Pisaster ochraceus, generally known as the Purple Sea Star or Ochre Sea Star, is a common starfish found among the waters of the Pacific Ocean.

Morphology

This sea star has five stout rays that range in length from 10 to 25 centimeters (4 to 10 in). The rays are arranged around an ill-defined central disk. While most individuals are purple, they can be orange, orange-ochre, and brown. The aboral surface contains many small spines (ossicles) that are arranged in a netlike or pentagonal pattern on the central disk. The ossicles are no higher than 2 mm.^[1][2] In Pisaster the tube feet have suckers on their distal ends which allow them to attach to the rocky substrate and live in heavily wave-swept areas.^[3]

Similar Species
Two species that can be mistaken as Pisaster ochraceus are Pisaster giganteus, which has blue rings around white or purple spines, and Pisaster brevispinus, which is pink with small white spines. These two species have different aboral spines and coloration which allows one to distinguish between the species. Evasterias troschelii may be confused with Pisaster ochraceus at times as well. It can be distinguished from Pisaster ochraceus because Evasterias troschelii has a smaller disk size and longer, tapering rays which are often thickest a short distance out from the base rather than at the base as in Pisaster ochraceus.^[2]

^{(From Wikipedia.org, June 23 2010)}

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Pisaster ochraceous can be found anywhere from Alaska to Baja California. It is most commonly found in the Northeastern Pacific, being that it is a cold-water species. However, it is common in bays all year. (Banister and Campbell, 1985; Meinkoth, 1981; Multi-Agency Rocky Intertidal Network, 2004)

(From Animal Diversity Web via Encyclopedia of Life, June 23 2010)