Reserved depths of the Far East. Presentation on the topic "Sea urchins and starfish" Cephalopods move

10. SEA urchins, stars, lilies and holothurians

TO what amazing animals live at the bottom of the sea! They don't have a right or left side. They can crawl in all directions and in each direction they move forward. They are called echinoderms. There are thousands of lime plates in their body. This external skeleton protects animals that are slow in their movement. Many, like sea urchins, are still protected by a mass of needles sticking out in all directions. The sea urchin calmly crawls along the bottom, not being afraid of voracious predators. It has the shape of a slightly flattened ball, on which there are five rows of thin transparent sucker legs. With the help of these legs, the sea urchin slowly crawls along the bottom with its mouth down.

The starfish is either a pentagon or a five-pointed star. There are also multiple stars. Along the lower surface of the rays of the star protrude five rows of the same transparent sucker legs, like those of a hedgehog. But the hedgehog is a peaceful animal, and the star is a predator. In pursuit of prey, she must move quickly. Her mobile rays come to her aid. Quickly bending and unbending its rays, the star moves in search of food. Often she attacks animals that are larger than her size, which she cannot swallow. Then the star throws out the stomach, envelops the caught prey with it, digests it, and then draws the stomach into the body. There are enemies and the starfish. A predatory fish will catch it, bite off one or more rays. Another animal would have died from such an operation. But the star not only survives, it quickly grows new rays to replace those torn off. This ability to repair damaged body parts perfectly protects the starfish from death.

Swaying on a thin stem, similar to a flower, a sea lily lives at the bottom of the sea. This is not a plant, but an animal, but only it grows to the ground. At great depths, where waves do not reach, there is no need for strong supports. You can live on a thin leg. Spreading its arms, which serve it not to grasp the passing prey, but to create a current of water that drives small organisms floating in the water into its mouth, the sea lily feels great at the bottom of the sea.

Echinoderms also include bag-shaped holothurians or, as they are also called for their body shape, sea cucumbers. By the presence of small calcareous bodies in the skin, along five rows of legs, we see that holothurians are relatives of sea urchins, stars and lilies. They crawl on rocks, dig in sand and silt. There are always many remains of dead animals and plants in the silt. They feed on holothurians. Among the holothurians there is a very valuable breed in terms of commercial use, called trepang. Trepang lives at the bottom of our Far Eastern seas. In China, trepang is valued as a tasty dish. Large batches of these holothurians in dried form are sent to China and other countries of the Far East.

Echinoderms are very ancient animals. In the deepest layers of the earth, you can find the imprints of sea urchins, lilies and stars. Among them there are forms that are not among those living now. But there are also those who live today.

Echinoderms are real marine animals, they are not at all not only in fresh water, but even in slightly salty seas.

TO there are no fish in the sea! In some, the body, like a torpedo, is elongated. Others are flat and lie at the bottom of the sea. There are fish long like snakes and round like balls. All this variety of forms is connected with the way of life of fish. Once upon a time, fish were not the same as they are now. The living conditions in the seas changed, and the appearance and organs of the body of fish changed. They became more diverse and more and more different breeds appeared. Fish began to live not only in warm seas, but also in cold ones.

Some fish eat where they live. Others hunt for fleeing prey. Still others make huge journeys in search of food. Fry often live in the surface layer of water, and adults at great depths. Herrings spend their whole lives in the water column, and lay their eggs on the bottom. Most fish live their entire lives in the sea. Some enter to spawn in rivers. It is difficult to describe the diversity of the fish population of the sea.

The fish are of great commercial importance. Fishing is the richest branch of the national economy. Thousands of ships come from the sea, loaded with a rich catch. Hundreds of factories on the shore freeze, salt, smoke fish or make canned food from it. Fish meat is very tasty and nutritious, fish oil saves children from rickets - it contains a lot of vitamins. Heads and bones are used to make fishmeal, a good pet food. Even the skin of fish finds use.

We hear a lot of stories about sharks. These are excellent swimmers, voracious predators. One appearance of them causes a commotion in the school of fish. The body of a shark, elongated in length, is like a torpedo. It is wider at the head than at the tail, and easily cuts through the water. The strong tail serves as the main organ of movement. The shark can reach speeds of up to 20 kilometers per hour. Usually sharks have a size of 2-4 meters. Sharks are predatory. You have to be very nimble or inconspicuous (disguised) to escape from sharp teeth voracious fish. It happens that sharks attack humans. There are real giants among sharks, reaching 30 meters in length, but these sharks are peaceful inhabitants of the sea. They feed on small crustaceans that develop in huge numbers in the seas. Such a shark will swim into a huge flock of crustaceans and sip water. All this little thing remains in her mouth. Each crustacean weighs a milligram (1/1000 of a gram), and millions and billions of these crustaceans are quite capable of feeding a giant shark.

Other fish predators, hunting for food, resort to cunning. Quietly lies at the bottom among the stones a fish called "sea devil". A mustache moves on his head. Some fish will pounce on an imaginary worm and end up in the huge mouth of the sea devil. And you don’t have to swim, and food goes into your mouth by itself!

To disguise yourself, to become invisible, is very beneficial in that ongoing war that is being waged in the depths of the sea. Among the stones, quite pressed to the bottom, lies a flat fish flounder. The upper part of her body is painted to match the color of the surrounding soil. She is not visible at all. Moreover, the flounder will swim from sandy to rocky soil and its color and location of spots on the body will immediately change. On sandy soil, the pattern is small, on rocky soil it will become spotty. The skin of the flounder has special colored cells that can rise to the surface or sink into the depths of the skin. With the help of these cells, the pattern and color of the flounder's skin quickly changes when it gets from one soil to another. This is how a defenseless flounder is saved from its enemies. A shark swam, darted in different directions, examined the bottom with a keen eye and found nothing. Everything hid, disguised itself, as if the turbulent life had not been here a minute ago.

Among the branches of corals, colorful small fish swim, somewhat reminiscent of butterflies in their color and body shape. Variegated, brightly colored, they catch the eye in the aquarium, but become completely invisible among a variety of corals. Military cloakers could learn a lot from coral reef fish. What military science has come to has developed in these fish for a long time in the struggle for existence.

What is this strange phenomenon? Like a flock of sparrows fluttered from the wave and scattered in different directions. They flew several tens of meters, barely touched the wave and quickly flew on. Some of them even flew onto the deck of the ship. These are wonderful silvery fish, whose pectoral fins have turned into wings. How many progenitors of these flying fish died from generation to generation until their fins developed into wings, allowing them to fly away from the chase for a hundred meters. This is beneficial to them also because the enemy loses the direction of the chase. But the wing of a fish is not the wing of a bird, but of an airplane. A flying fish does not flap its wings. Fleeing from the pursuer, the fish quickly swims, working with its tail, to the surface of the sea. Wings-fins are pressed to the sides of the body, the whole body is directed upwards. Finally, the fish reached the surface. Like a real hydroplane, it quickly takes off, then spreads its wings against the oncoming air flow and takes off. She flies in the air like a glider. "Motor" - her tail, he worked in the water. If you need to fly further, the fish will touch the wave, pick up speed again and take off again.

There are more than a hundred natural reserves in Russia, but only one of them, the Far East, is marine, it was created in 1978 to preserve the gene pool of marine and coastal communities, 98% of its territory is a water area.

In the Peter the Great Bay, where the Far East Marine Reserve is located, cold (boreal) waters mix with the warm waters of the subtropics, which creates favorable conditions for the appearance of rich and diverse marine flora and fauna. The water area is inhabited by more than five thousand inhabitants, plants and marine hydrobionts.

The density of the marine population is maximum at a depth of 5-10 m. Thickets are often found here. kelp, sargasso and other algae and sea grasses, where numerous invertebrates live.

Small algae crabs, hermit crabs, starfish live at the bottom, and spherical sea urchins come across.

On the stones - sea acorns, sea anemones, echinoderms: sea urchins and starfish. Also settled here Far Eastern sea cucumbers, and in sandy crevices - sea anemones.
According to preliminary estimates of scientists, there are more than two thousand species of invertebrates in the reserve, and among them there are many unique ancient creatures, this fully applies to sea ​​urchins and trepangs.

Sea urchin

The class of sea urchins consists of 7 orders, including 950 different species.

They live only in highly saline water, therefore, sea urchins are not found in the relatively low-salinity Caspian, Black and Baltic Seas.

The sizes of hedgehogs are very diverse: from the size of a tennis ball to 30 cm in diameter. The body of the sea urchin is covered with a dense calcareous shell and needles, with the help of which it moves, and also protects itself from the predatory inhabitants of the deep sea.

The needles of most species contain a venom that causes sharp pain and even temporary paralysis of the limbs.

Despite the protective shell and sharp spines, the sea urchin is eaten by predatory fish, birds, and mammals. They have learned how to get to the tasty contents: birds drop the caught hedgehog on the stones, breaking its shell and spines, sea crayfish prick the shells of hedgehogs with their claws, and starfish are able to get the soft contents of the hedgehog between the needles with their rays and eat it without "undressing".

Most of the inhabitants of Central Russia, living far from the habitats of sea urchins, first get to know them "from the bad side", on foreign beaches, accidentally stepping on sharp needles while swimming.

However, these ancient creatures (they appeared on Earth over 500 million years ago) can also be of great benefit. In particular, the healing properties of sea ​​urchin caviar.

Foreign biologists are also engaged in large-scale studies of sea urchins. British scientists have discovered in sea urchins a peptide similar to the human hormone calcitonin, which is responsible for bone strength. With age, hedgehogs do not lose their ability to reproduce, and they show practically no signs of aging. In sea urchins, as scientists have found, the most difficult the immune system among all the animals studied to date, this may explain the existence of long-lived hedgehogs, a 200-year-old "aksakal" was found off the coast of California.

Specialists of the Pacific Research Fisheries Center (TINRO) are successfully engaged in research useful properties marine life and the development of health products based on them. Sea urchins were not left without attention. Studies of sea urchins of the strongylocentrotus family common in the Sea of ​​Japan showed that “due to the content of unique biologically active substances (phospholipids, polyunsaturated fatty acids Omega 3 and Omega 6, carotenoids, vitamins, macro- and microelements, essential amino acids, nucleic acids), sea urchin caviar is widely known as a product to increase the protective properties of the body, has a powerful antioxidant effect, prevents the natural aging of the body.

Scientists are studying in detail the unique properties of sea urchins, hoping to uncover the secret in the future eternal youth and for people.

But even now there are many useful products from a sea urchin, which allow, if not to stop, then to significantly delay old age.

Trepang

The Far Eastern trepang Apostichopus japonicus is another hydrobiont actively used for human health, for example, in Southeast Asia, it is primarily valued for its tonic properties. References to the miraculous properties of trepang can be found in treatises of the 16th century.

The Far Eastern trepang is the only absolutely sterile marine inhabitant - there is not a single microbe or virus either in it or in its vicinity. If you cut off a piece of trepang and throw it into the water, then in a few months this piece will turn into a full-fledged adult - such is the unique ability of the sea holothurian to regenerate.

Trepang contains triterpene glycosides, lipids, hexosamines, methionine, organically bound iodine, various trace elements, vitamins, prostaglandins. Triterpene glycosides have strong antifungal activity. Far Eastern trepang extracts contain a high content of polyunsaturated fatty acids and phospholipids, which helps to cleanse blood vessels. including those supplying the genitals with blood for.

slide 2

Sea hedgehog flat

The sea urchin (Echinarachnius parma) lives in soft ground where it can move in all directions. This brownish or lilac hedgehog, covered with greenish needles, has a low shell with a rather thin edge, the diameter of which reaches 10 cm. With the help of needles, it digs soil on itself and can disappear from view in 10-15 minutes. These hedgehogs have been found at depths up to 1625 m and in some places form large aggregations. Representatives of this species are found in the northern and northwestern parts of the Atlantic Ocean, then in the southern part of the Chukchi Sea and in the northern regions of the Pacific Ocean along the Asian coast south to Posyet Bay and the coast of Japan, and along the American coast to Puget Sound, including the Aleutian Islands . It is interesting that young hedgehogs Echinarachnius parma select black heavy grains of iron oxides from sand and fill diverticula (outgrowths) of the intestines with them. By doing this, they make their body heavier, since the density of such grains is 2.5 times greater than the density of the hedgehogs themselves. In this way, they resist washing them out of the ground. Adult hedgehogs do not accumulate heavy grains.

slide 3

Strongylocentrus purple

Strongylocentrus purple (Strongylocentrotus purpuratus), according to Irwin, makes a large number of holes in the steel piles of the port facilities of the Pacific coast of California. This medium-sized hedgehog is covered with numerous strong, long, purple-colored needles, which it rotates to drill holes for itself. Obviously, his teeth help him in this work.

slide 4

Hedgehog sea red-green

Red-green sea hedgehog (Sphaerechinus granularis) This species, distributed mainly in the littoral zone, is very beautiful. Its large, up to 13 cm in diameter, shell has a purple color, with lighter zones on the ambulacras and a greenish apical field. On the shell are purple or purple needles with white ends. The hedgehog often climbs into the crevices between the rocks, but he never makes minks. Like many shallow water animals, it often covers itself with pieces of algae, shells, or other objects. It usually crawls slowly among thickets of algae, feeding on them. Sometimes collects detritus with small organisms in it. Its poisonous globiferous pedicellariae are a protective device against the attack of the main enemies - starfish. The hedgehog manages to escape if only one star attacks, but even poisonous pedicellaria cannot save it if several predators attack at the same time.

slide 5

Tripneus

Tripneustes (Tripneustes ventricosus) Fishermen on the island of Martinique catch it on coral reefs that border a large lagoon in the Atlantic Ocean. It is obtained either by divers or from rafts using a bamboo stick split at the end. The collected hedgehogs are opened on the shore, the caviar is taken out of the shell and boiled in a cauldron over low heat until it looks like a thick mass of beeswax color, after which it is again laid in the peeled shell of the hedgehogs. Shells of hedgehogs with boiled caviar are sold by peddlers by the piece. Every year, the Creole population consumes such a large number of hedgehogs that in some places on the island their shells form whole mountains.

slide 6

sea ​​shore hedgehog

Sea hedgehog (Psammechinus miliaris) It can be found along the European coast of the Atlantic Ocean from Norway to Morocco. It is fairly common on oyster banks and in surf spots. He is not afraid of strong waves, since with the help of coarse short needles he makes a depression in the ground, where he hides. The diameter of its shell is not more than 50 mm, its color is greenish, the needles are green with a purple tip. Feeding on all kinds of animal food (hydroids, sessile polychaetes, young oysters, etc.), it, like starfish, harms oyster farms. This hedgehog is so omnivorous that in the aquarium he ate ascidians, dead fish, caviar, raw meat, crayfish, dead crabs, soft parts of mollusks, bryozoans, worms, hydroids, sponges, various algae, including calcareous ones. There are cases when this hedgehog lived in an aquarium for three years. When feeding in captivity, food is placed directly on the animal's shell, then he quickly begins to move it into his mouth with the help of legs and needles.

Slide 7

Sea rock hedgehog

The sea rock hedgehog (Paracentrotus lividus), distributed from the coast of Great Britain to Africa, including the Mediterranean Sea, is the most famous rock driller. It forms often huge aggregations on sloping rocky surfaces and in seagrass beds. It can be found from the littoral to a depth of 30 m. It is curious that the Mediterranean race of these urchins differs somewhat in behavior from the behavior of the Atlantic race. So, individuals living in the Atlantic Ocean settle in the recesses of the rocks, made by them with the help of needles and teeth. On the contrary, in the Mediterranean Sea they never drill rocks, but settle on slightly inclined surfaces and cover themselves with pieces of shells, sea grass and other objects. The drilling of shelters is obviously associated with the great destructive power of the ocean surf. Sometimes sea urchins are walled up in shelters, as the diameter of the entrance to the mink becomes smaller than the diameter of the urchin's body. Fleeing from the waves, the little hedgehog makes a refuge in the rock and stays there for a long time. His body grows, he expands the depression around him, but the entrance to it remains the same, and after a while the hedgehog becomes a prisoner of his house, eating only what the waves bring him into the mink. These hedgehogs are herbivorous, they eat various algae and sea grass. Their shell reaches a diameter of 7 cm. Its color varies from dark purple to greenish-brown. According to some observations, males and females differ in color: males are darker, females are brighter. Sexual dimorphism is also manifested in the outline of the shell, which is flatter in females. Sexual products are swept into the water in small portions during the summer. For many animals, this hedgehog is dangerous. Its pedacellaria are poisonous. An extract of 30 pedicellaria quickly killed a crab 4-5 cm long. However, other echinoderms, as well as humans, were immune to this poison. Caviar of a rocky sea urchin is eaten. Its main fishery is carried out in the Mediterranean Sea.

Slide 8

Edible sea hedgehog

Edible sea hedgehog (Echinus esculentus) harvested off the coast of Portugal, in some areas of Great Britain, in the North Sea. It is distributed from the Barents Sea to the coasts of Spain and Portugal, prefers to settle in coastal waters from the littoral to a depth of 40 m, less often to 100 m, but there is a case of its being at a depth of 1200 m. Appearance this hedgehog is very handsome. It has a large, up to 16 cm in diameter, spherical reddish shell, covered with short, thin, reddish needles with purple tips and a large number of pedicellaria, with the help of which the animal keeps the shell clean and also gets its own food. This hedgehog is omnivorous. His intestines are always densely packed with various algae, especially seaweed, as well as the remains of various small animals: barnacles, hydroid polyps, bryozoans, and even the remains of other sea urchins. This makes it easy to keep in an aquarium. In a calm state, he can sit for a long time at the bottom of the aquarium, stretching up a whole forest of ambulacral legs. With the help of legs, needles and pedicellaria, it delivers food to the mouth. It is curious that when moving, this hedgehog often uses the teeth of an Aristotelian lantern. At the same time, the teeth sink into the substrate, close and lift the hedgehog, then it moves forward with the help of needles. Moving on ambulacral legs, he can walk 15 cm in 1 minute.

Slide 9

Heterocentrotus

Heterocentrotus (Heterocentrotus mammillatus) has very thick, coarse needles that help it dig caves in the coral polypnyak. He does this mainly with the needles of the oral side, the ends of which are equipped with thin teeth. This mink is so small that the animal in it can hardly turn. Sometimes a growing hedgehog remains walled up in a cave and feeds only on what the sea surf brings to its shelter, so the minks of this hedgehog are literally licked.

Slide 10

Colocentrotus

Colobocentrotus (Colobocentrotus atratus) has adapted well to life in a strong surf zone. Its shell is low, oval, armed with short polygonal needles. Spatulate needles are located along the edge of the oral side. The flat mouth surface of the shell, together with spatulate marginal needles directed obliquely downwards, and numerous ambulacral legs create such a powerful suction disk that the hedgehog can only be unhooked from the rock with a knife. The flattened aboral surface of the shell, armed with short polygonal needles, perfectly resists the action of waves. This hedgehog feeds on various organisms living next to it, such as calcareous algae. The commensal of this hedgehog can be considered the planaria Ceratoplana colobocentroti, which hides under its shell to stay in the surf. Among its cohabitants are the small crab Proechinoecus dimorphicus and one species of molluscs.

slide 11

Sea hedgehog heart-shaped

The sea urchin (Echinocardium cordatum) lives in the temperate latitudes of the Atlantic and Pacific Oceans from the littoral to a depth of 230 m. This hedgehog lives by burrowing into the sandy soil, where it makes moves, strengthening their walls with mucous secretions. It burrows into the ground with the help of lateral needles to a depth of approximately 20 cm. When the hedgehog sits in the ground, it is connected to the surface by a vertical passage cemented with mucus. Through this passage, thanks to the movements of the needles, which cause the water cycle in the mink, fresh water enters it, containing oxygen necessary for breathing. The cystic forelegs of the animal are strongly elongated, protruding outward through a vertical passage (tube). The sticky outgrowths of these legs rather quickly collect the required amount of food from the ground surface and, being pulled back into the mink, transfer food particles to the needles on upper lip which direct them to the mouth. At the same time, the hind legs are stretched a few centimeters back into the posterior tube and contribute to better removal of excrement. Hedgehogs in search of food slowly crawl in the ground, pushing off with paddle-like abdominal spines. In this case, the back tube crumbles, and the upper (breathing) tube is made anew. Hedgehogs rarely appear on the surface of the ground, as they risk being carried away by the waves of the tide.

slide 12

Hedgehog heart-shaped purple

Purple heart-shaped hedgehog (Spatangus purpureus) makes not very deep moves. He lives more often on a broken shell and deepens only 5 cm from the surface, does not construct a respiratory passage. This large hedgehog, reaching a length of 12 cm, has a purple carapace and lighter, sometimes even white, curved spines on the dorsal side. It is distributed in the northern part of the Atlantic Ocean along the European coast to the Azores and the Mediterranean Sea. It occurs up to a depth of 900 m. This hedgehog breeds in the summer months, like most of its fellows, lays eggs in the water, where they pass through the larval stage of Echinopluteus, characterized by a long posterior process.

slide 13

Sea stars (Asteroidea)

Slide 14

acanthster

Acanthaster planci or the crown of thorns, a large star, 40-50 cm in diameter, is often found on the coral reefs of the Pacific and Indian oceans. It is generally accepted that all starfish are completely harmless to humans, but careless handling of acanthaster can cause serious trouble. Numerous short rays extend from the wide flattened disk of the acanthaster. However, young stars have a five-ray structure typical of most stars, and the number of rays increases only as the star grows. Acanthaster is one of the few stars that has not only a large number of rays, but also numerous madrepore plates, the number of which also increases with age. In the largest stars of this type, the number of rays can reach 18-21, and madrepore plates - 16. The entire dorsal surface of the disk and rays is armed with hundreds of large and very sharp needles 2-3 cm long, sitting on movable legs, the ends of which are shaped like a spearhead . For the shape, abundance and sharpness of the spikes, this star was called the “crown of thorns”. The color of the crown of thorns can vary from bluish or greenish gray tones to violet-purple and crimson. Acanthaster feeds on coral polyps. The stars crawl among the reefs, leaving behind a white streak of calcareous coral skeletons with cleanly eaten soft tissues. The variable coloration of the crown of thorns camouflages it well against the bright and varied colors of the coral reef, and the star is not easy to spot at first sight. The crown of thorns is notorious among the inhabitants of many tropical islands. It is impossible to pick it up without receiving burning pain pricks of sharp needles. Pearl collectors on Tongareva Atoll in the central Pacific often have to deal with these stars. Miner writes that if a diver accidentally steps on one of these terrible creatures, the needles pierce the foot and break off, infecting the blood with poisonous secretions. Local residents believe that the one who received such a wound should immediately turn the star upside down with a stick and press his foot to her mouth. They claim that the star sticks to the leg with force and sucks out fragments of needles and poison, after which the wounds heal quickly.

In the 60s. of our century, on many coral reefs of the islands of the western part of the Pacific Ocean, catastrophic increases in the number of acanthasters were discovered, which led in a number of places to the local destruction of coral reefs. Fears arose for the fate of some of the islands, as the living coral reefs that served as protection from ocean waves began to collapse after the death of corals. I had to develop urgent measures to combat acanthaster. The most effective was the destruction of stars by injecting formalin into the body of a star with a syringe by scuba divers. In this way, for example, on the reef of the island of Guam, a team of scuba divers destroyed more than 2.5 thousand acanthasters in 4 hours. Various hypotheses have been proposed to explain the reasons for the extraordinary increase in the number of stars. But, apparently, these outbreaks of reproduction of acanthasters are similar to similar outbreaks that periodically occur in some other animals (for example, locusts, silkworms, lemmings, etc.) and then fade (their reasons are not yet fully elucidated). Similarly, by now, acanthaster populations have declined to normal levels everywhere, and coral recovery and growth has begun in areas of coral reefs that they have destroyed.

slide 15

Anzeropod

Anseropoda (Anseropoda placenta) is distributed along the Atlantic coast of Western Europe and in the Mediterranean Sea. Anzeropod - an asterisk burrowing into the sand, about 10 cm in diameter, is distinguished by an extremely flattened body, the pale pink or bluish surface of which is completely covered with bundles of very small needles. According to the texture of the surface and the insignificant thickness of the body, the anzeropod resembles a waffle. Her body is so thin that the upper and lower sides seem to be pressed tightly against each other, with no room for any internal cavities. Nevertheless, the anzeropod manages to swallow whole small crabs and hermit crabs, as well as small mollusks and echinoderms.

slide 16

Patiria scallop

Patiria scallop (Patiria pectinifera), having the appearance of a regular pentagon, an exceptionally spectacularly colored small star is common in the littoral of the Sea of ​​​​Japan. On the upper side of this star, bright orange spots are scattered against a background of juicy pure blue, and the oral side has a uniform fawn color.

Slide 17

Culcite New Guinea

The New Guinean cultite (Culcita novaeguineae) looks like a small pillow. Culcite is remarkable not only for its unusual shape for stars, but also for the fact that a small so-called pearl fish Carapus (Carapus), also known by the older name Fieraster, is sometimes found in its body cavity. Carapus usually keeps close to some holothurians and, in case of danger, uses their water lungs as a temporary shelter. Apparently, the carapace penetrates the cultite when its usual host is not nearby in case of danger. But the carapace can probably penetrate into the body cavity of the star only by getting through its mouth into the stomach and then drilling through its wall. Whether the fish manages to get out of such an unusual shelter again is not yet known.

Slide 18

Linkia

Linkia (Linckia laevigata) Very common in the tropical shallow waters of the Pacific and Indian Oceans. It is a bright blue star with five long, almost cylindrical rays. For this star and for other species of the genus Linckia, a special type of asexual reproduction is very characteristic, not found in other stars. Linkias have the ability to periodically autotomize, i.e. spontaneously break off their rays. This process begins with the separation of the skeletal plates from each other, most often at a certain distance from the disk. Then the detached part of the arm begins to crawl away from the mother, still being connected to it by soft tissues and skin. Within three to four hours, these tissues are increasingly stretched (sometimes up to 5 cm) and finally torn, after which the detached hand begins an independent life. After some time, a new star begins to develop at the site of the break near such an arm, as a result of which the so-called cometary form of a star is first formed with a group of tiny rays at the end of a single large arm. In the future, new rays grow and the star acquires a normal appearance. At the mother star, a new one grows in place of the torn off hand. In places where links are numerous, both comet stars and stars regenerating one or more arms are not uncommon. If an autotomized arm of the linkia is additionally cut off its tip, then sometimes regeneration can begin from both ends and thus two young stars can be formed, connected by a thick section of the mother's hand.

Slide 19

Asterias

Asterias (Asterias forbesi) has been studied in the most detail and comprehensively, and therefore the life of the most typical starfish can be traced on the description of this starfish. Asterias is a small five-pointed star, the distance between the ends of opposite rays usually does not exceed 20 cm, but stars with a diameter of about 10 cm are most often found. The color of A. forbesi varies from orange-red to greenish-black tones. A. forbesi feeds mainly on oysters and mussels, but also eats other mollusks, small crustaceans, worms and dead fish, and on occasion attacks the living, especially those who are sick or entangled in a net. With a lack of food, cases of cannibalism were also noted in asterias - larger stars eat smaller individuals of their own species. asterias causes great harm to oyster farms. Therefore, the American scientists P. Galtsov and V. Luzanov devoted a number of years to studying the biology of this star and developing measures to combat it. According to these authors, the gluttony of asterias is so great that one medium-sized star can destroy several one-year-old oysters daily. At the same time, A. forbesi are very prolific and, under favorable conditions, multiply in huge numbers, literally devastating and ruining oyster beds. In the 20s. of the past century, starfish annually destroyed about 500 thousand bushels of oysters off the Atlantic coast of the United States (a bushel is a measure of volume, about 35 liters), which caused losses in the amount of about half a million dollars a year. Asterias breeding usually occurs several times during the summer. In this case, even a slight increase in water temperature can serve as a stimulus for the start of reproduction. The stars of both sexes raise the body above the bottom at the ends of the rays and sweep the reproductive products into the water through paired holes at the base of each ray. The remnants of the gonads after the procreation of the reproductive products degenerate, in the fall the formation of new gonads begins, which grow rapidly and by the beginning of the next summer are again filled with mature eggs and spermatozoa. After three to four weeks of free existence in the water, the larvae settle and turn into tiny stars about 1 mm in diameter, which soon begin to feed on young mollusks and other animals that have recently settled to the bottom. They eat young stars and each other, as a result of which their number greatly decreases in the first month after settling. During their life in plankton, the larvae do not travel far from the place where the eggs are laid, and the most massive settling of juveniles usually occurs precisely where adult stars are especially numerous.

slide 21

Astrometis

Astrometis (Astrometis sertulifera) prefers to settle in places protected from bright light. This small five-pointed star lives in the shallow waters of the Pacific coast of North America, from California to Vancouver Island. The length of the rays of astrometis usually does not exceed 8 cm. Its dorsal surface is painted in an unusual dark green color and is lined with numerous spikes with bright red tips and dark blue or purple bases. The lower surface of the star is straw yellow, and the ambulacral legs are a bright canary color. The bases of the dorsal spines are surrounded by rosettes of numerous small pedicellaria, while larger single pedicellaria are scattered over the surface of the body. According to Jennings, the main purpose of pedicellaria is to protect the delicate skin gills located between the spines. When the surface of the skin is irritated by small crustaceans or other animals crawling onto the star, the papules contract and retract, and the pedicellaria begin to open and close their tweezers until they manage to grab the irritated animal or the foreign particle that has fallen on the skin. Captured small crustaceans, pedicellaria can be kept without releasing more than two days. All seized cedicellaria are held so firmly that, for example, one can lift a star out of the water by the pedicellaria, which grasp the hairs on the skin of the hand.

slide 22

Pisaster

Pisaster (Pisaster brevispinus) over this large predatory five-pointed star were very interesting observations. Crawling along the bottom, this star unmistakably stops over the place where one of the burrowing mollusks from the genera Saxidomus and Protothaca is located. After that, the star begins to tear the ground, throwing sand and small pebbles up to 2 cm in size with its legs to the sides. This work continues for two or three days, and digging occurs only at night, and during the day the star lies motionless at the site of its excavations. In the end, the star digs a hole equal in diameter to the size of its body (up to 70 cm) and a depth of about 10 cm. Having reached the mollusk, which always turns out to be in the very center of the hole, just opposite the mouth of the star, the star sticks its legs near the mouth to the top shells. Then she lifts, leaning on the ends of the rays, the central part of her body and pulls the mollusk out, after which she deals with it in the usual way for asteriids, opening the shell and sticking her stomach into its cavity. Sometimes stars of the same species from different habitats differ significantly from each other in biology, in particular in the nature of feeding and the behavior associated with it. So, pizasters living off the coast of California eat mainly flat hedgehogs of the genus Dendraster, and to the north - in the Puget Sound, crawl among the settlements of these hedgehogs, not paying attention to them, and feed on mollusks, digging them up, as described above. Correspondingly, the reaction of Dendraster in both regions to the proximity of this star is also different. Californian hedgehogs immediately begin to burrow into the sand when a dangerous star crawls near them, and Puget Sound hedgehogs do not react to stars even at a distance of several centimeters and begin to burrow only when disturbed by a star accidentally creeping up on them.

Defensive reactions to touch or the proximity of predatory stars are also developed in many other animals. For the most part, this is a reaction of flight from the star. X. Feder very colorfully describes such a reaction in a large gastropod mollusk abalone (Haliotis). When touched by a pizazster, the mollusk lifts the shell on its thick leg and begins to rapidly turn it 180° either in one direction or the other. Having freed itself from the legs of the star attached to the shell with such shaking movements, the mollusk turns and crawls away from the predator with a “gait resembling a gallop”. At the same time, its leg sharply contracts and stretches, producing movements more characteristic of a leech or moth caterpillar than a large snail. The gastropod molluscs (Astaea) react in the same way to predatory stars.

slide 23

pycnopodia

Pycnopodia (Rusnopodia helianthoides) living on rocky bottom areas covered with thickets of brown algae, off the northeast Pacific coast from California to the Aleutian Islands, is a real giant among starfish. The dorsal skeleton of this star is practically absent, and its numerous rays are extremely flexible and mobile. The largest stars reach 80 cm in diameter and weigh 4.5 kg. When such a star crawls, spreading two dozen of its rays along the bottom, its body occupies an area of ​​​​about 0.5 m. The red-brown surface of the body is covered with numerous groups of gray-violet branched papules, between which bunches of pedicellaria are scattered. The well-known starfish specialist W. Fisher describes the behavior of pycnopodia as follows: “It feeds mainly on sea urchins, hermit crabs and other animals that it manages to catch, attacks large holothurians and eats dead or weakened fish. The latter she catches with her rays, almost as mobile as the arms of an octopus. Excited by the proximity of food, it moves very quickly and is more active than any other star I have seen. When it crawls fast with its thousands of writhing legs, it makes an imposing impression, and its many pompoms of prehensile pedicellariae and wide, lithe body make it a formidable weapon of destruction. In the fight against a resisting fish or crab, it can activate more than 15 thousand legs with suction cups. The pycnopodium swallows the large sea urchin Strongylocentrotus whole, and after some time throws out the clean shell of the hedgehog, devoid of needles. After a battle with a sea urchin, the legs of the pycnopodia are abundantly planted with urchin pedicellaria, which stand out brightly with their purple color against the light yellow background of the legs. Sometimes pycnopodia even catch the bait of fishermen, grabbing the bait from fish meat or shellfish. Pycnopodium is interesting not only for its large size and predatory way of feeding. This star has secondarily developed some features of bilateral symmetry in addition to those inherited by the stars from their ancestors. The pycnopodium begins its life at the bottom in the form of a small five-rayed asterisk, in which the sixth ray soon grows, which, as a rule, occupies a strictly defined position in relation to the interradius with the madrepore plate. A further increase in the number of rays occurs through the formation on both sides of the sixth ray of more and more pairs of symmetrical rays, the number of which may eventually reach 24. Bilateral symmetry is also manifested in the physiology of the star. The pycnopodium usually moves forward with the same definite rays, and it uses these same rays primarily to turn it over to its normal position when placed with its mouth side up.

slide 24

Evasterias

Evasterias (Evasterias troschelii) The way starfish manage to open bivalve mollusks and eat them has been well studied using this star as an example. Evasterias lives in shallow waters off the Pacific coast of North America. In bivalve mollusks of the genus Protothaca, the locking muscle was cut and then their valves were pulled together with a rubber belt, which is a kind of dynamometer. Observing how stars eat such mollusks, it was possible to establish that a star with rays 20 cm long can stretch the valves with a force of more than 5 kg. With this star, it is enough just to slightly open the sashes. Even in a gap a few tenths of a millimeter wide, she is able to stick her stomach stretching like rubber. In mussels, at the point of exit from the shell of thin byssus filaments, with which the mollusk is attached to the substrate, there is a non-closing gap about 0.1 mm wide. Such an insignificantly small hole is enough for a star to stick its stomach inside the shell, and in order to feast on a mussel, it does not even have to expend effort on opening the shell. To find out how long a star can stretch its inside-out stomach, the stars were offered mussels placed inside plastic tubes at different distances from their end. It turned out that the star is able to destroy a mussel located 10 cm from the hole, stretching its stomach to a distance equal to half the length of the beam, and in some cases to its entire length. Until now, it has not been finally clarified whether evasterias secrete any substances poisonous to molluscs that cause relaxation of the locking muscle. For a number of species, it has been proven that the star opens the shell only by mechanical force. But it is possible that for some stars both methods are used simultaneously.

Slide 25

blood star

The blood star (Henricia sanguinolenta), named for its rich red coloration, is common in the Arctic and North Atlantic Ocean. This star feeds exclusively various types sea ​​sponges. At the same time, she can recognize through chemoreception her preferred types of sponges, even being at a considerable distance from them.

View all slides

They raise many questions, among which the following are of particular interest: "What does a starfish eat?", "For whom does it pose a mortal threat?".

Stars at the bottom of the sea

These unusual decorations of the seabed have existed on the planet for a long time. They appeared about 450 million years ago. There are up to 1600 types of stars. These animals inhabit almost all the seas and oceans of the earth, the water of which is quite salty. Stars do not tolerate desalinated water; they cannot be found in the Azov and Caspian Seas.

Rays in animals can be from 4 to 50, sizes range from a few centimeters to a meter. The life span is about 20 years.

Marine inhabitants do not have a brain, but on each ray there is an eye. The organs of vision resemble insects or crustaceans, they distinguish between light and shadow well. Many eyes help animals hunt successfully.

Stars breathe almost through their skin, so a sufficient amount of oxygen in the water is very important for them. Although some species can live at decent depths of the ocean.

Structural features

It is interesting how they breed, how starfish feed. Biology classifies them as invertebrate echinoderms. The starfish has no blood as such. Instead, the heart of the star pumps through the vessels sea ​​water enriched with some trace elements. The pumping of water not only saturates the cells of the animal, but also, by pumping fluid in one place or another, helps the star move.

Starfish have a ray structure of the skeleton - rays extend from the central part. The skeleton of sea beauties is unusual. It is composed of calcite and develops inside a small star from almost a few calcareous cells. What and how starfish eat depends largely on the characteristics of their structure.

These echinoderms have on their tentacles special pedicellaria in the form of tweezers at each end of the outgrowth. With their help, the stars hunt and clean their skins from litter clogged between the needles.

Sly hunters

Many are interested in how starfish eat. Briefly about their structure digestive system can be found below. These amazing beauties give the impression of perfect security. In fact, they are marine predators, voracious and insatiable. Their only drawback is their low speed. Therefore, they prefer a motionless delicacy - shells of mollusks. With pleasure, the starfish eats scallops, is not averse to eating sea urchin, trepang, and even a fish that has inadvertently swam too close.

The fact is that the starfish has almost two stomachs, one of which can turn outward. A careless victim, seized by pedicellaria, is transferred to the mouth opening in the center of the rays, then the stomach is thrown over it like a net. After that, the hunter can release the prey and slowly digest it. For some time, the fish even drags its executioner along with it, but the victim can no longer escape. Everything that a starfish eats is easily digested in its stomach.

She acts somewhat differently with shells: she slowly approaches the dish she likes, braids the shell with her rays, places the mouth opening opposite the slit of the shell and begins to push the valves apart.

As soon as a small gap appears, the external stomach immediately pushes into it. Now the sea gourmet calmly digests the owner of the shell, turning the mollusk into a jelly-like substance. Such a fate awaits any victim eaten, no matter whether the starfish feeds on scallops or small fish.

Features of the structure of the digestive system

The predator does not have any devices for capturing prey. The mouth, surrounded by an annular lip, connects to the stomach. This organ occupies the entire interior of the disc and is highly flexible. A gap of 0.1 mm is enough to penetrate the shell flaps. In the center of the aboral side, a narrow short intestine opens from the stomach. What a starfish eats largely depends on the unusual structure of the digestive system.

The love of the stars at the bottom of the ocean

Most starfish are heterosexual. At the time of love games, individuals are so busy with each other that they stop hunting and are forced to fast. But this is not fatal, because in one of the stomachs these sly ones tend to deposit nutrients for the entire time of mating in advance.

The sex glands are located near the stars near the base of the rays. When mating, the female and male individuals connect the rays, as if merging in a gentle embrace. Most often, caviar and male sex cells fall into sea water, where fertilization occurs.

In the event of a shortage of certain individuals, the stars can change sex to maintain the population in a certain area.

These eggs most often remain on their own until the larvae hatch. But some stars turn out to be caring parents: they carry eggs on their backs, and then larvae. In certain types of starfish, for this, during mating, special bags for caviar appear on their backs, which are well washed with water. There she can stay with the parent until the larvae appear.

Reproduction by division

A completely unusual ability of starfish is reproduction by division. The ability to grow a new hand-ray exists in almost all animals of this species. A star caught by a predator by the beam can throw it away like a lizard's tail. And after a while grow a new one.

Moreover, if a small particle of the central part is preserved on the beam, a full-fledged starfish will grow out of it after a certain time. Therefore, it is impossible to destroy these predators by cutting them into pieces.

Who are the starfish afraid of?

The representatives of this class have few enemies. No one wants to mess with the poisonous needles of sea celestials. Animals still know how to secrete odorous substances to scare off especially voracious predators. In case of danger, the star can burrow into the silt or sand, becoming almost invisible.

Among those who feed on starfish in nature, large sea birds predominate. On the shores of warm seas, they become prey for gulls. In the Pacific Ocean, cheerful sea otters are not averse to feasting on stars.

Predators harm underwater plantations of oysters and scallops - what the starfish eats. Attempts to kill animals by cutting them apart have led to an increase in the population. Then they began to fight with them, bringing the stars to the shore and boiling them in boiling water. But there was nowhere to use these remains. There have been attempts to make fertilizer from animals that repels pests at the same time. But this method has not received wide distribution.