Montistrongylus kaindiensis, Smales, 2015

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 : 14-15

3.3.2.4 Montistrongylus kaindiensis

3.3.2.4.1 Synlophe. Concerning the male section of the proximal body ( Fig. 3L ), the presence of only one ridge-free space and then the absence of ridge sets prevents us from relating this synlophe to any of the remaining sections studied. A section of the esophagus is observed, which means that the body section has been taken very proximally. Thus, it is difficult to compare the male with the female “proximal” body section ( Fig. 3M ), taken much more distally. The latter, in addition, has two ridge sets vs. three in the midbody sections.

The female section at midbody ( Fig. 3O ) seems congruent with the other Montistrongylus spp. by ridge set 1 situated on the left. Instead, the orientation of the male section ( Fig. 3N ) is less clear. The reversion of the male section on its sagittal axis and further rotation about 30° clockwise ( Fig. 3N’ ) results in both sections at midbody (male and female) having a similar pattern of ridge sets and ridge-free spaces. Such manipulation of the male section changes the original ridge set 3 into set 1 and the ridge set 1 into set 3.

In spite of the clear presence of three sets of ridges alternating with three ridge-free spaces, this synlophe description shows several inconsistencies. Apart from the ridges of set 1, which are perpendicular to body surface, the remaining ridges show an anarchical orientation. Ridges in set 2 in the male section (regardless of the orientation of the section) are oriented in opposite directions, so that there are divergent ridges within the ridge set. By contrast, in the female section, all ridges of set 2 are oriented from left to right, contrarily to what is usual for the dorsal ridges in the Nippostrongylinae . Ridges of set 3 in the reoriented male section ( Fig. 3N’ ) are oriented from left to right, contrarily to what is expected for the ventral ridges in the Nippostrongylinae ; whereas in the female section, the same ridges are oriented, as expected, from right to left ( Fig. 3O ). The disparate orientation of most ridges prevents the identification of an axis of orientation and does not allow a reliable interpretation of the synlophe. Moreover, no attempt at reorientation of any of these sections will make them comparable to each other or to any other species in the genus or in the family. We are not able to interpret these particularities or to state whether both sections correspond to the same species.

3.3.2.4.2 Bursa. From the original illustration, the pattern is of type 1-4 in both lobes with rays 3 diverging proximally to rays 6, and rays 6 diverging first from common trunk to rays 4-6.

3.3.3 Conclusion

3.3.3.1 Synlophe

From a descriptive point of view we observed, throughout the descriptions, three types of synlophe.

Type I is observed in the male sections at midbody of M. ingati and M. karungi ( Figs. 3C, 3J ): it is characterized by two sets of ridges alternating with two ridge-free spaces; and an oblique axis of orientation of the ridges.

Type II is observed in the female section at midbody of M. ingati ( Fig. 3D’ ) and the male and female sections of M. giluwensis ( Figs. 3G’ , 3H’): it is characterized by three sets of ridges alternating with three ridge-free spaces; and an axis of orientation subfrontal at midbody. It would be possible to relate to this second type the male and female sections of M. kaindiensis ( Figs. 3N’ , 3O) based on the presence of three ridge sets and three ridge-free spaces, but the orientation of the ridges in these two sections is completely disparate.

Type III is observed in a male section within the proximal part of the body ( Fig. 3I’ ) and in a female section at midbody in M. karungi ( Fig. 3K ): it is characterized by two sets of ridges alternating with two ridge-free spaces. This type differs from the male section of M. karungi at midbody ( Fig. 3J ) by the position of the dorsal ridge-free space situated on the left side in the female versus the right side in the male.

That said, we can state that, besides the absence of a careen, all the taxa described within Montistrongylus may be characterized by the alternation of 2 or 3 sets of ridges with 2 or 3 ridge-free spaces and ridges small and more or less regularly spaced within the sets.

3.3.3.2 Bursa

Even if the original descriptions of M. ingati , M. giluwensis and M. karungi describe only one type of bursa, the illustrations show two types of dorsal lobes in each species mentioned, which probably means that there are at least two different taxa within each “species” studied. For M. kaindiensis , the illustration of the dorsal lobe is incomplete, the right ray 8 not being figured.

Though the taxa described within Montistrongylus are characterized by ridge sets alternating with ridge-free spaces, and ridges small and regularly spaced within the sets, Montistrongylus is considered a genus inquirendum. In our interpretation, the type species is composed of two different taxa, each represented by a body section with different synlophe types: type I in the male and type II in the female. In the article by Smales & Heinrich [ 45], a male was designated as holotype but its description is mixed with that of the paratypes and it is not possible to know if its synlophe corresponds to type I or to type II.

Since we do not know what type of synlophe the holotype corresponds to, Montistrongylus ingati is considered a species inquirenda. Montistrongylus giluwensis and M. karungi are also considered species inquirendae since their descriptions seem to involve two different taxa each. Montistrongylus kaindiensis is similarly considered a species inquirenda because its synlophe description shows several inconsistencies, which were explained above. The three types of synlophe recognized (type I, II and III) seem to be distributed into six different taxa as follows: “ M. ingati ” (male); “ M. karungi ” (male) (both with synlophe of type I); Nippostrongylinae i.s. 2 (“ M. ingati ” female); “ M. giluwensis ”; “ M. kaindiensis ” (all with synlophe of type II) and Nippostrongylinae i.s. 3 (“ M. karungi ” male section within proximal part of body and female section at midbody) (with synlophe of type III).

Figures

Figure 3a. Montistrongylus Smales & Heinrich, 2010. Body sections. A–D’ Montistrongylus ingati Smales & Heinrich, 2010. A–B’ within proximal body. A male, B, B’ female. C–D’ at midbody. C male, D, D’ female. E–H’ Montistrongylus giluwensis Smales, 2011. E, F within proximal body. E male, F female. G–H’ at midbody. G, G’ male, H, H’ female. Sources: A, D redrawn from [45]; E–H redrawn from [33]. B’, D’, G’, H’ modified figures: B’ rotated ca. 75° counterclockwise with respect of the original. D’–H’ reinterpreted orientation of the axis (subfrontal). G’ reversed on its frontal axis then rotated 30° clockwise with respect to the original. H’ rotated ca. 10–20° counterclockwise with respect to the original.