Daptonema Cobb, 1920

Leduc, Daniel, 2015, One new genus and five new nematode species (Monhysterida, Xyalidae) from Tonga and Kermadec Trenches, Southwest Pacific, Zootaxa 3964 (5), pp. 501-525 : 509

Daptonema Cobb, 1920

Diagnosis (modified from Fonseca & Bezerra (2014)): Cuticle striated. Somatic setae generally shorter than 1.5 times the corresponding body diameter. Inner labial sensillae papilliform; outer labial and cephalic setae in one circle. Amphideal fovea circular, of varying size and position relative to anterior end. Buccal cavity conicalshaped. Post- and/or pre-vulval sac may be present. Spicules usually short (1–2 cbd), often strongly curved or Lshaped. Gubernaculum usually present, often with lateral crurae and sometimes with dorso-caudal apophyses. Tail conico-cylindrical with 2–4 terminal setae.

Remarks. The genus was revised by Lorenzen (1977). Molecular analyses by Neres et al. (2010) suggest that Daptonema is paraphyletic, with some species of the genus more closely related to Theristus , and species of Metadesmolaimus grouped with Daptonema . These three genera are similar morphologically; Theristus is distinguished from Daptonema based solely on tail shape (conical without terminal setae) ( Venekey et al. 2014), whereas Metadesmolaimus is distinguished from Daptonema based on presence of setose inner labial sensillae and extended, cylindrical anterior buccal cavity ( Platt 1983). In some Metadesmolaimus species, the cylindrical part of the anterior buccal cavity is very thin (e.g., M. aversivulva Gerlach, 1953 and M. canicula (Wieser & Hopper, 1967)) , and some Daptonema species possess a buccal cavity with a small, cuticularised extension (cheilostom, e.g., D. biggi (Gerlach, 1965) , D. amphorum n. sp.) so that the distinction between the two genera is sometimes based mainly on the presence of setose ( Metadesmolaimus ) vs papillose ( Daptonema ) inner labial sensillae. A revision of these genera based on further morphological and molecular data is needed; such a revision would likely result in changes in the assignment of species.