Ophiuroidea

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Related to ophiuroids: class Ophiuroidea, Brittle stars, echinoids

Ophiuroidea

[äf·ə·yə′rȯid·ē·ə]
(invertebrate zoology)
The brittle stars, a subclass of the Asterozoa in which the arms are usually clearly demarcated from the central disk and perform whiplike locomotor movements.

Ophiuroidea

 

(brittle stars), a class of benthic marine animals of the phylum Echinodermata. The body consists of a flat disk, which usually measures about 2 cm across (sometimes up to 10 cm). Five or, less frequently, ten flexible arms extend from the disk. The length of each arm is several times (sometimes 20 to 30 times) greater than that of the disk. In contrast to the arms of starfishes, the arms of brittle stars are sharply marked off from the disk and are jointed, consisting of numerous vertebrae. Most brittle stars have simple, unbranched arms. The disk and the arms are covered with thin calcareous plates.

In most species the sexes are separate. Development is usually by metamorphosis; the free-swimming larva is called an ophiopluteus. Some species are viviparous; others are capable of reproducing by division.

Brittle stars crawl by flexing their arms, or they bury themselves in the bottom. They feed on small animals or detritus. Many tropical species that inhabit shallows are brightly colored. Some species are capable of luminescence. The regeneration of arms is well developed.

Brittle stars are found throughout the world on ocean and sea bottoms (to depths of 8 km). They often form large colonies and serve as food for fishes. Some species live commensally with algae, sponges, corals, and sea urchins. Of the approximately 2,000 species, about 120 are encountered in the seas of the USSR. Fossils of extinct species have been traced to the Ordovician.

G. M. BELIAEV

References in periodicals archive ?
2] was the same between the two studies, our biomass was higher because NCC had ophiuroids throughout the sampling period, adding about 4 g [m.
Unlike cuttlefish, however, grenadiers are known to feed quite extensively on ophiuroids (1) and small epifauna (Meyer and Smale, 1991) and did not seem to show any strong association with extremes of substrata and were observed in both soft and hard habitats (Table 5).
Otherwide, it might be expected that they would be associated with areas rich in benthic food, such as ophiuroids, which are known to form part of the diet of other gobies (Gibson, 1982).