Tylencholaimus vulvulatus Rahman, Jairajpuri, Ahmad & Ahmad, 1987

Ahad, Sumaya & Ahmad, Wasim, 2016, Description of two new and six known species of the genus Tylencholaimus de Man, 1876 (Nematoda: Dorylaimida) with a diagnostic compendium and key to species, Zootaxa 4107 (4), pp. 451-490: 460-464

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Tylencholaimus vulvulatus Rahman, Jairajpuri, Ahmad & Ahmad, 1987


Tylencholaimus vulvulatus Rahman, Jairajpuri, Ahmad & Ahmad, 1987 

( Figs. 5View FIGURE 5 & 6View FIGURE 6)

Measurements: See Table 3.

Description. Female: Small sized nematodes, 0.68–0.92 mm, slightly curved upon fixation; body cylindrical, tapering gradually towards both extremities. Cuticle with two distinct layers, 2–4 Μm thick at midbody and 3–4 Μm on tail. Outer cuticle smooth; inner layer irregular with radial refractive elements. Lateral chords occupying about one-fifth of midbody diameter. Lateral, dorsal and ventral body pores indistinct.

Lip region cap-like, offset by constriction, 2.3 times as wide as high or about one-third of the body diameter at neck base; lips amalgamated and rounded, inner part projecting. Amphids cup-shaped, their aperture located at level of cephalic constriction and occupying about one-third of lip region diameter. Stoma a truncate cone. Odontostyle 0.8 –1.0 times the lip region diameter long, its aperture about one-third of its length. Odontophore with minute basal knobs, 1.0– 1.3 times the odontostyle length. Guiding ring simple, refractive, at 0.5–0.6 times lip region diameter from anterior end. Pharynx consists of a slender, slightly muscular anterior part, expanding gradually into a cylindrical basal bulb with thick-walled lumen, occupying about 37–44 % of total neck length. Pharyngeal gland nuclei and their orifices are located as follows: DO = 55–56, DN= 58–61, S 1 N 1 = 74–76, S 1 N 2 = 77–79, S 2 N = 85–93, S 2 O = 86–93. Nerve ring located at 38–47 % of neck length from anterior end. Cardia rounded, hemispheroid, about one-fourth of the corresponding body diameter long.

Genital system pseudo-monoprodelphic. Ovary reflexed, measuring 54–123 µm long, reaching the oviductuterus junction; oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 117–160 µm, consisting of a tubular distal and a wider proximal part containing spindle-shaped sperms. Oviductuterus junction marked by weak sphincter. Uterus long and tubular, measuring 66–86 µm. Posterior genital branch reduced to a long uterine sac, 2.7–3.6 times the corresponding body diameter. Vagina cylindrical; pars proximalis vaginae 5–9 µm long, its wall encircled by muscles; pars distalis vaginae short, 2–4 µm with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit; vulval lips asymmetrical, anterior lip enlarged, swollen, rarely symmetrical. Prerectum 4.6–6.3 and rectum 0.8 –1.0 anal body diameter long. Tail convex-conoid with bluntly rounded terminus, 0.7–0.9 times anal body diameter long, with a distinct terminal caudal pore.

Male: General morphology similar to female but the posterior body region is more ventrally curved. In addition to adcloacal pair, situated at 10 µm from cloacal aperture, there are three ventromedian supplements, located outside the range of spicules; first ventromedian supplement located at 43 µm from adcloacal pair, second at 30 µm from first and third at 22 µm from second ventromedian supplement. Spicules 1.4–1.6 times cloacal body diameter long. Lateral guiding pieces prominent, about one-fourth the spicules length. Tail short and conoid, ventrally almost straight and dorsally convex, 0.7–0.8 anal body diameter long, with a distinct terminal caudal pore.

Habitat and locality. Soil samples collected from the grassland and forest trees of the Kaziranga National Park, Assam, India.

Remarks. Rahman et al. (1987) described T. vulvulatus  from Meghalaya, India. Peña-Santiago and Coomans (1996), redescribed this species based on the study of a paratype female and a male. Our present population agrees fairly well with the original material, except for having slightly longer odontostyle (6–7 µm vs 5.5 µm), and shorter neck (150–197 µm vs 202 µm) and the tail is more rounded (vs more conoid) and shorter (13–17 µm vs 19–20 µm; c = 50–61 vs 40–49). The tail length is quite variable in our specimens and is distinctly shorter than the original material.

T. vulvulatus  is closely related to T. stecki Steiner, 1914  and T. koreanus Ahmad, Park, Lee & Choi, 2009  because of its perioral region without disc; slender part of pharynx muscular, expanding gradually and posterior genital branch with large post-uterine sac. However, it differs, from T. stecki  in having comparatively higher a ratio (vs 22.6–25.6); slightly longer odontostyle (vs 5.0– 5.5 µm); shorter neck (vs 213–236 µm); vulval lips asymmetrical (vs symmetrical); long prerectum (vs 38 µm); tail convex-conoid with bluntly rounded terminus (vs hemispherical, sometimes conoid); slightly longer spicules (vs 23–27 µm) and lateral guiding piece (vs 4–6 µm).

From T. koreanus  , it differs in having larger body size (vs 0.49–0.58 mm); higher a, b, and c ratios (vs 22.1–24.5, 3.2–3.5 and 33.1–41.4 respectively); longer anterior genital branch (vs 113–141 µm); asymmetrical vulval lips (vs symmetrical); relatively long prerectum (vs 55–77 µm); more ventromedian supplements (3 vs 2); and longer spicules (28–32 µm vs 20–22 µm).

Peña-Santiago (2008) synonymised Protylencholaimus longisaccus Dhanam & Jairajpuri, 1999  with T. vulvulatus  , an action which is accepted here. However, the present population differs from P. longisaccus  in having smaller body size (vs 0.90 –1.0 mm), lower a ratio (vs 34–37), smaller pharyngeal bulb (vs 78–101 µm) and shorter tail (vs 18–22 µm).

Table 3. Morphometrics of Tylencholaimus vulvulatus Rahman, Jairajpuri, Ahmad & Ahmad, 1987 (All measurement in µm)

    National Park grassland Population Kaziranga National park forest tree Population
Guiding ring from anterior end      














Tylencholaimus vulvulatus Rahman, Jairajpuri, Ahmad & Ahmad, 1987

Ahad, Sumaya & Ahmad, Wasim 2016

T. koreanus

Ahmad, Park, Lee & Choi 2009

Protylencholaimus longisaccus

Dhanam & Jairajpuri 1999

T. stecki

Steiner 1914