Ochre Starfish, Pisaster ochraceous

Ochre Starfish, Pisaster ochraceous. Starfish collected in coastal waters off Bandon, Oregon,  August 2009. Pictured stars wingspan: 25 cm (10 inches).

Ochre Starfish , Pisaster ochraceous. Underwater photographs taken in coastal waters off  Bremmerton, Washington. September 2023. Photographs and identifications courtesy of Bob Hillis, Ivins, Utah.

Phylogeny:  The Ochre Starfish, Pisaster ochraceus (Brandt, 1835), is a member of the Asteriidae family of Sea Stars. The genus Pisaster is one of thirty-nine genera in this family. There are three species in this genus, all of which are found along the Pacific Coast of North American. They are also known as  the  Ochre Stars and the Purple Starfish and in Mexico as Estrella Ocre.

Morphology:  Ochre Starfish have a central disk and, normally, five arms, though this can vary from four to seven. The arms are fairly thick in build, with a wide attachment point at the disk. The arms taper to rounded points.  The disk contains most of the organs, with the mouth on the ventral side and the anus and madreporite (entry plate for the water vascular system) on the dorsal surface. They have crossed pedicellariae (tiny pincers) on their dorsal surface, as well as small white spines that form a net-like pattern on the arms and a star shape on the central disk. The tube feet have suckers. These sea stars have a mesh-like aboral skeleton. The aboral (top) surface may be purple, yellow, orange, or reddish brown in color.  Ochre Stars reach a maximum of 50 cm (19 inches) in diameter.

Habitat and Distribution: Ochre Starfish are found on rocks, usually in areas exposed to surf and surge. They live intertidally and can be found at  depths up to 97 m (318 feet). Ochre Stars are a temperate Eastern Pacific species. In Mexican waters they have a very limited range being found along the west coast of the Baja peninsula south to Cedros Island, Baja California.

Diet: Adult Ochre Starfish are predators which consume barnacles, bivalves, chitons, crustaceans, gastropods and other sea stars. They are capable of everting their stomach over the prey if it is too large to be swallowed whole. They then digest the prey before swallowing it. At the larval stage, Ochre Starfish are filter feeders that consume plankton.

Predators:  Predation of adult Ochre Stars is limited to Sea Gulls and Sea Otters.

Reproduction:  Ochre Starfish are gonochoric (male or female for life). They can reproduce asexually, through regeneration, or sexually through broadcast spawning, with external fertilization. The eggs hatch into planktonic larva. The larvae start life in a bilaterally symmetrical form and in adulthood gain their radial symmetry. They are in their larval form for 3 to 4 weeks before beginning their benthic life.

Ecosystem Interactions:  Ochre Starfish play an important role in increasing biodiversity in an area. They do this by consuming mussels, which would otherwise outcompete other plant and animal species. Throughout much of their range Ochre Starfish have been significantly impacted by Sea Star Wasting Disease. Sea Star Wasting Disease is poorly understood. Studies showing it was caused by a densovirus have been discredited.  The disease seems to work more quickly in warmer water temperatures, but cold water environments have still been impacted. The disease could possibly be exacerbated by warmer sea temperatures, but the evidence is insufficient to blame the “Climate Crisis”. The cause is still not understood. Populations are recovering slowly in some areas.

Human Interactions: Ochre Starfish have a limited direct impact on human activities. Historically they were heavily collected to be dried and sold as curios. Fortunately, this practice has diminished. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.

Synonyms: Asteracanthion margaritifer, Asterias conferta, Asterias fissispina, Asterias ianthina, Asterias janthina, Asterias margaritafera, Asterias ochracea, Pisaster confertus, Pisaster fissispinus, Pisaster ochraceus ochraceus, Pisaster ochraceus segnis, and Pisaster ochraceus var. nodiferus.