Hystrignathus baihualingensis, Zhang & Yin & Zhang, 2022

Zhang, Ningning, Yin, Shi & Zhang, Luping, 2022, A new genus and two new species of nematodes (Nematoda: Thelastomatoidea) from Ceracupes fronticornis (Westwood) (Insecta: Passalidae) in China, Zoological Systematics 47 (2), pp. 109-116 : 110-111

Hystrignathus baihualingensis sp. nov.

Diagnosis. The new species has its cervical region armed with opposite rows of spines, of which, the first row with 16 spines, and has the clavate procorpus and amphidelphic female productive system. Those are confirmed to the characters of the genus Hystrignathus Leidy, 1850 . The new species can be easily distinguished from most species of the genus by having a notably expanded first cephalic annule, except H. inflatus Travassos & Kloss, 1957 from Brazil, H. splendidus Morffe & García, 2010 from Cuba and H. tarda (Artigas, 1928) from Brazil. It differs from the latter three species by having very short stoma (stoma extending to the middle of the first cephalic annule in the former vs. stoma extending further than the end of the first cephalic annule in the latter three). In addition, the new species can be differentiated from H. inflatus by having a comparatively stout body (a = 10.9–16.2 vs. 19.75–20.07) and comparatively short tail (c = 5.9–7.5 vs. 4.74–5.04), from H. splendidus by having smooth instead of ridged eggs, and from H. tarda by having larger sized eggs (97–115 × 43–53 vs. 85 × 30) and the extent of cervical spines (spines ending at the end of procorpus vs. ending at the middle of the basal bulb).

Description. Female body robust. Cervical cuticle bearing opposite rows of spines, first row with 16 elements ( Figs 1D, G ). Maximum body diameter in middle of body. Cuticle markedly annulated in spiny region, annuli less marked in rest of body. Spines originating just behind first cephalic annule, extending to end of procorpus ( Figs 1A , 2A ). Lateral alae beginning at about one body-width posterior to basal bulb and ending at about one body-width posterior to vulva ( Fig. 2C ). Head simple with 8 papillae arranged in pairs, first cephalic annule notably inflated, about three head-lengths long and setoff from head by single groove ( Figs 1A–D , 2A–B ). Stoma very short, about two head-lengths long. Oesophagus consisting of a muscular, clavate procorpus, short isthmus and basal bulb. Basal bulb sub-spherical, valve plate well developed. Nerve ring encircling at middle of procorpus ( Figs 1A–B , 2A–B ). Excretory pore located just posterior to basal bulb ( Figs 1B , 2B ). Intestine simple, with anterior region slightly dilated. Reproductive system didelphic-amphidelphic. Vulva located near midbody. Vagina slightly extending anteriorly, connecting with two opposite uteri. Anterior ovary reflexed at level of excretory pore, posterior ovary reflexes forward about two maximum body widths anterior to anus ( Figs 1A , 2A ). Eggs elliptic, smooth-shelled. Tail conical, attenuated, sharply pointed. Male unknown.

Measurements. Female (n = 10). a = 10.9–16.2 (13.2); b = 4.7–5.8 (5.4); c = 5.9–7.5 (6.7); V = 46–54 (51); V' = 53–65 (60). Total body length 1840–2400 (2200); maximum body width 140–179 (167). Stoma 19–29 (24). Head 10–14 (11) long, 30–39 (34) wide, first cephalic annule 35–40 (38) long, 63–70 (65) wide. Total oesophagus length 391–449(410); procorpus 280–314 (291) long; isthmus 39–53 (44) long; basal bulb 63–87 (74), 63–87 (76) wide. Nerve ring 179–203 (190) from anterior end; excretory pore 411–470 (438) from anterior end. Vulva 1000–1220 (1113) from anterior end. Eggs 97–116 (105) long, 43–53 (48) wide. Tail 310–350 (330) long.

Type-host. Ceracupes fronticornis (Westwood, 1842) .

Site of infection. Hindgut.

Prevalence. 2.6% (3/115 hosts examined).

Mean intensity. 3 (1–6 worms per host).

Material examined. Holotype female (HBNU-I-2021070), Baihualing, Baoshan City, Yunnan Province, China, 16 Aug. 2018, coll. Zuozhen Li. Paratypes. 9 females (HBNU-2021071–2021079), same data as holotype .

Etymology. The new species is named after the typical locality, Baihualing, Yunnan Province, China.

Remarks. To date, 21 species of Hystrignathus are reported worldwide. Among them, 11 species are from Brazil, the rest were from North America, Cuba, Venezuela, Trinidad, Panama, Ivory Coast and Madagascar, respectively (Adamson & van Waerebeke, 1992; García et al., 2009b; Morffe & García, 2010a, b). This is the first record of Hystrignathus from China.

Figures

Figure 1. Hystriganthus baihualingensis sp. nov., female. A. Whole worm, lateral view; B. Anterior part of body, lateral view; C–D. Anterior end of body, lateral view; E. Posterior part of body, lateral view; F. Egg; G. Transverse section just posterior to first cephalic annule, showing first row of spines. Scale bars=100μm.

Figure 2. Hystriganthus baihualingensis sp. nov., female, light microscopical images. A. Whole worm, lateral view; B. Anterior part of body, lateral view, showing first cephalic annule and excretory pore (ep); C. Posterior part of body, lateral view, showing lateral alae (la). Scale bars=100μm.