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Ochre Sea Star

Other Invertebrates

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The ochre sea star is a five-armed starfish of rocky, wave-battered shores from Prince William Sound in Alaska to central California, usually purple but sometimes orange, yellow, reddish, or brown, with rays 10 to 25 centimeters long gripped to rock by suckered tube feet. It is the textbook keystone species of marine ecology: experiments by zoologist Robert Paine showed that removing it from a shoreline let mussels take over and crowd out other invertebrates, since a single sea star can consume roughly eighty mussels a year by prying open their shells and everting its stomach inside. Individuals can live up to twenty years, and a 2013 wasting-disease outbreak devastated populations that have since been slowly recovering.

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