Sea cucumbers are a class of echinoderms, the Holothuroidea. They have a longish body, and leathery skin. Sea cucumbers live on the floor of the ocean. Most sea cucumbers are scavengers. There are about 1500 species of sea cucumbers. Sea cucumbers have a unique respiratory system, and effective defences against predators. The Chinese people eat them.
Like all echinoderms, sea cucumbers have an endoskeleton just below the skin, calcareous structures that are usually reduced to isolated ossicles joined by connective tissue. These can sometimes be enlarged to flattened plates, forming an armour. In pelagic species the skeleton is absent.
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