Ochre Sea Star, Pisaster ochraceus

The ochre sea star (Pisaster ochraceus), also known as the ochre starfish or the purple sea star, is a species of starfish that is classified within the Asteriidae family. This species can be found in the Pacific Ocean in a range that extends from Santa Barbara Co., California to Prince William Sound in Alaska. This species holds one subspecies, known as Pisaster ochraceus segnis, which can be found in warmer waters that the ochre sea star. Adult individuals prefer a habit in rocky areas at depths of up to 295 feet, while young individuals prefer to hide in rock crevices.

The ochre sea star has an irregular shaped body with five thick arms that range in length between four and ten inches. Although most members of this species are purple, some may be red, brown, orange, or yellow in color. As is typical to sea star species, the ochre sea star is covered in small spines, or ossicles, that reach .2 centimeters in height.  The underside of the arms hold a number of tube feet, which help the species to move, remain attached to substrate, and eat. This species can be confused with Pisaster giganteus or Pisaster brevispinus, although these have differences in coloration.

The ochre sea star can be either male or female, but there is no difference in size, shape, or color between the sexes. The breeding season occurs between the months of May to July in Pudget Sound, but can vary in other regions. This species, like other starfish species, breeds by releasing gametes, or eggs and sperm, into the water at the same time. Once the eggs are fertilized, they undergo many transformations while in the water column, eventually falling to the sea floor and changing into young sea stars once they are large enough. Although most sea stars only live between four to six years, this species can live as long as twenty years.

The ochre sea star consumes many species including plankton when in the larval form and snails, limpets, barnacles, chitons, and other species. If the chosen pray has a protective shell, the sea star will use its tube feet to pry open the shell and consume the creature within. The species is known to be a keystone species due its preference for mollusks, which can be harmful to the sea star’s habitat in high numbers.

Image Caption: Ochre sea star (Pisaster ochraceus) taken at Ganges Harbour, Salt Spring Island, British Columbia. Credit: D. Gordon E. Robertson/Wikipedia (CC BY-SA 3.0)