Keeled Sea Star, Asteropsis carnifera

Keeled Sea Star, Asteropsis carinifera. Starfish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, November 2015. Wingspan:  15 cm (5.9 inches).

Phylogeny:  The Keeled Sea Star, Asteropsis carinifera (Lamarck, 1816), is a member of the Asteropseidae family of Sea Stars. The genus Asteropsis is one of five genera in this family. This is the only species in this genus. They are also known as the Sheriff-badge Sea Star and in Mexico as estrella de mar con quilla.

Morphology:  Keeled Sea Stars have a disc that is almost as wide as the arms are long. The arms are wide, tapering, and triangular in cross-section. A ridge of low, conical spines runs the length of each arm, and longer spines run along the margins of the arms and disc.  These stars are fairly soft and pliable. The skin has a slippery rubber texture. Keeled Sea Stars have a mottled appearance and may be gray, brown, green, or orange in color. They reach a maximum  of 25 cm (9.7 inches) in diameter.

Habitat and Distribution: Keeled Sea Stars are found on, and under, rocks. They live intertidally, and to a depth of 36.5 M (120 feet). They range throughout the tropical Indo-Pacific and Eastern Pacific Ocean. In Mexican waters they are found in the Gulf of California, from Bahia San Luis Gonzaga, Baja California, and south along the coastline to Guatemala, including the Revillagigedo Islands. However, they are absent from the West coast of the Baja Peninsula.

Diet:   Keeled Sea Stars are omnivores that feed on algae, detritus, small invertebrates, and coral polyps.

Predators:   Keeled Sea Stars are preyed upon by crabs, fish, and other sea stars.

Reproduction: Keeled Sea Stars are gonochoric (male or female for life). They can reproduce asexually through paratomy or budding. They can also reproduce sexually through broadcast spawning with external fertilization. The fertilized eggs hatch into planktonic larva. The larva settle to the bottom and begin their benthic existence.

Ecosystem Interactions: In some regions, Keeled Sea Stars host the scale worm Hololepidella nigropuntata with which they have a commensal relationship. It is unknown if similar relationships occur in other regions. In the Indo-Pacific these stars are parasitized by shrimp in the genus Hymenocera. It is unknown if similar parasitism occurs in the Eastern Pacific.

Human Interactions:   Keeled Sea Stars have been collected on a limited basis as curios. They are thought to be the most common and widely distributed sea star in the Indo-Pacific. From a conservation perspective the Keeled Sea Star has not been formally evalua ted but based on their wide distribution they should be considered to be of Least Concern.

Synonyms: Asterias carinifera, Asterope carinifera, Gymnasteria biserrata, Gymnasteria carinifera, Gymnasteria spinosa, Gymnasteria valvulata, and Gymnasterias carinifera.