Platyctenida

Article By:

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

Last reviewed:January 2021

DOI:https://doi.org/10.1036/1097-8542.527500

An order of the phylum Ctenophora comprising four families (Ctenoplanidae, Coeloplanidae, Tjalfiellidae, Savangiidae) and six genera. All species are highly modified from the planktonic ctenophores. The platyctenes are fairly small (1–6 cm or 0.4–2.4 in.) and brightly colored. They have adopted a variety of swimming, creeping, and sessile habits, with concomitant morphological changes and loss of typical ctenophoran characteristics. The body is compressed in the oral-aboral axis, and the oral part of the stomodeum is everted to form a creeping sole (see illustration). Platyctenids have a fairly typical cydippid larva, and comb rows are retained in adult ctenoplanids, which are capable of swimming or creeping on a substrate. The remaining families all have a benthic habit and have lost the comb rows, and even the statocysts as adults in the Savangiidae. Sexual reproduction involves internal fertilization in many species, with retention of the developing cydippid larvae in brood pouches. Some species also reproduce asexually by fission. Most platyctenids are found in tropical coastal waters, where many are ectocommensals on benthic organisms. See also: Ctenophora

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