Cuvierian tubules are clusters of fine tubes located at the base of the respiratory tree in some

sea cucumber Sea cucumbers are echinoderms from the class (biology), class Holothuroidea ( ). They are benthic marine animals found on the sea floor worldwide, and the number of known holothuroid species worldwide is about 1,786, with the greatest number be ...

s in the

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

Bohadschia ''Bohadschia'' is a genus of sea cucumbers in the family Holothuriidae. They are among the largest, most common, and conspicuous sea cucumbers on coral reefs. They have large, loaf-like bodies that are often strikingly colored. Species , the Wo ...

'', ''

Holothuria ''Holothuria'' is the type genus of the marine animal family Holothuriidae, part of the class Holothuroidea, commonly known as sea cucumbers. Members of the genus are found in coastal waters in tropical and temperate regions. They are soft-bodied ...

'' and '' Pearsonothuria'', all of which are included in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Holothuriidae Holothuriidae is a Family (biology), family of sea cucumbers, a type of echinoderm. Description Members of the family Holothuriidae have thick fleshy bodies and several rows of tube feet which are used for moving around and for adhering to the s ...

. The tubules can be discharged through the anus when the sea cucumber is stressed. They lengthen when they come into contact with seawater and become adhesive when they encounter objects, functioning as a form of defense against predators or sources of danger. Cuverian tubules are named after the French zoologist

Georges Cuvier Jean Léopold Nicolas Frédéric, baron Cuvier (23 August 1769 – 13 May 1832), known as Georges Cuvier (; ), was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuv ...

, who first described them.

Mode of action

There may be several hundred Cuvierian tubules which are attached to the left respiratory tree and lie freely in the coelomic fluid in the body cavity. When stressed, the sea cucumber faces away from the attacker and contracts its body wall muscles sharply. This causes the wall of the

cloaca A cloaca ( ), : cloacae ( or ), or vent, is the rear orifice that serves as the only opening for the digestive (rectum), reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles, birds, cartilagin ...

to tear and the anus to gape and the free ends of some of the tubes to be ejected. Water from the respiratory tree is forced into these tubules causing a rapid expansion and they elongate by up to 20 times their original length. They have great tensile strength and become sticky when they encounter any object. The adhesive is unique among marine invertebrates and a firm grip is obtained in under ten seconds. The mass of threads can entangle and immobilize potential predators such as small

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

s. The threads become detached from the sea cucumber which crawls away. The tubules contain a toxic

saponin Saponins (Latin ''sapon'', 'soap' + ''-in'', 'one of') are bitter-tasting, usually toxic plant-derived secondary metabolites. They are organic chemicals that become foamy when agitated in water and have high molecular weight. They are present ...

called holothurin, which is also present in the body wall in some sea cucumber species. Cuverian tubules are readily regenerated, a process that takes about 17 days in '' Holothuria leucospilota'' and five weeks in '' Holothuria forskali''. Image:Ashy pink sea cucumber (Holothuria fuscocinerea).jpg, '' Holothuria fuscocinerea'' Image:Tubes de Cuvier émis par Holothuria pervicax.jpg, ''

Holothuria pervicax ''Holothuria pervicax'' is a species of sea cucumber in the genus ''Holothuria''. It is commonly called the stubborn sea cucumber due to its inability to be kept alive in captivity. It is commonly found buried beneath rocks on reefs in warm water ...

'' Image:Holothuria sanctori Cuvieran Tubes.jpg, ''

Holothuria sanctori ''Holothuria sanctori'' is a species of sea cucumber in the genus ''Holothuria ''Holothuria'' is the type genus of the marine animal family Holothuriidae, part of the class Holothuroidea, commonly known as sea cucumbers. Members of the genus ar ...

'' Image:Holothuria-Maldives.jpg, '' Bohadschia vitiensis'' held in hand out of the water Image:Holothuria forskali Rab2011 h 3798.JPG, '' Holothuria forskali''

References

Echinoderm anatomy {{echinoderm-anatomy-stub

Mode of action

See also

References