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.

Phylogeny: The Tan Sea Star, Phataria unifascialis (Gray, 1840) is a member of the Ophidiasteridae Family of Ophidiasterid Sea Stars.  The genus Phataria is one of twenty-three genera in this family, and there are two species in this genus.  Tan Sea Stars are also known as Polychromatic Sea Stars and in Mexico they as estrella de mar bronceada.

Morphology:  Tan Sea Stars have a small central disc and five long tapering arms that are round in cross section. Their body is stiff with a granulated aboral(dorsal) side. They may be brown, gray, tan or white in color which vary with their diets. They have two irregular, often broken, brown or reddish brown stripes running the length of the arms. Tan Sea Stars reach a maximum of 20 cm (7.9 inches) in diameter.

Habitat and Distribution: The Tan Sea Star is found on and under rocks from the intertidal zone to depths up to 139 m (450 feet). They are usually associated with coralline algae. 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 the Baja Peninsula. They are less abundant in the cold water environments of the northern portions of the Sea of Cortez.

Diet: Tan Sea Stars are primarily herbivores, feeding on algae. Some sources say that they also eat echinoderms, and other small invertebrates.

Predators:  Predation of the Tan Sea Stars has not been documented. Other members of this family are eaten by crabs, fish, gastropods, marine mammals, sea turtles, shrimp and other sea stars. This species is most vulnerable when it is in its larval or juvenile stages. Adults of this species seem to have few predators.

Reproduction: Tan Sea Stars are gonochoric (male or female for life). They  reproduce asexually, by fission, and sexually, through broadcast spawning. Fertilization is external. Embryos hatch into planktonic larvae and later metamorphose into pentamorous juveniles, which develop into young sea stars.

Ecosystem Interactions:  The Tan 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 and sucks fluids from the sea star host.

Human Interactions:  Tan Sea Stars have no direct impact on human activities. 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:  Linkia bifascialis, Linkia unifascialis, Ophidiaster suturalis, and Phataria bifascialis.