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. Diameter 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 coastal waters of the greater Loreto area, Baja California Sur, October 2024. 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 Verrill, 1867 is a member of the Mithrodiidae Family of Mithrodiid Sea Stars. The Mithrodia Genus is one of two genera in the Mithrodiidae Family, and there are three species in the Mitrodia Genus. This species is also known as the Studded Sea Star and in Mexico as Estrella de Mar de Bradley. This species is named in honor of Frank Howe Bradley, an American geologist who collected zoological specimens during his expeditions.
Morphology: Bradley’s Sea Stars are most easily recognized by their long, rubbery, arms and a relatively small central disk. The upper (aboral) surface is covered with short, rounded spines. On the underside, they have wide ambulacral grooves and tube feet with suckers. They may be brown, orange, or whitish in color with orangish to reddish-brown spots, bands, blotches, or spines. They have a reach a maximum of 35 cm (14 inches) in diameter.
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 are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific with the exception that they are absent from north of from Punta Eugenia, Baja California Sur, along the central and northwest coasts of the Baja Peninsula and north of Isla Ángel de la Guarda, Baja California, in the Sea of Cortez.
Diet: Bradley’s Sea Stars are opportunistic omnivores. They consume detritus and small invertebrates.
Predation: Bradley’s Sea Stars are preyed upon by crabs, fish, and shore birds.
Reproduction: Bradley’s Sea Stars are gonochoric (male or female for life). They reproduce sexually, through broadcast spawning, with external fertilization. The fertilized eggs develop into planktonic larvae. They can also reproduce asexually through fragmentation.
Ecosystem Interactions: Bradley’s Sea Star has a commensal relationship with the Sea Star Shrimp, Periclimenes soror, which may be found living on the underside of this sea star. Otherwise, their parasitic, commensal, and symbiotic relationships are poorly documented.
Human Impact: Bradley’s Sea Stars have a very limited impact on human activity. From a conservation perspective they have not been evaluated.
Synonym: Mithrodia enriquecasoi.