Gordius chiashanus Chiu, 2020
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publication ID |
https://dx.doi.org/10.3897/zookeys.941.49100 |
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publication LSID |
lsid:zoobank.org:pub:9095718C-8FB0-4618-8F9A-466CD3B0D3BF |
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persistent identifier |
https://treatment.plazi.org/id/E904851F-6F48-423D-9AC2-5A7BB595FA7B |
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taxon LSID |
lsid:zoobank.org:act:E904851F-6F48-423D-9AC2-5A7BB595FA7B |
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treatment provided by |
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scientific name |
Gordius chiashanus Chiu |
| status |
sp. nov. |
Gordius chiashanus Chiu sp. nov.
Type locality.
Dinghu (23°29'29.10"N, 120°43'19.00"E), Alishan township, Chiayi county, Taiwan (holotype). Paratypes were collected from Dasyueshan (Heping district, Taichung city), Xitou (Lugu township, Nantou county), Shihjhuo, Fenqihu (Zhuqi township, Chiayi county), Dinghu (Alishan township, Chiayi county), and Hongshi forest road (Haituan township, Taitung county). Table 1 View Table 1 presents detailed information of the locality.
Type material.
Partial bodies of the holotype and allotype were deposited at the National Museum of Natural Science, Taichung, Taiwan. Paratypes were deposited at the National Museum of Natural Science, Taichung, Taiwan and Lake Biwa Museum, Shiga, Japan (Table 1 View Table 1 ).
Type hosts.
Spirobolus sp. nov. (Hsu and Chang, unpublished) ( Diplopoda: Spirobolidae ) (Fig. 5E, F View Figure 5 )
Etymology.
The specific name is the combination of chia, referring to the place (Chiayi county) where the first sample was found, and shan, referring to the Chinese word for “mountains.” The word chia is also in memory of our friend, Chia-Chih Lin, who died in an accident in a field experiment.
Description.
Male adults (N = 11) (Figs 1 View Figure 1 - 3 View Figure 3 , 5 View Figure 5 ). Body length 627.94 ± 154.75 (383-860) mm, width (widest, after dehydration) 1.30 ± 0.31 (0.81-2.06) mm, light to dark brown, smooth, and covered with mucus-like structure (viscous liquid on live worms with rainbow-like reflection (Fig. 5C View Figure 5 , Suppl. material 1: Video S1), and created haze that surrounded the body surface in hot water (Fig. 5A View Figure 5 ).
Anterior end columnar and spherical; anterior tip white (white cap) with a dark -brown collar and a vertical white stripe on the ventral side (Fig. 1A View Figure 1 ). Under SEM, surface of anterior end appeared smooth (Fig. 1B View Figure 1 ) or wrinkled (Fig. 1C View Figure 1 ) on the tip of one sample; scattered short bristles (11.24 ± 6.57 (4.92-22.24) µm in length) scattered except on tip in most samples (Fig. 1B, D View Figure 1 ).
Cuticle in mid-body ornamented with a dorsal and a ventral dark pigment line; white spots scattered across entire body surface (Figs 3C, D View Figure 3 , 5A View Figure 5 ). Under SEM, cuticle surface appeared smooth (Fig. 3A View Figure 3 ) with a few scattered short or cone-like bristles (6.75 ± 2.37 (2.31-10.34) µm in length) (Fig. 3A, B View Figure 3 ).
Posterior end divided into two tail lobes (Fig. 2A, B View Figure 2 ), each lobe 855.24 ± 100.89 (658.39-994.88) µm long and 458.55 ± 76.52 (365.95-643.00) µm wide with length-to-width ratio of 1.89 ± 0.26 (1.49-2.42). Inner side of lobe tips white (Fig. 2A View Figure 2 ). Under SEM, inner side of tail lobes concave in some samples; cuticle surface smooth, but one sample exhibited flat areoles on inner side of lobe tips; short bristles scattered across the surface and concentrated in most samples on lobe tips (Fig. 2C View Figure 2 ) and on inner side of lobe tips forming a bristle field (322.67 ± 99.34 (187.60-412.75) µm long and 71.82 ± 35.49 (44.81-114.54) µm wide) on each of tail lobe posterior to tips of postcloacal crescent (Fig. 2D View Figure 2 ). Postcloacal crescent (Fig. 2A, B View Figure 2 ) 718.61 ± 118.77 (536.14-984.34) µm long and 86.7 ± 15.62 (54.73-118.65) µm wide and located on ventral side near base of tail lobes. Crescent generally semicircular or slightly angled, but a few samples exhibited a straightened form of crescent. Branches of postcloacal crescent usually ended at tail lobes. Cloacal opening circular (40.5 ± 21.87 (27.41-56.14) µm) and anterior to postcloacal crescent (Fig. 2A, B View Figure 2 ). Wall inside cloacal opening exhibited areoles (Fig. 2E View Figure 2 ); no circumcloacal spine or bristles observed in region next to cloacal opening.
Female adults (N = 4) (Figs 4 View Figure 4 , 5 View Figure 5 ). Body length 659.75 ± 77.06 (549-717) mm, width (widest, after dehydration) 1.54 ± 0.54 (1.00-2.03) mm, light to dark brown, smooth, and covered with mucus-like structure. White spots scattered on surface but relatively less obvious than those of male adults (Fig. 4F, G View Figure 4 ). Anterior end columnar and spherical. Anterior tip white (white cap) with a dark-brown collar and exhibited a vertical white stripe on the ventral side (Fig. 4A View Figure 4 ). Under SEM, surface of anterior end smooth and exhibited scattered short bristles (16.75 ± 4.60 (13.39-23.56) µm in length) except at tip (Fig. 4B View Figure 4 ). Cuticle in mid-body ornamented with a dorsal and a ventral dark pigment line (Fig. 4G View Figure 4 ). Under SEM, cuticle surface smooth with a few short or cone-like bristles (7.24 ± 2.01 (4.94-9.99) µm in length) scattered. Posterior end columnar and rounded at tip (Fig. 4E View Figure 4 ) and did not exhibit scattered bristles (Fig. 4D View Figure 4 ). Cloacal opening on terminal end (Fig. 4C, D View Figure 4 ) circular and 36.56 ± 23.23 (24.68-48.45) µm in diameter.
Eggs (N = 12) (Fig. 6C-E View Figure 6 ). Egg strings (Fig. 6E View Figure 6 ) 7.41 ± 3.46 (3.78-13.70) mm in length and 1.13 ± 0.12 (0.86-1.25) mm in width; white or light yellow in color, deposited in water as short pieces not adhering to substrate. Eggs round, 54.16 ± 242 2.89 (49.88-58.61) µm in diameter. Developing embryo surrounded by an inner membrane (Fig. 6C, D View Figure 6 ) separated by a distinct space from outer egg shell 14.35 ± 1.41 (12.43-17.33) µm).
Living larvae (N = 10) (Fig. 6B View Figure 6 ). Eggs developed for approximately 49 days. Hatched larvae remained near egg strings or moved inside eggshells. Under light microscopy, living larvae appeared cylindrical with a single posterior spine. Preseptum length 32.33 ± 4.53 (27.06-40.04) µm, and the width 18.04 ± 0.86 (16.70-19.12) µm. Postseptum length 83.05 ± 8.31 (66.50-92.66) µm, width 15.05 ± 0.73 (14.21-16.10) µm; proboscis length 14.94 ± 1.99 (12.35-18.48) µm, width 4.11 ± 0.85 (2.77-5.34) µm; pseudointestine length 60.60 ± 5.40 (54.99-70.12) µm, width 11.66 ± 1.42 (8.84-13.56) µm, unequally subdivided, elongated oval with a depression in anterior end (Fig. 6B View Figure 6 ).
Larvae treated with hot water (N = 2) (Fig. 6A View Figure 6 ). Larvae treated with hot water similar in morphology but larger than living larvae. Preseptum length 44.57 ± 0.13 (44.48-44.66) µm, width 17.96 ± 0.16 (17.85-18.08) µm. Postseptum length 118.23 ± 1.91 (116.88-119.58) µm, width 15.36 ± 0.68 (14.88-15.84) µm. Proboscis length 12.63 ± 1.18 (11.80-13.47) µm, width 3.26 ± 0.05 (3.23-3.30) µm; pseudointestine length 77.99 ± 5.22 (74.30-81.68) µm, width 13.99 ± 0.81 (13.41-14.56) µm (Fig. 6A View Figure 6 ).
Field-collected cysts (N = 5) (Fig. 6F-H View Figure 6 ). Larvae in cysts unfolded (N = 4) (Fig. 6F View Figure 6 ) or exhibited a postseptum folded twice (N = 1) (Fig. 6G, H View Figure 6 ). Unfolded larvae morphologically similar to larvae but larger in size; preseptum length was 60.18 ± 6.72 (50.40-65.18) µm, width 20.87 ± 0.52 (20.28-21.33) µm; postseptum length 127.33 ± 20.05 (105.10-146.05) µm, width 19.82 ± 2.27 (17.61-22.91) µm; proboscis length 15.46 ± 1.67 (13.84-17.56) µm, width 4.10 ± 0.68 (3.09-4.52) µm; pseudointestine not visible (Fig. 6F View Figure 6 ). Folded larva (length 34.97 µm, width 30.47 µm) fold twice and surrounded by a clear cyst wall, 47.86 µm in total length and 42.40 µm in total width; proboscis length 15.57 µm, width 5.09 µm (Fig. 6G View Figure 6 ); a single posterior spine visible after treatment with a solution of 5% KOH (Fig. 6H View Figure 6 ).
Phylogeny.
The partial COI sequences of the 18 free-living adults contained 15 haplotypes with 392 invariable sites, nine singletons, and 21 parsimoniously informative sites. The genetic distance among them was 0.0024 within the range of 0.0000-0.0510. The three living adults and six worms inside the hosts were considered conspecific with the 18 free-living adults because of their small genetic distances (0.0000-0.0719). The mean interspecific genetic distances between Gordius chiashanus sp. nov. and other Gordius species or clades were in the range of 0.2320-0.4242, and that between Gordius chiashanus sp. nov. and Acutogordius taiwanensis was 0.3648 (Table 3 View Table 3 ). In addition to short genetic distances, the conspecific status of the 18 free-living adults was also supported because all the samples were located in a single clade, as indicated by a high bootstrap value. No subgroup was detected because the polytomic topology exhibited low bootstrap values and short genetic distances. The Gordius species/clades in the present result were consistent with the results of Hanelt et al. (2015) and Tobias et al. (2017), despite slight differences in the relative relationships among species, which might be attributable to the differences in models used or the shorter sequence adopted in previous studies. The clade of A. taiwanensis was located within that of the Gordius species, and it did not behave as a sister group (Fig. 7 View Figure 7 ).
Reproductive season.
Free-living adult worms frequently aggregate and mate on wet ground (Fig. 5B, C View Figure 5 ) after rain or fog, and they are sometimes found in water or soil (Fig. 5D View Figure 5 ). They suddenly emerge in early December, and their number decreases within 1-2 months (Fig. 8 View Figure 8 ). During the reproductive season, no infected host was found. The seasonality and pattern of Gordius chiashanus sp. nov. differed from the graph constructed using data from C. formosanus ( Chiu et al. 2016).
Diagnosis and comments.
The 21 free-living Gordius adults and six juvenile worms from round-backed millipedes were judged as belonging to the same species in accordance with the results that they all were located in the same clade in the phylogenetic tree and had low genetic distances (Fig. 7 View Figure 7 , Table 3 View Table 3 ). These samples were regarded as a new species, Gordius chiashanus sp. nov., on the basis of their distribution patterns of bristles on the male tail and presence of a vertical white stripe on the anterior ventral side and areoles on the inside wall of the cloacal opening.
The concentration of bristles and spines on the male tail lobes has been previously described in species from the Palaearctic ( Spiridonov 1984; Schmidt-Rhaesa 2010) and Nearctic realms ( Anaya et al. 2019). In Gordius chiashanus sp. nov., this dense patch of bristles is a stable characteristic that was detected in all samples. The distribution pattern was similar to that of G. helveticus ( Schmidt-Rhaesa 2010) because the bristles exhibited a progressively broader distribution instead of being concentrated along the row of the ventral border, such as in G. karwendeli Schmidt-Rhaesa, 2010 ( Schmidt-Rhaesa 2010) and G. terrestris ( Anaya et al. 2019), or in a circular patch of concentrated spines, such as in G. spiridonovi Schmidt-Rhaesa, 2010 ( Spiridonov 1984).
Although the distribution pattern of the bristles is similar to that of G. helveticus , G chiashanus sp. nov. is morphologically distinct because of the presence of stout bristles on the mid-body, a vertical white stripe on the anterior ventral side, and areoles on the inside wall of the cloacal opening. The vertical white stripe on the anterior ventral side can be easily observed by the naked eye, but it has rarely been mentioned thus far. The presence of a white stripe was previously reported in the terrestrial hairworm, G. terrestris ( Anaya et al. 2019), which exhibits a broad white patch; however, the patch is likely to be the intensive aggregation of white spots in Gordius chiashanus sp. nov. The presence of areoles on the inside wall of the cloacal opening has only been reported in an unknown Gordius ( Schmidt-Rhaesa 2012, fig. 3.2.2). Although cloacal openings are usually covered by contamination in many Gordius species, as was the case in most of our samples, the areole on the inside wall of cloacal opening might not be a general characteristic of the genus Gordius because it is absent in at least some species (e.g., G. serratus Schmidt-Rhaesa, 2010, G. terrestris , G. spiridonovi ) ( Schmidt-Rhaesa 2010; Schmidt-Rhaesa and Prous 2010; Anaya et al. 2019).
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