sea cucumber

Any echinoderm of the class Holothuroidea with a cylindrical body that is tough-skinned, knobbed, or spiny. The size ranges from 3 cm/1.2 in to 2 m/6.6 ft. There are around 900 species, which are mostly black, brown, or olive green in colour. Sea cucumbers are sometimes called ‘cotton-spinners’ because of the sticky filaments they eject from the anus in self-defence.

The dried flesh of sea cucumbers is a delicacy in Japan and Taiwan, and overfishing has threatened some populations. A high density is vital to sustain a population as they reproduce by releasing sperm or ova into the water; other sea cucumbers must also be releasing sperm or ova nearby.