Starfish Ecology

The well-known species of starfish tend to be generalist predators, eating pretty much anything that's too slow to escape. Many prey heavily on bivalves (mussels, clams, and oysters). Some species are more specialized, such as Henricia, which feeds on sponges, or the infamous crown-of-thorns (Acanthaster planci) which feeds on coral. Some groups, like the Brisingids, are adapted for suspension feeding (trapping and eating plankton suspended in the water).

Starfish aren't a major prey item for any species, probably because their highly calcified skin is difficult to eat and not terribly nutritious. However, various species of crustaceans and fish are known to eat them. I don't think any human culture eats starfish, which is really just as well.

Asterias eating mussels. Starfish that eat bivalves can use their tube feet to hang on to the shell while pulling the two halves of the shell apart. As soon as a gap opens, even a small one, they extend their stomach into the shell and digest the mussel inside!

Many starfish share this ability to extend ("evert") their stomach, whether for eating bivalves or in less specialized ways as an alternative to swallowing their food.

Acanthaster planci, or the crown-of-thorns starfish, is well known for eating corals. Under normal circumstances this is simply part of the coral reef food-web, but occasionally huge outbreaks of starfish wreak havok on large regions of reef.

(Picture from NOAA.)
The Brisingid sea stars are adapted for suspension feeding. They have a minimum of six rays, all long and thin, with extremely long tube feet, seen extended here. They live exclusively in the deep sea.


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Last updated May 10, 2000.