Some species may have up to 40 arms.
Colors vary from brilliant scarlets, oranges and purples to mottled rusts and creamy yellows.
Hard, blunt spines, projections of the internal skeleton, cover the upper body surface. Each pincer will snap shut when touched and serves to keep the body free of debris and may help to capture food. The mouth occupies the center of the disk on the underside of the body. The sea star is an extremely aggressive nocturnal carnivore. It has a unique adaptation for consuming shellfish.