Cestida

Article By:

Madin, Laurence P. Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts.

Last reviewed:October 2019

DOI:https://doi.org/10.1036/1097-8542.122300

An order of the phylum Ctenophora (comb jellies) containing two monospecific genera, Cestum and Velamen, which have an unusual morphology. The transparent bodies of members of the order Cestida (cestids) are flattened in the tentacular plane and greatly elongated in the stomodeal plane so that they have the shape of a belt or ribbon (hence, the specific name Cestum veneris, “Venus' girdle”; see illustration). The mouth is at the midpoint of the length. Individuals of Cestum may be more than 39 in. (1 m) long, and of Velamen about 8 in. (20 cm). Brown or yellow pigment spots sometimes occur on the tips of the body. If disturbed, cestids, like other ctenophores, produce brilliant bioluminescence along their meridional canals. They occur worldwide in tropical and subtropical waters; C. veneris is one of the most common species in the oceanic Atlantic. The extreme fragility of their bodies makes cestids difficult to collect and maintain, and living specimens have been seen by few biologists. See also: Bioluminescence; Ctenophora

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