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The Class Holothuroidea contains
over 1,400 species of soft-bodied animals known as sea cucumbers. These
animals live on the bottoms of oceans and seas around the world, where they
often make up the majority of the deep ocean biomass. The elongated ("cucumber-shaped") body has a mouth
that is surrounded by retractile tentacles at one end and an anus at the other. Although most are fairly drab in color, some forms are remarkably beautiful.
The muscular body wall
of the sea cucumber is covered with a cuticle and tough, leathery skin in which microscopic ossicles
are embedded (the only vestige of the calcareous exoskeleton seen in most
echinoderms). These animals move slowly using tube feet and waves of contraction of their powerful body muscles. They feed on small organisms captured by the sticky mucus on their tentacles. Some sea cucumbers possess sticky structures inside the anus called tubules of Cuvier that can be shot out to capture prey or discourage predators (since, in addition to being sticky, they are toxic!). When seriously threatened, sea cucumbers can squeeze out their own internal organs using powerful muscular contractions, thus distracting a potential predator;
these organs are soon regenerated! |
