Parvinema helgeni, Smales, 2017

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 : 21

3.7.1.2 Parvinema helgeni ( Fig. 7C )

3.7.1.2.1 Synlophe (based on section of one male). Section analyzed herein is at midbody (Fig. 31/7C); lateral cords illustrated; ridges numbered. Careen absent. Ridge 1’ very large and slightly curved (inner curvature upwards). Sixteen ridges irregularly spaced with two gaps (arrowheads): one between ridges 3 and 4, another one between 8 and 9’. Two groups of dorsal ridges: on left three small ridges, serried, oriented from right to left; on right, five small ridges, more widely spaced, oriented perpendicular to body surface. Ventral ridges regularly spaced with median ridges smallest, oriented from right to left. Axis of orientation oblique.

3.7.1.2.2 Bursa (illustrated in [ 40]: Fig. 32). Figure 32: dorsal ray, left ray 8 and left rays 4-6, left latero-dorsal view; rays 2 and 3 not illustrated. From the written description [ 40]: bursa dissymmetrical with left lobe larger and pattern of type 1-3-1.

3.7.2 Comments

3.7.2.1 Synlophe

Although in the definition of the genus [ 40] a careen is mentioned, in the written descriptions of P. bafunminense and P. helgeni , there is no reference to such a structure. Illustrations of P. bafunminense show some flaws: in Figure 7A , ridge 1 does not reach the margin of the section, and the dorsal hypodermis is not correctly illustrated (present on the left, absent on the right).

The male section of P. bafunminense is clearly different from the female section of the same species and from that of P. helgeni by the ridge 1’ not very large and straight.

In the male section of P. helgeni , the orientation of ridge 1’ is unusual for a Nippostrongylinae and it is likely that the section should be reversed on its frontal axis ( Fig. 7C’ ). After reversion and a slight rotation clockwise, the section becomes similar to that of P. bafunminense female at midbody: large left ridge oriented with the inner curvature downwards; dorsal ridges regularly spaced and unequal in size, the mid-dorsal ones being small and the left-dorsal (1, 2) and right-dorsal ones (6 to 8) being larger. On the reoriented section the dorsal ridges are oriented from right to left; the ventral ridges 9’ to 5’ oriented perpendicularly to body surface and left ventral ridges (4’ to 1’) oriented from right to left.

The synlophes of P. bafunminense female and P. helgeni male share the left ridge (ridge 1’) very large and curved and a left-ventral gap. However, in P. bafunminense female, the gap is situated between ridges 1’ and 2’ whereas in P. helgeni male, it is situated between ridges 5’ and 4’. In both species the inclination of the axis of orientation is uncertain due to the disparate orientation of the ridges.

The male and the female of P. bafunminense do not appear to belong to the same taxon, the differences between both synlophes being too marked. The synlophe of Parvinema bafunminense (female) is closely related to that of P. helgeni (male) by the hypertrophy of the left ridge and they should probably be included in the same genus. They differ from each other by the relative size and spacing of the gaps, characters which could be attributed to specific differences.

3.7.2.2 Bursa

Parvinema bafunminense : Figure 21, judging from the shape of the bursa, is in dorsal view. In Figures 25 and 26 the margins are illustrated with dotted lines, which indicates that the lateral lobes are in latero-dorsal view. Judging from the illustrations, the pattern is 2-2- 1 in both lobes, even if left ray 2 is not illustrated. Parvinema helgeni : the unique drawing provided is incomplete and does not allow us to confirm or to dismiss either the dissymmetry or the pattern 1-3-1 of the bursa.

3.7.3 Conclusion

It is possible that under Parvinema there are at least three taxa described. This hypothesis is reinforced by the fact that in [ 40] it is noted that “ Parvinema helgeni and P. bafunminense were found in mixed infections in four of the 27 individuals of P. lorentzii examined” (p. 770).

Unfortunately, the original description did not provide more precision. For P. bafunminense it is not possible to know if the description and illustration of the bursa come from the same individuals used for the study of the synlophe. On the other hand, the female synlophe of P. helgeni is not described nor illustrated. In these conditions, Parvinema bafunminense and Parvinema helgeni are considered species inquirendae and the genus Parvinema a genus inquirendum.

The three types of synlophe recognized seem to be distributed into three different taxa, as follows: “ P. bafunminense ” (male section), Nippostrongylinae i.s. 4 (female section of P. bafunminense ), and “ P. helgeni ” (male section).

Figures

Figure 7. Genus Parvinema Smales, 2017. Midbody sections. A, B Parvinema bafunminense Smales, 2017. A male, B, B’ female. C, C’ Parvinema helgeni Smales, 2017, male. Source: A–C redrawn from [40]. B’, C’ modified figures with respect to the original: B’ numbering of ridges added. C’ reversed on its frontal axis, then rotated 30° clockwise.