Sea Stars Of The Pacific North West

Class Asteroidea
Order Forcipulatida
Family Asteriidae

PURPLE STAR

Pisaster ochraceus

Identification:
5 stiff arms with arched disc. Aboral surface very rough, with spiny ridges. Purple, ochre or brown. To 50 cm (20 in) across.

Range:
Prince William Sound, Alaska to Baja California; intertidal to 97 m (320 ft).
Notes:
This is the most conspicuous star in the PNW intertidal. It feeds on mussels, barnacles, snails and limpets. It is well adapted to desiccation, but retreats to damp crevices to avoid exposure when the tide is out. Specimens from sheltered waters are usually purple but those found on exposed coasts are more often ochre or brown. This is believed to be due to the different types of food they eat.
This species is often host to an internal parasite that infests the male gonad and stops sperm production. The parasite was first observed here in 1988 and was previously endemic to the North Atlantic.