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 Starfish. The genus Asteropsis is one of five genera in the Asteropseidae Family. This is the only species in the Asteropsis genus. They are also known as the Sheriff-badge Sea Star and in Mexico as Estrella de Mar con Quilla. The genus name Asteropsis comes from the Greek words meaning “star-like”. The species name carinifera comes from the Latin words meaning “ridge-bearing” or “keel-bearing”. This name refers to the ridge of spines along the top of each arm.

Morphology:  Keeled Sea Stars have a disk 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 disk.  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 subtropical to tropical waters of the Indo-Pacific and Eastern Pacific Ocean. The Keeled Sea Star is found in all Mexican waters of the Pacific Ocean with the exception that they are absent from the west coast of the Baja Peninsula and from north of Bahía San Luis Gonzaga, Baja California, in the Gulf of California.

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

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 evaluated 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.