Ophionereididae Family of Brittle Stars
One Bittle Star of the Ophionereididae Family can be found in this website:
Ringed Brittle Star, Ophionereis annulata. A representaitve of the Ophionereididae Family of Brittle Stars.
Phylogeny: The Brittle Stars of the Ophionereididae Family, are in the phylum Echinodermata (meaning spiny skin), which includes the basket stars, sea cucumbers, sea stars and sea urchins. Ophionereidid Brittle Stars are in the subphylum Asterozoa, the class Ophiuroidea, the subclass Myophiuroida, the infraclass Metophiurida, the superorder Ophintegrida, the order Amphilepidida, the suborder Ophionereidina, and the superfamily Ophionereidoidea. The Ophionereididae Family is one two families in this superfamily. The Ophionereididae Family contains five genera, one subgenus, and sixty species. The name Ophionereididae 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 as a self defense mechanism while under attack by predators.
Morphology: Ophionereidid Brittle Stars are agile relatives of the sluggish sea stars. They have a flattened central disk and most have five robust arms that insert ventrally on the disk. The arms may widen distal to the attachment point, before tapering. 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. The arms are used for locomotion as they can rapidly “row” or pull themselves along the ocean floor. They have small, thin scales on the dorsal surface of the central disk, giving the disk a granular texture. On the ventral side of the disk hey have five triangularly shaped jaws that frame a centrally placed mouth. They are characterized by a clump of dental papillae at the jaw apex with numerous papillae along the edges of the oral plates. Some species within this family will change color from daytime to nighttime. Identifying brittle star species 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. Ophionereidid Brittle Stars tend to be colorfully banded. Larger species in this family have disk diameters that exceed 2.5 cm (1 inch) and arms up to 15 cm (5.8 inches) in length.
Habitat and Distribution: Ophionereidid Brittle Stars are found in a variety of habitats including coral, gravel, rock, rubble, sand, and sponges. They generally hide during the day and emerge at night to feed. They live from the intertidal zone to depths of 585 m (1,920 feet). Ophionereidid Brittle Stars are found worldwide in subtropical to tropical seas. At least six species from this family are found in Mexican waters.
Reproduction: Ophionereidid Brittle Stars are gonochoric (male or female for life). Reproduction is sexual, through broadcast spawning, with external fertilization. The eggs hatch into planktonic larvae, which later metamorphose into juvenile brittle stars. They can also reproduce asexually through fission.
Ecosystems Roles: Ophionereidid Brittle Stars are primarily nocturnal omnivores being depositional feeders, suspension feeders, grazers, predators and scavengers. As suspension feeders, they feed by using mucous webs, attached to the spines on their arms, and filter suspended detritus and plankton from the water column. They prey on algae, crustaceans, detritus, fish, and fish eggs. Unlike Sea Stars, Ophionereidid 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, and shrimps.