Presentation on the biology of sea urchins. Sea urchins

“Species diversity” - Indicators of species fitness. Giant deer. Executive Director of the UN Environment Program Achim Steiner. Why is it necessary to preserve all the diversity of species? Who is interested in this problem? Steller's sea cow. Conclusion: Causes of species extinction: State level.

"The Extinction of the Dinosaurs" - A History of Disasters. Catastrophe. But why then did the crocodiles that lived nearby survive? Explosions. But the most plausible theory today is considered to be the theory of linear evolution. “Dinosaur” is translated from Greek as “terrible lizard.” But there were still more large “terrible lizards”. Reasons for disappearance. Here is your own “set” of versions.

“Characteristics of chordates” - Type chordates. Work plan. The concept of chordates, the systematic position of the type in the animal world, the main classes of the type of chordates, a brief description of the classes. The concept of chordates. The main classes of the phylum Chordata. Tsymbal Tatyana Yuryevna teacher of biology, school No. 5, Dalnerechensk, issue No. 35 September 2003. Systematic position of the type.

“Lesson Population” - Genetic and phenetic structure - the relationship in a population of individuals with different genotypes and phenotypes. Siberian Crane. Lesson topic: The concept of population in ecology. Basic properties of populations. The population has a certain structure. Spatial structure - features of the placement of individuals in space. Common Apollo.

“Structure and dynamics of populations” - Type II curve is typical for predators, large rodents, birds, when P = C. The age of a population depends on fertility, mortality and survival rates. Density, birth rate, survival rate, and population size can change. Population structure. A population is a dynamic system that changes over time.

“Lesson Coelenterates” - Cross-shaped jellyfish. Gorgon Medusa mask in Didim (Türkiye). The youngest of the Gorgons is Medusa. In unity with the ocean, a healthy, strong personality is formed. Painting by P.P. Rubens. 1621 The influence of the Ocean on Man is diverse and beneficial. Your emotional mood. Cyanea. Vodolazov A.G. Lesson objectives.

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Sea urchins (Echinoidea)

FLAT SEA URGNISH FLAT SEA URGNISH (Echinarachnius parma) lives in soft soil, where it can move in all directions. This brownish or lilac-colored hedgehog, covered with greenish needles, has a low shell with a rather thin edge, the diameter of which reaches 10 cm. It digs up soil onto itself with the help of needles and can disappear from view in 10-15 minutes. These hedgehogs were found at depths of up to 1625 m and in some places form large concentrations. 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. Interestingly, young hedgehogs Echinarachnius parma select black heavy grains of iron oxides from the sand and fill the intestinal diverticula (outgrowths) with them. This makes 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 being washed out of the soil. Adult hedgehogs do not accumulate heavy grains.

Strongylocentrotus purpuratus is reported by Irwin to make large numbers of burrows in the steel pilings of port facilities on the Pacific Coast of California. This medium-sized hedgehog is covered with numerous strong, long, purple spines, which it rotates to drill holes for itself. Obviously, his teeth help him in this work.

RED-GREEN SEA HURGINE RED-GREEN SEA HURGINE (Sphaerechinus granularis) This species, distributed mainly in the littoral zone, is very beautiful. Its large shell, up to 13 cm in diameter, is purple in color, with lighter zones on the ambulacra and a greenish apical field. The shell has violet or purple needles with white tips. The hedgehog often climbs into crevices between rocks, but never makes holes himself. Like many shallow-water animals, it often covers itself with pieces of algae, shells or other objects. Usually it slowly crawls among algae thickets, feeding on them. Sometimes it collects detritus with small organisms in it. Its poisonous globiferous pedicellariae are a protective device against the attack of the main enemies of sea stars. The hedgehog manages to escape if only one star attacks, but if several predators attack simultaneously, even poisonous pedicellariae cannot save it.

TRIPNEUS TRIPNEUS (Tripneustes ventricosus) Fishermen of the island of Martinique catch it on the coral reefs bordering 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 on the shore are opened, the caviar is removed from the shell and boiled in a cauldron over low heat until it looks like a thick mass the color of beeswax, after which it is again placed in the cleaned shells of the hedgehogs. Hedgehog shells with boiled caviar are sold by peddlers individually. Every year the Creole population consumes such a large number of hedgehogs that in some places on the island their shells form entire mountains.

SEA URCHINE COAST URCHINE (Psammechinus miliaris) It can be found along the European coast of the Atlantic Ocean from Norway to Morocco. It is quite common on oyster banks and surf areas. Strong waves are not scary for him, since with the help of rough short needles he makes a depression in the ground, where he hides. The diameter of its shell is no 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 where this hedgehog lived in an aquarium for three years. When feeding in captivity, food is placed directly on the animal's shell, then it quickly begins to move it into the mouth with the help of legs and needles.

ROCK SEA URGNISH The ROCK SEA urchin (Paracentrotus lividus), distributed from the coast of Great Britain to Africa, including the Mediterranean Sea, is the most famous rock borer. It often forms huge accumulations on sloping rocky surfaces and in thickets of sea grass. It can be found from the littoral zone to a depth of 30 m. It is curious that the Mediterranean race of these hedgehogs is somewhat different in behavior from the behavior of the Atlantic race. Thus, individuals living in the Atlantic Ocean settle in rock cavities made by them with the help of needles and teeth. On the contrary, in the Mediterranean Sea they never drill into 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 find themselves walled up in shelters, since the diameter of the entrance to the burrow becomes smaller than the diameter of the urchin's body. Fleeing from the waves, a small hedgehog makes a shelter for itself in a rock and remains there for a long time. His body grows, he expands the depression around himself, but the entrance to it remains the same, and after a while the hedgehog becomes a prisoner of his home, feeding only on what the waves bring him into the hole. These urchins are herbivores; 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. Reproducts are swept into the water in small portions during the summer. This hedgehog is dangerous for many animals. Its pedacellariae are poisonous. An extract of 30 pedicellaria quickly killed a crab 45 cm long. However, other echinoderms, as well as humans, turned out to be immune to this poison. Rock sea urchin caviar is eaten. Its main fishery is carried out in the Mediterranean Sea.

EDIBLE SEA HURGESH EDIBLE SEA HURDOSH (Echinus esсulentus) is caught off the coast of Portugal, in some areas of Great Britain, and 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 zone to a depth of 40 m, less often to 100 m, but there are known cases of its presence at a depth of 1200 m. The appearance of this hedgehog is very beautiful. 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 pedicellariae, with the help of which the animal keeps the shell clean and also obtains food for itself. This hedgehog is omnivorous. Its 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, it can sit for a long time at the bottom of the aquarium, stretching upward a whole forest of ambulacral legs. With the help of legs, spines and pedicellaria, it delivers food to the mouth. It is curious that when moving, this hedgehog often uses the teeth of an Aristotelian lantern. In this case, the teeth plunge into the substrate, close and lift the hedgehog, then it moves forward with the help of needles. Moving on ambulacral legs, it can walk 15 cm in 1 minute.

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

Colobocentrotus atratus has adapted well to life in the strong surf. Its shell is low, oval, armed with short polygonal needles. Along the edge of the oral side there are spade-shaped needles. The flat oral surface of the shell, together with the shovel-shaped marginal spines directed obliquely downwards and numerous ambulacral legs, creates 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 spines, perfectly resists the action of waves. This hedgehog feeds on various organisms living next to it, for example calcareous algae. The commensal of this hedgehog can be considered the planarian Ceratoplana colobocentroti, which hides under its shell to stay in the surf. Its companions include the small crab Proechinoecus dimorphicus and one species of mollusk.

HEART-SHAPED SEA HURGNISH HEART-SHAPED SEA HURCHINE (Echinocardium cordatum) lives in temperate latitudes of the Atlantic and Pacific oceans from the littoral zone to a depth of 230 m. This hedgehog lives burrowing into sandy soil, where it makes passages, strengthening their walls with mucous secretions. It burrows into the ground with the help of lateral spines 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 a water cycle in the burrow, fresh water containing oxygen necessary for respiration enters it. The animal's brush-shaped front legs are strongly extended and protrude out through a vertical passage (tube). The sticky outgrowths of these legs quite quickly collect the required amount of food from the surface of the ground and, retracting back into the burrow, transfer food particles to the needles on the upper lip, which direct them into the mouth. At the same time, the hind legs extend a few centimeters back into the posterior tube and facilitate better removal of excrement. Hedgehogs crawl slowly in the ground in search of food, pushing off with paddle-shaped abdominal spines. In this case, the rear 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 tidal waves.

HEART-SHAPED PURPLE SEA URGNISH HEART-SHAPED PURPLE SEA URGNISH (Spatangus purpureus) does not make very deep moves. It often lives on a broken shell and goes deep only 5 cm from the surface, and does not construct a breathing 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 is found up to a depth of 900 m. This hedgehog reproduces in the summer months, like most of its fellows, laying eggs in the water, where they go through the larval stage of echinopluteus, characterized by a long posterior process.

Sea stars (Asteroidea)

ACANTHASTER ACANTHASTER (Acanthaster planci) or crown of thorns, a large star, 4050 cm in diameter, is often found on 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-rayed structure typical of most stars, and the number of rays increases only as the star grows. Acantaster 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 1821, and madrepore plates - 16. The entire dorsal surface of the disk and rays is armed with hundreds of large and very sharp needles 23 cm long, sitting on movable legs, the ends of which are shaped like the tip of a spear. For its shape, abundance and sharpness of thorns, 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. Acantaster feeds on coral polyps. The stars crawl among the reefs, leaving behind a white stripe of calcareous coral skeletons with their soft tissues completely eaten away. The variable coloration of the crown of thorns camouflages it well among the bright and varied colors of the coral reef, and the star is not easy to notice at first glance. The crown of thorns is notorious among the inhabitants of many tropical islands. It is impossible to pick it up without receiving stinging injections from sharp needles. Pearl collectors on Tongarewa Atoll in the central Pacific Ocean often have to deal with these stars. The 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 someone who has received such a wound should immediately use a stick to turn the star over with its mouth side up and press its foot to its mouth. They claim that the star attaches itself to the leg with force and sucks out needle fragments and poison, after which the wounds quickly heal. In the 60s In our century, on many coral reefs of the islands of the western Pacific Ocean, catastrophic increases in the number of Acantasters were discovered, which led in a number of places to the local destruction of coral reefs. Concerns arose for the fate of some islands, since the living coral reefs that served them as protection from ocean waves began to collapse after the death of the corals. It was necessary to develop urgent measures to combat the acanthaster. The most effective way to destroy stars was by injecting formaldehyde into the star's body 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 die out (their reasons are not yet fully understood). In the same way, to date, the number of acanthasters has decreased everywhere to the usual norm, and in the areas of coral reefs destroyed by them, restoration and growth of corals has begun.

ANZEROPODA ANZEROPODA (Anseropoda placenta) is distributed along the Atlantic coast of Western Europe and in the Mediterranean Sea. Anseropod, a star burrowing in 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 bunches of very small needles. The texture of the surface and the insignificant thickness of the anseropod's body resembles a wafer. Its body is so thin that the upper and lower sides seem to be pressed tightly against each other, without room for any internal cavities. Nevertheless, the anzeropod manages to swallow whole small crabs and hermit crabs, as well as small mollusks and echinoderms.

PATIRIA SCUMB PATIRIA (Patiria pectinifera) having the appearance of a regular pentagon, an exceptionally impressively colored small star is common in the littoral zone of the Sea of ​​​​Japan. The upper side of this star has bright orange spots scattered against a background of rich pure blue, while the oral side is a uniform fawn color.

NEW GUINEA CULCITA NEW GUINEA CULCITA (Culcita novaeguineae) looks like a small pillow. Cultsita is remarkable not only for its unusual shape for stars, but also because in its body cavity a small so-called pearl fish, Carapus, also known under the older name Fieraster, is sometimes found. Karapus usually stays close to some sea cucumbers and, in case of danger, uses their aquatic lungs as a temporary shelter. Apparently, the carp penetrates the culcite when, in case of danger, its usual host is not nearby. But the carp can probably penetrate into the body cavity of a star only by crawling through its mouth into its stomach and then drilling through its wall. It is not yet known whether the fish will be able to escape from such an unusual shelter again.

LINKIA LINCIA (Linckia laevigata) Very common in tropical shallow waters of the Pacific and Indian Oceans. It is a bright blue star with five long, almost cylindrical arms. This star and other species of the genus Linckia are very characterized by a special type of asexual reproduction that is not found in other stars. Linkia have the ability to periodically autotomize, that is, spontaneously break off their rays. This process begins with the separation of skeletal plates from each other, most often at a certain distance from the disk. Then the separated part of the arm begins to crawl away from the mother, while still connected to it by soft tissues and skin. Over the course of three to four hours, these tissues stretch more and more (sometimes up to 5 cm) and finally rupture, after which the severed arm begins an independent life. After some time, a new star begins to develop at the site of the break in such an arm, as a result of which the so-called cometary shape of a star is first formed with a group of tiny rays at the end of a single large arm. Subsequently, new rays grow and the star acquires a normal appearance. The mother star grows a new one in place of the severed arm. In places where links are numerous, both comet stars and stars that regenerate one or more arms are often found. If the tip of an autotomized hand is also cut off, sometimes regeneration can begin at both ends and thus two young stars can form, connected by a thick section of the mother's hand.

ASTERIAS ASTERIAS (Asterias forbesi) has been studied in the most detail and comprehensively, and therefore, using the description of this starfish, one can trace the life of the most typical sea stars. Asterias is a small five-rayed star, the distance between the ends of the opposite rays usually does not exceed 20 cm, but most often stars with a diameter of about 10 cm are 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 living ones, especially sick ones or those entangled in a net. When there is a lack of food in Asterias, cases of cannibalism have also been noted; larger stars eat smaller individuals of their species. Asterias causes great harm to oyster farms. Therefore, American scientists P. Galtsov and V. Luzanov specially 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 every day. At the same time, A. forbesi is very prolific and, under favorable conditions, reproduces in enormous quantities, literally devastating and ruining oyster beds. In the 20s last century, starfish annually destroyed an average of 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 amounting to 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. Stars of both sexes raise their bodies above the bottom at the ends of their rays and sweep their reproductive products into the water through paired holes at the base of each ray. The remnants of the gonads degenerate after the release of reproductive products; in the fall, the formation of new gonads begins, which grow rapidly and by the beginning of next summer are again filled with mature eggs and sperm. The larvae, after three to four weeks of free existence in the water, settle and turn into tiny stars with a diameter of about 1 mm, which soon begin to feed on the young mollusks and other animals that have recently settled to the bottom. Young stars eat each other, as a result of which their numbers greatly decrease in the first month after settling. During their life in plankton, larvae do not travel far from the place where eggs are laid, and the most massive settling of juveniles usually occurs precisely where adult stars are especially numerous.

ASTROMETIS ASTROMETIS (Astrometis sertulifera) prefers to settle in places protected from bright light. This small five-rayed 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 seated with numerous spines 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 pedicellariae, and larger single pedicellariae are scattered over the surface of the body. According to Jennings' observations, 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 pedicellariae begin to open and close their forceps until they manage to grab the animal that caused the irritation or a foreign particle that has landed on the skin. Pedicellariae can keep captured small crustaceans without releasing them for more than two days. The pedicellariae hold everything they grasp so firmly that it is possible, for example, to lift a star out of the water by the pedicellariae grasping the hairs on the skin of the hand.

PISASTER PISASTER (Pisaster brevispinus) Very interesting observations were made over this large predatory five-rayed star. Crawling along the bottom, this star unmistakably stops over the place where one of the mollusks from the genera Saxidomus and Protothaca is located. After this, the star begins to tear up the soil, throwing sand and small pebbles up to 2 cm in size with its legs. 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 ends up in the very center of the hole, just opposite the star’s mouth, the star sticks to the top with its legs located near the mouth 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 their feeding patterns and associated behavior. Thus, pizasters, living off the coast of California, eat mainly flat urchins of the genus Dendraster, and further north in the Puget Sound, they crawl among the settlements of these urchins, not paying attention to them, and feed on mollusks, digging them up, as described above. Accordingly, the reaction of Dendraster in both regions to the proximity of this star is different. California hedgehogs immediately begin to bury themselves in the sand when a dangerous star creeps near them, and hedgehogs from Puget Sound do not react to stars even at a distance of several centimeters and begin to bury themselves only when disturbed by a star accidentally creeping towards them. Many other animals also develop defensive reactions to the touch or proximity of predatory stars. Mostly this is a reaction to escape from the star. X. Feder very colorfully describes such a reaction in the large gastropod mollusk abalone (Haliotis). Upon contact with the pizazster, the mollusk lifts the shell on its thick leg and begins to rapidly turn it 180° in one direction or the other. Having freed itself with such shaking movements from the star’s legs attached to the shell, the mollusk turns and crawls away from the predator in a “gait resembling a gallop.” At the same time, its leg sharply contracts and extends, producing movements more characteristic of a leech or a moth caterpillar than a large snail. Gastropod limpets (Astaea) react in a similar way to predatory stars.

PYKNOPODIA PYKNOPODIA (Rusnopodia helianthoides) living on rocky areas of the bottom covered with thickets of brown algae off the northeastern coast of the Pacific Ocean from California to the Aleutian Islands is a real giant among starfish. This star has virtually no dorsal skeleton, and its numerous rays are extremely flexible and mobile. The largest stars reach 80 cm in diameter and a mass of 4.5 kg. When such a star crawls, spreading its two dozen 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 clusters of pedicellaria are scattered. The well-known expert on sea stars, 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 sea cucumbers and eats dead or weakened fish. She catches the latter 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 ever observed. As this star crawls quickly with its thousands of writhing legs, it makes an imposing impression, and its numerous pom-poms of tenacious pedicellariae and its wide, flexible 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. Pycnopodia swallows large sea urchins Strongylocentrotus whole, and after some time throws out the clean shell of the urchin, devoid of spines. After a battle with a sea urchin, the legs of the pycnopodia are abundantly planted with pedicellariae of the urchin, which stand out clearly with their purple color against the light yellow background of the legs. Sometimes pycnopodia even fall into the fishing rods of fishermen, grabbing bait from fish or shellfish meat.” Pycnopodia is interesting not only because of its large size and predatory mode 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 star, which soon grows a sixth ray, 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 can eventually reach 24. Bilateral symmetry also appears in the physiology of the star. The pycnopodia usually moves by directing forward the same specific rays, and uses these same rays primarily to turn over into a normal position if it is placed with its mouth side up.

EVASTERIAS EVATERIAS (Evasterias troschelii) Using this star as an example, the way in which starfish manage to open bivalves and eat them has been well studied. Euasterias lives in shallow waters off the Pacific coast of North America. The locking muscle of bivalves of the genus Protothaca was cut, and then their valves were tightened with a rubber belt, which was a kind of dynamometer. By 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. In this case, the star only needs to open the doors a little. Even into a gap a few tenths of a millimeter wide, she is able to insert her stomach, which stretches like rubber. In mussels, at the point where the thin byssal threads emerge from the shell, with which the mollusk is attached to the substrate, there is an unclosable gap about 0.1 mm wide. To push its stomach inside the shell, such an insignificant hole is enough for the star, and in order to feast on the mussel, it does not even have to waste effort on opening the shell. To find out how long a star can stretch its outward-turned stomach, the stars were offered mussels placed inside plastic tubes at different distances from their ends. It turned out that the star is capable of destroying a mussel located 10 cm from the hole, extending its stomach to a distance equal to half the length of the beam, and in some cases to its entire length. It has not yet been definitively clarified whether elasterias secrete any substances that are toxic to mollusks and cause relaxation of the locking muscle. For a number of species, it has been proven that the star opens the shell only through mechanical force. But it is possible that some stars use both methods simultaneously.

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

Anastasia Kazantseva
Presentation “Inhabitants of the seas and oceans”

Slide 1. « Inhabitants of the seas and oceans»

Slide 2. Sea inhabitants

Slide 3. Dolphin. Dolphins live in all open seas and sometimes enter the mouths of large rivers. Representatives of the family of freshwater, or river, dolphins have a much more limited distribution. For the most part they inhabit inland fresh water bodies, although some of them can even penetrate coastal areas seas.

Slide 4. Sea turtles are excellent swimmers and divers. These large reptiles, clumsy on land, glide gracefully through the water with the help of flipper-like forelimbs and streamlined carapace. When sea turtles are active, they often come to the surface to breathe. And during rest, some species can remain under water for several hours.

Slide 5. Starfish Sea stars got their name due to their original form (rays)

Slide 6. Starfish got their name due to their original form: they have from 5 to 40 limbs (rays). These animals are predators. The stars feed on mollusks and various bottom invertebrates.

Slide 7. Whales are the largest among animals. In adulthood, they reach an average body length of 25 m (the largest is 33 m, and their weight is 90-120 tons.

Slide 8. Sea urchin. These representatives of marine fauna live on the bottom. They move with the help of special legs. The legs are long elastic processes. They have suction cups at the ends, so the marine life can crawl not only on horizontal, but also on vertical surfaces.

Slide 9. Seahorses live in tropical and subtropical seas. They lead a sedentary lifestyle, attaching their flexible tails to plant stems and changing body color, completely blending into the background. This is how they protect themselves from predators and camouflage themselves while hunting for food. Skates feed on small crustaceans and shrimp.

Slide 10. Octopuses are the most intelligent among all invertebrate animals. Octopuses are often colored brown, red, or yellowish, but they can change color no worse than chameleons.

Slide 11. Sharks live in waters all over the world ocean, that is, in all seas and oceans. Some species of sharks are able to live in both salt and fresh water, swimming into rivers. The depth of habitat of sharks is on average 2000 meters, in rare cases they descend to 3000 meters.

Slide 12. Crabs inhabit all seas and oceans of the planet. Along with a special body shape, crabs are characterized by the presence of 10 pairs of limbs.

Sly 13. Stingrays live in all seas and oceans and live both in the cold waters of the Arctic and Antarctic, and in the tropics. Stingrays have organs that produce electricity.

Slide 14. Jellyfish. These amazing animals live only in salt water, and therefore can be found in all oceans and seas of our. Among the representatives of this class there are both heat-loving animals and those that prefer cold waters, species that live only near the surface of the water, and those that live only at the bottom ocean

Slide 15. Thank you for your attention!

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Summary of direct educational activities in the preparatory group “Inhabitants of the Seas and Oceans” Topic: Inhabitants of the seas and oceans Purpose: To introduce children to the inhabitants of the seas and oceans. Objectives: 1. Educational: expand children's understanding.

Goal: Introducing children to the World Oceans Day holiday. Objectives: Developmental: introduce children to the purpose of this holiday. Shape.

Good evening colleagues! Today I want to share with you a small master class, don’t judge strictly for the first time I’m exhibiting my work. Us.

NOD “We are the inhabitants of the Earth” Nod on the topic: "WE ARE THE EARTH'S RESIDENTS." Goals: to consolidate the concept of “Solar System”, to clarify children’s knowledge about the planets of the Solar System and their features.

GCD in the senior group “Animal world of the seas and oceans” TASKS: EDUCATIONAL: Clarify and activate the vocabulary

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The presentation on the topic “Sea Urchins” can be downloaded absolutely free on our website. Project subject: Biology. Colorful slides and illustrations will help you engage your classmates or audience. To view the content, use the player, or if you want to download the report, click on the corresponding text under the player. The presentation contains 25 slide(s).

Presentation slides

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SEA HEDGEHOG FLAT

The sea urchin (Echinarachnius parma) lives in soft soil, where it can move in all directions. This brownish or lilac-colored hedgehog, covered with greenish needles, has a low shell with a rather thin edge, the diameter of which reaches 10 cm. It digs up soil onto itself with the help of needles and can disappear from view in 10-15 minutes. These hedgehogs were found at depths of up to 1625 m and in some places form large concentrations. 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 the Puget Sound, including the Aleutian Islands . Interestingly, young hedgehogs Echinarachnius parma select black heavy grains of iron oxides from the sand and fill the intestinal diverticula (outgrowths) with them. This makes 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 being washed out of the soil. Adult hedgehogs do not accumulate heavy grains.

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STRONGYLOCENTROTHUS PURPLE

Strongylocentrotus purpuratus, reported by Irwin, makes large numbers of burrows in the steel pilings of port facilities on the Pacific Coast of California. This medium-sized hedgehog is covered with numerous strong, long, purple spines, which it rotates to drill holes for itself. Obviously, his teeth help him in this work.

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SEA HEDGEHOG RED-GREEN

RED-GREEN SEA HURCHINE (Sphaerechinus granularis) This species, distributed mainly in the littoral zone, is very beautiful. Its large shell, up to 13 cm in diameter, is purple in color, with lighter zones on the ambulacra and a greenish apical field. The shell has violet or purple needles with white tips. The hedgehog often climbs into crevices between rocks, but never makes holes himself. Like many shallow-water animals, it often covers itself with pieces of algae, shells or other objects. Usually it slowly crawls among algae thickets, feeding on them. Sometimes it collects detritus with small organisms in it. Its poisonous globiferous pedicellariae are a protective device against the attack of its main enemies - starfish. The hedgehog manages to escape if only one star attacks, but if several predators attack simultaneously, even poisonous pedicellariae cannot save it.

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TRIPNEUS

TRIPNEUS (Tripneustes ventricosus) Fishermen of the island of Martinique catch it on the coral reefs bordering 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 on the shore are opened, the caviar is removed from the shell and boiled in a cauldron over low heat until it looks like a thick mass the color of beeswax, after which it is again placed in the cleaned shells of the hedgehogs. Hedgehog shells with boiled caviar are sold by peddlers individually. Every year the Creole population consumes such a large number of hedgehogs that in some places on the island their shells form entire mountains.

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SEA HEDGEHOG

SEA HEDGEHOG (Psammechinus miliaris) It can be found along the European coast of the Atlantic Ocean from Norway to Morocco. It is quite common on oyster banks and surf areas. Strong waves are not scary for him, since with the help of rough short needles he makes a depression in the ground, where he hides. The diameter of its shell is no 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 where this hedgehog lived in an aquarium for three years. When feeding in captivity, food is placed directly on the animal's shell, then it quickly begins to move it into the mouth with the help of legs and needles.

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SEA ROCK HEDGEHOG

The SEA ROCK URCHINE (Paracentrotus lividus), distributed from the coast of Great Britain to Africa, including the Mediterranean Sea, is the most famous rock borer. It often forms huge accumulations on sloping rocky surfaces and in thickets of sea grass. It can be found from the littoral zone to a depth of 30 m. It is curious that the Mediterranean race of these hedgehogs is somewhat different in behavior from the behavior of the Atlantic race. Thus, individuals living in the Atlantic Ocean settle in rock cavities made by them with the help of needles and teeth. On the contrary, in the Mediterranean Sea they never drill into 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 find themselves walled up in shelters, since the diameter of the entrance to the burrow becomes smaller than the diameter of the urchin's body. Fleeing from the waves, a small hedgehog makes a shelter for itself in a rock and remains there for a long time. His body grows, he expands the depression around himself, but the entrance to it remains the same, and after a while the hedgehog becomes a prisoner of his home, feeding only on what the waves bring him into the hole. These urchins are herbivores; 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. Reproducts are swept into the water in small portions during the summer. This hedgehog is dangerous for many animals. Its pedacellariae are poisonous. An extract of 30 pedicellariae quickly killed a crab 4-5 cm long. However, other echinoderms, as well as humans, turned out to be immune to this poison. Rock sea urchin caviar is eaten. Its main fishery is carried out in the Mediterranean Sea.

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SEA HEDGEHOG EDIBLE

EDICABLE SEA HURDOSH (Echinus esсulentus) is caught off the coast of Portugal, in some areas of Great Britain, and 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 zone to a depth of 40 m, less often to 100 m, but there are known cases of its presence at a depth of 1200 m. The appearance of this hedgehog is very beautiful. 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 pedicellariae, with the help of which the animal keeps the shell clean and also obtains food for itself. This hedgehog is omnivorous. Its 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, it can sit for a long time at the bottom of the aquarium, stretching upward a whole forest of ambulacral legs. With the help of legs, spines and pedicellaria, it delivers food to the mouth. It is curious that when moving, this hedgehog often uses the teeth of an Aristotelian lantern. In this case, the teeth plunge into the substrate, close and lift the hedgehog, then it moves forward with the help of needles. Moving on ambulacral legs, it can walk 15 cm in 1 minute.

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HETEROCENTROTHUS

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

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COLOCENTROTHUS

COLOBOCENTROTUS (Colobocentrotus atratus) has adapted well to life in the strong surf. Its shell is low, oval, armed with short polygonal needles. Along the edge of the oral side there are spade-shaped needles. The flat oral surface of the shell, together with the shovel-shaped marginal spines directed obliquely downwards and numerous ambulacral legs, creates 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 spines, perfectly resists the action of waves. This hedgehog feeds on various organisms living next to it, for example calcareous algae. The commensal of this hedgehog can be considered the planarian Ceratoplana colobocentroti, which hides under its shell to stay in the surf. Its companions include the small crab Proechinoecus dimorphicus and one species of mollusk.

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HEART-SHAPED SEA HURCHINE

The heart-shaped sea urchin (Echinocardium cordatum) lives in temperate latitudes of the Atlantic and Pacific oceans from the littoral zone to a depth of 230 m. This hedgehog lives burrowing into sandy soil, where it makes passages, strengthening their walls with mucous secretions. It burrows into the ground with the help of lateral spines 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 a water cycle in the burrow, fresh water containing oxygen necessary for respiration enters it. The animal's brush-shaped front legs are strongly extended and protrude out through a vertical passage (tube). The sticky outgrowths of these legs quite quickly collect the required amount of food from the surface of the ground and, retracting back into the burrow, transfer food particles to the needles on the upper lip, which direct them into the mouth. At the same time, the hind legs extend a few centimeters back into the posterior tube and facilitate better removal of excrement. Hedgehogs crawl slowly in the ground in search of food, pushing off with paddle-shaped abdominal spines. In this case, the rear 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 tidal waves.

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HEART-SHAPED SEA URCHINE PURPLE

HEART-SHAPED PURPLE SEA URCHINE (Spatangus purpureus) does not make very deep moves. It often lives on a broken shell and goes deep only 5 cm from the surface, and does not construct a breathing 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 is found up to a depth of 900 m. This hedgehog reproduces in the summer months, like most of its fellows, laying eggs in the water, where they go through the larval stage of echinopluteus, characterized by a long posterior process.

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Sea stars (Asteroidea)

http://www.floranimal.ru

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ACANTASTER

ACANTHASTER (Acanthaster planci) or crown of thorns, a large star, 40-50 cm in diameter, is often found on 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-rayed structure typical of most stars, and the number of rays increases only as the star grows. Acantaster 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 spear tip . For its shape, abundance and sharpness of thorns, 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. Acantaster feeds on coral polyps. The stars crawl among the reefs, leaving behind a white stripe of calcareous coral skeletons with their soft tissues completely eaten away. The variable coloration of the crown of thorns camouflages it well among the bright and varied colors of the coral reef, and the star is not easy to notice at first glance. The crown of thorns is notorious among the inhabitants of many tropical islands. It is impossible to pick it up without receiving stinging injections from sharp needles. Pearl collectors on Tongarewa Atoll in the central Pacific Ocean often have to deal with these stars. The 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 someone who has received such a wound should immediately use a stick to turn the star over with its mouth side up and press its foot to its mouth. They claim that the star attaches itself to the leg with force and sucks out needle fragments and poison, after which the wounds quickly heal. In the 60s In our century, on many coral reefs of the islands of the western Pacific Ocean, catastrophic increases in the number of Acantasters were discovered, which led in a number of places to the local destruction of coral reefs. Concerns arose for the fate of some islands, since the living coral reefs that served them as protection from ocean waves began to collapse after the death of the corals. It was necessary to develop urgent measures to combat the acanthaster. The most effective way to destroy stars was by injecting formaldehyde into the star's body 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 die out (their reasons are not yet fully understood). In the same way, to date, the number of acanthasters has decreased everywhere to the usual norm, and in the areas of coral reefs destroyed by them, restoration and growth of corals has begun.

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ANZEROPODA

Anseropoda (Anseropoda placenta) is distributed along the Atlantic coast of Western Europe and in the Mediterranean Sea. Anseropod is a star burrowing into the sand, about 10 cm in diameter, distinguished by an extremely flattened body, the pale pink or bluish surface of which is completely covered with bunches of very small needles. The texture of the surface and the insignificant thickness of the anseropod's body resembles a wafer. Its body is so thin that the upper and lower sides seem to be pressed tightly against each other, without room for any internal cavities. Nevertheless, the anzeropod manages to swallow whole small crabs and hermit crabs, as well as small mollusks and echinoderms.

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PATIRIA GREBESHKOVA

PATIRIA pectinifera, having the appearance of a regular pentagon, an exceptionally impressively colored small star is common in the littoral zone of the Sea of ​​​​Japan. The upper side of this star has bright orange spots scattered against a background of rich pure blue, while the oral side is a uniform fawn color.

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CULTITA NEW GUINEA

NEW GUINEA CULCITA (Culcita novaeguineae) looks like a small pillow. Cultsita is remarkable not only for its unusual shape for stars, but also because in its body cavity a small so-called pearl fish, Carapus, also known under the older name Fieraster, is sometimes found. Karapus usually stays close to some sea cucumbers and, in case of danger, uses their aquatic lungs as a temporary shelter. Apparently, the carp penetrates the culcite when, in case of danger, its usual host is not nearby. But the carp can probably penetrate into the body cavity of a star only by crawling through its mouth into its stomach and then drilling through its wall. It is not yet known whether the fish will be able to escape from such an unusual shelter again.

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LINCIA (Linckia laevigata) Very common in tropical shallow waters of the Pacific and Indian Oceans. It is a bright blue star with five long, almost cylindrical arms. This star and other species of the genus Linckia are very characterized by a special type of asexual reproduction that is not found in other stars. Linkia have the ability to periodically autotomize, that is, spontaneously break off their rays. This process begins with the separation of skeletal plates from each other, most often at a certain distance from the disk. Then the separated part of the arm begins to crawl away from the mother, while still connected to it by soft tissues and skin. Over the course of three to four hours, these tissues stretch more and more (sometimes up to 5 cm) and finally rupture, after which the severed arm begins an independent life. After some time, a new star begins to develop at the site of the break in such an arm, as a result of which the so-called cometary shape of a star is first formed with a group of tiny rays at the end of a single large arm. Subsequently, new rays grow and the star acquires a normal appearance. The mother star grows a new one in place of the severed arm. In places where links are numerous, both comet stars and stars that regenerate one or more arms are often found. If the tip of an autotomized hand is also cut off, sometimes regeneration can begin at both ends and thus two young stars can form, connected by a thick section of the mother's hand.

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ASTERIAS

ASTERIAS (Asterias forbesi) has been studied in the most detail and comprehensively, and therefore, using the description of this starfish, one can trace the life of the most typical sea stars. Asterias is a small five-rayed star, the distance between the ends of the opposite rays usually does not exceed 20 cm, but most often stars with a diameter of about 10 cm are 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 living ones, especially sick ones or those entangled in a net. When there is a lack of food in Asterias, cases of cannibalism have also been noted - larger stars eat smaller individuals of their species. Asterias causes great harm to oyster farms. Therefore, American scientists P. Galtsov and V. Luzanov specially 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 every day. At the same time, A. forbesi is very prolific and, under favorable conditions, reproduces in enormous quantities, literally devastating and ruining oyster beds. In the 20s last century, starfish annually destroyed an average of 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 amounting to 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. Stars of both sexes raise their bodies above the bottom at the ends of their rays and sweep their reproductive products into the water through paired holes at the base of each ray. The remnants of the gonads degenerate after the release of reproductive products; in the fall, the formation of new gonads begins, which grow rapidly and by the beginning of next summer are again filled with mature eggs and sperm. The larvae, after three to four weeks of free existence in the water, settle and turn into tiny stars with a diameter of about 1 mm, which soon begin to feed on the young mollusks and other animals that have recently settled to the bottom. Young stars eat each other, as a result of which their numbers greatly decrease in the first month after settling. During their life in plankton, larvae do not travel far from the place where eggs are laid, and the most massive settling of juveniles usually occurs precisely where adult stars are especially numerous.

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ASTROMETHIS

ASTROMETIS (Astrometis sertulifera) prefers to settle in places protected from bright light. This small five-rayed 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 seated with numerous spines 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 pedicellariae, and larger single pedicellariae are scattered over the surface of the body. According to Jennings' observations, 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 pedicellariae begin to open and close their forceps until they manage to grab the animal that caused the irritation or a foreign particle that has landed on the skin. Pedicellariae can keep captured small crustaceans without releasing them for more than two days. The pedicellariae hold everything they grasp so firmly that it is possible, for example, to lift a star out of the water by the pedicellariae grasping the hairs on the skin of the hand.

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PIZASTER

PISASTER (Pisaster brevispinus) Very interesting observations were made over this large predatory five-rayed star. Crawling along the bottom, this star unmistakably stops over the place where one of the mollusks from the genera Saxidomus and Protothaca is located. After this, the star begins to tear up the soil, throwing sand and small pebbles up to 2 cm in size with its legs. 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 ends up in the very center of the hole, just opposite the star’s mouth, the star sticks to the top with its legs located near the mouth 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 their feeding patterns and associated behavior. Thus, pizasters, living off the coast of California, eat mainly flat urchins of the genus Dendraster, and further north, in the Puget Sound, they crawl among the settlements of these urchins, not paying attention to them, and feed on mollusks, digging them up, as described above. Accordingly, the reaction of Dendraster in both regions to the proximity of this star is different. California hedgehogs immediately begin to bury themselves in the sand when a dangerous star creeps near them, and hedgehogs from Puget Sound do not react to stars even at a distance of several centimeters and begin to bury themselves only when disturbed by a star accidentally creeping towards them. Many other animals also develop defensive reactions to the touch or proximity of predatory stars. Mostly this is a reaction to escape from the star. X. Feder very colorfully describes such a reaction in the large gastropod mollusk abalone (Haliotis). Upon contact with the pizazster, the mollusk lifts the shell on its thick leg and begins to rapidly turn it 180° in one direction or the other. Having freed itself with such shaking movements from the star’s legs attached to the shell, the mollusk turns and crawls away from the predator in a “gait resembling a gallop.” At the same time, its leg sharply contracts and extends, producing movements more characteristic of a leech or a moth caterpillar than a large snail. Gastropod limpets (Astaea) react in a similar way to predatory stars.

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PYKNOPODIA

PYKNOPODIA (Rusnopodia helianthoides) living on rocky areas of the bottom covered with thickets of brown algae off the northeastern coast of the Pacific Ocean from California to the Aleutian Islands is a real giant among starfish. This star has virtually no dorsal skeleton, and its numerous rays are extremely flexible and mobile. The largest stars reach 80 cm in diameter and a mass of 4.5 kg. When such a star crawls, spreading its two dozen 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 clusters of pedicellaria are scattered. The well-known expert on sea stars, 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 sea cucumbers and eats dead or weakened fish. She catches the latter 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 ever observed. As this star crawls quickly with its thousands of writhing legs, it makes an imposing impression, and its numerous pom-poms of tenacious pedicellariae and its wide, flexible 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. Pycnopodia swallows large sea urchins Strongylocentrotus whole, and after some time throws out the clean shell of the urchin, devoid of spines. After a battle with a sea urchin, the legs of the pycnopodia are abundantly planted with pedicellariae of the urchin, which stand out clearly with their purple color against the light yellow background of the legs. Sometimes pycnopodia even fall into the fishing rods of fishermen, grabbing bait from fish or shellfish meat.” Pycnopodia is interesting not only because of its large size and predatory mode 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 star, which soon grows a sixth ray, 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 can eventually reach 24. Bilateral symmetry also appears in the physiology of the star. The pycnopodia usually moves by directing forward the same specific rays, and uses these same rays primarily to turn over into a normal position if it is placed with its mouth side up.

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EVASTERIAS

EVASTERIAS (Evasterias troschelii) Using this star as an example, the way in which starfish manage to open bivalves and eat them has been well studied. Euasterias lives in shallow waters off the Pacific coast of North America. The locking muscle of bivalves of the genus Protothaca was cut, and then their valves were tightened with a rubber belt, which was a kind of dynamometer. By 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. In this case, the star only needs to open the doors a little. Even into a gap a few tenths of a millimeter wide, she is able to insert her stomach, which stretches like rubber. In mussels, at the point where the thin byssal threads emerge from the shell, with which the mollusk is attached to the substrate, there is an unclosable gap about 0.1 mm wide. To push its stomach inside the shell, such an insignificant hole is enough for the star, and in order to feast on the mussel, it does not even have to waste effort on opening the shell. To find out how long a star can stretch its outward-turned stomach, the stars were offered mussels placed inside plastic tubes at different distances from their ends. It turned out that the star is capable of destroying a mussel located 10 cm from the hole, extending its stomach to a distance equal to half the length of the beam, and in some cases to its entire length. It has not yet been definitively clarified whether elasterias secrete any substances that are toxic to mollusks and cause relaxation of the locking muscle. For a number of species, it has been proven that the star opens the shell only through mechanical force. But it is possible that some stars use both methods simultaneously.

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BLOOD STAR

BLOOD STAR (Henricia sanguinolenta), named for its rich red color, is common in the Arctic and North Atlantic Ocean. This star feeds exclusively on various types of sea sponges. At the same time, she can recognize through chemoreception the types of sponges she prefers, even while being at a considerable distance from them.