Tylencholaimellus striatus Thorne, 1939

Ahmad, Wasim & Ahad, Sumaya, 2018, Description of two new and two known species of the Genus Tylencholaimellus Cobb in M. V. Cobb, 1915 (Nematoda: Dorylaimida: Tylencholaimoidea), Zootaxa 4375 (3), pp. 301-324 : 302

Tylencholaimellus striatus Thorne, 1939

( Figs. 1 & 2 )

Material examined. Seven females in good state of preservation.

Description. Measurements, see Table 1.

Female: Moderately slender nematodes of small size; body cylindrical, slightly tapering towards both extremities, slightly curved ventrad upon fixation. Cuticle with two distinct layers, 3 µm thick at midbody and 4 µm on tail. Outer cuticle with fine transverse striations; inner layer with strong radial refractive elements. Lateral, dorsal and ventral body pores obscure. Lateral chords occupying about 22–26% of the midbody diameter. Lip region offset by a distinct constriction, about twice as wide as high and about one-third as wide as body diameter at neck base; lips amalgamated, with rounded contour; its inner portion transformed into a perioral disc. Amphids cup-shaped, their aperture occupying about one-half of the lip region diameter. Stoma a truncate cone. Odontostyle 1.3–1.5 times the lip region diameter in length and provided with dorsal accessory piece covering the entire dorsal arm; aperture about one-sixth to one-fifth of the odontostyle length. Odontophore with basal knobs, 0.7–1.0 times the odontostyle length. Guiding ring simple, refractive, at 0.6–1.0 times lip region diameter from anterior end. Pharynx consisting of a slender and weakly muscular anterior part separated from basal bulb by a constriction. Pharyngeal basal bulb cylindroid, occupying about 17–22% of total neck length. Pharyngeal glands often visible. Cardia rounded to conoid. Nerve ring located at 49–55% of neck length. Genital system monodelphicopisthodelphic. Ovary reflexed, measuring 54–77 µm long; in one specimen ovary surpasses the vulva region; provided with oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 58–69 µm and consist of a slender distal part and a poorly developed pars dilatata. Oviduct-uterus junction marked by a weak sphincter. Uterus short and tubular, measuring 21–28 µm long. Anterior genital branch reduced to small sac, 0.3–0.4 times midbody diameter in length. Vagina cylindrical; pars proximalis vaginae 5–9 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. Sperms absent. Prerectum 4.0–8.0 times anal body diameter long. Intestine-prerectum junction guarded by three cells. Rectum 0.7–1.2 times anal body diameter in length. Tail relatively long, 1.3–1.7 anal body diameter long, cylindroids, outer layer of cuticle thickened in its posterior portion forming a distinct hyaline layer. Caudal pores two, one sub-dorsal and one sub-ventral.

Male: Not found.

Habitat and locality. Soil around the roots of unidentified grasses from Kangan Valley, Jammu and Kashmir State, India. Latitude/ Longitude: 34°17′21″N, 74°48′45″E.

Remarks. Thorne (1939) described this species from Utah, U.S. A and he (1974) also reported it from South Dakota. Goseco et al. (1975) restudied Thorne’s original specimens, provided a detailed description and also designated a lectotype and paralectotype. Peralta & Peña-Santiago (1995) recorded this species from several localities in Spain and provided a redescription. Mushtaq et al. (2007) reported it for the first time from India while Zhang et al. (2012) reported it from China. The morphometrics of the present population conform well with the type population as well as with the South Dakota population, except for having slightly smaller body size (0.53–0.59 vs 0.64–0.74 mm), outer portion of lips rather rounded (vs lip region very angular), and cardia rounded to conoid (vs cardia flat). Thorne in both descriptions mentioned the absence of the anterior uterine sac, while Goseco et al. (1975) reported a small anterior uterine sac, about 7 µm long. A small anterior uterine sac can also be seen in our present specimens. Our population also agrees fairly well with the Spanish population except in having a slightly lower lip region diameter (6 vs 7–8 µm), and pharyngeal bulb slightly shorter (20–28 vs 28–35.5 µm). The present population also conforms well with the Indian population of Mushtaq et al. (2007) except in having slightly longer odontophore (7–8 vs 6.5 µm) and with Zhang et al. ’s (2012) Chinese population, except for its slightly shorter body (0.53–0.59 vs 0.67–0.79 mm), slightly lower b value (4.3–5.0 vs 5–6) and slightly shorterr tail (20–25 vs 25–27 µm).

Figures

FIGURE 2. Tylencholaimellus striatus Thorne, 1939. A. Anterior region; B. Anterior end showing amphid; C. Pharyngeal bulb; D. Pharyngo-intestinal junction; E & F. Female genital system; G. Vulval region; H. Female posterior region.(Scale bar A, B, D, = 10 µm; C, E–H = 20 µm)

FIGURE1. Tylencholaimellus striatus Thorne, 1939. A. Entire female; B. Anteriorregion; C. Anterior end showing amphid; D. Pharyngeal region; E. Pharyngeal bulb; F. Female genital system; G. Female posterior region.