Pawsonia saxicola
Pawsonia saxicola, the sea gherkin, is a species of sea cucumber in the family Cucumariidae. It is found in the northeastern Atlantic Ocean and the Mediterranean Sea. Description. "Pawsonia saxicola" has a solid, cylindrical body and can grow to a length of . The mouth is at the anterior end and is surrounded by a circle of ten, black and white, mottled, branching, tentacles used for feeding, up to long. The cuticle of the body is smooth with five longitudinal rows of tube feet. The ventral rows are double and clearly visible, while the dorsal rows are largely replaced  by low button-shaped protuberances, except near the mouth. The cuticle contains calcareous spicules which are star-shaped. This sea cucumber may be confused with "Aslia lefevrei". Both live in crevices with their dark-coloured tentacles projecting; "P. saxicola" is white, but may darken somewhat when exposed to light, while "Aslia lefevrei" is brown. Distribution and habitat. This sea cucumber is native to the northeastern Atlantic Ocean and the Mediterranean Sea. Its range extends from the west and south coast of the British Isles to the coasts of France, Spain and Portugal and to the Azores. Its habitat is rocky  shores where it conceals itself in crevices and under rocks, from the lower shore down to around . Ecology. "Pawsonia saxicola" is a suspension feeder, consuming diatoms and single-cell algae and also zooplankton, such as copepods, ostracods, protozoans, nematodes, jellyfish and larvae, as well as drifting organic particles. The food is gathered by the feeding tentacles which each in turn shrinks and bends and is inserted into the mouth; the two ventral tentacles are short and forked, and are used at the mouth to push particles inside. Although in some related species the short tentacles co-ordinate their activities with  the longer tentacles, this is not the case in "P. saxicola" where they seem to act independently.