Ophiocomidae Family of Brittle Stars

Four Brittle Stars of the Ophiocomidae Family can be found in this website:

Phylogeny: The Brittle Stars are members of the Ophiocomidae Family, a family that dates to the Cambrian Age (over 500,000,000 years ago) with approximately 20,000 species of which more than half are extinct.  They are in the phylum Echinodermata (meaning spiny skin), which includes the basket stars, sea cucumbers, sea stars and sea urchins. Brittle Stars are in the subphylum Asterozoa, the class Ophiuroidea, the subclass Myophiuroida, the infraclass Metophiurida, the superorder Ophintegrida, the order Ophiacanthida, the suborder Ophiodermatina, and the superfamily Ophiocomoidea. The Ophiocomidae Family is the only family in this superfamily. The Ophiocomidae Family contains four genera and forty-four species.  The name Ophiocomidae comes from the Greek words meaning “snake tail”, referring to their thin, flexible, wiggly, arms. Brittle Stars owe their common name to their capability of voluntarily severing arms, which occurs as a self defense mechanism while under attack by predators.

Morphology: Brittle Stars are agile relatives of the sluggish sea stars with anatomical structures that includes a flattened central disk and most have five slender arms, though a few have up to ten arms. Identifying Brittle Stars can be challenging. Many species cannot be determined without close examination of the shape of various plates and mouth parts. Because the arms are fragile, and difficult to measure, Brittle Stars are often measured by diameter of the disk. They all have radial symmetry and they are large and colorful. Ophiocomidae Brittle Stars are characterized by a clump of dental papillae at the jaw apex with numerous papillae along the edges of the oral plates. They have relatively stout arms, inserted ventrally, that can be wider away from their insertion at the disk. The arms have tube feet on their underside, but unlike the tube feet of sea stars, these feet lack suction cups. The spines along their arms are long and erect and are used primarily for feeding and movement and to a lesser extent for protection from predation. 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 dorsal surface of the disk has a granular texture. Some species within this family will change color from daytime to nighttime. Ophiocomidae Brittle Stars can have disk diameters that exceed 3.2 cm (1.3 inches).

Habitat and Distribution:  Ophiocomidae Brittle Stars are found in a variety of habitats including algae bases, coral, gravel, rock, rubble, sand and sponges.  Ophiocomids are primarily found in shallow waters, though some species are found as depths up to 370 m (1,210 feet). They are the dominant species of brittle stars in the tropics and are found in all subtropical and tropical seas globally. At least  five species from this family are found in Mexican waters.

Reproduction: Ophiocomidae Brittle Stars are gonochoric (male or female for life). Reproduction is sexual, through broadcast spawning, with external fertilization. They are known to brood their fertilized eggs within their respiratory structures. The eggs hatch into planktonic larvae, which later metamorphose into juvenile brittle stars. They can also reproduce asexually through fission.

Ecosystems Roles:  Ophiocomidae Brittle Stars are primarily nocturnal  omnivores being depositional feeders, suspension feeders, grazers, predators and scavengers collecting particles with their arms which they transport to their mouth. They prey on algae, crustaceans, detritus, fish, and fish eggs. Unlike Sea Stars, Ophiocomidae Brittle Stars cannot extend their stomach out though their mouth to digest prey externally. In turn they are preyed upon by crabs, fishes, sea stars, shrimps and other brittle stars.