Lamyronema, Leduc, Daniel, 2015

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 : 503

Lamyronema n. gen.

Diagnosis. Annulated cuticle. Six outer labial setae and four cephalic setae in one circle. Sub-cephalic setae present between anterior edge of amphideal fovea and cephalic setae, not arranged in groups; somatic setae short and sparse. Amphideal fovea outline not cuticularised, conspicuously larger in males than females (sexual dimorphism). Buccal cavity almost entirely surrounded by pharyngeal tissue, large, heavily cuticularised, without teeth, tripartite; anterior-most portion is a thin cuticularised ring, middle portion is deep, wide, barrel to cupshaped, and posterior portion is narrow and funnel-shaped. Pharyngeal lumen lightly but distinctly cuticularised. Spicules short. Females with one ovary to the left side of intestine. Males with two testes, the anterior one to the left side of intestine, the posterior one to the right side.

Differential diagnosis. Lamyronema n. gen. is similar to other genera of the family possessing large cuticularised buccal cavities, namely Elzalia Gerlach, 1957 , Hofmaenneria Gerlach & Meyl, 1957 , Parelzalia Tchesunov, 1990 , and Sphaerotheristus Timm, 1968 ( Fig. 1 ). Lamyronema n. gen. can be distinguished from these genera by the pharyngeal tissue almost completely surrounding the buccal cavity (vs buccal cavity surrounded only at the base by pharyngeal tissue); it can also be distinguished from these genera (except Parelzalia ) by the presence of sub-cephalic setae positioned anteriorly to the amphideal fovea. In addition, Lamyronema n. gen. can be distinguished from Elzalia by the presence of short spicules and absence of gubernaculum (vs elongated spicules and often complex gubernaculum present in Elzalia ); from Hofmaenneria by the tripartite buccal cavity (vs cylindrical buccal cavity); from Parelzalia by the absence of long somatic setae (vs present in Parelzalia ), and buccal cavity with three well-defined portions without cuticularised rhabdions (vs buccal cavity without clear divisions and with cuticularised rhabdions); from Sphaerotheristus by the absence of longitudinal ridges in the anterior portion of the buccal cavity (vs longitudinal ridges present in Sphaerotheristus ), presence of a cuticularised, funnel-shaped posterior buccal cavity (vs absent), and presence of two testes (vs one testis). Lamyronema n. gen. is also similar to Megalamphis De Coninck, 1965 (family Sphaerolaimidae ), but can be differentiated from the latter by the absence of longitudinal ridges and teeth in the buccal cavity, absence of gubernaculum, and short spicules (vs elongated spicules and gubernaculum present in Megalamphis ).

Etymology. The genus name is derived from the greek lamyros (= greedy) and nema (= thread) and refers to the large buccal cavity full of food particles observed in all specimens.

Type species. Lamyronema horizonensis n. gen. n. sp.

Figures

FIGURE 1. Head region of xyalid genera with large, cuticularised buccal cavities similar to Lamyronema n. gen. Drawings modified from Hope & Aruythaka (2009) (Elzalia), Coomans & Eyualem-Abebe (2006) (Hofmaenneria), Tchesunov (1990) (Parelzalia), and Timm (1968) (Sphaerotheristus).