Tylencholaimellus striatus Thorne, 1939

Zhang, Min, Ahad, Sumaya, Liang, Wenju & Ahmad, Wasim, 2012, A new and three known species of the genus Tylencholaimellus Cobb in M. V. Cobb, 1915 (Nematoda: Dorylaimida) from Changbai Mountain, China, Zootaxa 3499, pp. 46-62 : 51-54

Tylencholaimellus striatus Thorne, 1939

( Figs. 3 , 4 )

Measurements: Table 2.

Mean ± SD (Range)

n 5

L (mm) 718±52 (674–791) Body width at neck base 24.2±1.5 (23–27) Body width at mid body 26.8±2.6 (24–31) Body width at anus 15.6±1.3 (14–18) a 26.9±1.5 (25–28) b 5.5±0.3 (5–6)

c 27.6±2.3 (25.0–31.6) c`1.6±0.12 (1.5–1.8) V 33.3±2.15 (30.7–37) G1 1.06±0.10 (0.9–1.18) G2 14.8±2.2 (10.75–17.2) Lip region width 6.9±0.2 (6.5–7) Lip region height 3.4±0.48 (3–4)

Amphid aperture 3.7±0.25 (3.5–4) Odontostyle length 8.6±0.48 (8–9)

Odontophore length 7.6±0.5 (7–8)

Guiding ring from anterior end 6±06–6

Nerve ring from anterior end 70.6±3.5 (65–74) Neck length 130±10.3 (113–143) Expanded part of pharynx 27±2.3 (25–31) Cardia length 5.8±1.1 (4–7)

Anterior genital branch 7.6±0.48 (7–8)

Posterior genital branch 107±21.9 (73–133) Vaginal depth 11.2±0.4 (11–12) Vulva from anterior end 239±25 (215–286) Prerectum length 81.4±7.4 (73–94) Rectum length 16±0.8 (15–17) Tail length 26±0.8 (25–27)

Description. Female: Moderately slender nematodes of small size. Body cylindrical, slightly tapering towards both extremities. Body slightly curved upon fixation. Cuticle with two distinct layers, 2 µm thick at mid body and 3 µm on tail. Outer cuticle with distinct transverse striations; inner layer thick with prominent transverse striations; radial refractive elements abundant. Lateral body pores obscure. Lateral chords occupying about one-fifth to onefourth of the mid body diameter. Lip region slightly offset by a distinct constriction, 1.7–2.3 times as wide as high and one-third of body diameter at neck base. Lips amalgamated, with rounded contour; its inner portion transformed into a perioral disc. Amphid cup-shaped, opening at level of the cephalic constriction and occupying one-half of the lip region diameter. Stoma a truncate cone. Odontostyle 1.1–1.3 times the lip region width long and provided with dorsal accessory piece covering the entire dorsal arm; its aperture one-sixth of the odontostyle length. Odontophore with basal knobs; 0.7–1 times the odontostyle length. Guiding ring simple, refractive, at 0.8–0.9 times lip region width from anterior end. Pharynx consist of a slender and weakly muscular anterior part and separated from basal bulb by a constriction. Pharyngeal basal bulb cylindroid, which occupies about 19.5–22% of the total neck length. Pharyngeal glands often visible. Cardia rounded to hemispherical, surrounded by the intestine. Nerve ring located at 50–57% of the neck length. Genital system monodelphic-opisthodelphic. Ovary reflexed, measuring 51–107 µm long, and provided with oocytes arranged in single row except near the tip. Oviduct joining the ovary subterminally, measuring 41–72 µm and consisting of a slender distal part and a poorly developed pars dilatata. Oviduct-uterus junction marked by a weak sphincter. Uterus short and tubular, measuring 23–36 µm long. Sperms not seen either in oviduct or uterus. Anterior genital branch a rudimentary cell mass with inconspicuous lumen. Vagina cylindrical, pars proximalis vaginae 5–6 µm long, its wall encircled by muscles. Pars distalis vaginae short, 1.5–2.0 µm long with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 4–6 anal body diameters long. Intestine-prerectum junction guarded by three cells. Rectum 0.9–1.0 anal body widths long. Tail cylindroid and relatively long; outer layer of cuticle thickened in its posterior portion forming a distinct hyaline layer.

Male: Not found

Habitat and locality: Dark-coniferous spruce-fir forest, Changbai Mountain, Northeast China (42°09ʹN, 128°08ʹE): 1250m a.s.l., annual mean temperature 0.3ºC, annual mean precipitation 811 mm; tree species dominated by Abies nephrolepis and Picea jezoensis on Bori-Udic Cambosols.

Remarks: Thorne (1939) described T. striatus from Utah, U.S. A and he (1974) further reported this species from South Dakota. Goseco et al. (1975) restudied the Thorne’s original specimens, provided a detailed description and also designated lectotype and paralectotype. The morphometrics of the present population confirms well with the type population as well as the South Dakota population, except for having outer portion of lips rather rounded (vs lip region very angular); odontostyle slightly longer than odontophore (vs odontostyle as long as odontophore); cardia rounded to hemispheroid (vs cardia flat), and slightly longer tail (vs c = 35). Thorne in both the descriptions mentioned anterior uterine sac as absent while Goseco et al. in their redescription reported a small anterior uterine sac of about 7 µm. In our present specimens a small anterior uterine sac could be recognized. Our present population also agrees fairly well with Spanish population described by Peralta & Peña-Santiago (1995) except for having pharyngeal bulb occupying about one-fifth of the total pharyngeal length (vs occupying one-fourth of the total pharyngeal length), prerectum slightly long (vs 2–4 anal body diameters long); male absent (vs male present). The present population also agrees fairly well with Indian population described by Mushtaq, Naz & Ahmad (2007).

Figures

FIGURE 3. Tylencholaimellus striatus Thorne, 1939. A: Entire female. B: Anterior region. C: Anterior end showing amphid. D: Pharyngeal region. E: Expanded part of pharynx. F: Female genital system. G: Female posterior region.

FIGURE 4. Tylencholaimellus striatus Thorne, 1939. A: Anterior region. B: Anterior end showing amphid. C: Expanded part of pharynx. D: Female genital system. E: Vulval region. F: Female posterior region. G: Female posterior end (scale bar: A – B: 10 µm; C – G: 20 µm).