Thorny Sea Cucumber

Seen in the area of Sihanoukville, Cambodia (May, 2011).
Colochirus quadrangularis is a sea cucumber of up to 10 cm (4 in) in length. The roughly cylindrical body has four longitudinal ridges giving it a square cross section and a flat base. It has irregular, thorn-like, soft projections called papillae lying along these ridges. The leathery body wall is reinforced by calcareous spike-like structures which in this species include basket-shaped spicules and perforated ellipsoids. There is a ring of large, branched feeding tentacles round the mouth. There are three rows of red tube feet on the underside and the body tapers at the posterior end, the anus being surrounded by 5 tooth-like projections. The colour is mainly grey often with pink on the ridges and thorns, and with yellow or reddish tentacles