Ophiozonella depressa

Background

Ophiozonella depressa was first described by Theodore Lyman in 1878, with later confirmation by H. Matsumoto in 1915. Specimens have been found in benthic environments at depths of roughly 1-2 kilometers, with 24 records of occurrences from locations including off the eastern coast of Tasmania, near the northern coast of New Zealand, off the northwestern coast of Australia, in the Makassar Strait in Indonesia, and as far north as the southern coast of Taiwan. The species has not been observed in the wild, but shares common characteristics with its class Ophiuroidea.

Anatomy

Anatomically, O. depressa has pentaradial symmetry with five arms extending from a central body disk. The arms are recorded at roughly 37 mm long, thick at the base (1.8 mm), and taper to a fine tip. The aboral side of the central body features many calcareous plates of varying size, covered by the epidermis and collectively called the 'test.' Radial shields on the sides of the central body between arms are no more than a single row of plates apart, and in most cases are touching. The connection between arms and central body holds particularly large and rhomboidal arm shields on the aboral side.

On the oral side, four short papillae ring the mouth on each side, and the mouth shields are longer and thinner. The digestive system includes papillae and teeth lining the mouth, an esophagus, and a sac-like stomach. Gas exchange occurs via internal sacs called bursae, which take in water through slits alongside the arm margins. The nervous system consists of a nerve ring and radial nerves, with sensory system limited to epithelial sensory cells for touch only.

Reproduction

Reproduction specifics for O. depressa have not been studied or observed, though as with other Ophiuroidea, it contains gonads (genital bursae) and can undergo asexual reproduction through regeneration of lost limbs and internal structures. The larval stage and diet remain unknown or unstudied.