Sea stars (Asteroidea)
Sea stars (Asteroidea) – the denizens of the deep, the class of invertebrates such as echinoderms. Starfish being relatives of sea cucumbers, brittle stars, sea lilies, sea cucumbers, sea urchins, – currently there are about 1600 species, having star-shaped or pentagonal shape. The starfish, despite its inactivity and the absence of the head itself, well developed nervous and digestive systems. Why, in fact, “echinoderms”. It’s all in the hard skin of sea stars – from the outside it is covered with short needles or spikes. Conventionally, these whimsical creatures can be divided into three groups: common sea stars, feather stars, known for wriggling rays (up to 50!), and “fragile” stars, casting its beams in case of danger. However, for this animal is not difficult to grow themselves new, and from each beam soon there will be new stars. How is that possible? – Due to the characteristics of the structure of stars – each of its rays made in the same way, and contains: two digestive outgrowth of the stomach, performing the function of the liver red eye spot at the tip of the beam, protected by a ring of needles radial bundles of nerves olfactory organs (they are the same suction cups and method of transportation) located in the groove on the ventral side papules is skin gills in the form of fine short fibers, located on the back and producing the gas exchange processes of genital organs (usually two of gondina each beam) skeleton consisting of a longitudinal series of vertebrae within, and hundreds of calcareous plates with spines, covering the skin and connected with muscle that not only protects the animal from damage, but also makes it very flexible rays. The bodies of starfish are made of 80% calcium carbonate. Thus, each ray of the starfish, being separated from her body, it is a viable and rapidly regenerates.
But, United together, form the rays in the center of the confined animal systems: digestive system goes into a stomach of the two divisions, and opens the disk in the form of buttons, which performs the function of the mouth; the bundles of nerves combine to form nerve ring. The main system of the sea star, which we had deliberately left “for dessert” – ambulacraria. The so-called water-vascular system, echinoderms simultaneously serves for respiration, separation, touch, and movement, along with muscles providing musculoskeletal function. From the circumoral ring in each beam diverging channels, they, in turn, with lateral branches to the hundreds of cylindrical tubes on the surface of the body – legs ambulacral containing special ampoules and ending in suction cups. The hole on the back, called andreopoulos plate, serves to connect this system with the external water environment. So how does ambulacraria system? – It is filled with water under slight pressure, which, entering through andriopoulou plate in the circumoral canal is divided into five channels of rays and fills vials at the base of the feet. Compression, in turn, fills with water legs and stretches them. When the sucker feet are attached to different objects in the seabed, and then sharply reduced,- ambulacral legs are shortened, and thus the body of the animal moves flowing smoothly.
Sea stars are voracious predators, although there are exceptions in the form of a herbivorous species, feeding on algae and plankton. But in General favorite delicacies of these animals are mollusks, mussels, oysters, scallops, pathways lead back into the, sea ducks, reef-building corals and various invertebrates. The star locates prey by smell. Finding the clam, and she sticks two rays to one fold of the shell, the remaining three – to the other flap, and begins long struggle that the starfish always wins. When the clam gets tired and leaves his home to become compliant, the predator opens them and literally throws the victim on his stomach, twisting it out! By the way, digestion and occurs outside the body of the animal. Some sea stars are even able to dig out hiding in the sand extraction. As for reproduction, most starfish are divided into males and females. Fertilization occurs in the water, and then formed free-floating larvae, called brachiolaria. Unlike adults, their structure is subject to the laws of symmetry, and includes ciliated cord, needed to collect food particles (planktonic unicellular algae), activeness, make fat not
to esophagus and posterior intestine. Usually the larvae close to the adult starfish of the same species – and after a few weeks, under the influence of her pheromones, with them is metamorphoses: a foothold on the bottom, they turn into tiny (0.5 mm in diameter), but patisserie starfish. And to produce offspring, these children will only through two-three years.
If the larvae perform the function of settlement types, and drift over large distances, they can delay their transformation into adults and settle to the bottom a few months – they can grow to nine cm in length. There among the sea stars and hermaphrodites – the young they carry in a special bag or pin cavities on the back. Given the large numbers of the starfish, it is clear that they also affect the growth of populations of species that are hunted. They do not risk hunting nobody, because their bodies contain highly toxic substances – asteraspadise. Being almost invulnerable, sea stars are at the top of the marine food pyramid, and therefore their life expectancy can reach 30 years. According to scientists, these brightly colored legendary inhabitants of the seas also contribute to the process of recycling carbon dioxide produced including industrial facilities, planet – their share is about 2% CO2, that is more than 0.1 gigatons of carbon per year, which for such a seemingly small creatures, agree, not weakly! Lavender starfish. This starfish is absolutely incredible painting inhabits the reefs of the Bunaken island in Sulawesi, Indonesia. Deltoid starfish. Deltoid starfish between emerald corals in the Western Pacific.