What do starfish eat?
December 16, 2006
Almost anything that moves slower than they do – which is a lot of sea creatures.
Sea stars are successful scavengers and predators. Some attack mollusks, like mussels and oysters, which don’t move, and some feed on dead fish or other carrion. Others take in organisms from seawater.
Sea stars have an interesting feeding behavior. When feeding on a mollusk, such as a clam, oyster or mussel, the sea star slowly climbs onto its prey’s shell. Using its hundreds of tiny tube feet on its underside, it steadily tugs on its prey’s hard exterior. Some species can apply as much as 12 pounds of pressure! When the prey’s shell opens just a crack, the sea star everts its stomach through its mouth and slips it into its prey’s soft interior and the feasting begins.
The mouth of sea stars is on the underside of its body. Around the mouth is a nerve ring, which connects to radial nerves in each arm. Sea stars have no brain, just a simple nervous system which relays impulses from arm to arm. At the tip of each arm are delicate sensors that detect food or chemicals, and a sensitive eyespot that can perceive shadows and light.
The modus operandi of sea stars is slow and steady. Because some mollusks, such as oysters and mussels, anchor themselves in one spot for life, an attack by sea stars on a bed of these animals can be devastating. Another sea star, the voracious crown-of-thorns (Acanthaster planci), which ranges from the Red Sea throughout the Indian and Pacific oceans and to the Pacific coast of Panama, feeds on live coral. In some areas, this voracious predator has completely wiped out coral populations.
In recent years, starfish have been more correctly renamed “sea stars,” because they are echinoderms and related to sand dollars, sea urchins and sea cucumbers.