Holothurians

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Holothurians

 

(sea cucumbers), a class of invertebrates (Holothurioidea) of phylum Echinodermata.

The skeleton of the holothurians is greatly reduced. The body is pentactinally symmetrical, which is characteristic of the phylum in general, but in the holothurians it is marked by the biliterally symmetrical arrangement of many of the organs. The largest holothurians reach 2 m in length. The body is vermiform, with a mouth at one end and an anal opening at the other. The mouth, surrounded by a crown of tentacles that serve to capture the food, leads into a long tubular gut. Respiration is accomplished by an ambulacral system and a so-called respiratory tree—branched sacs leading to the rectum. Holothurians develop by metamorphosis; free-swimming larvae hatch from the eggs. There are some 1,100 species.

The holothurians are exclusively marine, benthic, sluggish, creeping animals, feeding on sediment or tiny plankton. When greatly irritated they are capable of self-mutilation (au-totomy), but the lost organs readily regenerate. In China the sea cucumber is dried and used as food. The animals (particularly the trepang) are also of some commercial importance in the USSR, in the Far East.

REFERENCES

Dogel’, V. A. Zoologiia bespozvonochnykh, 5th ed. Moscow, 1959.
Bol’shoi praktikum po zoologii bespozvonochnykh, part 2. Moscow, 1946.
Zhizn’ zhivotnykh, vol. 2. Moscow, 1968.
References in periodicals archive ?
Weight-length relationship and relative condition of the holothurian Isostichopus fuscus at Espiritu Santo Island, Gulf of California, Mexico.
Methods of studying growth in holothurians (bechede-mer), and preliminary results from a beche-de-mer tagging experiment in New Caledonia.
Blank holothurian samples were obtained from the breeding base of Shandong Marine Resource and Environment Research Institute (Yantai, Shandong, China) which were previously characterized using UPLCMS/MS.
Complexes of cholesterol with triterpene glycosides extracted from holothurian were prepared by ultrasound dispersion of the cholesterol film in solution of triterpene glycosides [5].
The last review on holothurian asexual reproduction was published 18 years ago [37].
Slow-moving echinoderms that produce saponins (i.e., asteroids and holothurians), which can defend both larval and adult stages, constitute an exception to this general pattern for mobile invertebrates (Lucas et al.
The annual reproductive cycle of the holothurian Aslia lefevrei (Dendrochirota: Echinodermata).
Indeed, most of the saponin content would be conserved inside Cuvierian tubules because they are not expelled outside the holothurian. It was observed that, while carapids are less sensitive to saponins than other fishes, they are affected by high saponin concentrations and, as they are permanently in contact with holothuroids, they must have particular, efficient adaptations to protect themselves.
Lampe, " Holothurian density, distribution and diversity comparing sites with different degrees of exploitation in the shallow lagoons of Mauritius," SPC Beche-de-Mer Information Bulletin, vol.
Aspects of the reproductive and larval biology and ecology of the temperate Holothurian Stichopus mollis (Hutton).
Recruitment in the Holothurian Cucumaria frondosa in the Gulf of Maine.