwellers sea ​​waters. They attract people's attention with a variety of shapes and colors.

Body sizes range from a few millimeters to a meter.

Characteristic features of echinoderms are radial symmetry of the body, a unique water-vascular system and the presence of an internal calcareous skeleton.

Development occurs with transformation: the larva has bilateral symmetry of the body and floats freely in the water column.

The type is quite numerous, includes more than 6,500 species, distributed into 5 classes: starfish, sea urchins, sea lilies, brittle stars, sea cucumbers.

Systematics of the type Echinoderms:

Subphylum/Division: Eleutherozoa Bather, 1900 = Freely mobile, or Eleutherozoa

Subphylum/Division: Homalozoa = Homalozoa †

Class: Ctenocystoidea = †

Class: Homoiostelea Gill et Caster, 1960 = †

Troop/Order: Soluta Jaekel, 1901 = †

Class: Homostelea = †

Class: Stylophora = †

Subphylum/Division: Pelmatozoa Leuckart, 1848 = Attached

Class: Blastoidea = Seabuds †

Class: Cystoidea = Ballfish or Sea Bladder †

Class: Edrioasteroidea = Edrioasteroidea †

Class: Eocrinoidea = †

Class: Glyptocystida = †

Class: Paracrinoidea = †

Class: Rhombifera =

Brief characteristics of the echinoderm type:

Echinoderms are secondary-cavity animals, which in adulthood have radial symmetry of the body. In most species, the organs are located along five radii, but in some the number of rays is different. If in coelenterates radial symmetry of the body is primary, then in echinoderms it will be secondary, since their ancestors had bilateral body symmetry. Free-swimming echinoderm larvae are bilaterally symmetrical. Echinoderms are characterized by the presence of an ambulacral system, which serves for movement and participates in the processes of respiration and excretion. The secondary body cavity is well defined and filled with cavity fluid. Echinoderms are inhabitants of the sea. These are predominantly bottom animals, capable of moving slowly along the substrate, less often attached to it. Some echinoderms serve as commercial objects.
Echinoderms, as the studies of I.I. Mechnikov first showed, are interesting for identifying phylogenetic connections of invertebrate animals with representatives of the phylum Chordata. Despite the radial symmetry of the body of adult individuals, the organization and development of echinoderms have many similarities with chordates. The secondary body cavity in them, like in chordates, is formed by separating the mesodermal sacs from the intestine. Like chordates, they are secondary cavity animals, in which, during development, the gastropores overgrow or turn into the anus, and the larval mouth is formed anew. Representatives of both types have two-layer skin and skeletal elements of a mesodermal nature. These similarities suggest that lower chordates are phylogenetically related through common ancestors to echinoderms. Remains of echinoderms were found in sediments of the Paleozoic era.
Structure and vital functions. The integument of echinoderms consists of two layers: the outer, which has the character of a single-layer epithelium, and the inner, formed by fibrous connective tissue. Various elements of the calcareous dermal skeleton develop in the inner layer. In starfish, they have the appearance of calcareous plates, arranged in longitudinal (along the rays) rows and usually bearing spines protruding outward. In sea urchins, the body is enclosed in a calcareous shell made of rows of tightly connected plates with long spines sitting on them. Holothuria has small calcareous bodies different shapes scattered in the skin.
Musculature developed to varying degrees depending on the mobility and nature of the skin skeleton. It is composed of individual muscles and muscle bands.
The ambulacral system begins with a porous madrepore plate located on the dorsal side of the body. From it, a stony canal stretches deep into the body, which opens into a ring canal surrounding the esophagus. The annular canal gives radial canals into each ray of the body. Short tubules branch off from the radial canals in both directions, from which contractile vesicles - ampoules - extend into the cavity, and contractile tubular ambulacral legs with suction cups at the ends extend outwards. The ambulacral system is filled with water entering through the madrepore plate. When the ampoules contract, the water from them passes into the cavity of the legs, causing them to lengthen and stretch. The suction cups located at the ends of the legs are sucked to the substrate, after which the length of the legs is reduced, since water from their cavity is drained back into the ampoule. Through the combined efforts of many simultaneously contracting legs, the body of the echinoderm is pulled up, and the animal slowly moves along the bottom. Thanks to the suckers on their ambulacral legs, echinoderms can even crawl along a vertical rock surface.
Nervous system echinoderms have a radial structure. Radial nerve cords extend from the peripharyngeal nerve ring according to the number of body rays.
Sense organs poorly developed. Primitive ocelli are located at the ends of the rays of sea stars, and on the upper part of the body in sea urchins. There are also organs of touch, etc.
Digestive system. The mouth opening is located in the middle for most bottom surface bodies. The mouth leads into a short esophagus, followed by the midgut and short hindgut. Some people have no anus.
Respiratory organs sea ​​stars and urchins have cutaneous gills - thin-walled outgrowths on the upper side of the body. Apparently, the ambulacral system also takes part in the respiratory process. In a number of echinoderms, respiration occurs through the integument of the body.
Circulatory system usually consists of two annular vessels, one of which surrounds the mouth and the other the anus, and radial vessels, the number of which coincides with the number of rays of the body. Both annular vessels are connected by a hematopoietic axial organ, penetrated by a network blood vessels.
Excretory organs. Echinoderms do not have special excretory organs. The release of dissimilation products occurs through the walls of the canals of the ambulacral system and with the help of special amoeboid blood cells migrating inside the body.
Genitals have different structures. Most echinoderms are dioecious, but there are also hermaphroditic forms.
Development occurs through a series of complex transformations. Bilaterally symmetrical echinoderm larvae swim in the water column.
Many echinoderms have the amazing ability to regenerate body parts. For example, one ray of a starfish can restore an entire animal.

Brief description of the classHolothurians, or sea egg pods:

Sea capsules or sea cucumbers are animals whose body contracts strongly at the slightest touch, after which in many forms it becomes similar to an old capsule or fresh cucumber. About 900 species are known.
The name “sea cucumbers” was given to these animals by Pliny, and the description of some species belongs to Aristotle, so long ago these animals attracted attention.
Holothurians, or sea capsules, are not only interesting for their external features, bright colors, interesting lifestyle and some habits, but also have quite significant economic importance. Over 40 species and varieties of sea cucumbers are used for human food. Edible sea cucumbers, which are called sea cucumbers, have long been valued as a very nutritious and healing dish, so their fishing has been practiced since ancient times. The main sea cucumber fisheries are concentrated mainly in tropical areas: in the waters of the Indo-Malayan archipelago, the Pacific Islands, the Philippine Islands, off the coast of China and Japan.
Smaller fisheries are carried out in Indian Ocean, in the Red Sea, off the coast of America, in the region of Africa and Italy. In our Far Eastern seas, two types of edible sea cucumbers are caught, which are used to prepare canned food and dried foods. Sea cucumbers are most often consumed as food in the form of broths and stews and their boiled skin, previously subjected to lengthy processing and drying. Some modern European companies produce various canned foods from sea cucumbers, which are in great demand. In Italy, fishermen eat fried sea cucumbers without subjecting them to complex pre-processing, and residents of the Pacific Islands eat raw caviar and aquatic lungs of these animals. Production of sea cucumbers in Pacific Ocean is about 10 thousand centners per year.
Holothurians are quite large animals, the average size of which ranges from 10 to 40 cm. However, among them there are also dwarf species, barely reaching a few millimeters, and real giants, whose body length with a relatively small diameter, about 5 cm, can reach 2 m or even more. Holothurians are very diverse in body shape.

Literature: Zoology course. B. A. Kuznetsov, A. Z. Chernov, L. N. Katonova. Moscow, 1989

Echinoderms are unsegmented invertebrates, radially symmetrical, three-layered secondary cavities, whose bodies have the shape of a star, ball, cucumber, etc. The phylum echinoderms is the second largest (after chordates) phylum of deuterostome animals, uniting more than 6,000 species that live on the bottom only in seas with high salinity. The body sizes of modern echinoderms range from 5 to 50 cm, but the small ones are several millimeters, and the largest ones reach more than 5 m. The ancestors of echinoderms were free-living binary-symmetrical animals, they switched to a sessile lifestyle and acquired radial symmetry. The most common features echinoderms are: 1 ) water-vascular system; 2) radial body type and many organ systems (nervous, circulatory, reproductive, ambulacral) ; 3 ) well developed limestone endoskeleton.

structural features

Body multicellular, non-segmented, has a central part ( central disk) And rays, that radii extend from the central part. Most species have a radial five-ray symmetry(although there are types with 6, 9, 11, 13 and more rays). Echinoderms are divided into the lower (oral) side of the body, on which the mouth is located, and the upper (aboral), which may have an anus.

Veils . Body covered single layer epithelium, that cilia, as well as cells: receptor cells - for the perception of mechanical irritations, pigment cells - cause a variety of colors, glandular cells - secrete mucus and poison.

Secondary cavity (in general). It is lined with ciliated epithelium and filled with fluid, constantly moving. The fluid of echinoderms contains a large number of coelomic elements (coelomocytes), which take part in the distribution of nutrients, the release of metabolic products, respiration, and also perform a phagocytotic function. One of the most original features of the structure of echinoderms should be considered the complex differentiation of the coelom into ambulacral and perihemal systems.

Features of life processes

Movement muscular with the participation of smooth muscles. Only echinoderms have a coelom formed water-vascular (ambulacral) system, which serves for movement. This is connected to environment through the madrepore plate and the petrosal canal there is a system of annular and radial canals, from which many ambulacral legs arise. At the base of each leg there are muscle ampoules, when they contract, water enters the legs and they elongate and adhere to the substrate using suction cups. When the muscles of the legs themselves contract, the water is pushed back into the ampoules, and the legs themselves contract greatly. At the same time, the animal’s body is slightly pulled in the direction of movement. Then the legs lag behind the substrate, and everything repeats. Movement speed is 5-8 cm per minute. Ambulacral (lat. Ambulacrum - walking) the system is also involved in respiration and food acquisition. Thus, with the help of the joint work of many ambulacral legs, a starfish can open the shell of a bivalve mollusk.

Nutrition - plant food (sea urchins), detritus (holothurians), small animals (starfish). Among the echinoderms there are polyphags (brittle stars).

Digestion carried out by the digestive system, which in most echinoderms (except starfish) does not have a radial type of structure. The generalized digestive system begins with the mouth on the lower (oral) side of the body, continues with a short pharynx, passes into the elongated intestine, which ends with the anus on the upper (aboral) side of the body. There is a lot in the intestinal walls amebocytes, involved in intracellular digestion. Extracellular digestion is carried out with the participation of enzymes that are formed secretory cells intestinal epithelium.

Transportation of substances carried out open circulatory system radial type. It consists of a peripharyngeal lower ring, five radial vessels and a peripharyngeal upper ring, from which branches extend to the gonads and intestines. The two blood rings are connected by an axial organ, surrounded by sections of the coelom - the left and right axial sinuses. The circulatory system circulates a fluid whose composition is close to coelomic. The main function of such a system is the transport of nutrients, and only in holothurians it also performs the function of transporting gases. The movement of “blood” occurs due to the pulsation of the abdominal and dorsal vessels or the coelom region (right axial sinus) - the pericardium. Support for circulatory system is the perihemal system - a set of canals and cavities (sines). It consists of a peripharyngeal ring and radial canals and is filled with coelomic fluid. The perihemal system also serves to nourish the nervous system.

Breath occurs with the participation of specialized bodies, such as cutaneous gills(starfish) and water lungs(holothurians). The respiratory function is also performed by organs of other systems. Thus, oxygen can enter by diffusion through: a) the ambulacral legs of the rays into the coelomic fluid and spread throughout the body using the ambulacral system, which contains respiratory pigments like hemoglobin; b) branched tentacles in holothurians.

Selection carried out using amebocytes, which are present in the coelomic fluid, circulatory and ambulacral systems. These cells accumulate metabolic products and are excreted through the thin integument of the body or deposited in connective tissue. Most echinoderms do not have specialized excretory organs.

Process regulation occurs with the participation of primitive radial nervous system, which consists of three peripharyngeal nerve rings and radial nerve trunks. The nervous system consists of three sections: the lower nerve ring with radial nerves (ectoneural section), which performs a sensitive function; the middle and superior nerve rings with nerves (hyponeural and apical sections) that carry out motor function.

Irritability provided by various sense organs, which have a simple structure. They are diffusely distributed throughout the body in the form of various sensitive cells that function as receptors for touch, smell, and taste. Light-sensitive cells can be collected into cells. In starfish, the eyes are located at the ends of the rays, in sea urchins - around the anus. Certain echinoderms (holothurians *) also have balance organs - otocysts, which have the shape of a bubble with small otoliths inside.

Reproduction is carried out mainly dioecious system with gonads at the base of the rays. Fertilization external, in water. In starfish, brittle stars are known vegetative propagation dividing the body into two or more parts, from which the whole organism is restored. Many echinoderms express concern for their offspring. For example, in some holothurians and sea stars, brood chambers are formed for the young, covered on top with limestone plates or a film with holes.

Development indirect(with conversion). The larva - dipleurula - unlike adults, actively swims in water with the help of cilia and has bilateral symmetry and small sizes (less than 1 mm).

Regeneration well developed. Echinoderms are capable of autotomies. For example, in case of danger, sea cucumbers can throw out their entrails, starfish (for example, links) break off rays from the body, and some echinoderms break into pieces.

BIOLOGY +Autotomy, self-mutilation is the involuntary rejection of body parts by an animal when they are suddenly irritated. This is a protective reflex reaction characteristic of many invertebrates. (for example, some hydroid polyps and sea anemones cast tentacles, starfish, brittle stars, sea lilies - rays, holothurians - entrails, some crustaceans - claws) , and from vertebrates - only for lizards (throw away their tail) . Autotomy is also known as an adaptation to reproduction. (for example, in some annelids).