Rodentanema aenigma

Smales, L. R., 2016, The gastrointestinal helminths of Rattus niobe (Rodentia: Muridae) with descriptions of two new genera and three new species (Nematoda) from Papua New Guinea and Papua Indonesia, Zootaxa 4117 (2), pp. 183-197 : 191-192

Rodentanema aenigma

( Figs 27–34 )

Type host. Rattus niobe (Thomas)

Site in host. Small intestine.

Material examined. Holotype male, allotype female from Rattus niobe hill south of Tifalmin (5° 7´S 141° 25´E), West Sepik district, Sanduan Province, Papua New Guinea, coll. T. Flannery 15. iv. 1987, AM W.48490, W.48491; paratypes, 1 male, 2 females same data AM W.48521.

Etymology. The species name reflects the problematic position of this species.

Description. General: Tiny worms, coiled, cephalic vesicle present, without annulations. Buccal capsule relatively well developed, not annulate, without lips or teeth. Labial papillae and amphids not observed, 4 cephalic papillae. Mouth circular. Oesophagus claviform; nerve ring excretory pore and deirids not observed.

Synlophe (mid body sections of 1 male, 1 female): Longitudinal ridges continuous, 6 in mid body male, 7 in mid body female, not symmetrical to frontal axis; 2 dorsal, 4 ventral ridges, male; 2 dorsal, 5 ventral ridges, female. Axis of orientation not determined.

Male (measurements of 2 specimens): Length 1.25, 1.55 mm, width 67, 72. Cervical vesicle 42 long, 19 wide. Bursa slightly dissymmetrical, left lobe larger, rays 3 arise first from common trunk, rays 4, arise from common trunk before rays 5, 6; dorsal lobe well marked, shorter than laterals. Rays 8 large, recurved dorsally, arise from dorsal trunk at about same level, dorsal ray slender, divided at distal tip. Genital cone prominent, Spicules equal, filiform, 130–150 (141) long. Gubernaculum not observed.

Female (Measurements of 3 specimens): Length 1.50–1.75 (1.61) mm, width 40–50 (45). Cephalic vesicle 30 long, 20 wide. Oesophagus 260 long. Vulva opens 122–190 (160) from tail tip, posterior end flexed ventrally. Monodelphic ovejector with sphincter, 20, the shortest element, vestibule, 25, 30 and infundibulum, 25, about same length, vagina shorter, 10, 15 long. Tail slender, ending in blunt knob, 50–80 (66) long. Eggs thin shelled, ellipsoidal, 3–4 in utero, 52.7–61.0 (56.9) long, 26.4–30.0 (28.8) wide.

Remarks. Only a small number of specimens were available for study and, being small in size and fragile, were therefore difficult to examine. Their fixation had been inadequate and consequently details of the body wall, including the location of the lateral cords, could not be determined with any certainty, although the relative positions of intestine and reproductive system and synlophe ridges were indicative of the dorso-ventral orientation of the transverse body sections. However neither the axis of orientation of the synlophe nor the exact positions of the ridges could be determined. Nor could the bursa be completely unrolled, precluding the determination of the arrangement of the ventral rays. Sufficient morphological information, however, was available to characterise the new genus. Following the keys of Beveridge et al. 2014 Rodentanema n. gen. can be placed in the family Heligmonellidae , subfamily Nippostrongylinae . The genus differs from all other genera described in the subfamily in having a well developed buccal capsule, the number, arrangement and sizes of the ridges of the synlophe at the mid body, the relative proportions of rays 8, 9, 10 and the shape of the female tail. If additional material from New Guinea becomes available for examination then a more complete description can be prepared which would allow an improved characterization of the species and the clarification of its taxonomy.

Figures

FIGURES 27 – 34. Rodentanema aenigma n. gen., n. sp.. In all illustrations of the synlophe the dorsal aspect of the body is oriented towards the top of the page and the left side of the nematode is on the left side of the page. 27. Female, cephalic end; 28. Female, en face view; 29. Female posterior end, right lateral view; 30. Male posterior end, left lateral view, bursal rays numbered; 31. Male transverse section, mid body; 32. Female transverse section, mid body; 33. Bursa partially unrolled, left lateral and dorsal aspects, rays numbered; 34. Bursa, dorsal ray. Scale bars in µm: 27, 28, 31, 33, 34, 12.5; 29, 30, 50.; 32, 25.