role in ecosystem

Morgan Hunt
Science A
April 29, 2009
Asteroidea
For the most part, asteroids are scavengers and carnivores. They eat slow moving prey, feeding on anything that is too slow to escape. They feed on sponges, shellfish, crabs, corals, worms, and even on other echinoderms.They obtain their prey by grasping it, turning their stomach inside out, and releasing secreting primary enzymes on the prey. The prey’s tissues are broken down by the enzymes, and then the asteroid sucks up the broken down tissues.
There is another form of eating, other than breaking down their prey with their stomach enzymes, it is called suspension feeding. This means that they filter prey and food particles from the water. Sometimes plankton and organic detritus sticks to mucus on the body surface. These are then moved by cilia to the mouth.
The Crown of Thorns Starfish generally feeds at night, known for eating hard coral. It is capable of eating an estimated 3.1 mi2 of coral per year, however, it can go 6 months without eating.
Although they have food preferences, they often change due to the availability of prey, which can change geographically and seasonally.
Asteroids are becoming a problem for coral reefs, because some asteroids, such as Acanthaster planci, have increased in population and have damaged coral reefs as a result of their feeding.

"Asteroidea (Sea Stars)." Grzimek's Animal Life Encyclopedia. The Gale Group, Inc, 2005. Answers.com 29 Apr. 2009. http://www.answers.com/topic/asteroidea-sea-stars-biological-family
Mulcrone, R. 2005. "Asteroidea" (On-line), Animal Diversity Web. Accessed April 29, 2008 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Asteroidea.html.