Tan Sea Star, Phataria unifascialis

Tan Sea Star, Phataria unifascialis. Stars provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, December 2017. Pictured stars wingspan: 20 cm (7.9 inches).

Tan Sea Star, Phataria unifascialis. Underwater photographs taken in Zihuantanejo Bay, Guerrero, December 2020. Photographs courtesy of Ron Woheau, Zihuantanejo.

The Tan Sea Star, Phataria unifascialis (Gray, 1840) is a member of the Ophidiasteridae Family of Ophidiasterid Sea Stars, that is also known as the Polychormatic Sea Star and in Mexico as estrella de mar bronceada. This genus differs from the others of the family Ophidiasteridae by having the papular areas in a longitudinal row or two in the radios, small granules in papular areas and big granules in the abactinal plates. There are two global members of the Phataria Genus with this species being the only one found in Mexican waters of the Pacific Ocean.

Tan Sea Stars have a small central disc and five long tapering arms that are round in cross section with one row of papular and two rows on both sides of the main rows . Their body is stiff with a granulated aboral side. They may be brown, gray, tan or white in color that vary based on diet with two irregular, often broken brown or reddish brown stripes running the length of the armd. Tan Sea Stars reach a maximum of 20 cm (7.9 inches) in diameter.

The Tan Sea Star is found on and under rocks from the intertidal zone to depths up to 50 m (115 feet) associated with coralline algae. They feed on algae, echinoderms, and other small invertebrates. They are capable of reproducing asexually by fission and the majority reproduce by fertilization. This Sea Star and the Pyramid Sea Star, Pharia pyramidata, are sometimes parasitized by the Parasitic Cup Shell, Thyca callista. The cup shell attaches to the underside of the sea star’s arms. They suck fluids from their sea star host.

The Tan Sea Star is a resident of all Mexican waters of the Pacific Ocean with the exception of the coastal waters from Magdalena Bay, Baja California Sur, northward along the central and northwest coasts of Baja. They less abundant in the cold water environments of the northern portions of the Sea of Cortez.

Synonyms include Linkia bifascialis, Ophidiaster suturalis, and Phataria bifascialis.