Scientific report on the Belgian expedition to The Great Barrier Reef in 1967. Nematodes VI. Morphological observations on a new genus Quadricomoides of marine Desmoscolecida

Abstract

Quadricomoides, gen. nov., is an unusual genus of nematodes in several important morphological characters including the presence of a triradially symmetric head end and the structure of the oesophagus with a terminal symmetric bulb.

The genus is represented by four new species: Q. coomansi, sp. nov., is characterized by the rectangular shape of its head, by fine spines which line the buccal cavity and interlock like a zip fastener, and by the shape of the spicules and the complex gubernaculum accompanied by a strongly developed muscular system; Q. alleni, sp, nov., is distinguished by its dome-shaped triradially symmetric head end and by the presence of a tubular structure at each Side of the vas deferens at the level of concretion rings 22-25; Q. pedunculata, sp. nov., is close to Q. coomansi in its comparable head shape but is different in several aspects including the presence of long peduncles to the somatic setae and the position of the connection between the internal differentiation and the outer wall of the oesophageal bulb (i.e. halfway along and sublateral instead of terminal and subventral). A female specimen from the Bahamas, identified by Timm (1970) as Quadricoma loricata Filipjev, 1922, is placed in the new genus and considered as a new species. Quadricoma angulocephala Freudenhammer, 1975, and Quadricoma magna Timm, 1970, are transferred to Quadricomoides.