The Class Holothuroidea contains over 1,400 species of soft-bodied animals known as sea cucumbers. These animals live on the bottoms of oceans and seas around the world, where they often make up the majority of the deep ocean biomass. The elongated ("cucumber-shaped") body has a mouth that is surrounded by retractile tentacles at one end and an anus at the other. These animals move slowly using tube feet and waves of contraction of their powerful body muscles. They feed on small organisms captured by the sticky mucus on their tentacles.