Chordodes tjorvenae, Schmidt-Rhaesa, Andreas, 2016

Schmidt-Rhaesa, Andreas, 2016, New records of Indian Nematomorpha, with the description of a new species from the genus Chordodes, Zootaxa 4158 (2), pp. 272-280 : 273-278

Chordodes tjorvenae n.sp.

( Figures 1–3 )

Holotype. One female from the type locality, deposited in the Zoological Museum of the Department of Zoology at Pachhunga University College, Aizawl-Mizoram, India, accession number PUCZM -A/V/16001.

Etymology. The species name “ tjorvenae ” is chosen after a daughter of the senior author, Tjorven Finja.

Type locality. Sala River , in the vicinity of Lungpuk Village, Saiha District, Mizoram, India (22°04’53 N; 92°55’28 E). Collected on November 14, 2012. Found in a small river-side pool together with a female determined here as Chordodes sp. (specimen 1), half buried in the sand.

Further specimens. Three females from the Tuichang River , in the vicinity of Chhawrtui , Champhai District, Mizoram, India (23°28’12 N; 93°04’52 E). Collected on November 20, 2014. All the specimens were collected close to each other (around a 500 m stretch). One of the specimens (not recorded) is from an undetermined praying mantid. Both the Sala and Tuichang Rivers are tributaries of the Kaladan River drainage.

Description of the holotype. The female holotype is 200 mm long with a diameter of 1.7 mm. The anterior end tapers towards a whitish tip. The body color is light to medium brown, a “leopard pattern” (darker patches) is not present. In the midbody region different types of areoles are present (the names of the structures used here follow the terminology proposed by Schmidt-Rhaesa et al. (2008)). Most abundant are simple areoles. These are at moderate distances from each other, so that the structure of the interareolar region can be observed ( Fig. 1 A). It is composed of ridges and grooves arranged perpendicular to the longitudinal axis of the animal. The ridges are confluent with the simple areoles, which are elevated roundish structures ( Fig. 1 A). The surface is irregularly structured and has a few fine bristles on the apex ( Fig. 1 A). Tubercle areoles are present, being quite long and thin and originating either on an areole-like elevation ( Fig. 1 B) or more or less directly from the cuticular surface ( Fig. 1 C). Most tubercles are straight, some are curved ( Fig. 1 B, C). Scattered thick ‘thorns’ are present ( Fig. 1 A, E). In one case the ‘thorn’ is situated between two areoles that are taller than the simple areoles and have an apical tuft of bristles ( Fig. 1 A). Such areoles correspond to bulging areoles, but they are the only ones of this type that could be observed. Crowned areole clusters are composed of approximately 22–25 areoles of similar appearance but different shape ( Fig. 1 B, C). Distinction between circumcluster areoles and crowned areoles cannot be made. All areoles carry apical filaments. These are 5–7 µm long in the largest areoles ( Fig. 1 D) and shorter in smaller ones. Few filaments are bifurcate ( Fig. 1 D). Filaments originate from the marginal region of the areoles, the center of the areole contains very short structures, but no longer filaments ( Fig. 1 D). Crowned areoles with very long (> 40 µm) apical filaments are present ventrally ( Fig. 1 E, F). The long filaments are not branching. Two or exceptionally three crowned areoles with long filaments are present per cluster ( Fig. 1 E). They are surrounded by circumcluster areoles that correspond to the areoles from the “normal” crowned areole clusters.

The posterior end is, as usual for Chordodes females, swollen, meaning that the diameter decreases slightly towards the posterior tip and then increases again for the last 0.7 mm ( Fig. 2 A). The cloacal opening is terminal in a slight depression. In this depression, radial grooves spread from the cloacal opening ( Fig. 2 B). The areoles change towards the posterior end. They become more and more uniform in structure and resemble the crowned areoles described above, differing only in size, with the crowned areoles being the largest ones ( Fig. 2 D). Slender tubercles are present. Along the ventral midline are pairs of crowned areoles without surrounding circumcluster areoles ( Fig. 2 E, F). These crowned areoles are larger than the surrounding ones. At the most posterior part where areoles are present, irregular elevations occur, carrying scattered bristles, but no crown of bristles or filaments ( Fig. 2 C). A number of tubercles is present in this region ( Fig. 2 C).

Description of other specimens. Three females from the Tuichang River, deposited in the Zoological Museum in the Department of Zoology at Pachhunga University College, Aizawl-Mizoram, India, accession number PUCZM -A/V/16002.

Three further female specimens are assigned here to C. tjorvenae n.sp. Specimens are 175, 190 and 295 mm long and have diameters of 1.2, 1.2 and 1.4 mm, respectively. Cuticular structures are in part not as clear as in the holotype and specimen 3 is covered with dirt, crystals and diatoms ( Fig. 3 I). Simple areoles correspond to those of the holotype. Single tubercle areoles were found in specimens 1 and 2, these are slightly (specimen 1) or distinctly (specimen 2) curved and their tip is often pointed ( Fig. 3 B, E). A ‘thorn’ was observed in specimen 1, enclosed by a pair of elevated areoles with a tuft of bristles as in the holotype ( Fig. 3 A). The clusters of crowned areoles are similar to the ones described for the holotype ( Fig. 3 C, F–K). Crowned areoles with long filaments were observed only in specimen 1 ( Fig. 3 C).

Discussion. There are few species of Chordodes in which clusters of crowned areoles include only one type of areoles, but which have crowned areoles with long filaments on the ventral side. There is some resemblance of the specimens examined here to C. compressus and C. polycoronatus , both species from Malaysia described by Schmidt-Rhaesa & Brune (2008). However, C. compactus has very long and slender areoles in the crowned areole cluster which form very dense clusters and C. polycoronatus has very large clusters composed of about 40 areoles ( Schmidt-Rhaesa & Brune 2008). There is also some resemblance to C. curvicillatus , a species described from Sumatra, Indonesia by Kirjanova & Spiridonov (1989). The crowned areole clusters are very similar in C. curvicillatus and C. tjorvenae n.sp. and both species possess distinctly curved as well as straight tubercles. The difference is that a ‘thorn’ is described in C. curvicillatus only from the center of a crowned areole cluster and that pointed areoles are present close to the crowned areole cluster ( Kirjanova & Spiridonov 1989). Due to these differences we regard Chordodes tjorvenae n.sp. as a separate, new species.

Chordodes sp.

Seven further specimens, one male and six females, belong to the genus Chordodes , but with structures not preserved well enough to identify them with certainty. At least some of these specimens probably belong to C. tjorvenae n.sp. described above. Specimens are deposited in the Zoological Museum in the Department of Zoology at Pachhunga University College, Aizawl-Mizoram, India, accession number PUCZM -A/V/16003 for Chordodes sp. (specimen 1) and PUCZM -A/V/16004 for Chordodes sp. (specimens 2–7).

Chordodes sp. (1). Locality: Sala River, India (22°04’53 N; 92°55’28 E). Male, length 160 mm, diameter 1.0 mm. Cuticle covered with dirt. Only a few bristles around the cloacal opening were observed ( Fig. 4 A, B).

Chordodes sp. (2). Locality: Tuichang River, India (23°28’12 N; 93°04’52 E). Female, length 250 mm, diameter 1.7 mm. Cuticle eroded, fine apical structures of areoles not present ( Fig. 4 C). Basal structure of areoles in crowned areole clusters are present, simple areoles flat, roundish, with few small surface structures. Bulging areoles are present ( Fig. 4 D).

Chordodes sp. (3). Locality: Tuichang River, India (23°28’12 N; 93°04’52 E). Female, length 250 mm, diameter 1.3 mm. Cuticular pattern similar to Chordodes sp. (2) ( Fig. 4 E, F).

Chordodes sp. (4). Locality: Tuichang River, India (23°28’12 N; 93°04’52 E). Female, length 160 mm, diameter 1.1 mm. Cuticular pattern similar to Chordodes sp. (2) ( Fig. 4 G). Additionally, a few complete crowned areoles were observed, with very short apical filaments ( Fig. 4 I). Distinctly curved and pointed tubercles were observed ( Fig. 4 H).

Chordodes sp. (5). Locality: Tuichang River, India (23°28’12 N; 93°04’52 E). Female, length 225 mm, diameter 1.2 mm. Cuticular pattern generally resembles Chordodes sp. (2). Simple areoles have longer bristles than those observed in other specimens ( Fig. 4 J). Straight tubercles are present ( Fig. 4 J).

Chordodes sp. (6). Locality: Tuichang River, India (23°28’12 N; 93°04’52 E). Female, length 235 mm, diameter 1.5 mm. Cuticle eroded and covered with dirt and diatoms, it resembles specimen (2) ( Fig. 4 K).

Chordodes sp. (7). Locality: Tuichang River, India (23°28’12 N; 93°04’52 E). Female, length 150 mm, diameter 1.1 mm. Cuticular pattern similar to Chordodes sp. (2). Crowned areoles with long filaments and distinctly curved ‘thorns’ are present ( Fig. 4 L, M).

Figures

FIGURE 1. Chordodes tjorvenae, n. sp., holotype. A. Simple areoles (sar) and one thorn areole (thar) enclosed between two larger (bulging) areoles. B, C. Cluster of crowned and circumcluster areoles (encircled in B), showing similar appearance of both types of areoles. Arrows point to tubercle areoles. D. Magnification of largest crowned areoles showing their fine structure. E. Clusters containing crowned areoles with long apical filaments along one side of the ventral midline. Arrow indicates one thorn areole. F. Magnification showing fine structure of areoles with long filaments.

FIGURE 2. Chordodes tjorvenae, n. sp., holotype. A. Posterior end with terminal cloacal opening (co). The ventral midline (ml) is indicated. B. Radial furrows are present around the cloacal opening (co). C. In the posterior region cuticular structures are stongly modified and more tubercles are present than in other body regions. D. In the region anterior to C areoles are present and the majority resembles crowned areoles. E. On both sides of the ventral midline, pairs of crowned areoles (selective pairs are encircled) are present. F. Magnification of crowned areoles from E, with abundant tubercles (arrows).

FIGURE 3. Chordodes tjorvenae, n. sp., additional specimens. A – C: specimen (1), D – H: specimen (2), I – K: specimen (3). A. Thorn areole (thar) surrounded by two large areoles. B. Curved tubercle or thorn. C. Cluster containing crowned areoles with long apical filaments. Adjacent to the cluster is a thorn areole (thar). D. Simple areoles and one tubercle areole with distinctly curved tubercle (encircled). E. Magnification of tubercle areole. F. Cluster of crowned areoles with short filaments. G. Magnification of crowned areoles. H. Lateral view on cluster. I – K. Cluster with crowned areoles and different magnifications of areoles.

FIGURE 4. Chordodes sp., cuticular details. A. Posterior end of specimen (1) with ventral cloacal opening (co). B. Detail of region around cloacal opening (co) with circumcloacal spines (ccs). C, D. Crowned areole clusters with eroded apical structures and bulging areoles (in D, selectively encircled) from specimen (2). E, F. Clusters (in E) and bulging areoles (in F) of specimen (3). G. Cluster in specimen (4). H. Curved and twisted tubercle areole in specimen (4). I. Some entire crowned areoles are present in specimen (4). J. Simple areoles and straight tubercle in specimen (5). K. Cluster in specimen (6). L. Cluster containing crowned areoles with long filaments in specimen (7). M. Curved thorn in specimen (7).