Class Asteroidea (starfish)

1. Generally a flattened body shape.
2. Adult is radially symetrical while the young is bilateral.
3. Usually 5 ( up to 40 ) arms.
4. Freely mobile.
5. Tube feet for locomotion.
6. Regenerative abilities.

Class Asteroidea is the best known of the Echinoderms and contains 1500 known species. The asteroid body is composed of a central disk surrounded by its radiating arms. The central disk contains the major organs. Ventrally on the starfish are five grooves that all meet in the center to form the mouth. The anus and the madreporite are located on the dorsal surface. Their external dorsal surface bears an assortment of spines and turbercles, that are protective extensions of the dermal skeleton.

• The locomotion of asteroids is accomplished by the specialized tube feet in the arms. These tube feet are small suction cups and are controlled by the water vascular system.
• Asteroids feed primarly on sessile or sedimentary organisms such as small invertebrates and molluscs.

1. Banister, Dr. Keith and Dr. Andrew Campbell. 1985. The Encyclopedia of Aquatic Life. New York: Facts on File.
2. Barnes, R.S.K., Calow, P., Olive, P.J.W. 1988. The Invertebrates: a new synthesis. Oxford: Blackwell Scientific Publicatons.
3. Barth, R. and R. Broshears. 1982. The Invertebrate World. New York: CBS College Publishing.