Gulf Sun Star, Heliaster kubiniji

Gulf Sun Star, Heliaster kubiniji. Sea Star collected from a tidal pool in the greater Los Cabos area, Baja California Sur, January 2009. Wing-span: 15 cm (5.9 inches).

Gulf Sun Star, Heliaster kubiniji. Sea Star collected from a tidal pool within Bahía Concepción, Baja California Sur, March 2020. Photographs courtesy of Barry Mastro, Escondido, California.

Phylogeny:  The Gulf Sun Star, Heliaster kubiniji (Xántu, 1860),  is a member of the Hellasteridae Family of Starfish. The genus Heliaster is the only genus in this family, and there are seven species in this genus. The Gulf Sun Star is also known as the Common Sun Star and the Mexican Sun Star and in Mexico as estrella de mar sol del golfo. The naturalist, Hungarian immigrant, and sometimes charlatan John Xántus named this species after his countryman M. Kubiniji,  the Director of the Hungarian National Museum.

Morphology:  Gulf Sun Stars are circular in outline. Adults have 20 to 25 stout, tapering, arms encircling the disk. Juveniles start with 5 arms and add them as they grow in diameter. These sea stars can be multi-colored, displaying brown, tan, green, and pink on a single individual. Juveniles may also display dark banding. Gulf Sun Stars reach a maximum diameter of 20 cm (7.9 inches).

Habitat and Distribution:  Gulf Sun Stars are found on rocks, boulders, and reefs, from the intertidal zone to a depth of about 37 m (120 feet). Historically, in Mexican waters, this species was found along the entire Pacific coast, with the exception of the west coast of the Baja Peninsula, north of Magdalena Bay. Occasionally, there were sighting of this species north to Southern California. It used to be considered the most abundant sea star species in the Gulf of California. In 1978, Sea Star Wasting Disease killed almost all Gulf Sun Stars within the Gulf of California. Today, it is difficult to describe the current range of this species because populations are recovering in some areas, but not in others.

Diet:  Gulf Sun Stars are both predators and scavengers. They eat barnacles (especially the Acorn Barnacle, Chthamalus anisopoma), mussels, crabs, anemones, sea cucumbers and carrion.

Predators:   The Gulf Sun Stars are an apex predator, with no known predators, however there is limited mentions of gulls feeding on the juveniles.

Reproduction:  Gulf Sun Stars are gonochoric (male or female for life). They reproduce both asexually (regeneration and clonal) and sexually. They are broadcast spawners, with external fertilization. The eggs hatch into a planktonic larva and later metamorphose into benthic, five-armed, juveniles.

Ecosystem Interactions:  Gulf Sun Stars engaging in any types of parasitic, commensal, or symbiotic relationships has not been documented.

Human Interactions:  Historically Gulf Sun Stars have been collected, dried and sold as curios. However, this practice has been largely discontinued, due to a lack of availability or because of widespread awareness of the risk of extinction or extirpation. They are currently offered for sale on many internet sites. From a conservation perspective this species has not been formally evaluated however they have long recovery cycles and should be considered to be a species of concern.

Synonyms:  Heliaster kubiniji var. nigra.