Tylencholaimellus projectus Siddiqi, 1964

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 : 305-309

Tylencholaimellus projectus Siddiqi, 1964

( Figs. 3 & 4 )

Material examined. Ten females and eleven males from Kaziranga National Park and six females and a male from Ladakh in good state of preservation.

Description. Measurements, see Table 2.

Female: Small, moderately slender nematodes under 1 mm long, slightly curved upon fixation, tapering gradually towards the anterior end. Cuticle with two distinct layers, 2 µm thick at midbody and 3–4 µm on tail. Outer cuticle with fine transverse striations, inner layer with distinct transverse striations. Lateral chords occupying about 21–28% of the midbody diameter. Lateral, dorsal and ventral body pores indistinct. Lip region cap-like, offset from body by a less marked constriction, about 1.6–2.4timesas wide as high or about one-third of body diameter at neck base; lips amalgamated, with rounded contour, inner portion forming a perioral disc. Amphids cup-shaped, their aperture occupying about one-half of lip region diameter. Stoma truncate cone, weakly sclerotized. Odontostyle 1.7–2.1 times the lip region diameter long, provided with dorsal accessory piece covering the entire dorsal arm; its aperture about one-seventh to one-sixth of odontostyle length. Odontophore with basal knobs, 0.3–0.5 times the odontostyle length. Guiding ring simple, refractive, at 0.8–1.3 lip region diameters from anterior end. Pharynx consisting of a slender and weakly muscular anterior part and a cylindrical, constricted basal bulb, occupying 19–24% of the total neck length. Cardia rounded-hemispherical, about one-sixth to one-fifth of the corresponding body diameter long. Nerve ring located at 45–56% of neck length. Genital system monodelphicopisthodelphic. Ovary reflexed, measuring 65–179 µm, not reaching the oviduct-uterus junction; oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 81–166 µm, consisting of a slender distal part and a well-developed pars dilatata. Oviduct-uterus junction marked by well-developed sphincter. Uterus short, tubular, measuring 33–51 µm. Anterior genital branch reduced to a simple sac, 1.0–2.5 times midbody diameter long. Vagina cylindrical; pars proximalis vaginae 5–11 µm long, its wall encircled by muscles; pars distalis vaginae short, 1.0–2.5 µm long with slightly curved walls; pars refringens absent.Vulva apparently a transverse slit. Sperm present throughout the genital tract. Prerectum 2.4–4.2 and rectum 0.6–1.2 times anal body diameter long. Tail short, 0.8–1.2 anal body diameters in length, cylindroid to rounded-conoid; caudal pores two on each side.

Male: General morphology similar to female except for the posterior region being more ventrally curved. Sperms spindle-shaped. Apart from the adcloacal pair situated at 8 µm from cloacal aperture, there is only one ventromedian supplement, located outside the range of spicules at 18–28 µm from adcloacal pair. Spicules 1.1–1.5 times anal body diameter long. Lateral guiding pieces about one-fourth of the spicule length. Tail short, roundedconoid, 0.9–1.1 anal body diameter in length.

Habitat and locality. Soil samples collected:

i) from the rhizosphere of unidentified grasses from Kaziranga National Park , Assam, India; 26.5775° N, 93.1711° E, and

ii) from the rhizosphere of Populus sp. near the bank of Suru river , bulbul bagh, Kargil, Ladakh, Jammu and Kashmir, India; 34.1526° N, 77.5771° E.

Remarks. Siddiqi (1964) described T. projectus from India. Goseco et al. (1975) in their revision of the genus Tylencholaimellus , redescribed it from New York, USA, and also examined the type specimens. Yeates (1970) described Tylencholaimellus fenensis from England, a species that was later synonymised with T. projectus by Goseco et al. (1975). Peña-Santiago et al. (1993) recorded it from grasslands of Malawi, Africa. The morphometrics of the present population conform well with the type population except in having slightly smaller lip region diameter and comparatively smaller odontophore. The present population agrees well with Goseco et al.’s (1975) population except in having comparatively lower a ratio and shorter neck length in males. However, Yeates’ specimens have a ratio 26–34; and a and c ratio of males larger as compared to the present population. Our present population also agrees well with the Malawi population except for having comparatively narrower lip region (6–7 vs 9.5 µm) and longer prerectum (44–81 vs 37–43 µm).

Figures

FIGURE 4. Tylencholaimellus projectus Siddiqi, 1964. A. & B. Anterior region; C. Anterior end showing amphid; D. Pharyngeal bulb; E. Pharyngeal expansion; F. Female genital system; G. Vulval region; H. Female posterior region. I & J. Male posterior region. (Scale bar A–C, E = 10 µm; D, F–J = 20 µm)

FIGURE3. Tylencholaimellus projectus Siddiqi, 1964. A.Entire female; B. Entire male; C. Anterior region; D. Anterior end showing amphid; E. Pharyngeal region; F. Pharyngeal bulb; G. Female genital system; H. Female posterior region; I. Male posterior region.