Diversity of echinoderms. Interesting facts about sea cucumbers Body coverings and skeleton

Type of echinoderm: characteristics

The size of invertebrate creatures belonging to this type ranges from 5 cm to 50. But there are species whose size can be several millimeters or, conversely, two meters.

All the “inhabitants” studied by scientists differ from each other in their structure. But, of course, there are a number of signs by which these vertebrates can be distinguished from others sea ​​creatures. All these characteristics have not undergone any changes and have not undergone evolution over time.

Starfish are echinoderms

Type echinoderm, main features:

1. Only these marine inhabitants have a special ambulacral (water-bearing) system. It consists of a group of channels with thin walls filled with liquid;
2. In their structure they are radiant (usually it is an internal skeleton, well developed, the rays are multiples of five).

Holothuria (sea cucumber) - a representative of echinoderms

With the help of the ambulacral system, representatives of the echinoderm type are able to move and touch objects. And in some varieties of sea lilies and urchins, it can perform the function of respiration. This whole system consists of the same type: a ring channel, which with inside surrounds the oral opening, and radial canals, multiples of 5, extending from the annular one. They end in a blind or sensitive process.

If we talk about the characteristics of echinoderms, then another distinctive feature of these vertebrates is that their skeleton is laid in the connective layer of the skin and it is calcareous. The outer epithelium of most representatives of echinoderms is covered with an uneven layer of cilia. They are designed to cleanse the body of impurities, perform the respiratory function and deliver food into the mouth.

Sea lily

The outer layer of the epidermis may contain a large number of specific glandular cells that secrete a toxic or sticky enzyme. There are some species like echinoderms that secrete enzymes that can glow.

The skeletal plates of echinoderms are arranged like rays. But this manifests itself not only on the outside, but is also reflected on the internal organs of these sea creatures. For example, nervous and circulatory system also have a radiant arrangement.

Representative of echinoderms - brittle star

Zoologists believe that the senses of smell and taste are quite well developed. They are presented big amount sensitive cells located on the ambulacral legs, which is an important aspect in the characteristics of echinoderms. Creatures of this class are capable of perceiving taste stimuli over long distances.

They also have a radiant structure reproductive system. It consists of a cord and gonads. Much depends on the type of echinoderm; the sex glands are located in grape-shaped sacs, which are placed either in the radial base or go deep into it.

The digestive organs do not have a similar structure. U different types in echinoderms they are located differently. This may be due to differences in diet. The presence or absence of skeletal plates can also depend on nutrition. In some species of these vertebrate representatives, the mouth may be surrounded by tentacles, which help in catching prey.

Sea urchin "Lead pencil"

Despite various characteristics echinoderms, scientists have not yet fully studied the complete process of digestion in these creatures. What is clear is that the walls of their intestines contain a large number of cells that secrete digestive juices and enzymes. Also, the answer to the question of the removal of decay products of these invertebrates has not been found. Representatives of the echinoderm type do not have special organs for their removal.

Echinoderms are a special type of invertebrate animals that live on the bottom of the World Ocean. These amazing creatures existed on Earth long before man appeared on it (more than 500 million years ago). There are up to 7,000 species of echinoderms, but paleontologists emphasize that about 2/3 (13,000) of the species disappeared in the evolutionary process. Today, the main representatives of echinoderms are starfish, lilies, urchins, holothurians (“sea cucumbers”) and brittle stars (“snaketails”). We invite you to learn about echinoderms - interesting facts about appearance, internal structure, impact on the environment.

Appearance

Growths on a calcareous skeleton. It is thanks to this that the animals got their name. Often, growths, thorns and needles can be movable - this is how they defend themselves.

Various sizes. Since echinoderms have a large number of species, it is obvious that they all differ from each other in size and appearance(balls, flowers, barrels). Fossil remains of prehistoric representatives confirm that very long ago they could reach even up to 20 meters in length.

Body symmetry. This feature due to the fact that these living organisms move extremely little. Some species even have a sedentary lifestyle (for example, sea ​​lilies).

Internal structure

Flexible body. The most striking feature of echinoderms is their ability to change the hardness of their body. Depending on the need, they can vary the rigidity of the connective tissues and integuments of their body and become elastic (up to the consistency of jelly) or, on the contrary, hard.

Nutrition. The diet is unlimited - these marine inhabitants are omnivores. However, some individuals, due to the characteristics of their organism, are not able to digest food entirely. Thanks to the above-mentioned ability, such species can envelop food with their body and carry out the process of external digestion.

Simple internal system. Echinoderms are able to get along both in depths and in shallow waters. And yet, the rather primitive internal water-vascular system does not allow them to tolerate changes in the salinity of the water.

Environmental impact

Threat to fishermen. Representatives of the fishing industry are not particularly fond of these sea inhabitants. The reason is simple: these creatures (most often referring to starfish and other predators of this species) destroy many shellfish that are suitable for human food.

Marine orderlies. In general, echinoderms are an integral part of the marine fauna. They not only destroy the remains of dead living organisms, but also act as excellent natural filters, as they feed on planktonic organisms that pollute the upper layers of the ocean.

Disposal carbon dioxide. And starfish and other species absorb up to 2% of the carbon emitted by humans, which means 0.1 gigatons annually.

Of course, echinoderms deserve the title of one of the most extraordinary and beautiful marine inhabitants. Don't forget about environmental benefits!

Phylum Echinodermata combines five classes modern species, among which the largest in terms of the number of species is the Ophiura class.

sea ​​lilies- a group of echinoderms whose body shape resembles a flower. The class unites about 620 species of animals with bright colors that live exclusively in the seas and oceans. Among sea lilies, there are representatives that lead an attached lifestyle (stem lilies), and there are those that can slowly swim and crawl (stemless lilies). The body of sea lilies has the shape of a cup, in the center of which there is a mouth. Five rays (arms) extend from the calyx, each of which bifurcates or divides many times. The difference between lilies and other echinoderms is that their body is directed with the cavity (oral) side up, not down. Another feature of crinoids is the well-developed limestone skeleton, consisting of large plates various shapes and sizes. For attachment (in stalked parts) or for movement (in stalkless parts), root-like movable outgrowths extend from the stems or from the calyx - Tsire. A typical representative stemless lilies are heliometer cold water, distributed in all Arctic seas, in the Japanese and Okhotsk seas

Sea lily ptilomera

seas and the North Atlantic Ocean. This is a ten-promeneva yellowish lily with rays up to 35 cm long, in some places it forms real thickets.

Holothurians, or sea cucumbers, are a group of free-living echinoderms with an elongated cylindrical or worm-like body, which contracts very much at the slightest irritation. The class unites about 1,200 species of animals, distributed throughout all seas and oceans. Holothurians can withstand desalinated waters better than other echinoderms, which is why they are also found in the Black Sea (8 species). A characteristic feature Holothurians have tentacles that surround the mouth and are modified ambulacral legs. their number ranges from 8 to 30 and are designed to collect nutrient particles, as well as for movement, perception of touch and breathing. Another feature of holothurians is a soft skin-muscular sac and a highly reduced skeleton (only some species have an exoskeleton with plates). Holothurians are detritivores by their feeding method. Another unusual feature of sea cucumbers is their cuvian organs and water lungs. Cuverov's organs They are internal glandular tubular formations that flow into the cloaca. When an animal is irritated, they are able to shoot out through the cloaca and stick and confuse predators. Water lungs They look like two branched trunks with lateral extensions. In the rear part they are connected and by a common strait they open into the cloaca. The walls of the water lungs have well-developed muscles, thanks to which water is either drawn through the cloaca into the lungs or pushed out of them. The ability to regenerate is very well developed in holothurians. Representatives of sea cucumbers are edible sea cucumbers ( Far Eastern sea cucumber), sea cucumbers ( Japanese sea cucumber, or cucumaria, tricolor sea cucumber), legless holothurians ( leptosynapta small), true sea cucumbers ( sand sea cucumber up to 30 cm long), etc.

Sea urchins - a group of free-living echinoderms whose bodies are predominantly spherical, slightly flattened at the poles. The class includes about 900 species, distributed mainly in warm seas. Absent in the seas of Ukraine. The entire body of hedgehogs is covered with a continuous shell of limestone plates. Only two areas - around the mouth and anus - remain soft. On the surface of the shell are tubercles to which spines and pedicellaria are attached. Needles can be long (in tiara more than 30 cm), pedicellaria have heads with sharp-toothed 2-4 valves, and often a poisonous gland. In their mouths, sea urchins have a gnawing apparatus called Aristotle's lantern. It consists of movably connected plates with denticles. With their help, these animals can eat algae and gnaw holes in rocks for protection from wave impacts, as does rock sea urchin Sea urchins lay 10-60 million eggs. There are two subclasses in the class - regular sea urchins ( black, edible, coastal, tiaras etc.) And irregular sea urchins (for example, flat, heart-shaped, ovoid and etc.).

Sea stars - a group of free-living echinoderms whose body has the shape of a flattened five-rayed, sometimes multi-rayed, star or pentagon. The class unites about 1,700 species common in waters high salinity(over 30 ppm) from the coast of Antarctica to the equatorial waters of the World Ocean. stars

may also have an unusual shape, for example, a small pillow ( New Guinea culcites). There is a real giant among the stars pycnopodia(Pycnopodia helianthoides), living on the rocky coastal areas of the northern part Pacific Ocean. Normal view shallow seas temperate zone northern hemisphere is asterias red, the length of the rays reaches 30 cm. One type of star lives in the Black Sea. Sea stars are often brightly colored and lead a bottom-dwelling lifestyle. According to their feeding method, they are predominantly predators that feed on sponges (for example, blood star), worms, mollusks, crustaceans, then echinoderms (brittle stars, sea urchins feed on starfish of the genus Luidius), as well as fish. Starfish can open the shells and push their stomach inside through the gap and gradually digest the body of the mollusk. So, in starfish there is external digestion. The most aggressive and voracious stars are crossaster(Crossaster papposus) and (Acanthaster plansi). The fertility of sea stars is very high and can amount to up to 200 million eggs.

Brittle stars- a group of free-living echinoderms with a pentagonal flattened body and long, sharply separated from the disk, thin articulated mobile rays. The class unites about 2000 species of animals that live on the seabed and are mobile among echinoderms. In the Black Sea, 4 species are common (for example, Amphiura Stepanova, Ophiothrix brittle). The rays are often simple and there are 5 of them, but there can be from 6 to 9. They are quite long, several times the length of the disk. The size of the disc is usually small (from a few millimeters to 2 cm), less often large (up to 10 cm). In some species (for example, Chairman of the Gorgon) the rays branch and form a complex plexus. Characteristic feature brittle star is that the rays have a well-developed external (made of limestone plates) and internal skeleton (consists of vertebrae connected by muscles and ligaments). On the ventral side of the beam there are openings for the exit of the ambulacral legs. They serve as organs of breathing and touch. The outer disk of brittle stars is also covered with limestone plates that look like scales. Among them, large paired plates - radial scutes - stand out on the dorsal surface. On the ventral side there is a pentagonal mouth opening, which has 5 projections - jaws. Darterwhistles often have bright color. There are shapes that glow green.

Or caterpillars. They are capable of shrinking strongly even with a slight touch, which is why they are sometimes associated with egg pods.

Sea cucumber - echinoderm an invertebrate mollusk with more than a thousand species. The varieties of these marine inhabitants differ in size, tentacles, and the structure of some organs.

They have a wrinkled, leathery body that resembles a cucumber due to its oval shape. On thick skin, growths resembling thorns are noticeable. On one side of its body there is a mouth surrounded by tentacles, on the other there is an anus. Sea cucumbers can be quite different colors- black, brown, green, gray, red.

Sea cucumbers also differ in size - some species look like dwarfs and reach sizes from several millimeters to several centimeters, other varieties can reach a length of up to two and even five meters. Miners hunt such giants with particular enthusiasm. Sea urchins and starfish are closest to sea cucumbers.

Pictured is a sea cucumber

The most ancient sea cucumbers were known already in the Silurian period; the name “sea cucumber” itself belongs to the Roman philosopher Pliny, and Aristotle created the first descriptions of some species.

About a hundred species of these mollusks live in Russia, the most popular Japanese variety sea ​​cucumber – cucumaria. This kind sea ​​cucumbers differ useful composition and beautiful taste qualities, and are often used in cooking. Sea cucumbers are the species of sea cucumbers that can be eaten.

Sea cucumber lifestyle and habitat

Sea cucumbers found in different parts ocean, and in shallow waters near the shore, and in deep-sea depressions, and in coral reefs, V tropical latitudes. They are common in sea ​​depths almost all over the world.

Holothurians are slow and lazy, they crawl along the bottom, and this makes them easy prey for hunters. Most of the time they lie at the bottom, “on their side.” Deep-sea species may have elongated ambulacral legs that serve as animal stilts and help move along the bottom and rocks.

The muscles of echinoderms are developed enough to move along the bottom and contract sharply in case of danger. Some species are able to attach themselves to rocks or burrow into mud. Holothurians themselves can become prey for starfish, fish, crustaceans or gastropods.

Similarly, in the event of an attack or other danger, sea cucumbers “explode” - scattering their body into pieces. While the opponent chooses a tastier piece, at this time the front part of the cucumber is saved.

In case of danger, the sea cucumber can throw back part of its intestine to create a diversionary maneuver.

The body of echinoderm mollusks subsequently quickly regenerates. Sea cucumbers are animals, which can regenerate if half of the body is preserved, they can even recover from a quarter of their body. The regeneration process can take from one and a half to five weeks.

Sea cucumber nutrition

How do sea cucumbers hunt? All types of sea cucumbers have special tentacles located around the mouth. The number of tentacles can vary from 8 to 30.

The tentacles are usually short, designed to collect nutrients from the ground surface. Holothurians also have branched tentacles that can cover a large area of ​​water in order to catch prey.

Their diet consists of plankton, plants, small animals and organic matter that can be extracted from bottom sand or silt. They are sometimes called marine orderlies because they clean the bottom surface of the remains of dead animals, using these organic substances as a nutrient.

American scientists carefully studied the features of the nutritional system of sea cucumbers. They discovered that holothurians feed primarily through the mouth, but the anus can also perform food capture functions, which in these simple invertebrates is also involved in respiratory system. The respiratory functions of these invertebrates are also performed by water lungs.

In Russia, cucumaria and other types of sea cucumbers are common on Sakhalin, Primorye, as well as in the Seas of Okhotsk, Japan and Barents, at a depth of half a meter to one hundred meters.

Sea cucumber reproduction and lifespan

Holothurians are hermaphrodites; they produce male and female reproductive cells alternately, sometimes even simultaneously. They reproduce by spawning; they have bright green eggs; the eggs hatch into larvae that can swim.

Spawning often occurs in the evening or at night; darkness may be important. Cucumaria spawns twice, in May and July. Holothurians living in Atlantic Ocean, spawn off the coast of Sweden in the fall, from October to December. Some species can spawn year-round. The larvae swim in plankton for about two weeks, then sink to the bottom.

The sea cucumber uses its tentacles to collect food from the bottom.

About 30 species of sea cucumbers are sexual and are divided into males and females. They care for the young and carry the young on the surface of the mother's body.

Rare cases of reproduction by division have also been recorded and described by scientists: half of the body is able to recover to its full volume. Holothurians live quite a long time, from five to ten years.

Due to the great popularity of cucumaria and its demand as a culinary product, as well as in pharmacology, it is practiced artificial breeding sea ​​cucumbers, including in Russia, on Far East.

About useful properties of sea cucumber It was also known in ancient Eastern medicine; it has long been called sea ginseng. Cucumaria meat is practically sterile, not susceptible to viruses and bacteria, these mollusks are unusually rich useful substances, microelements, especially iodine, as well as fluorine, calcium, amino acids and others.

Sea cucumbers are very low in calories, so their products can form the basis of a diet for those who want to lose weight. This product is used as a healing agent that stimulates the body's defenses for people suffering from increased fatigue and loss of strength. Sea cucumbers help a person quickly regain strength after surgery or a long illness.

Sea cucumber meat is beneficial for health, it normalizes metabolism, stimulates heart function, can help reduce blood pressure, promotes rapid tissue regeneration, so it is used during operations.

Sea cucumbers have a healing effect on joints and help with arthritis. Sea cucumbers are also used to produce nutritional supplements and pharmaceuticals.

You can buy sea cucumber not only for the sake of useful and medicinal properties- they are prepared from them delicious dishes. Sea cucumbers make excellent salads, invertebrate molluscs, after cleaning, frying and stewing, and also canning. Some types of sea cucumber are considered delicacies and attract a lot of attention from gourmets.

Phylum Echinodermata - Echinoddermata - are exclusively marine forms with an internal skeleton formed by calcium carbonate crystals, and often with pentaradial radial symmetry. This well-known group includes starfish, brittle stars, crinoids, sea cucumbers (holothurians) and sea urchins. Their diversity was maximum in the Paleozoic: 6 modern classes are known, 15 extinct ones.

The class Sea urchins - Echinoides - have been known in fossil form since the Ordovician, characteristic of post-Paleozoic marine deposits. Modern sea ​​urchins up to 940 species.

Sea urchins. Photo: Revital Salomon

The body of sea urchins is usually almost spherical, ranging in size from 2-3 to 30 cm; covered with rows of limestone plates. The plates, as a rule, are connected motionlessly and form a dense shell (shell), which does not allow the hedgehog to change shape. Based on body shape (and some other characteristics), sea urchins are divided into regular and irregular. U the right hedgehogs the shape of the body is almost round, and they are built according to strictly radial five-ray symmetry. U wrong hedgehogs The body shape is flattened, and the anterior and posterior ends of the body are distinguishable.

Needles of various lengths are movably connected to the shell of sea urchins (using a joint capsule with muscle fibers). The length ranges from 1-2 mm ( flat urchins, Echinarachniidae) up to 25-30 cm (diadem hedgehogs, Diadematidae). There is a species completely devoid of needles - Toxopneustes, whose body is strewn with pedicellariae. Spines often serve sea urchins for movement, nutrition and protection. In some species they are poisonous, as they are connected to special poisonous glands. Poisonous species (Asthenosoma, Diadema) are distributed mainly in tropical and subtropical regions of the Indian, Pacific and Atlantic oceans.

In addition to the needles, on the surface of the shell of sea urchins there are pedicellariae, as well as, at the mouth opening, special organs of balance - spheridia. In some species, pedicellariae are also equipped with poisonous glands (Toxopneustes, Sphaerechinus).

The ambulacral system is common in echinoderms. Each ambulacral leg, equipped with a sucker, passes through the skeletal plates of the shell with two branches (through 2 pores). The ambulacral legs on the underside serve sea urchins for locomotion and burrowing. The legs on the dorsal side were transformed into organs of touch and breathing. In some species, the ambulacral legs, along with spines and pedicellariae, take an active part in the process of cleaning the shell and feeding.

The mouth of sea urchins is located in the center of the lower (oral) side of the body; anal and genital openings - usually in the center of the upper (aboral) side. Regular sea urchins have a mouth equipped with a chewing apparatus (Aristotle's lantern), which is used to scrape algae from stones. The Aristotelian lantern consists of 5 complex jaws, each of which ends in a sharp tooth. The teeth of the Aristotelian lantern are involved not only in processing food, but also in movement (piercing into the ground), and also, presumably, in digging holes. Irregular sea urchins that feed on detritus do not have a chewing apparatus.

The intestine does not have a radial structure, but is a tube extending from the mouth opening along a spiral inside the body cavity. Sometimes an adnexal intestine runs along it, opening into the intestine at both ends. The respiratory organs are the external cutaneous gills located near the mouth, the ambulacral system and the accessory gut.

The sense organs and nervous system are rather poorly developed. In addition to tactile ambulacral legs and spheridia, hedgehogs have primitive ocelli located on the upper side of the body.

Widely distributed in oceans and seas with normal salinity at depths of up to 5 km; absent in the lightly salted Caspian, Black and partially Baltic seas. Widely distributed on coral reefs and coastal waters, often settling there in crevices and recesses of rocks. Correct sea urchins prefer rocky surfaces; incorrect - soft and sandy soil.

Sea urchins are bottom crawling or burrowing animals. They move with the help of ambulacral legs and needles. According to some assumptions, with the help of the “Aristotelian lantern”, sea urchins drill holes for themselves in rocks, even granite and basalt, where they hide during low tide and from predators. Other species bury themselves in the sand or simply cover themselves with pieces of shells, algae, etc.

Almost omnivorous. The diet includes algae, sponges, bryozoans, ascidians and a variety of carrion, as well as mollusks, small starfish and even other sea urchins. The purple hedgehog Sphaerechinus granularis easily copes with the mantis crab Squilla mantis. Species living on soft soil swallow sand and silt, digesting small organisms that come with them.

Sea urchins serve as food for lobsters, starfish, fish, birds, fur seals. The main natural enemy of the sea urchin is the sea otter. Having caught a hedgehog, the sea otter either twirls it in its paws for a long time (sometimes after wrapping it in seaweed) to crush the needles and then eats it; or smashes the hedgehog with a stone on his own chest. The amount of urchins eaten by sea otters is so great that the intestines, peritoneum and even the bones of these marine mammals are sometimes painted purple with sea urchin pigments.

The reproductive organs consist of grape-shaped gonads (usually five), opening outward on the upper side of the body. Sea urchins are dioecious; sometimes males differ slightly in appearance from females. Development with planktonic larva (Echinopluteus); Some Antarctic species are viviparous - the eggs develop under the protection of spines on the upper side of the body or in the brood chamber, so that the young hedgehog leaves the mother fully formed.

Urchins reach sexual maturity and commercial size in the 3rd year of life. According to calculations of growth rings on shell plates, the age of sea urchins is on average 10-15 years, with a maximum of up to 35 years.

Many sea urchins are fished for. They are traditional dish residents of the Mediterranean, Northern and South America, New Zealand and Japan. Their milk and especially caviar, which contains up to 34.9% fat and 19.2-20.3% protein, are highly valued. The shell is a good fertilizer for marginal lands, as it contains a lot of calcium and phosphorus. In addition, modern research has established that the pigment isolated from the sea urchin (Subclass True [correct] sea urchins - Euechinoidea

In Primorye there are two species of Regular sea urchins, which are found in abundance in any bay on coastal stones and rocks. These are the gray hedgehog Strongylocentrotus intermedius and the black hedgehog Strongylocentrotus unarmed.

Of these two species, the dark purple, almost black, unarmed sea urchin carries needles that are longer and thicker than those of the gray urchin. Their tips easily stick into the body of a careless swimmer and, breaking off, remain in the body. Gray hedgehog you won't see it right away. It covers itself with pieces of shells, pebbles, and scraps of algae, which it adheres to its body and holds with its ambulacral legs. However, this camouflage, as a rule, does not protect against swimmers. The gray sea urchin is one of the objects of industrial production, and several thousand tons are caught per year. inochrome), has strong antioxidant activity.