Laxus, COBB, 1894

Armenteros, Maickel, Ruiz-Abierno, Alexei & Decraemer, Wilfrida, 2014, Taxonomy of Stilbonematinae (Nematoda: Desmodoridae): description of two new and three known species and phylogenetic relationships within the family, Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 171 (1), pp. 1-21 : 6-7

LAXUS COBB, 1894

Diagnosis (emended from Ott et al., 1995 and Tchesunov, 2013): Stilbonematinae . Cuticle finely striated. Cephalic cuticle reinforced by a ‘block-layer’ inserted in the median layer of the cuticle. Amphidial fovea small, spirally coiled with about 1.5 turns, located close to the apex. Subcephalic lateral setae (four) at level of amphidial fovea and very close to cephalic setae. Anterior region of the pharynx slightly swollen and not sharply marked from the narrow median region. Spicule strongly cephalated. Gubernaculum directed dorsally. Tail short, conical, 1.4–2 anal diameters long. Symbiotic bacteria coccoid or rod shape.

Tchesunov (2013) included as a diagnostic feature the presence of ‘fingerprint’ pattern in the surface of the head cuticle but this feature is also present in other noncongeneric species examined by us (e.g. E. hopperi and R. porosum ). In Laxus parvum sp. nov. we could not observe the relief of the cuticle surface clearly because it was covered by a film of secretion. We included the presence of the ‘block-layer’ in the head capsule as a diagnostic feature as stated by Ott et al. (1995); the reinforcement of the head capsule is also present in other genera of Stilbonematinae (e.g. Robbea , Stilbonema ) but in Laxus it is clearly visible under the LM as small internal vertical rods in the layer. The diagnosis of the genus Laxus provided by Ott et al. (1995) indicated that ectosymbiotic bacteria were rod-shaped, with the longitudinal axis perpendicular to the cuticle surface; Tchesunov (2013) mentioned only coccoid bacteria. Therefore we included in the diagnosis both bacteria shapes: rod-shape (e.g. Laxus cosmopolitus and Laxus oneistus ) and coccoid shape (e.g. La. parvum and Laxus sigma ).

Type species: Laxus longus Cobb, 1894 .

Valid species (6): Laxus cobbi (Inglis, 1968) Ott, Bauer-Nebelsick & Novotny,1995 ; La. cosmopolitus Ott, Bauer-Nebelsick & Novotny, 1995 ; La. gerlachi ( Hopper & Cefalu, 1973) Tchesunov, 2013 ; La. oneistus Ott, Bauer-Nebelsick & Novotny, 1995 ; La. parvum sp. nov.; La. sigma ( Gerlach, 1963) Tchesunov, 2013 .