Bradley’s Sea Star, Mithrodia bradleyi

Bradley’s Sea Star, Mithrodia bradleyi. Starfish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, November 2015. Wingspan:  22 cm (8.7 inches).

Bradley’s Sea Star, Mithrodia bradleyi. Underwater photograph taken in coastal waters of the greater Los Cabos area, Baja California Sur, May 2018. Photograph courtesy of Bob Hillis, Ivins, Utah.

Bradley’s Sea Star, Mithrodia bradleyi. Underwater photograph taken in Zihuatanejo Bay, Guerrero, March 2020. Photograph courtesy of Ron Woheau, Zihuatanejo.

Phylogeny:  Bradley’s Sea Star, Mithrodia bradleyi, is a member of the Mithrodiidae Family of Mithrodiid Sea Stars that is also known as the Studded Sea Star and in Mexico as Estrella de Mar de Bradley. There are nine global members of the Mithrodia Genus with this species being the only one found in Mexican waters of the Pacific Ocean.

Morphology:  Bradley’s Sea Stars are most easily recognized by irregular short, rubbery skin on their aboral surface, and a relatively small central disk. They may be brown, orange, or whitish in color with orangish to reddish-brown spots, bands, blotches, or spines. They reach a maximum “wing spans” of 35 cm (14 inches).

Habitat and Distribution:  Bradley’s Sea Star is found attached to and under rocks in coastal areas and tide pools from the intertidal zone to depths up to 50 m (165 feet). They consume detritus and small invertebrates. The commensal Sea Star Shrimp, Periclimenes soror, may be found living on the underside of this sea star. Bradley’s Sea Star is a resident of Mexican waters of the Pacific Ocean but they have a limited range being found from Punta Eugenia, Baja California Sur, southward to the Guatemala. In the Sea of Cortez, they range from Isla Angel de la Guarda to the greater Cabo San Lucas area, Baja California Sur.

Behavior:  Under stress, Bradley’s Sea Star can disintegrate rapidly, losing arms at the disk when removed from the water. Bradley’s Sea Star is poorly studied and very little is known about their behavior patterns otherwise.

Human Impact:  Bradley’s Sea Star are sold on a limited basis for use in home aquariums but are generally not suitable, requiring colder water environments in the range 10^oC (50^oF) to 20^oC (68^oF) for survival.

Synonym:  Mithrodia enriquecasoi