Chordodes formosanus Chiu, 2011

Chiu, Ming-Chung, Huang, Chin-Gi, Wu, Wen-Jer & Shiao, Shiuh-Feng, 2011, A new horsehair worm, Chordodes formosanus sp. n. (Nematomorpha, Gordiida) from Hierodula mantids of Taiwan and Japan with redescription of a closely related species, Chordodes japonensis, ZooKeys 160, pp. 1-22 : 3-9

Chordodes formosanus Chiu, 2011 sp. n.

Type locality.

Wufengqi Waterfalls (24°49'55.62"N, 121°44'50.10"E), Jiaushi Township, Yilan County, Taiwan (Holotype). Dachijieu (24°56'59.21"N, 121°34'2.12"E), Sindian (New Taipei City) (allotypes). Paratypes collected from Taiwan and Jap an: Taipei Zoo (Taipei City), Sindian (New Taipei City), Taroko National Park (Hualien County), Wufengqi Waterfalls (Yilan County), Taiwan and Miyazaki Prefecture and Sakado (Saitama Prefecture), Japan. For detailed data, see Table 1.

Type material.

Partial bodies of holotype (male, 167 mm), and allotype (female, 282 mm) deposited at the Department of Entomology, National Taiwan University with the hosts. Paratypes deposited at the Department of Entomology, National Taiwan University, Taipei, and National Museum of Natural Science, Taichung, Taiwan and Lake Biwa Museum, Shiga, Japan. For detailed information, see Table 1.

Type-host.

Hierodula formosana Giglio-Tos ( Mantodea : Mantidae ). Hierodula formosana endemic to Taiwan, and the adult always emerging from late June to early August. Hosts of some samples belonging to Hierodula patellifera which distributed in both Taiwan and Japan. Their adults usually emerging in late autumn, about 2 months later than Hierodula formosana .

Etymology.

The specific name refers to Taiwan, the collection locality of the type specimens.

Description.

(Figs 1-5)

Male adult (n = 17) (Figs 1, 2). Body length 74-277 mm, width (widest) 0.7-1 mm (after dehydration). In alcohol-preserved specimens, body rough and flat with dorsal and ventral grooves; dark-brown with bright lengthwise regions on both dorsal and ventral sides and darkly pigmented line on ventral side in most specimens (Fig. 1D).

Posterior end (Fig. 1C) not lobed, with short spines (ca. 5-12 μm) among areoles on margin. Cloacal opening subterminal, oval, 27-78 μm long and 17-63 μm wide. A pair of oval regions without areoles posterior to cloacal opening, each with scattered bristles extending as two rows of ventral strips (155-160 μm wide), structured by cord-like folds or flat areoles; flat areoles ornamented with short filaments in a cluster on top or scattered on cord-like folds, or absent. Paired oval bristlefields (70-77 μm wide and 145-243 μm long) bearing bristles on borders between flat areoles and normal areoles on lateral side of cloacal opening; bristles in bristlefields varying among individuals; some bearing only shorter or thinner unbranched bristles and some with both branched and unbranched bristles (Figs 2 D–F). Anterior end tapered, same color as body, with white tip (white cap) but no dark collar under a stereomicroscope. Under SEM, anterior end round with moderately flat areoles and short bristles on surface; about 10 of them elevated and cone-like near anterior terminal; long thick bristles scattered among areoles, some between areoles and some penetrating areoles (Fig. 2C). Anterior end on one individual with residual larval cuticle tapered but flat terminally (Fig. 2A); also flat surrounding ornamentations and bristles (Fig. 2B). Mouth opens terminally in some individuals.

Entire body covered by areoles with cord-like folds in between. Areoles characterized into five types (simple, tubercle, thorn, circumcluster, and crowned areoles). Simple areoles (Fig. 1A), most abundant, covering most of body surface except anterior end and ventral side of posterior end; each 5-8 μm in diameter, more or less circular or oval, generally with a smooth surface but some with dots, grooves, or short bristles on surface. Simple areoles varying in height and some significantly elevated areoles in clusters of two to ten, looking like bulging areoles as mentioned by Schmidt-Rhaesa et al. (2008); but darker under light microscopy (Fig. 1D). Tubercle areoles (Fig. 1A) scattered among simple areoles, each shaped similarly to simple areole but with a tubercle (6-9 μm long) on apically concave center. Thorn areoles (Fig. 1A) distributed slightly along dorsal and ventral middle lines, similar to tubercle areoles but with a long solid thorn (22-57 μm long) instead of a tubercle. Thorn areoles small or absent in two samples. Crowned areoles clustered in pair with a central tubercle in between and surrounded by 12-20 circumcluster areoles with short filaments on apical surface (short-crowned areoles) (Figs 1A, B); scattered over trunk except anterior and posterior ends; each with medium filaments (10-15 μm) originating from apical center and sidelong to edges; only one male with a few crowned areoles containing a few filaments of around 100 μm.

Female adult (n = 14) (Fig. 3). Length 263.7 (78-440) mm; body width (widest) 1-1.5 mm (after dehydration); body rough, flattened, dorsal and ventral grooves present; light to dark-brown with lengthwise regions on both dorsal and ventral sides, and darkly pigmented line on ventral side in most specimens. Some individuals with dark patches on bodies.

Posterior end (Fig. 3B) rounded, slightly swollen, covered by moderately flat areoles with cord-like folds surrounding cloacal opening; short bristles (10-27 μm) scattered between borders of moderately flat areoles and cord-like folds. Cloacal opening on terminal end, circular, 18-33 μm in diameter, no circumcloacal spine.

Anterior end with similar structure and color to males except lower cone-like areoles; terminally flat anterior end also appearing in one individual. Pattern and distribution of areoles (Fig. 3A) also similar to those of males but much more crowded in most individuals. Thorns of areoles shorter than those of most males (11-30 μm) but small or absent in three females. Cord-like folds present between areoles. Crowned areoles scattered over trunk as in males while roughly arranged in two lines on ventral and dorsal midlines, bearing significantly longer filaments (longest apical filaments ranging 65.57-392.25 μm (237.47 ± 66.22 μm, for details see “Diagnosis”)) (Figs 3A, C).

Eggs (Fig. 4).In laboratory, egg strings stuck onto substrate or drifting on bottom. Eggs (6 days after being laid) (Fig. 4B) nearly circular, 30.39 ± 1.15 μm (n = 10) in diameter. Egg strings white when laid and becoming light-brown within 1 day, turning dark-gray just before hatching. Eggs collected in field (Fig. 4C) all stuck onto rocks; mostly brown to gray, but some light-brown as those just laid in laboratory.

Larvae (Figs 4, 5). Larvae remaining near egg strings after hatching, not active. Under light microscopy, larval preseptum (Fig. 4A) averaging 20.55 (16.32-24.78) μm long and 13.21 (10.93-16.34) μm wide; postseptum averaging 24.91 (22.52-27.44) μm long and 10.06 (9.25-11.49) μm wide, stylet averaging 11.04 (9.59-13.25) μm long and 3.36 (2.76-3.91) μm wide. Pseudointestines V-shaped (Fig. 4A) with one small and one large branch, both with a swelling on posterior ends. Large branch averaging 8.27 (7.28-9.82) μm, small branch averaging 6.70 (5.43-7.59) μm long. Under SEM, larvae superficially annulated with 13 segments on preseptum and 10 on postseptum, ectodermal septum as a single segment between them. Three sets of hooks arranged in three rings on anterior preseptum (Fig. 5A): outer ring containing seven hooks (outer hooks), two ventrally positioned and closely together on base (ventral double hook); six hooks on second ring located between each outer hook (middle hook); inner ring containing at least three inner spines, but real number unknown. A stylet (Figs 5A, C) appearing inside preseptum, ornamented with two sets of spines: nine spines on dorsal and ventral sides of stylet, five small lateral papillae on left side. A pair of anterior and posterior terminal spines (Fig. 5B) on posterior of postseptum. Pseudointestine exterior opening (Fig. 5B) centrally located between anterior terminal spines on ventral body. Several larvae covered by residual skin: one observed in broken egg suggesting that molting had occurred before emergence (Fig. 4D).

Diagnosis.

Horsehair worms from the mantids Hierodula formosana and Hierodula patellifera were characterized by all six types of areoles, including simple, tubercle, thorn, circumcluster, short-crowned, and long-crowned areoles in the female. The same six areole types are similar to those of Chordodes japonensis described by Inoue (1952) and Baek (1993). Nevertheless, the significantly longer filaments on female crowned areoles suggest they belong to a new species, Chordodes formosanus sp. n. By the way, the absence of long-crowned areoles in our male sample of Chordodes formosanus sp. n. probably implies their potential for distinguishing these two different species. However, since the dimorphism of male crowned areoles has not been mentioned in Chordodes japonensis , more studies are needed to uncover this phenomenon.

The crowned areole is an autapomorphy of the genus Chordodes . In Chordodes formosanus sp. n. and Chordodes japonensis , it is composed of two major areoles ornamented with apical filaments and several surrounding circumcluster areoles. The dimorphic length of the apical filaments divides the crowned areoles into two types, short-crowned areoles with short ornamental filaments and long-crowned areoles with long ones. All samples we checked (both sexes of Chordodes formosanus sp. n. and one male Chordodes japonensis ) had short-crowned areoles scattered all over the body trunk, with the long-crowned areoles only appearing on the ventral and dorsal midlines of the female Chordodes formosanus sp. n. andmale Chordodes japonensis , but not themale Chordodes formosanus sp. n. We did not personally observe the female Chordodes japonensis , but these dimorphic crowned areoles must be present according to the descriptions of Inoue (1952) and Baek (1993). Additionally, the apical filament lengths of long-crowned areoles were significantly longer on Chordodes formosanus sp. n. We randomly chose two to five sets of long-crowned areoles from our female samples and measured each of their longest apical filaments. In the 68 sets of long crowned areoles, the longest apical filaments ranged 65.57-392.25 (237.47 ± 66.22) μm. Fifty-one of these 68 (75%) sets of crowned areoles had apical filaments of> 200 μm. The longest apical filaments in our male Chordodes japonensis were 92.03-139.70 μm. Significantly shorter filaments in Chordodes japonensis were also described by Inoue (1952) and Baek (1993). Chordodes japonensis has long-crowned areoles with filaments of around 50 μm ( Inoue 1952; fig. 1a) and filaments of <200 μm in the description by Baek (1993). For other differences and detailed comparisons, see Table 2 and the “Discussion”.