Echinoderm inhabitants of the sea - Sea urchins. Type echinoderms, class sea urchins Echinoderm urchins

Echinoderms - the name of animals with "Prickly peel". Unlike other echinoderms (starfish, sea ​​lilies, sea ​​cucumbers), sea ​​urchins have radial symmetry.

The sea urchin can be found in any ocean in the world, but sea urchin populations are rare in the cold, polar regions.

These invertebrate spiny hedgehogs live either on the rocky bottom of the sea or burrow into the soft sand.

The “correct” hedgehogs have an almost round, strictly five-beam spherical shape. In the "wrong" hedgehogs, the front and back parts of the body are distinguishable.

• Those that live on rocky bottom spurs are spherical and have bulging, defensive spines.
• Those that live in the sand are flattened in shape and have short spines that give them a furry appearance.

There is a species of hedgehog that has no spines at all. Instead, it has claw-like structures. This hedgehog Toxopneustes is an inhabitant of the tropical Indo-Pacific region. Sometimes it is called a hedgehog flower.

There is poisonous species sea ​​urchins, the tips of which are supplied with poison.

The most poisonous are Asthenosoma varium (it is also called the Fire hedgehog) - common in seabed Indo- Pacific Ocean, from the Red Sea to Australia and the southern coast of Japan.

Diadema setosum have the largest needles. Diadem hedgehogs are real sea porcupines. The length of their needles reaches 70 cm. This makes them dangerous for divers.

In total, researchers have described 950 species of sea urchins. There are hedgehogs that can shed their quills. There are translucent glass hedgehogs.

The smallest representative (1-2 mm in diameter) is the Purple sea urchin - Echinarachniidae. And the largest is the Red Sea Urchin - the giant Strongylocentrotus franciscanus.

The deepest sea urchins occupy a niche 5000 m below sea level. And the most shallow live at a depth of 3 meters.

Hedgehog lead (Eucidaris tribuloides) is sold for aquariums in zoological shops.

The sea urchin exoskeleton consists of calcareous plates. Hard "shell" does not allow the hedgehog to change its shape.

Sea urchins have a unique system of channels filled with water - a kind of vascular water system. She uses water pumps to help the animal move, eat, breathe and sense its environment.

Sea urchins have external gills to breathe. They don't have eyes to see; but the whole body is equipped with eye spots (which function as eyes) - they are able to feel light.

They are also sensitive to touch and chemicals.

Most echinoderms feed on the way they purify and filter water. This is how they extract food from the water.

The diet of the Sea Urchin is mainly decaying matter: dead fish, mussels, sponges, shells, and algae.

Echinoderms usually reproduce sexually. For fertilization, males release sperm into the water, while females release eggs into the water. When the sperm fertilizes the eggs, larvae are formed.

The form of asexual reproduction and hermaphroditism, which occurs in other echinoderms (in the form of a norm or anomaly), are completely uncharacteristic of sea urchins. And unlike other echinoderms, they are incapable of regenerating their bodies.

Sea urchin caviar and milk are highly valued, as well as the pigment echinochrome, which has antioxidant power.

Or caterpillars. They are able to shrink strongly even with a slight touch, therefore they are sometimes associated with egg capsules.

Sea cucumber - echinoderm an invertebrate mollusc with more than a thousand species. Varieties of these marine life differ in size, tentacles, as well as 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 spikes are noticeable. On one side of his body is a mouth surrounded by tentacles, on the other - an anus. Sea cucumbers can be very different colors - black, brown, green, gray, red.

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

On the picture sea ​​cucumber

The most ancient sea cucumbers were already known in the Silurian period, the very name "sea cucumber" 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 is the Japanese variety sea ​​cucumber - cucumaria. This type of sea cucumber is distinguished useful composition and beautiful palatability, and are often used in cooking. Trepangs are the types of sea cucumbers that can be eaten.

Sea cucumber lifestyle and habitat

sea ​​cucumbers meet in different parts ocean, and in shallow water near the coast, and in deep sea trenches, and in coral reefs, in tropical latitudes. They are common in sea ​​depths practically 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 on the bottom, "on their side". Deep-sea varieties may have elongated ambulacral legs that serve as animal stilts and help move along the bottom and rocks.

The musculature of echinoderms is 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 silt. Holothurians themselves can become prey starfish, fish, crustaceans or gastropods.

Similarly, in the event of an attack or other danger, holothurians "explode" - they scatter their body to 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 the intestine for a distracting maneuver.

The body of echinoderm mollusks subsequently quickly regenerates. Sea cucumbers are animals, which can regenerate if half of their torso is preserved, they can recover even 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 placed around their mouths. 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 expanse of water in order to catch prey.

Their diet consists of plankton, plants, small animals and organic remains 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.

Features of the nutritional system of holothurians were carefully studied by American scientists. They found that holothurians feed mainly through the mouth, but the anus can also perform the function of capturing food, which in these protozoan invertebrates is also involved in respiratory system. Respiratory functions in these invertebrates are also performed by water lungs.

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

Reproduction and lifespan of sea cucumber

Holothurians are hermaphrodites; they produce male and female germ cells alternately, sometimes even simultaneously. They reproduce by spawning, they have eggs of a bright green color, larvae capable of swimming are hatched from the eggs.

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

Tentacles sea cucumber collects food from the bottom

About 30 species of holothurians have a gender and are divided into male and female individuals. They take care of 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 full volume. Holothurians live long enough, from five to ten years.

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

About useful sea ​​cucumber properties Ancient Oriental medicine also knew it, it has long been called sea ginseng. Cucumaria meat is practically sterile, not affected by viruses and bacteria, these mollusks are unusually rich in 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, loss of strength. Sea cucumbers help a person recover quickly after surgery or a long illness.

Benefits of Sea Cucumber Meat for health, it normalizes metabolism, stimulates the work of the heart, can help lower blood pressure, promotes rapid tissue regeneration, so it is used during operations.

Sea cucumbers have a healing effect on the joints, help with arthritis. Sea cucumbers are also used to produce food additives and pharmacology products.

You can buy sea cucumber not only for useful and medicinal properties- are made from them delicious food. Excellent salads are obtained from sea cucumbers, invertebrate mollusks, having previously been cleaned, fried and stewed, and also preserved. Some types of sea cucumber are considered delicacies and attract a lot of gourmet attention.

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

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 (lily stems), and there are those that can slowly swim and crawl (stemless lilies). The body of sea lilies has the form of a cup, in the center of which there is a mouth. Five rays (arms) depart 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, and not down. Another feature of sea lilies is a well-developed limestone skeleton, consisting of large plates. various shapes and sizes. For attachment (in stalked) or for movement (in stemless parts), root-shaped mobile outgrowths depart from the stems or from the calyx - Cire. A typical representative of stemless lilies is heliometer cold water, common in all Arctic seas, in Japan and Okhotsk

sea ​​lily ptilomera

seas and northern Atlantic Ocean. This is a yellowish lily with a length of rays up to 35 cm, in some places it forms real thickets.

Holothurians, or sea cucumbers - a group of free-living echinoderms with an elongated cylindrical or worm-like body, which shrinks very much at the slightest irritation. The class includes about 1200 species of animals distributed throughout all seas and oceans. Holothurians withstand fresh water better than other echinoderms, so they are also found in the Black Sea (8 species). 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 breath. Another feature of holothurians is a soft skin-muscle sac and a strongly reduced skeleton (only some species have external skeleton from plates). Holothurians are detritophages in terms of feeding habits. One more unusual feature holothurians have cuvere organs and water lungs. Cuveri organs are internal glandular tubular formations that flow into the cloaca. When an animal is irritated, they are able to move out through the cloaca and stick and entangle predators. water lungs have the form of two branched trunks with lateral extensions. In the back, they are connected and open in a common strait into the cloaca. The walls of the water lungs have well-developed muscles, due to which water is drawn in through the cloaca into the lungs, then pushed out of them. In holothurians, the ability to regenerate is very well developed. Representatives of holothurians have edible trepangs ( trepang far eastern), sea cucumbers ( Japanese sea cucumber, or cucumaria, tricolor sea cucumber), legless holothurians ( leptosynapta small), true holothurians ( sea ​​cucumber up to 30 cm long), etc.

sea ​​urchins - a group of free-living echinoderms, whose body is predominantly spherical, slightly flattened at the poles. The class is connected by about 900 species, distributed mainly in warm seas. In the seas of Ukraine are absent. The entire body of hedgehogs is covered with a solid shell of limestone plates. Only two areas - around the mouth and anus - remain soft. On the surface of the carapace there are tubercles to which needles and pedicellariae are attached. The needles can be long (in diadem more than 30 cm), pedicelaria have heads with sharp-toothed 2-4 valves, and often a poisonous gland. In the mouth, sea urchins have a gnawing apparatus called Aristotelian lantern. It consists of movably connected plates with teeth. With their help, these animals can eat algae, gnaw holes in the rocks to protect themselves from wave blows, as does rocky 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 looks like a flattened five-ray, sometimes multi-beam, star or pentagon. The class unites about 1700 species distributed in the waters high salinity(over 30 ppm) from the coast of Antarctica to the equatorial waters of the oceans. stars

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

Ofiury- a group of free-living echinoderms with a pentagonal flattened body and long, sharply separated from the disk, thin jointed movable 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, brittle ophiotrix). Rays are often simple and there are 5 of them, but sometimes 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), rarely large (up to 10 cm). Some species (for example, gorgon chairman) rays branch and form a complex plexus. characteristic feature ofiur is that the rays have a well-developed external (from limestone plates) and internal skeleton (consists of vertebrae connected by muscles and ligaments). On the ventral side of the beam there are holes for the exit of the ambulacral legs. They serve as organs of respiration and touch. The disk of the brittle star from the outside is also covered with limestone plates that look like scales. Among them, large paired plates - radial shields - stand out on the dorsal surface. On the ventral side there is a pentagonal mouth opening, which has 5 projections - jaws. Wyrmwhiskers often have bright color. There are shapes that glow green.

Echinoderms are peculiar animals. They cannot be compared in structure with other types. these animals are reminiscent of a flower, a star, a cucumber, a ball, etc.

History of study

Even the ancient Greeks gave them the name "echinoderms". Representatives of this species have long been of interest to man. The history of their study is connected, in particular, with the names of Pliny and Aristotle; and in the 18th and early 19th centuries they were studied by many famous scientists (Lamarck, Linnaeus, Klein, Cuvier). most zoologists at that time correlated them with either coelenterates or worms. I. I. Mechnikov, a Russian scientist, found out that they are related to the enterobranchs. Mechnikov showed that these organisms are closely related to representatives of chordates.

Variety of echinoderms

In our time, it has been established that echinoderms are animals that belong to the group of the most highly organized invertebrates - deuterostomes. They appeared on our planet more than 520 million years ago. The remains of echinoderms are found in sediments dating back to the early Cambrian. This type includes about 5 thousand species.

Echinoderms are benthic, most of which are free-living organisms. Less common are those attached to the bottom with a special stalk. The organs of most organisms are located along 5 rays, but their number in some animals is different. It is known that the ancestors of echinoderms had bilateral symmetry, which free-swimming larvae of modern species have.

Internal structure

In representatives of echinoderms, a skeleton develops in the subcutaneous connective layer, consisting of calcareous plates and needles, spines, etc. on the surface of the body. As in chordates, in these organisms the secondary body cavity is formed by the separation of mesodermal sacs from the intestine. The gastropore during their development overgrows or transforms into the anus. In this case, the mouth of the larva is formed anew.

Echinoderms have circulatory system. Nevertheless, their respiratory organs are rather poorly developed or completely absent. It is necessary to briefly describe other features of echinoderms. These animals lack special nervous system organisms of interest to us. It is located partially in the skin epithelium or in the epithelium of invaginating parts of the body.

External structure

Characteristics of echinoderms should be supplemented by features external structure these organisms. The outer epithelium of the main part of echinoderms (with the exception of holothurians) has cilia that create a flow of water. They are responsible for the supply of food, gas exchange and cleansing the body of dirt. In the integument of echinoderms there are various glands (luminous and poisonous) and pigments that give these animals an amazing color.

The skeletal elements of starfish are calcareous plates, which are placed in longitudinal rows, usually with spines protruding outwards. The body of sea urchins is protected by a calcareous shell. It consists of a series of plates tightly connected to each other, with long needles sitting on them. Holothurians have calcareous bodies that are scattered over their skin. The skeleton of all these organisms is internal in origin.

Musculature and ambulacral system

The musculature of these animals is represented by muscular bands and individual muscles. It is developed quite well, as much as this or that animal is mobile. In most species of echinoderms, the ambulacral system is used for touch, movement, and in some sea urchins and sea lilies it is for breathing. These organisms are dioecious; they develop with larval metamorphosis.

Classification of echinoderms

There are 5 classes of echinoderms: brittle stars, sea stars, sea urchins, sea lilies and sea cucumbers. The type is divided into 2 subtypes: freely moving echinoderms are represented by brittle stars, holothurians, sea urchins and starfish, and attached by crinoids, as well as some extinct classes. About six thousand modern species are known, as well as about twice more extinct. All echinoderms are marine animals that live only in salt water.

Sea stars

by the most famous representative the type of interest to us is a starfish (a photo of one of them is presented above). These animals belong to the class Asteroidea. Sea stars are not accidentally given this name. In their form, many of them are a five-pointed star or a pentagon. However, there are also such species, the number of rays of which reaches fifty.

See what interesting body has a starfish, the photo of which is presented above! If you turn it over, you can see that on the underside of the rays there are rows of small tubular legs with a suction cup at the end. The animal, sorting through them, crawls along the seabed, and also climbs vertical surfaces.

All echinoderms have the ability to quickly regenerate. In a starfish, every ray that has separated from the body is viable. It immediately regenerates and a new organism emerges from it. Most starfish feed on leftovers organic matter. They find them in the ground. Their diet also includes fish carcasses and algae. However, some representatives of starfish are predators that attack their prey (non-motile invertebrates). After the prey is found, these animals dump their stomach out. Thus, digestion in some predatory starfish is carried out externally. The rays of these animals have very powerful muscles. It allows them to easily open the clam shells. Starfish, if necessary, can crush its shell.

The most famous among them is Acanthasterplanci - the crown of thorns. This is the worst enemy of marine coral reefs. There are about 1500 species in this class (type echinoderms).

Sea stars are able to reproduce both sexually and asexually (regeneration). The bulk of these animals are dioecious organisms. They fertilize in water. The organism develops with metamorphosis. Some starfish live up to 30 years.

Serpenttails (brittle stars)

These animals are very reminiscent of stars: they have thin and long rays. The ophiuroids (type echinoderms) do not have liver appendages, anus and hindgut. In their way of life, they are also similar to starfish. These animals are dioecious, but are capable of both regeneration and asexual reproduction. Some species are luminous forms.

The body of the serpentine (ofiur) is represented by a flat disk, the diameter of which is up to 10 cm. 5 or 10 thin long segmented rays depart from it. Animals use these curving beams to move around, with which they crawl along the seabed. These organisms move in jerks. They stretch forward two pairs of their "arms", after which they sharply bend them back. Serpenttails feed on detritus or small animals. Ophiurs live on the bottom of the sea, sponges, corals, sea urchins. There are about 2 thousand of them. These animals have been known since the Ordovician.

sea ​​lilies

Echinoderms are very diverse. Examples of crinoids that are also of this type are presented above. These organisms are exclusively benthic. They lead a sedentary lifestyle. It should be emphasized that crinoids are not plants, but animals, despite their name. The body of these organisms consists of a calyx, stem, and arms (brachioles). They use their hands to filter food particles from the water. Most modern species are free-floating and stemless.

Stemless lilies can crawl slowly. They can even swim in water. Their diet consists of small animals, plankton, algae residues. Total number species is estimated at 6 thousand, of which less than 700 are currently represented. These animals have been known since the Cambrian.

Beautifully colored species of crinoids live mainly in the seas and oceans of the subtropics. They are attached to various underwater objects. It is believed that this, however, in the Mesozoic and Paleozoic era their role in the waters of the seas and oceans was very great.

Sea cucumbers (holothurians)

These organisms are called differently: sea-pods or holothurians. They represent a class of invertebrates such as echinoderms. There are species that humans eat. Common name edible holothurians - "trepang". Trepang is mined on a large scale in the Far East. There are also poisonous holothurians. They make various medicines(for example, holothurin).

Currently, about 1150 species of sea cucumbers are represented. Their representatives are divided into 6 groups. The Silurian period is the time to which the oldest fossils of holothurians belong.

These organisms differ from other echinoderms in their oblong, spherical or worm-like shape, as well as the reduction of the skin skeleton and the fact that they do not have protruding spines. The mouth of these animals is surrounded by a corolla, consisting of tentacles. With the help of them, holothurians capture food. These animals are benthic, although very rare and living in the silt (pelagic). They lead a sedentary lifestyle. Holothurians feed on small plankton or silt.

sea ​​urchins

These animals live at the bottom or in the bottom. The body of most of them is almost spherical, sometimes ovoid. Its diameter is from 2-3 to 30 cm. Outside, the body is covered with rows of spines, calcareous plates or needles. As a rule, the plates are interconnected motionlessly, forming a shell (dense shell). This shell does not allow the animal to change shape. Today, there are about 940 species of sea urchins. The largest number species were introduced in the Paleozoic. Currently, there are 6 classes, while 15 are extinct.

As for nutrition, some sea urchins use dead tissue (detritus) for food, while others scrape algae from stones. In the latter case, the animal's mouth is equipped with a special chewing apparatus called the Aristotelian lantern. In appearance, it resembles a drill. Some species of echinoderms (sea urchins) with its help not only get food, but also modify rocks by drilling holes in them.

The value of sea urchins

These animals are a valuable type of biological resources of the sea. Commercially interesting mainly In Japan and other countries of the Asia-Pacific region, it is a delicacy product. The caviar of these animals contains many biologically active substances. Scientists believe that the elements that are present in it can be used for cancer as a therapeutic and prophylactic agent. In addition, they normalize blood pressure, increase potency, remove human body radionuclides. It has been proven that eating caviar increases resistance to various infections, helps with gastrointestinal diseases, reduces the effects of radiation therapy, improves the functions of the genital and thyroid gland, of cardio-vascular system.

Considering the above, it is not surprising that the sea urchin is a marine echinoderm that is becoming a coveted dish. For example, the inhabitants of Japan every year eat about 500 tons of caviar of this animal, both in its natural form and as additives to dishes. By the way, the following is associated with the use of this food product: long duration life in this country where people live an average of 89 years.

In this article, only the main echinoderms were presented. We hope you remember their names. Agree that these representatives marine fauna very beautiful and interesting.