Sea cucumbers (Class Holothuroidea) are echinoderms, meaning that most move by way of tube feet along the length of their bodies. Unlike other echinoderms, they are elongate rather than circular, although they still possess radial symmetry along their length. Sea cucumbers have a mouth at one end, surrounded by a ring of tentacles. Most sea cucumbers are either filter feeders, or scavenge through substrate such as sand or silt.
