Identification Photos: Black Brittle Star, Ophiocoma echinata: The Black Brittle Star is very similar to but smaller than the largest of the brittle stars found in the Eastern Pacific region, the Giant Brittle Star. The Black Brittle Star has an armored central disk that can reach up to 1 inch in diameter with five long flexible arms that have a span between 8 and 10 inches.

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

The Black Brittle Star is common on rocky shores, under rocks in sand or muddy areas of the lower and intertidal zones. It is similar in appearance to the Giant Black Brittle Star, Ophiocoma aethiopsi, except that it is smaller and has shorter thinner legs.

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

The Black Brittle Star is one of the Echinoderms and a member of the Ophiuroidea Class and the Cidaridae Family. 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.

Globally there are 2,000 known species of brittle stars. They are agile relatives of the sluggish sea stars with anatomical structures that include a disk and five slender arms. 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. 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 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.

Black Brittle Star, Ophiocoma echinata: Collected from shore between the high tide water debris line and the water in July 2006, at Km. 20, Cabo Real, San Jose del Cabo, Baja California Sur, Mexico. Size approximately 6 inches. Description and photo courtesy of John Snow.