Identification Photos: Giant Black Brittle Star, Ophiocoma aethiops: The Giant Black Brittle Star is the largest of the brittle stars found in the Eastern Pacific region and has an armored central disk that can reach up to 1.5 inches in diameter with five long flexible arms that can have a span between 13 and 17 inches.

The arms of the Giant Black Brittle Star have a uniform coloration and the spines are long and perpendicular to the arm axis. The aboral or dorsal surface of the disk has a uniform purple-brown coloration and the disk is covered with minute granules.

The Giant Black Brittle Star is common on rocky shores, within coral structure, under rocks in sand or muddy areas of the lower and intertidal zones. It is similar in appearance to the Black Brittle Star, Ophiocoma echinata, except it is larger and has longer thicker legs.

In Mexico, the Giant Black Brittle Star is found throughout the Sea of Cortez and along the coast of the Mexican mainland south to Guatemala.

The Giant Black Brittle Star is one of the Echinoderms and a member of the Ophiuroidea Class and the Cidaridae Family. Globally there are 2,000 known species of Brittle Stars. The Echinoderms are a phylum of marine animals which include brittle stars, sea cucumbers, sea lilies, starfish and urchins that are of great scientific interest because, via fossil records, they date to the Cambrian Age (over 500 million years ago) with 7,000 living species and 13,000 extinct ones.

The brittle stars are agile relatives of the sluggish sea stars with anatomical structures that include a disk and five slender arms. They have five triangularly shaped jaws that frame a centrally placed mouth which is found on the ventral side. The arms are used for locomotion as they can rapidly “row” or pull themselves along the ocean floor. Brittle stars owe their name to the notorious capability of voluntarily severing arms which occurs as a self defense mechanism while under attack by predators. Complete regeneration of missing parts takes from two and eight weeks.

Brittle Stars feed via either the absorption of nutrients through the skin or via the collection of particles with their arms which they transport to the mouth. They lack eyes and are concealed during the day hiding under rocks. They come out at night and are extremely active. They are preyed upon by crabs, fishes, sea stars, shrimps and other brittle stars. Brittle stars have never been an important item of human commerce.

Giant Black Brittle Star, Ophiocoma aethiops: Collected off the beach between the high tide water debris line and the water during predawn hours in July 2006, at Km, 20, Cabo Real, San Jose del Cabo, Baja California Sur, Mexico. Size approximately 8 inches. Description and photo courtesy of John Snow.