Sea Stars

Starfish, or Sea Stars are not actually fish but echinoderms, like their cousins sand dollars and sea urchins. Many echinoderm species can use asexual reproduction to multiply, as well as regeneration. These animals, sea stars included, can regenerate tissue, organs, and whole limbs. Some species are even able to grow an entire new body from a single limb. Spread far and wide throughout the world's oceans are nearly 2000 sea star species thriving in a variety of depths and climates; some preferring the warm, shallow water of the tropics while others live deep in the frigid depths. They can not tolerate freshwater though, being strictly saltwater animals.

While most starfish have five arms, some have more, including one that can have up to 40 arms.
For protection from predators the skin of a sea star is calcified and bony, and many species display striking colours to warn off dangers. Starfish regeneration is aided by the fact that the creatures contain most of their vital organs in their arms. Regeneration is not a fast process however; to regrow an arm can take a year or longer. Some sea star species must have an intact main body for regeneration to occur, but several can regrow a complete organism from a one or two intact limbs.

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Most sea stars actually eat outside of their bodies, by using a kind of retractable stomach. They open up clams and oysters using a multitude of suction cup tube-feet to open the shells, whereupon the starfish's stomach emerges from its mouth in the center of the animal. Using its arms to keep the shell open, the stomach goes inside and digests the clam or oyster meal. Once digested, the stomach retracts back inside through the mouth, thereby enabling starfish to eat prey that they could never otherwise fit in their small mouths.

Instead of blood, sea stars pump saltwater through a water-based vascular system, using sift-plates in their tube-feet. As water filters into the tubes it also provides them with the rigidity and strength needed to move and manipulate their prey. The ends of each starfish arm contain a red anae spot, that functions as a simple eye, able to detect changes in light, if little else.