ophiuroides

Ophiuroidea, commonly known as brittle stars or ophiuroids, are a class of echinoderms that includes thousands of species found in oceans worldwide. They are closely related to starfish but differ in a number of characteristic features: a distinct central disk from which long, slender arms radiate, highly flexible and capable of rapid movement. The internal skeleton is formed by calcareous ossicles, and the arms are tightly articulated, enabling precise and varied motions. In contrast to many sea stars, the tube feet along the oral surface are mainly used for feeding and sensation rather than locomotion; locomotion is accomplished by coordinated arm movements.

Brittle stars occupy a broad range of habitats, from shallow reefs and kelp beds to the deep sea, often sheltering under rocks or within rubble. They are diverse in diet, with species acting as detritivores, predators of small invertebrates, or suspension feeders, depending on morphology and environment.

Reproduction is typically sexual, with separate sexes and free-swimming larvae known as ophiopluteus in many species; some reproduce asexually by autotomy, shedding an arm that regenerates. The clade comprises about two thousand described species, arranged into several orders, including Ophiurida and Ophiodermatida, and includes the well-known basket stars and serpent stars.

Ecologically, ophiuroids play important roles as scavengers, predators, and prey in benthic communities. They are also of interest in studies of morphology, development, and evolutionary biology, and are kept by some aquarists in marine tanks.