Giant Spined Starfish, Pisaster giganteus

Giant Spined Starfish, Pisaster giganteus. Underwater photograph taken in coastal waters off Anacapa Island, California, February 2021. Wingspan: 46 cm (18 inches). Photograph and identification courtesy of Bob Hillis, Ivins, Utah.

Phylogeny:  The Giant Spined Star, Pisaster giganteus (Stimpson, 1857), is a member of the Asteriidae Family of Starfish. 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. The Giant Spined Star is also known as the Giant Sea Star and the Knobby Sea Star and in Mexico as estrella espinosa gigante.

Morphology:  Giant Spined Stars are thick bodied with five thick arms. The aboral surface may be dark brown to reddish brown in color, with white or pink spines that are surrounded by blue circles. These blue circles have a perimeter of tiny pedicellariae, which look like brown fuzz. The spines are short and vary in number and pattern. The Giant Spined Star reaches a maximum of 60 cm (23.6 inches) in diameter.

Habitat and Distribution: The Giant Spined Star is found on rocky reefs, and occasionally on sand bottoms. They range from the lower intertidal zone to depths up to 374 m (1227 feet). The Giant Spined Star is a resident of Mexican waters of the Pacific Ocean with the exception that they are absent from from Cedros Island, Baja California, northward along the west coast of Baja California.

Diet:  Giant Spined Stars are predators, feeding on snails, chitons, worm shells, barnacles, limpets, and bivalves, such as the California Mussel Shell, Mytilus californianus.

Predators:  In their larval and juvenile stages, Giant Spined Stars are eaten by crabs, gastropods and nudibranchs. In their adult stage they have few predators with the exception of sea gulls and sea otters.

Reproduction:  Giant Spined Stars  are gonochoric (male or female for life). They reproduce sexually through broadcast spawning, with external fertilization. Giant Spined Stars breed from March through April. 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: The parasitic or commensal relationships between Giant Spined Stars and other species has not been formally documented. Throughout much of their range Giant Spined Stars 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:  Giant Spined Stars have 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:  Asterias capitata, Asterias exquisita, Asterias gigantea, Asterias luetkeni, Calliasterias exquisita, Pisaster capitatus, and Pisaster luetkeni.