Mysterious animal - Starfish. First of all, STAR. Where else can you find such a natural configuration? Secondly, for some reason it initially seemed to me that it was some kind of algae or coral. Look at the variety and beauty of these stars! However, check out the video below to see how they feed.
1. Starfish are veterans of the seabed; they appeared more than 450 million years ago, ahead of many forms of modern inhabitants of the underwater depths.
2. They belong to the class Echinoderms, being relatives of sea cucumbers, brittle stars, sea lilies, sea cucumbers, sea urchins - currently there are about 1600 species of them, having a star-shaped or pentagonal shape.
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4. The starfish, despite its inactivity and the absence of a head as such, has a well-developed nervous and digestive system. Why, exactly, “echinoderms”? It's all about the hard skin of the starfish - on the outside it is covered with short needles or spines. Conventionally, these bizarre creatures can be divided into three groups: ordinary starfish; feather stars, named for their writhing rays (up to 50!), and “fragile” stars that cast off their rays in case of danger.
5. True, it will not be difficult for this animal to grow new ones, and new stars will soon appear from each ray. How is this possible? - Due to the characteristic feature of the star’s structure, each of its rays is structured in the same way, and contains: two digestive outgrowths of the stomach, performing the function of the liver, a red eyespot at the tip of the ray, protected by a ring of needles, radial bundles of nerves, olfactory organs (they are also suckers and a method of movement), papules located in a groove on the ventral side - skin gills in the form of thin short villi, processes of the genital organs located on the back and producing gas exchange (usually two gonads on each ray), a skeleton consisting of a longitudinal row of vertebrae inside, and hundreds of calcareous plates with spines, covering the skin and connected by muscles, which not only protects the animal from damage, but also makes its rays very flexible. The bodies of starfish are 80% calcium carbonate.
6. Thus, each ray of a starfish, once separated from its body, is completely viable and quickly regenerates. Well, connected together, the rays form closed systems in the center of the animal: the digestive system passes into the stomach from two sections and opens with a button-shaped disk, which serves as the mouth; bundles of nerves unite into a nerve ring. The main system of the starfish, which we deliberately left “for dessert,” is the ambulacral system. This is the name given to the water-vascular system, which serves the echinoderm simultaneously for respiration, excretion, touch and movement, together with the muscles providing musculoskeletal function. Canals extend from the perioral ring into each ray, from which, in turn, lateral branches lead to hundreds of cylindrical tubes on the surface of the body - ambulacral legs containing special ampoules and ending with suction cups. An opening on the back, called the mandreoporous plate, serves to connect this system to the external aquatic environment.
7. So how does the ambulacral system work? – It is filled with water under slight pressure, which, entering through the mandreoporous plate into the perioral canal, is divided into five ray channels and fills the ampoules at the base of the legs. Their compression, in turn, fills the legs with water and stretches them. In this case, the suckers of the legs attach to various objects of the seabed, and then sharply contract, the ambulacral legs are shortened, and thus the animal’s body moves in smooth jerks.
8. Starfish are voracious predators, although there are exceptions in the form of herbivorous species that feed on algae and plankton. In general, the favorite delicacies of these animals are clams, mussels, oysters, scallops, littorinas, barnacles, reef-forming corals and various invertebrates. The star finds prey by smell. Having discovered a mollusk, it attaches itself with two rays to one shell valve, and the remaining three to the other valve, and a many-hour struggle begins, which the starfish always wins. When the mollusk gets tired and the doors of its home become pliable, the predator opens them and literally throws its stomach onto the victim, turning it outward! By the way, food digestion occurs outside the animal’s body. Some starfish are even capable of digging out prey hiding in the sand.
9. As for reproduction, most starfish are divided into males and females. Fertilization occurs in water, after which free-swimming larvae called brachiolaria are formed. Unlike adult individuals, their structure is subject to the laws of symmetry, and includes a ciliary cord necessary for collecting food particles (exclusively unicellular planktonic algae), a stomach, esophagus and hind intestine. Usually the larvae swim near an adult sea star of the same species - and after several weeks, under the influence of its pheromones, they undergo metamorphosis: having fixed themselves on the bottom, they turn into tiny (0.5 mm in diameter), but already five-linked sea stars. But these babies will be able to give birth only after two or three years. If the larvae serve as species dispersers and drift long distances, they are able to delay their transformation into adults and not settle to the bottom for several months - and they can grow up to nine cm in length. Among the starfish there are also hermaphrodites - they carry their young in a special brood pouch or cavities on their backs.
10. Taking into account the large number of starfish, it is clear that they also influence the growth of populations of species that are hunted. Nobody risks hunting them, since their bodies contain extremely toxic substances - asteriosaponins. Being virtually invulnerable, starfish are at the top of the marine food pyramid and can therefore have a lifespan of up to 30 years. If you believe scientists, then these brightly colored legendary inhabitants of the seas also make a significant contribution to the process of recycling carbon dioxide, including those produced by industrial facilities on the planet - their share is about 2% of CO2, that is, more than 0.1 gigatons of carbon per year , which for such seemingly small creatures, you see, is not at all weak!
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25. Lavender starfish. This absolutely incredible colored starfish lives on the reefs of Bunaken Island in Sulawesi, Indonesia.
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27. Deltoid starfish. A delta starfish between emerald corals in the western Pacific Ocean.
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