The ochre or purple sea star (Pisaster ochraceus) is a commonly encountered starfish on rocky beaches from Baja California to Prince William Sound, Alaska. P. ochraceus is considered an important indicator of the health of intertidal zones.
The ochre sea star feeds on mussels, chitons, limpets, snails, barnacles, and echinoids. P. ochraceus uses its tube feet to handle its prey. If the prey is too large to be swallowed whole, it can use its tube feet taking advantage of hydrostatic pressure to open shells.
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, yellow, reddish, or brown.
The surface furthest from the mouth 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.
Ochre Sea Star Reproduction
Pisasters are dioecious but there is no sexual dimorphism and sexes can be separated only by the presence of eggs or sperm in the gonads. They reproduce by broadcast spawning, which occurs in the Puget Sound around May to July.
There is no parental involvemnt beyond spawning. Fertilization occurs in the water column and Pisaster ochraceous develops through several larval stages. At the larval stage, ochre sea stars are filter feeders and their diet consists of plankton.
- Many sea stars live to a minimal age of four years. P. ochraceus can live as long as twenty years.
- Asteroidea (Sea Stars) is a class of echinoderms.
- There are 2171 species of Sea Stars, in 403 genera and 40 families.
References:
C. D. G. Harley; M. S. Pankey; J. P. Wares; R. K. Grosberg; M. J. Wonham (2006). Color Polymorphism and Genetic Structure in the Sea Star Pisaster ochraceus. The Biological Bulletin. 211 (3): 248–262.
Kozloff, E. N. 1993. Seashore life of the northern Pacific Coast. University of Washington Press, Seattle.
Pisaster ochraceus (Brandt, 1835). Encyclopedia of Life