Chordodes formosanus Chiu, 2011

Chiu, Ming-Chung, Huang, Chin-Gi, Wu, Wen-Jer & Shiao, Shiuh-Feng, 2017, A new orthopteran-parasitizing horsehair worm, Acutogordiustaiwanensis sp. n., with a redescription of Chordodesformosanus and novel host records from Taiwan (Nematomorpha, Gordiida), ZooKeys 683, pp. 1-23 : 6-8

Chordodes formosanus Chiu, 2011

Material examined.

Taipei Zoo (24°59′44.70′′N, 121°34′49.49′′E), Taipei City, Taiwan (three males from an Acromantis japonica individual); Wufengqi Waterfalls (24°49′55.62′′N, 121°44′50.10′′E), Jiaushi Township, Yilan County, Taiwan (two males from two Tettigoniidae species). For specimen details, see Table 1.

Hosts.

Acromantis japonica Westwood, 1889 ( Mantodea : Mantidae ). Leptoteratura sp., Holochlora japonica Brunner von Wattenwyl, 1878 ( Orthoptera : Tettigoniidae ). For host details, see Table 2.

Redescription

(Fig. 8). Male adult (n = 5). Body length 109 ± 64 (43-204) mm, width (widest, after dehydration) 0.56 ± 0.29 (0.32-0.88) mm, dark-brown, rough, and flat with dorsal and ventral grooves in alcohol-preserved specimens.

Except for one sample with the broken posterior end, which was not described, the posterior end of the other 4 samples (Fig. 8A) not lobed, ornamented areoles on margin with short spines between them. Oval cloacal opening subterminal, 61.14 ± 27.61 (44.41-93.00) μm long and 31.23 ± 11.42 (22.00-44.00) μm wide, circum-cloacal spines present. A pair of oval regions free with areoles posterior to cloacal opening with scattered bristles over it. Paired oval bristlefields 171.94 ± 48.32 (127.84-223.59) μm long and 55.94 ± 10.08 (46.34-66.43) μm wide, not found in one sample, located on lateral side of cloacal opening between areas adjacent to flat areoles and normal areoles. Anterior end (Fig. 8B) tapered, with white tip (white cap) under stereomicroscopy. Under SEM, anterior tip smooth or wrinkled, covered with abundant small spines, and scattered, thick bristles; mouth open on terminal end of anterior extremity.

Mid-body covered with areoles with some ornamentation on surface. Areoles characterized into five types (simple, tubercle, thorn, circumcluster, and crowned areoles). Simple areoles, most abundant, covering entire cuticle of mid-body, 9.70 ± 1.84 (8.18-12.51) μm in diameter, circular, surface smooth or uneven. Tubercle areoles and thorn areoles scattered among simple areoles, similar in shape, but with a tubercle (ca. 3.96-8.09 μm long) or a solid thorn (ca. 7.35-16.92 μm long), respectively, on the latter or on top of thorn areoles; thorn areoles less abundant than tubercle areoles and not found in one sample. Crowned areoles (Fig. 8C, E) (each 14.90 ± 3.40 (9.72-21.81) μm in diameter) surrounded by 7-12 circumcluster areoles with a central tubercle in between; each areole with a flat top and medium filaments (13.11 ± 4.96 (7.41-27.62) μm) originating from the apical center to edges; few long filaments (55.43-179.70 μm) found in one sample. In one small individual from Acromantis mantid, crowned areoles (Fig. 8D, F) smaller than usual (10.84 ± 0.84 (9.60-11.83) μm) and apical filaments (6.56 ± 1.11 (5.03-8.36) μm), with almost same-sized circumcluster areoles.

Phylogeny.

The genetic distances among all horsehair worms from Acromantis japonica (GenBank nos: KX591949- KX591951), Leptoteratura sp. (GenBank no.: KX591952), Holochlora japonica (GenBank no.: KX591953), and Hierodula mantid (sequences from Chiu et al. (2011)) COI sequences ranged from 0.000 to 0.010. The phylogenetic tree (Fig. 7) revealed a polytomic topology, whereas the five horsehair worm sequences from the Acromantis mantid and Tettigoniidae hosts were randomly inserted into this clade.

Comments.

The five male horsehair worms were all determined to be C. formosanus because of the low genetic distances between their COI sequences and those of C. formosanus individuals as described in Chiu et al. (2011). Their morphology was also similar to that of the species described in Chiu et al. (2011), which consisted of five areole types in male adults with slight differences found in the bristlefield and crowned areoles.

The size of the bristlefields was smaller in individuals in the present study than in those described in Chiu et al. (2011) (70-77 μm wide and 145-243 μm long, respectively) and were not found at all in one extremely small individual. Although the difference in the bristlefields in the male Chordodes species has not been used to distinguish the species, this character has been used to distinguish Gordionus kii from G. chinensis ( Schmidt-Rhaesa and Sato 2009).

Another abnormal morphological feature was the similar-sized paired crowned areoles and their surrounding circumcluster areoles. These "abnormal crowned areoles" were only found in one extremely small individual, but not in the other horsehair worms, including the two large ones that emerged from the same host individual. Because the molecular data suggested that this individual was conspecific with C. formosanus , we believe the abnormal crowned areoles may have been caused by incomplete development during synchronized maturation (see Discussion for details).