Identification Photos: Banded Brittle Star, Ophiocoma alexandri: The Banded Brittle Star is large with an armored central disk that is almost 1 inch in diameter with five long flexible arms attached that have spans that reach 13 inches.

The arms of the Banded Brittle Star are gray with white banding and spines that are long and perpendicular to the arm axis. The aboral or dorsal surface of the disk has a uniform brown coloration and is covered with minute granules.

The Banded Brittle Star is common on rocky shores, under rocks in sand or muddy areas of the lower and intertidal zones.

The Banded Brittle Star is similar in appearance to the Giant Black Brittle Star, Ophiocoma aethiops, except it is smaller and has long skinny legs. In Mexico, it is found throughout the Sea of Cortez and along the coast of the mainland south to Guatemala.

The Banded 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. They 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. 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. 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 lack eyes and are concealed during the day hiding under rocks. They come out at night and are extremely active. 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 are preyed upon by crabs, fishes, sea stars, shrimps and other brittle stars. Brittle stars have never been an important item of human commerce.

Banded Brittle Star, Ophiocoma alexandri: 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 5 inches. Description and photos courtesy of John Snow.