Subclass Apodacea
 Apodida
 Molpadiida

Subclass Aspidochirotacea
 Aspidochirotida
 Elasipodida

Subclass Dendrochirotacea
 Dactylochirotida
 Dendrochirotida The sea cucumber is an echinoderm of the class Holothuroidea, with an elongated body and leathery skin. Mostly found on the sea bottom. It is so named because of its cucumber-like shape.

Like all echinoderms, sea cucumbers have an endoskeleton just below the skin.

Sea cucumbers are generally scavengers, feeding on debris in the benthic layer. Their diet consist of plankton and other organic matter found in the sea. One way they might get a supply of food is to position themselves in a current where they can catch food that flow by with their tentacles when they open. Another way is to sift through the bottom sand using their tentacles.

They have the peculiar adaptation of expelling their internal organs when startled by a potential predator. These organs can then be regrown.

Sea cucumbers reproduce by broadcasting sperm and eggs into the ocean water. Depending on conditions, one organism can produce thousands of gametes.

Surprising as it may seem, sea cucumbers have inspired musical composition: in the first of his Embryons desséchés Erik Satie presents the "(desiccated embryo) of a Holothuroidean" and inserts a description of the animal in the score:

(...)

The Holothuroidean crawls across bolders and rocky surfaces.

This sea-animal purrs like a cat; also, it produces disgusting silky threads.

Light appears to have an incommodating effect on it.

(...)

The sea cucumber's closest relatives (the echinoidea) get more attention from scientists, both as embryos and as fossils.

Sea cucumber is one of the most unique food stuffs in Chinese cuisine. It is highly valued for its supposed medicinal properties. The flesh of the animal is cleaned in a process that takes several days. The product is often purchased dried and soaked in water before use. The product is used in Chinese stews and braised dishes as it has a gelatinous texture but is pretty tasteless on its own.