Discolaimus anemaqen, Wu, Wen-Jia, Yan, Lin, Xu, Chun-Ling, Wang, Ke, Jin, Sheng-Ying & Xie, Hui, 2016

Wu, Wen-Jia, Yan, Lin, Xu, Chun-Ling, Wang, Ke, Jin, Sheng-Ying & Xie, Hui, 2016, A new species of the genus Discolaimus Cobb, 1913 (Nematoda: Dorylaimida: Qudsianematidae) from Qinghai, China, Zootaxa 4088 (1), pp. 129-138 : 130-134

Discolaimus anemaqen n. sp.

Figs 1–3 .

Measurements. See Table 1 .

Material examined. Holotype, ♀, from soil around the roots of grasses from Graham Beach, Maqen, Guoluo Prefecture, Qinghai Province, China; GPS coordinate 100°12′36.3″ E, 34°28′03.2″ N; collected by Lin Yan and Sheng-Ying Jin in 2013. Holotype and seven female paratype specimens are deposited in the Lab of Plant Nematology/Research Center of Nematodes of Plant Quarantine, South China Agricultural University, Guangzhou, Guangdong 510642, China (slide numbers: 10–1. A and 10–1. B).

Description. Female ( Figs 1–3 ). Body slightly curved ventrad upon fixation. Cuticle two-layered, 2–3 Μm thick at mid-body and 4–6 Μm on tail; outer layer thin and with fine transverse striations throughout the body, inner layer thicker than the outer and distinctly thickened at the caudal region. Lateral chord 11–14.5 Μm wide or about one-fifth to one-fourth of the body diameter at mid-body, with 86 (82–90) lateral gland bodies on each side, 19–23 occurring in the neck region, 17–22 in the region from pharynx base to vulva, 40–46 in the region from vulva to anus, and 1–2 in the caudal region. Lip region offset by a distinct constriction, 0.4–0.6 times as wide as body diameter at pharyngeal base. With SEM, lip region seen to be disc-like, with six labial sectors separated by six Yshaped radial grooves which bifurcated before reaching the outer margin of lip region, and divided into six labial and six interlabial lobes by twelve longitudinal grooves. Amphid fovea an inverted-stirrup shape; aperture diameter about 0.3 times width at lip region. Odontostyle straight, strongly sclerotised with distinct lumen and opening, length 0.7–0.8 times the lip region diameter, its aperture 53–59% of its length. Odontophore rod-like, 1.7–2.0 times the odontostyle length. Guiding ring single. Nerve ring situated at 29–33% of neck length. Anterior part of pharynx muscular, with a swelling surrounding the base of odontophore, followed by another swelling then distinctly narrowing to about half its width at level anterior to the nerve ring until the anterior end of basal expanded part of pharynx, basal part of pharynx expanded gradually, 55–59% of the total neck length, with a sheath of tissue visible ventrally and at the base. Pharyngeal gland nuclei locations (Andrássy, 1998) as follows: D = 52–57%, AS1 = 42– 54%, AS2 = 53–62%, PS1 = 73.5–83%, PS2 = 78–82%. Cardia conoid, no groups of large cells observed in cardiac region. Genital system amphidelphic. Ovaries reflexed nearly to vulva, anterior 79–130 Μm and posterior 65–152 Μm long. Oocytes arranged in a single row, except near germinal cell where two or more rows are present. Oviducts straight, broad; anterior 46–99 Μm and posterior 61–114 Μm long. Sphincter present at junction of oviduct and uterus. Uteri tubular; short in absence of eggs, anterior 31–38.5 Μm and posterior 32–53 Μm long; with eggs anterior 88–169 Μm and posterior 93.5–168 Μm long. No spermatozoa observed in genital system. Vulva a transverse slit, measuring 9 Μm in width. Vagina extending inwards about one-third of corresponding body diameter. Pars proximalis vaginae 10–13×12–15 Μm with convex walls; pars refringens lacking; pars distalis vaginae oblong, 3–5×6.5–7 Μm. Egg about 1.5–2 times as long as body diameter at mid-body, one to four eggs in a single female. Prerectum without prerectal sac, prerectum 0.7–1.0 times and rectum 0.8–1.0 times the anal body diameter. Tail short, dorsally convex, conoid, with flat ventral side and bluntly rounded terminus.

Male. Not found.

Type locality and habitat. Soil around the roots of grasses growing on Graham Beach, Maqen, Guoluo Prefecture, Qinghai Province, China.

Etymology. The new species is named after the Animaqing Snow Mountain Legend, which is a part of China’s cultural heritage, and the mountain Anemaqen , which is located in Maqen, Guoluo Prefecture.

Diagnosis and relationships. Discolaimus anemaqen n. sp. is characterized by having a body length of 1.92– 2.15 mm; a disc-like lip region with six labial sectors separated by six Y-shaped radial grooves; amphid fovea an inverted-stirrup shape; strongly sclerotised odontostyle 0.7–0.8 times the lip region diameter in length, aperture 53–59% of its length; anterior part of pharynx with two swellings and distinctly narrowed from anterior to the nerve ring to the basal expanded part of the pharynx, basal part expanded with a sheath of tissue visible ventrally and at the base, occupying 55–59% of the total neck length; no groups of large cells in the cardiac region; female genital system amphidelphic; tail short (c’ = 1.1–1.3), dorsally convex conoid with straight ventral side and bluntly rounded terminus. Males were not found, and are either rare or absent.

Based on the morphological measurements provided by Nasira et al. (2008), the new species is close to D. major Thorne, 1939 , D. similis Thorne, 1939 and D. silvicolus Sauer & Annells, 1985 in the length of body and odontostyle. It differs from D. major by having a different surface on the lips (with six labial sectors separated by six Y-shaped radial grooves vs with six wedge shaped sectors, after Sauer & Annells 1985; basal part of the pharynx with a sheath of tissue visible ventrally and at the base (vs with an irregular sheath visible both dorsally and ventrally and at the base, after Sauer & Annells 1985) and lacking a prerectal sac (vs present, after Sauer &Annells 1985). From D. similis , it differs by having the basal part of the pharynx expanding gradually (vs abruptly, after Loof 1964); a different tail shape (dorsally convex, conoid with flat ventral side and bluntly rounded terminus vs regularly conoid with rounded tip, after Loof 1964); ovary with a large reflex reaching almost to the vulva (vs one-quarter to one-half, after Loof 1964; two-thirds the distance back to the vulva, after Thorne 1939) and relatively shorter eggs (1.5–2 times vs 3–4 times as long as body diameter at mid-body, after Thorne 1939). It differs from D. silvicolus (Sauer & Annells 1985) by having a larger body size (L = 1.92–2.15 mm vs L = 1.61– 1.89); lower V value (V = 46.3–49.0 vs 51–53); anterior part of the pharynx with a swelling surrounding the base of the odontophore and followed by another swelling (vs without the second swelling); basal part of pharynx with a sheath of tissue visible ventrally and at the base (vs with a thick irregular sheath visible on both ventrally and dorsally and at the base) and no large cells observed in the cardiac region (vs a group of large cells with usually prominent nucleoli present posterior to the cardiac region). The new species differs from D. albarossicus Merzheevskaya1951 , D. curvus Siddiqi 2005 , D. krugeri Furstenberg & Heyns 1965 , D. magnistylus Siddiqi 2005 , D. mariae Peña-Santiago, Torres, Liébanas & Abolafia 2002 and D. pakistanense Nasira, Shahina & Erum 2008 by having a body length less than 2.2 mm. It also differs from D. bicorticus Furstenberg & Heyns 1965 , D. constrictus Heyns 2001 , D. levinae Furstenberg & Heyns 1965 , D. neomajor Siddiqi 2005 , D. papillatus Khan, Ahmad & Jairajpuri 1994 , D. perplexans Siddiqi 1964 and D. trapezoides Siddiqi 2005 by having differing odontostyle lengths although similar body lengths. It is differentiated from the remaining species of Discolaimus by having a body longer than 1.8 mm.

Figures

FIGURE 1. Discolaimus anemaqen n. sp. (Female) A: entire body; B: anterior end; C: amphid; D: vulva; E: anterior region showing pharynx; F: genital system; G, H: posterior regions; I: cardia.

FIGURE 2. Micrographs of Discolaimus anemaqen n. sp. (Female) A: entire body; B: eggs; C: lateral organs; D: anterior end; E: amphid; F, G: vulva; H: anterior region showing pharynx; I: cardia; J: genital system; K: oviduct and uterus; L, M: tail regions. Scale bars: A = 200 µm; B = 100 µm; C – D, H – J, L – M = 20 µm; E – G, K = 10 µm.

FIGURE 3. Scanning electron micrographs of Discolaimus anemaqen n. sp. (Female) A, B: surface morphology of lip regions (Y-shaped radial groove is arrowed); C: anterior end showing amphid aperture (arrowed); D: vulva; E, F: tail regions; G: cuticle showing lateral pores (arrowed). Scale bars: A – C = 5 µm; D – G = 10 µm.

Tables

TABLE 1. Morphometric data for Discolaimus anemaqen n. sp. All measurements are in the form: mean ± s. d. (range), and in μm (except for ‘ L’ and ‘ Vulva from anterior end’ which are in mm). n = number of specimens observed, L = body length, a = L / max. width, b = L / pharyngeal L, c = L / tail length, c’ = tail length / body diameter at anus, V = distance of vulva from anterior end × 100 / L, G 1 = anterior genital branch reflection end to vulva × 100 / L, G 2 = posterior genital branch reflection end to vulva × 100 / L.

Character	Female
	Holotype	Paratypes
n	-	7
L	1.93	2.04 ± (1.92–2.15)
a	35.0	37.2 ± 3.0 (34.1–41.9)
b	3.9	4.2 ± 0.2 (4.0–4.4)
c	55.1	58.5 ± 3.7 (52.8–62.4)
c’	1.2	1.2 ± 0.1 (1.1–1.3)
V	47.9	47.3 ± 1.0 (46.3–49.0)
G1	7.4	9.2 ± 2.5 (5.2–11.9)
G2	8.0	8.7 ± 2.0 (5.2–11.0)
Lip region diameter	25	26 ± 0.8 (25.0–27)
Lip region height	8	7 ± 0.4 (6–7)
Amphid aperture	7	7 ± 0.9 (6–8)
Odontostyle length	20	20 ± 0.5 (19–20)
Odontophore length	38	36.5 ± 1.2 (34–38)
Guiding ring from anterior end	11	10.5 ± 0.1 (10–11)
Nerve ring from anterior end	152	149 ± 3.5 (146–155.0)
Pharyngeal L	492	490 ± 16.2 (467–516.0)
Expanded part of pharynx	279	282 ± 14.3 (257–299)
Cardia length	17	17 ± 3.3 (14–22)
Body diameter at neck base	51.0	50 ± 6.8 (42–59)
Body diameter at mid-body	55	55 ± 6.5 (46–62)
Body diameter at anus	30	30 ± 1.6 (28.0–32)
Anterior genital branch reflection end to vulva	143	189 ± 56.0 (100–252)
Posterior genital branch reflection end to vulva	154	178 ± 45 (100–232)
Vaginal depth	15	16 ± 1.5 (14–18)
Vulva from anterior end	0.93	0.96 ± 0.05 (0.89–1.03)
Prerectum length	29	26 ± 2.3 (22–28.5)
Rectum length	25	27 ± 2.9 (22–31)
Tail length	35	35.0 ± 3.0 (31–39)