Brittle stars are echinoderms (class Ophiuroidea) which are closely related to sea stars (starfish). They possess radial symmetry with a central body disc from which five highly flexible snake-like arms protrude. There is no replication of internal organs,as in the arms of sea stars, just one set in the central disk. Compared to starfish, brittle stars have a much smaller central disc and no anus. Wastes are eliminated through the mouth, which is situated on the undersideof the disc. The name is derived from their arms breaking off as a means of defense. New arms are easily regenerated. They are also called serpent stars because of the snakelike movements of the five arms.