There are approximately 1800 different species of the common starfish, none of which can be classified as fish, despite their name. This star-shaped carnivorous animal is usually a dull yellow or orange, but can also be brightly colored. As a natural defense mechanism, the starfish is able to change its body color to hide or escape from predators. The arms of the starfish are used for movement, catching prey and digestion. Unlike other animals, the starfish is able to grow a new arm if one is lost.
Many starfish have five arms, but there are some deep-water species that carry more than fifty.
The starfish's arms surround a small disc-like body, which houses a mouth in the center of the underside of the body. The starfish is capable of making itself surprisingly rigid through the use of skeletal plates that are imbedded in their flesh. Blunt spines project from these plates. By making itself rigid, the starfish is able to protect himself from being eaten, handled or moved by protracting these spines. In addition, some starfish are covered with an organ called, pedicellariae.