Caudinidae Family of Sea Cucumbers

One Sea Cucumber of the Caudinidae Family can be found in this website:

Sweet Potato Sea Cucumber, Caudina arenicola. A representative of the Caudinidae Family of Sea Cucumbers.

Phylogeny: Caudinid Sea Cucumbers are members of the Caudinidae Family and like sea stars and sea urchins belong to the phylum Echinodermata and the subphylum Echinozoa. They are characterized by a larval stage with bilateral symmetry and an adult stage with radial (5-rayed) symmetry. They lack the tube feet of other echinoderms. They belong to the class Holothuroidae the order Molpadida. The Caudinidae Family contains five genera and thirty-seven species. The family name Caudinidae comes from the Latin word meaning “tailed” (even though one genus in the Caudinidae Family is Acaudina, meaning without a tail).

Morphology:  Caudinid Sea Cucumbers are unsegmented and  shaped like a sweet potato or yam. They lack arms, and they have a soft body with branched, unbranched or pinnate tentacles around their mouth utilized to capture food. They have smooth, or slimy, skin with fine to large papillae (projections). The skin is thin but leathery. They have a water vascular system and a complete digestive system, but they lack eyes, a head, nervous system, or excretory system. They are primarily burrowers that possess  an internal madreporite (perforated plate covering entry port of water vascular system) to keep it out of the sediment. They often have an elongated caudal region (like a tail) that may extend to the end of their U-shaped burrow. This “tail” may help with gas exchange as they have respiratory trees, a type of water lung, attached to the cloaca. Caudinid Sea Cucumbers vary in color and pattern, but most are black, brown, or greenish. They range in size from small to over 60 cm (2 feet 0 inches) in length.

Habitat and Distribution: Caudinid Sea Cucumbers are perhaps the most sedentary of all the sea cucumbers and are found on, and under, rocks, rubble, mud, and sand. They live intertidally, and to depths exceeding 5,200 m (17,056 feet). Most species are found at depths greater than 100 m (328 feet). They spend the majority of their life cycle in their burrow. Caudinid Sea Cucumbers are found worldwide in tropical to polar seas. Three species from this family are found in Mexican waters.

Reproduction: Caudinid Sea Cucumbers are gonochoric )male or female for life) and they reproduce sexually with fertilization occurring externally. The embryos develop in to planktonic larvae and then doliolaria (barrel-shaped stage) larvae before becoming juvenile sea cucumbers.

Ecosystem Roles:  They are active nocturnally. They are suspension feeders and depositional detritivores that feed by filtering food from the surrounding water and by gathering food from the surface of the substrate. Some filter sand through their digestive tracts, removing food from the sand as it passes through. In  turn they are preyed upon by crabs, fish, gastropods, marine mammals, and sea stars. They may also play host to several species of commensal, or parasitic, crustaceans and mollusks. Some species of Caudinidae Sea Cucumbers are the subject of commercial fisheries and aquaculture operations. They are considered a food source and a source of pharmacological agents.