sea cucumber, Bohadschia argus

sea cucumber feeds on sandy bottom [92k] added 6 nov 00

Sea cucumbers, the common name given to holothurians (class Holothuroidea), are a type of echinoderm related to starfish. They are commonly spotted in the vicinity of coral reefs, usually on the shallow sandy bottom. Of the three basic types of sea cucumber, this type is the most commonly encountered by divers. It may reach lengths of about two feet. Their skin is generally thick and rough. This type is an aspidochirote holothurian, which has a characteristic tough leathery skin, with a size and texture similar to a loaf of french bread.

The name "sea cucumber" is probably derived from their shape and the fact that many are used for preparing soup in parts of the orient. Some members of the aspidochirote group are eaten in parts of Asia as a soup delicacy, often referred to as the "ginseng of the sea" and marketed as trepang, iriko or bêche-de-mer. The sea cucumber is dried, and the gelatinous, soaked skin is then used.

The sea cucumber shown here is a "sand gobbler", with the mouth and feeding tentacles shown on the lower left side of the photo. It slowly plows along the ocean bottom, with padded, sticky tentacles (black with white fringes) picking up organic nutrient-coated sand particles and passing them to the mouth. Other small tube-feet along the ventral surface serve to slowly propel the sea cucumber along the bottom. If threatened or roughly handled, some species (including this one) eject sticky threads from its anus (right side of photo) called Cuvierian tubules which are toxic to predators and irritating to an unsuspecting diver's skin.

Sea cucumbers are known to host commensal creatures such as Periclimenes shrimp. Other species may host a type of parasitic Pearlfish (family Carapidae), which enters and exits through the sea cucumber's anus, and feeds on its internal tissues.

Identification: Bohadschia graeffei