Diet
Most species are generalist predators, eating mollusks such as clams, oysters, some snails, or any other animal too slow to evade their attack (e.g. other echinoderms, or dying fish). Some species are detritivores, eating decomposing animal and plant material or organic films attached to substrates. Others such as members of the order Brisingida feed on sponges or plankton and suspended organic particles. The crown-of-thorns starfish consumes coral polyps and is part of the food chain on reefs. Occasionally, unexplained explosive outbreaks of these starfish occur and may cause major damage to coral reef ecosystems.
The processes of feeding and capture may be aided by special parts; Pisaster brevispinus, the short-spined pisaster from the West Coast of America may use a set of specialized tube feet to dig itself deep into the soft substrata to extract prey (usually clams). Grasping the shellfish, the starfish slowly pries open the prey's shell by wearing out its adductor muscle, and then inserts its everted stomach into an opening to devour the soft tissues. The gap between the valves need only be a fraction of a millimetre wide for the stomach to gain entry.
Read more about this topic: Starfish
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