Biology of Sea Cucumbers: An assessment towards conservation In: ICAR Sponsored Winter School on Recent Advances in Fishery Biology Techniques for Biodiversity Evaluation and Conservation, 1-21 December 2018, Kochi.

Sea cucumbers popularly called holothurians belong to the phylum Echinodermata, which is a distinct phylum in the animal kingdom. Echinoderms are almost exclusively marine, with a variably shaped body which is subdivided into ten areas. They are characterised by the possession of radial symmetry (generally pentamerous), an intradermic skeleton consisting of closely fitted plates, articulated plates, or ossicles, and a peculiar water vascular system of tubes filled with fluid. Holothurians have an orally-aborally elongated body (Fig.1). The body is formed like a short or long cylinder, with the mouth (at the anterior end) encircled by tentacles, and the anus (at the posterior end) often edged by papillae. Holothurians often lay on the substrate with their ventral surface or trivium, formed by the radii