Pisaster ochraceus is the most common, large intertidal sea star in the western United States and it occurs in great numbers on mussel beds on exposed coasts.
An adult P. ochraceus has tube feet which they use for slowly moving over the substrate and for handling prey. P. ochraceus feeds on mussels, chitons, and limpets, which they slowly pry open and devour. Snails, barnacles, echinoids, even decapod crustacea are also eaten. P. ochraceus everts its stomach over the prey if it is too large to be swallowed whole, and digests the prey before swallowing it. Its role as a keystone species has been well studied. In intertidal areas of Washington, when it was removed, the diversity of species in the area decreased.
P. ochraceus is mainly dioecious. The male gametes develop, but later only females ones are produced. During a transitional period, both eggs and sperm are produced. There are several pelagic larval stages. Eventually, the larva attaches itself to the substratum and undergoes metamorphosis to the five-armed adult. Adults continue growing and the rate of growth is dependent on its food supply.
Excerpted from: Pisaster ochraceus