Nugininema titokis, Smales, 2016

Durette-Desset, Marie-Claude & Digiani, María Celina, 2023, Revision of the genera of Heligmonellidae (Nematoda, Heligmosomoidea), parasitic in Muridae from New Guinea, Parasite (Paris, France) 30 (63), pp. 1-34 : 17-18

3.5.1 Analysis of data and difficulties encountered Nugininema titokis

3.5.1.1 Synlophe (based on sections from two males and two females)

Sections analyzed herein are those within proximal body: male (Fig. 16/5A) and female (Fig. 17/5B), and at midbody: male (Fig. 19/5C) and female (Fig. 20/5D). In all figures, lateral cords illustrated except right lateral cord of section 19/5C; ridges numbered only in Fig. 19/5C.

In all sections careen absent. Axis of orientation described as oblique within proximal body and subfrontal at midbody by Smales [ 38].

Within proximal body: in Figure 5A (male), 10 ridges separated into two groups by two gaps, situated on left-dorsal quadrant and on right-ventral quadrant (arrowheads). On ventral side, presence of two large comaretes. Remaining ridges small and subequal in size. Most ridges oriented from right-ventral to left-dorsal quadrant, except: two left dorsal ridges flanking axis of orientation (perpendicular to body surface), and ventral ridge situated left to lesser comarete (oriented from left to right).

Figure 5B (female), 13 ridges of which two large ventral comaretes (in same position than in male section, but smaller). Remaining ridges small and subequal in size and irregularly spaced. Two gaps in the same position than in male section, but smaller (arrowheads). Dorsal ridges and comaretes oriented from right-ventral to left-dorsal quadrant. Remaining ventral ridges show disparate orientation, perpendicular or from left to right.

At midbody: in Figures 5C (male) and 5D (female), 15–17 ridges, regularly spaced, small, subequal and oriented disparately.

From the written description, axis of orientation “prefrontal” (sic) at midbody and losing orientation posteriorly.

3.5.1.2 Bursa (number of studied males not specified; illustrated in [ 38]: Fig. 26)

Figure 26: right lobe, with right ray 8 and right branch of dorsal ray. From description [ 38], bursa dissymmetrical with right lobe slightly larger and pattern of type 1-3-1.

3.5.2 Comments

3.5.2.1 Synlophe

Within the proximal body ( Figs. 5A and 5B ) we interpret, as Smales [ 38], that the axis of orientation of the ridges is oblique. At midbody ( Figs. 5C and 5D ), instead, Smales [ 38] stated that the axis of orientation is “prefrontal” an affirmation that seems to us inaccurate. The disparate orientation of the ridges seems to be due to a misinterpretation, and it is likely that most ridges are oriented perpendicularly to the body surface. This means that there are not two groups of ridges with opposite directions, consequently, there is no axis of orientation of the ridges. It is clear that between the proximal body and the midbody, the number of ridges increased and the comaretes decreased progressively in size up to attain the same size as the other ridges. However, since the level of the “proximal” sections has not been specified and, besides, it is not equivalent in the male and the female, it is not possible to establish either homology of the male and female ridges or the level at which the ridges become subequal and perpendicular to the body surface.

3.5.2.2 Bursa

Without illustration of the left lobe, and the right lobe being folded ventrally, it is difficult to determine the pattern of the rays or the symmetry of the bursa.

As noted by Smales [ 38] the genus Nugininema is related to the genera Melomystrongylus and Hasanuddinia by the presence of at least one ventral comarete and an axis of orientation of the ridges oblique within the proximal part of the body. In Melomystrongylus and Nugininema , the comaretes are present only in the proximal part of the body, whereas in Hasanuddinia they are present all along the body length. There are two comaretes in Hasanuddinia and Nugininema and only one in Melomystrongylus . Nugininema also differs from Melomystrongylus and Hasanuddinia by the fact that in the proximal body all dorsal ridges are small and subequal, whereas in the other two genera, the ridges associated with the right lateral cord (one or two ridges) are more developed.

3.5.3 Conclusion

Concerning the synlophe, Nugininema can be differentiated unambiguously from the related genera. We thus consider Nugininema a valid genus. However, it would be necessary to describe and illustrate accurately the bursa to provide a proper definition of the genus.

3.5.4 Emended diagnosis

Nugininema : Synlophe without careen. Within proximal part of body, presence of two ventral comaretes and two gaps: right-ventral and left-dorsal; remaining ridges small and subequal; axis of orientation of ridges oblique. At midbody, 15–17 ridges regularly spaced, small and subequal; ridges oriented perpendicularly to body surface.

Figures

Figure 5. Genus Nugininema Smales, 2016. Body sections. A–D. Nugininema titokis Smales, 2016. A, B within proximal body. A male. B female. C, D, at midbody. C male, D female. Abbreviations: co, comarete. Source: A–D redrawn from [38].