Chordodes moutoni Camerano, 1895

Schmidt-Rhaesa, Andreas & Yadav, Arun K., 2015, Chordodes combiareolatus, a new species of horsehair worms (Nematomorpha) from Nagaland, India, with further comments on Chordodes moutoni, Zootaxa 3925 (2), pp. 202-210 : 206-209

Chordodes moutoni Camerano, 1895

( Figure 3 )

Material examined. From same location as holotype of C. combiareolatus , but collected in a small time difference on same date: Terrace paddy field in Tsupo, Viswema, Kohima, Nagaland, India (25°34’50.59”N / 94°09’56.89”E), elevation: 4175 feet.

Description of female. The specimen is 200 mm long and has a width of 1.6 mm in the midbody region. The anterior end is tapered, the anterior-most tip is white. The main body colour is moderately dark brown with darker patches forming the so-called “leopard pattern”. The posterior end is distinctly swollen, the cloacal opening is terminal.

In the midbody region, all 6 types of areoles known from the genus Chordodes are present. Some surface areas between areoles are visible and show the parallel superficial folds, which in some regions form slight elevations ( Fig. 3 A). Such elevations are low compared to areoles, so it is not clear whether they represent areoles. The most abundant type of areoles is simple areoles ( Fig. 3 A). They are of differing height and have an apical tuft of bristles. Tubercle areoles are present among simple areoles ( Fig. 3 A). They have a smooth surface, bristles could not be observed. The tubercle arises more or less from the center of the areoles. Thorn areoles were rarely observed, but are present (not figured here). Clusters of crowned areoles are present in the same distribution as in the previous species. On the lateral sides of the body the clusters are composed of two central crowned areoles and 10‒12 surrounding circumcluster areoles, although the number is hard to count because circumcluster areoles decrease gradually in size and then cannot be distinguished from simple areoles. The circumcluster areoles are slender and elongated and have a tuft of bristles apically. The crowned areoles do not have a flat apical surface, the apical bristles form a dense tuft of thin filaments. Their length is moderate (10‒15 µm). Division of filaments could not be observed, but cannot be excluded. A tubercle between the crowned areoles was not observed. Along the midline (ventral and/or dorsal could not be decided) crowned areoles occur on both sides next to the midline and have distinctly longer apical filaments ( Fig. 3 B). The length of the filaments is about 300 µm.

The arrangements of areoles, in which areoles resembling circumcluster areoles surround a central flat region in which the cuticular surface is rough could also be observed ( Figs. 3 C, 3D).

In the anterior end, the structure of the cuticle resembles the one described above for C. combiareolatus . The most abundant type of areoles has a large tuft of apical filaments on top ( Fig. 3 E). Between these areoles are tubercle areoles and thorn areoles. The thorn areoles carry a thin, apically curved thorn ( Fig. 3 E). As far as could be observed, the anterior-most areoles have no depressed surface.

In the posterior end ( Fig. 3 F) the terminal cloacal opening is surrounded by a region with finely striped cuticle. In the margin of this smooth circular region are some bristles and the transition to areoles.

Taxonomic comments. Exact species determinations are often difficult in Nematomorpha, because the fine structural details are in some cases difficult to compare between older descriptions including drawings and newer descriptions including SEM images. Additionally, many specimens deviate from each other by very small differences and it is not known whether such differences can be due to intraspecific variation or are a document of interspecific variation.

species C. combiareolatus C. moutoni Nagaland C. moutoni China, C. moutoni Malaysia C. moutoni Shillong

lectotype

source this investigation this investigation Zanca & De Villalobos Schmidt-Rhaesa & Brune Schmidt-Rhaesa & Yadav

2005 2008 2013

simple areoles with bristles with bristles rough surface, some with bristles with bristles

areoles (described as type

3) with bristles

In this case the specimens resembles in many details C. moutoni , a species first described from China ( Camerano 1895), later from Malaysia ( Camerano 1899, 1901, 1903, Schmidt-Rhaesa & Brune 2008) and again from China ( Wu & Tang 1933). The original material consisted of two males and two females, which were distributed among two museums, Paris and Torino. The male and the female specimen from the Muséum National d´Histoire Naturelle in Paris were reinvestigated by Zanca & De Villalobos (2005) and designated as lectotype (male) and paralectotype (female).

Our specimen from Nagaland resembles the female paralectotype in many respects, but differs in the following characters. For reasons of simplicity, the specimens are in the following named the Nagaland specimen and the China specimen. The simple areoles of the China specimen have a rough surface and no clearly visible bristles on their apical surface. However, one type of areoles is described, which has some apical bristles, but in the images bristles appear more or less attached to the surface and not clearly visible (see Zanca & De Villalobos 2005). Thorn areoles are not described for the China specimen, but are present in the Nagaland specimen. As thorns are generally rare structures, they may be overlooked, especially when only small pieces of cuticle are investigated. The posterior end of the China specimen is slightly invaginated, so a proper comparison to the posterior end of the Nagaland specimen is not possible. The structure of the anterior end is not described for the China specimen.

Two further specimens have been documented by SEM. One male specimen collected in Malaysia (see Schmidt-Rhaesa & Brune 2008) and one female from Shillong, North-Eastern India ( Schmidt-Rhaesa & Yadav 2013) correspond in most characters with the Nagaland specimen. One interesting difference is the shape of crowned areoles. While in the Nagaland specimen and in the Malaysia specimen apical filaments originate as a kind of unordered tuft from the apical surface of areoles, the apical surface of the China specimen and the Shillong specimen is more or less flat and filaments originate to the side. Asymmetrical patterns as in C. combiareolatus were not observed, but in the Shillong specimen filaments branch from both crowned areoles in all directions (see Schmidt-Rhaesa & Yadav 2013) and in the China specimen filaments do not originate from the sides where crowned areoles face each other (see Zanca & De Villalobos 2005). Until now, almost no attention has been paid to this character and these differences should be kept in mind for further investigations. With the mentioned exceptions, specimens described as C. moutoni appear to belong to the same species. The small differences in comparison with the paralectotype are regarded by us as not fundamental enough to describe a new species, but this possibility should be kept in mind. For a comparison of characters among specimens documented by SEM see Tab. 1.

Chordodes moutoni and C. combiareolatus were found in the same location. They show some correspondences and some differences. Most characters are common, widespread characters typical for Chordodes . Simple areoles are rarely described with apical bristles and a clear tuft of bristles was even used by Schmidt-Rhaesa et al. (2008) in a key of the genus Chordodes to separate two species, C. villalobi Schmidt-Rhaesa & Brune, 2008 from Malaysia and C. corderoi Carvalho, 1946 from Venezuela from all other species. It is suspected that tiny bristles are more commonly distributed than previously recorded, but this character can only be documented reliably with SEM.

The special form of the tubercle areoles forms the most prominent difference between C. combiareolatus and C. moutoni , as the Nagaland specimen of C. moutoni has tubercle areoles with a smooth surface, as described for almost all other Chordodes species. One further difference is the shape of the crowned areoles. In C. combiareolatus they have a flat surface and filaments extend only to the sides, while in C. moutoni filaments extend like a tuft in all directions. Both characters were already described or figured for other Chordodes species (flat surface e.g. in C. mizoramensis Schmidt-Rhaesa & Lalramliana, 2011 and C. parabipilus Kintsurashvili, Schmidt-Rhaesa & Gorgadze, 2011 , tuft of bristles e.g. in C. kenyaensis Bolek, Szmygiel, Kubat, Schmidt-Rhaesa & Hanelt, 2013 ; see Kintsurashvili et al. 2011, Schmidt-Rhaesa & Lalramliana 2011, Bolek et al. 2013), but this difference has not received much attention until now. The shape of crowned areoles should be described in more detail than has been done before., particularly the origin of the apical filaments, branching patterns of the apical filaments and their fine structure.

The specimen determined here as C. moutoni corresponds with C. combiareolatus in two special characters. First, the cuticle contains the circular arrangements of areoles around an “empty center”. As described above this is interpreted here as an artifact, but as this phenomenon has not been documented from other species, it remains unknown why two specimens of two different species should both show this kind of cuticular destruction. The second character is the areolar pattern in the anterior end. As described above, the anterior end is rarely investigated in detail and it remains to be shown whether the composition of areoles in the anterior end is particular or widely distributed among Chordodes .

Figures

FIGURE 3. Chordodes moutoni. A. Cuticle in mid-body region with simple areoles and tubercle areoles (encircled). B. Crowned areole clusters along the ventral mid-line with very long apical filaments. C. Clusters with a flat central surface (encircled). D. Magnification of a cluster with a flat central surface. E. Pattern of areoles in the anterior end. F. Posterior end with terminal cloacal opening (arrow).