Ringed Brittle Star, Ophionereis annulata

Ringed Brittle Star, Ophionereis annulata. Collected from under rocks within tidal pools at Km 17, El Tule, Baja California Sur, February 2011. Size 15 cm (5.9 inches).

The Ringed Brittle Star, Ophionereis annulata, is an Echinoderm and a member of the Ophiuroidea Class and the Cidaridae Family. In Mexico they are known as estrella frágil anillado. The Ringed Brittle Star has a light brown disk with dark purple and/or brown spots that is covered with small overlapping scales which increase in size towards the edges that party cover the first arm plate. They have long and slender arms are purplish with green bands with 3 spines on each lateral arm plate. The arms are banded on both the dorsal and ventral surfaces which is a key to identification. The arms are approximately 6 times longer than the diameter of the disk and they travel via “stepping” utilizing their tube feet rather than the entire arm. They reach a maximum size of 30 cm (12 inches).

The Ringed Brittle Star is found under rocks and crevices and on sponges, corals and sand within the intertidal zone up to water depths up to 213 m (700 feet). They are found in all Mexican waters of the Pacific and reported to be the most common Brittle Star within the Sea of Cortez.