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).

Phylogeny:  The Ringed Brittle Star  (Leconte, 1851), a member of the Ophionereididae family of Brittle Stars. The genus Ophionereis is one of five genera in this family, and there are thirty-one species in this genus. They are known in Mexico as Estrella Quebradiza Anillada.

Morphology: Ringed Brittle Stars have pentaradial symmetry. They have a flattened, almost circular, central disk and five arms. The arms are long, thin, and flexible. The arms have tube feet on their underside, but unlike the tube feet of sea stars, these feet lack suction cups. Each lateral arm plate has three spines. The dorsal (aboral) surface of the disk is covered with small, overlapping scales, which get larger toward the periphery. There is a mouth on the underside of the disk. The mouth consists of five “jaws”. Unlike sea stars, brittle stars cannot extend their stomach out though their mouth to digest prey externally. They use their arms and tube feet to pass prey into their mouth. Ringed Brittle Stars are highly mobile, appearing to “step” with their tube feet instead of swinging their entire arms. The arms are usually white to gray or tan in color, with darker gray to brown bands. Some may display more greenish or purple coloration. The bands can very in shape, and wrap around the arm. The disk may be white to gray-brown in color, and sometimes is marked with white speckles. The margins of the disk can be slightly to very scalloped. Ringed Brittle Stars reach a maximum of 31.5 cm (12.5 inches) in diameter.

Habitat and Distribution: Ringed Brittle Stars are found under rocks, in crevices, in coral, on sponges, in algae beds, and on sand and are found intertidally and at depths up to 27.5 m (90 feet). They are an Eastern Pacific species that are found in all Mexican waters of the Pacific. They are thought to be the most abundant brittle star species in the Sea of Cortez.

Diet:  Ringed Brittle Stars are a poorly studied and understood species. They are generally described as being omnivorous and as employing different methods of feeding, including, predation, suspension feeding, grazing, and scavenging. There is no documentation of their actual diet. Other species in this family consume algae, crustaceans, detritus, mollusks and plankton.

Predators:  There is limited documentation related to the predators of Ringed Brittle Stars. Other species in this genus are primarily eaten by crustaceans and fish.

Reproduction:  Ringed Brittle Stars are gonochoric (male or female for life). They can reproduce sexually or asexually. In sexual reproduction, they engage in broadcast spawning, with external fertilization. The fertilized egg turns into planktonic larvae that drift before settling on the ocean floor and then mature into adult brittle stars. Asexual reproduction is accomplished through regeneration.

Ecosystem Interactions: Banded Brittle Stars are known to host an epibiont scale worm of the genus  Malmgreniella. The scale worm attach itself to its host’s central disc. The exact nature of this relationship is unknown.

Human Interactions: Banded Brittle Stars have no direct impact on human activities. From a conservation perspective they have not been formally evaluated however they are fairly common with a relatively wide distribution and should be consider to be of Least Concern.

Synonyms: Ophiolepis annulata, Ophiolepis triloba, Ophionereis dictyota, Ophionereis triloba, Ophionereis xanthusii, and Ophionereis xantusii.