Body Parts of a Starfish

Starfish, which are sometimes referred to as sea stars, are members of the animal kingdom's phylum Echinodermata in the Asteroidea class. With more than 1,600 different species of starfish, it's no surprise that they vary widely in appearance, size and color. In fact, according to "The Gale Encyclopedia of Science," starfish sizes may range anywhere from .5 inches to 3 feet in diameter. Each body part of a starfish serves survival functions.

  1. Skin

    • The thick skin covering the starfish is comprised of bony plates and spines. Stalks containing tiny pincers keep debris from gathering on the skin. The gills of the starfish can be found in folds of skin located between the tiny bumps of the skin. The skin also contains chemoreceptors, which provide the starfish with its sense of smell. Chemoreceptors enable the starfish to smell the faintest scent of its prey, which is typically clams, and determine the direction the smell is coming from.

    Arms

    • The symmetrical shape of starfish enable them to possess anywhere from five to 50 arms, which extend from a disk-shaped center of the starfish body. The eyes of the starfish are located at the end of each arm. They have primitive vision capable of only detecting changes in lighting. An injured or broken arm will regenerate and a whole starfish may regenerate from an arm and a tiny bit of the central disk.

    Tube Feet

    • The bottom of each of arm is lined with tiny tube-shaped feet, which enable the starfish to move around. Water is drawn in and released out of the foot to create a suctioning process that allows mobility. The suctioning power of the tube feet is strong and enables the starfish to cling to rocks during storms. The feet are also used for catching and killing clams. They will suction their feet onto the shell and pull for hours or days if necessary to open and extract the clam.

    Mouth

    • The mouth of the starfish is located on the underside of the disc, at the center of the starfish's body. One of the starfish's two stomachs protrudes from the mouth and releases digestive enzymes onto its prey. The enzymes liquefy the prey so the starfish, which does not have teeth, can ingest it.