Mention the salient features of Holothuroidea.

Explanation

Holothuroidea : This class includes sea cucumbers. Body elongated in the oro-aboral axis, Arms, spines and pedicellariae are absent skin is soft.and leathery (Coriaceous). Dermis contains microscopic, isolated ossicles, Madreporite is internal, suspended in the perivisceral coelom. Tube feet are provided with suckers. Mouth is surrounded by retractile feeding tentacles, which are modified tube feet, chief gas exchange organs are a pair of respiratory trees that arise from the wall of cloaca and form branched tubes in the perivisceral coelom. Development includes auricularia and doljolaria larvae.