Truxonchus quangi, Vu, 2021, Vu, 2021

Vu, Tam T. T., 2021, A newspecies of araregenus, Truxonchus quangi sp. n. (Mononchida, Anatonchidae) from Bat Xat nature reserve in Lao Cai Province, Vietnam, Zootaxa 4985 (2), pp. 253-260 : 254-256

Results and discussion

Material examined: Holotype and two paratype females in good condition of preservation.

Measurements: see Table 1 .

Description: Females: Large-sized nematodes, body ventrally arcuate after fixation. Cuticle smooth, 7.6–8.5 µm thick at the base of pharynx, subcuticle distinctly striated. Labial region distinctly offset by a constriction from the body contour, 70–77 μm wide and 19–21 μm high, six separated lips in lotus shape. Buccal cavity large, about one to one and half times as long as wide, barrel shaped, walls strongly sclerotized. Amphidial fovea small, cupshaped, with slit-like aperture 5–5.5 μm wide, located 14–16 μm from the anterior end of buccal cavity. Dorsal tooth 7–8 μm long, three apices of teeth located at 36–39% of the buccal cavity length from its base. Praeparietale 26–33 μm long or about 38–46% of interparietale length (see Andrássy 1993b).

Body diameter at the pharynx base about 1.8–2.1 times head width. Pharynx cylindrical, surrounded by the nerve ring, which is located at 238–271 µm or 22–27.6% of its length, measured from the anterior body end. Secretory-excretory (SE) pore conspicuous, situated just posterior to nerve ring at 269–288 µm or 24.5–28.7% of pharynx length from anterior body end. Pharyngo-intestinal junction tuberculate; cardia with conoid projection into intestinal lumen. Distance between pharynx base and vulva 1.2–1.3 times of the pharynx length. Rectum straight, 58–73 μm long, its length less than one anal body width.

Reproductive system typical for the genus: didelphic-amphidelphic, both branches about equally developed with ovaries reflexed, sphincter at the oviduct-uterus junction not observed. Vulva a transverse slit, situated in the anterior half of the body. One to three pre- and two to three conspicuous post-advulval pores present. Vulva-anus distance 0.81–0.95 times tail length. Uterus in holotype with one large egg (209 μm long x 88.5 μm wide). Vagina long, 59–63 μm long or about two-fifth of corresponding body width with par refringens vaginae appearing as two prominent, rounded sclerotized pieces in longitudinal optical section.

Tail long, filiform, 1.40–1.63 mm long, ventrally curved, corresponding to 0.28–0.29% of body length or 18.8– 20.5 anal body diameters long, three small caudal glands in tandem and opening subventrally near tail terminus. Female tail with two pairs of sublateral caudal pores.

Male: unknown.

Type habitat and locality: Soil around the roots of forest trees in the Bat Xat nature reserve (N = 22º37´14” and E = 103º37’24”, altitude 1900 m), Bat Xat District, Lao Cai Province, Vietnam .

Type materials: Holotype female on slide Truxonchus quangi sp. nov. Nº 1; paratype females on slides Truxonchus quangi sp. n. Nºs 2–3. All slides have been deposited in the nematode collection of the Department of Nematology, Institute of Ecology and Biological Resources ( IEBR) of the Vietnam Academy of Science and Technology (VAST), Vietnam.

Etymology: The species is named after Vietnamese botanist Dr. Bui Hong Quang who has supported collecting these interesting specimens.

Diagnosis and relationships: Truxonchus quangi sp. nov. is characterized by large body size (L = 4.8–5.8 mm); buccal cavity large, barrel-shaped with apex of dorsal tooth located at 36–39% of the buccal cavity length from base; cardia tuberculate; reproductive system amphidelphic, vagina long, on anterior half of body length with distinct par refringens vaginae, sclerotized vaginal pieces rounded in longitudinal optical section; tail long filiform, ventrally arcuate with three small caudal glands in tandem and prominent spinneret on subventral tail terminus. Male unknown.

Truxonchus quangi sp. nov. is most similar to T. dolichurus , T. gracilicaudatus ( Cobb, 1917) Andrássy, 1993b and T. paralleni (Jairajpuri & Khan, 1982) Siddiqi, 1984b based on a mean body length longer than 4 mm, buccal cavity length longer than 80 µm, c’ index greater than 10 and comparisons of the main morphometric data shown in Table 2 ( Menzel 1913; Mulvey 1961 b, 1973; Peneva et al. 1999). It is closest to T. dolichurus but differs in having larger buccal cavity size (106–113 x 66–73 µm vs 100–105 x 60–65 µm), and buccal cavity shape less oblong (L/W ratio 1.5–1.6 vs 1.7–1.9); apex of dorsal tooth located more anteriorly (36.0–39.0% from buccal cavity base vs 31.6– 34.3%); amphidial aperture wider than ( 5–5.5 µm vs 4.5 µm); longer tail ( 1.4–1.65 mm vs 1.2–1.4 mm) with lower c (3.4–3.5 vs 4.3–5.4) ratio and higher c’ (18.8–20.5 vs 12–14) ratios; vulva position more anterior (V=45–47% vs V=49–55%) and present of advulval pores instead of advulval papillae (see table 2).

The new species differs from T. gracilicaudatus in its less slender body (a = 36–36 vs a = 50–71); larger buccal cavity size (106–113 x 66–73 µm vs 72–100 x 52–88 µm), buccal cavity shape less squarish (L/W ratio = 1.5–1.6 vs 1.2–1.3); position of amphidial aperture (at 14–16 µm from anterior end of buccal cavity vs at level of anterior buccal cavity); longer tail ( 1.4–1.65 mm vs 0.56–0.72 mm); position of vulva (in anterior half vs posterior half of the body); and the position of spinneret (subventral near terminus vs terminal).

From T. paralleni , the new species differs in having a larger buccal cavity (106–113 x 66–73 µm vs 75–80 x 52–58 µm); tail three times longer ( 1.4–1.65 mm vs 0.45–0.53 mm); lower c (3.4–3.5 vs 7.3–10) and V (45–47% vs 63–67%) ratios but higher c’ value (18.8–20.5 vs 10); more anterior dorsal tooth position (36–39 vs 27); and in spinneret position (subventral vs terminal).