The ochre seastar is most often found in association with mussel beds where it feeds primarily on mollusks such as the California mussel. This large, often bright1y colored seastar has four color phases: brown, purple, orange and yellow. The numerous spines are short, blunt, and form a net-like pattern on the upper surface, where a small pentagon of spines is usually recognizable in the center disc.

Seastars feed by using their tube feet to attach to mussel shells and exert pressure upon the muscles that hold the shell together. After the shell is forced apart, the seastar stomach is everted into the opening and the soft parts of the mussel are digested.