Starfish are invertebrates, which are called echinoderms (and all fish are vertebrates). There are nearly 2,000 species of sea stars. The dimensions of the sea star can reach 65 cm in diameter. In the sea star disc-shaped body, to which are attached five-ray source. Starfish have the ability to grow a new limb to replace lost. On the inside of the hands of the sea stars have tube feet that allow you to move and attach to rocks or coral. Mouth of the starfish is located on the inner side of the disc. Some species of sea stars turn inside your stomach outward to envelop and digest their prey (which can be used, such as oysters, mussels and a variety of bivalves).