Studies on the genus Sectonema Thorne, 1930 (Dorylaimida: Aporcelaimidae). Redescription of S-ventrale Thorne, 1930, the type species of the genus

摘要

Sectonema ventrale, the type species of the genus, is redescribed on the basis of type material as well as other specimens originally examined by Thorne. Description, morphometrics and LM pictures are provided. An updated diagnosis is given and the identity of several (other than type) populations is discussed. It is characterised by its 7.09-10.42 mm long body, lip region offset by deep constriction and 25-27 mu m broad, mural tooth 12-14 mu m long ventrally, pharyngeal expansion occupying 68-73% of total neck length, uterus 2.5-4.2 times the corresponding body diam., pars refringens vaginae well developed, V = 48-56, female tail rounded conoid (47-71 mu m, c = 117-174, c' = 0.7-0.8), spicules 120 mu m long, and eight or nine irregularly spaced ventromedian supplements with a hiatus. The nature of the stomatal protrusible structure is analysed and discussed, concluding that it is more a reduced odontostyle than a typical mural tooth, a point that should be the subject of further studies.