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The Pisaster genus lies within the phylum Ecinodermata and the class Asteroidea. It consists of three species: P. giganteus, P. brevispinus, and P. ochraceus. This well-known, robust sea star resides in the harsh intertidal zone of the North American Pacific coast. It has been observed as far north as Sitka, Alaska, and as far south as Ensenada, Mexico, though it is seldom seen in central and southern California (Feder 1959). Though most are reddish brown, some Pisaster are brilliant purple and orange shades, and are frequently collected by admiring tourists and fishermen (Harley et al. 2006). Pisaster and its role in its intertidal community was the initial inspiration for the term “keystone species.” The carnivorous sea star is vital in promoting diversity in its habitat by controlling the competitively dominant population of Mytilus californianus mussels. Without Pisaster, diversity of the community decreases drastically (Fly et al. 2012). Though the mussel is its prey of choice, Pisaster also eats a wide variety of other organisms, including barnacles, snails, and small crabs (Feder 1959). Pisaster reproduces through broadcast spawning and can live for twenty years (Menge 1975).
Feder, H. M. 1959. The Food of the Starfish, Pisaster Ochraceus Along the California Coast. Ecology 40:721–724.
Fly, E. K., C. J. Monaco, S. Pincebourde, and A. Tullis. 2012. The influence of intertidal location and temperature on the metabolic cost of emersion in Pisaster ochraceus. Journal of Experimental Marine Biology and Ecology 422-423:20–28.
Harley, C. D. G., M. S. Pankey, J. P. Wares, R. K. Grosberg, and M. J. Wonham. 2006. Color polymorphism and genetic structure in the sea star Pisaster ochraceus. The Biological bulletin 211:248–62.
Menge, B. a. 1975. Brood or broadcast? The adaptive significance of different reproductive strategies in the two intertidal sea stars Leptasterias hexactis and Pisaster ochraceus. Marine Biology 31:87–100.