Helgenema keablei, Smales, 2020

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 : 27

3.10.2.1 Helgenema keablei

Synlophe: from the original description [ 43], the synlophe within the proximal region possesses 13-14 ridges in one male, 13 ridges in another male, 9-11 in one female, 11-15 in another female; and, the synlophe at midbody 14 ridges in males, 15 in females. Variation in ridge number from nine to 15 within the proximal body seems to us unlikely, and we assume that the “proximal” sections in different specimens have not been taken at homologous levels, the sections with more ridges having been probably taken closer to midbody.

The section in 10A should be reversed on its frontal axis, to match the usual arrangement of the Nippostrongylinae . In the re-oriented section ( Fig. 10A’ ) the excretory glands are situated ventrally with respect to the excretory pore, and the large left ridge can be interpreted as ridge 1’, with its tip pointing dorsally, allowing the numbering of the remaining ridges according to the usage in the Nippostrongylinae .

Concerning the midbody male section (10B), the position of the right lateral field is unlikely because a hypothetical frontal axis passing through the illustrated fields would determine a ventral part much larger than the dorsal one. We propose to displace the right lateral field up to the axis originally illustrated in [ 43] in order to have two equivalent dorsal and ventral parts. We think that this section should be reversed on its frontal axis so that the large left ridge, which we interpret as ridge 1’, is directed dorsally. We propose a further rotation (ca. 15°) of the re-oriented section so that the new axis of orientation passes, on the left, between tips of the ridges 1 and 1’ which are clearly convergent. On the right-ventral side the ridges are oriented perpendicularly to the body, which does not allow us to determine the start of the axis. However, given the position of the ridges 1 and 1’, it is probably oblique ( Fig. 10B’ ).

In the midbody female section (10C) the tips of the ridges 1 and 2 being convergent, the numbering must be modified and ridge 1 becomes ridge 1’ and ridge 2 becomes ridge 1 ( Fig. 10C’ ). For the same reasons than in the male, the axis of orientation is possibly oblique.

Figures

Figure 10. Genus Helgenema Smales, 2020. Body sections. A–C’ Helgenema keablei. A, A’ within proximal body, female. B–C’ at midbody. B, B’, male. C, C’ female. D–F’ Helgenema lamia Smales, 2021. D within proximal body, male. E–F’ at midbody. E, E’ male, F, F’, female. Sources: A–C redrawn from [43]. D–F redrawn from [44]. A’–C’, E’, F’ modified sections: A’ reversed on its frontal axis with respect to the original, B’ reversed on frontal axis then rotated ca. 15° clockwise with respect to the original. C’, E’, F’ re-numbering of ridges.