Tylencholaimus singaporensis Ahmad, 2010, n. sp.

Tylencholaimus singaporensis n. sp.

(Figs. 5, 6)

Measurements: Table 2.

Description. Female: Body slightly curved ventrad upon fixation. Outer cuticle smooth, inner cuticle distinctly striated, loose, 1.0 µm thick at mid body and 1.5–2 µm on tail. Lateral chords about one-third of body width at mid body. Lateral, dorsal and ventral body pores indistinct.

Lip region cap-like, offset by constriction, about one-half as wide as high or about one-third as wide as body width at neck base. Lips somewhat separate; papillae slightly raised. Amphids stirrup-shaped, their aperture occupying about one-third of the lip region width. Odontostyle typical of the genus, about 0.75–0.85 times lip region width long, its aperture about one-third of its length. Guiding ring ‘single’, at 0.6–0.8 times lip region width from anterior end. Odontophore rod-like with small but distinct basal knobs, 1.1 times the odontostyle length. Nerve ring encircling the anterior slender part of pharynx at 35–40% of neck length from anterior end. Pharynx consists of a slender and weakly muscular part which expands abruptly into a cylindrical basal bulb occupying about 43–45% of total neck length. Cardia short, conoid, about one-forth to one-third of corresponding body width long. Pharyngeal gland nuclei located as follows: D = 60–63%; AS 1 = 28–32%; AS 2 = 40–43%; PS1 = 72–74%; PS2 = 73–75%

Genital system mono-prodelphic. Anterior genital branch well developed; ovary reflexed, measuring 33– 72 µm, with oocytes arranged in a single row except near tip. Oviduct joining the ovary subterminally, measuring 32–50 µm long. A weak sphincter present at oviduct-uterus junction. Uterus a small tube, measuring 25–30 µm. Vulva transverse. Vagina anteriorly directed, about half of corresponding body width deep; pars proximalis vaginae 5–6 µm with thickened walls encircled by circular muscles; pars distalis appearing as two rod-shaped refractive area measuring 2.5 x 1.7 µm. Prerectum about 2.1–2.6 anal body widths long. Rectum about 0.68–0.75 anal body width. Tail short, hemispheroid with rounded terminus, 0.7– 0.9 times anal body width long with a distinct terminal caudal pore.

Male: Not found.

Tylencholaimus singaporensis n. sp. T. intermedius Characters Holotype female Paratype females females

n 5 4

Type habitat and locality: Soil around roots of forest trees from Kent Ridge Park near the National University of Singapore; Collected on September 1, 2003.

Diagnosis and relationships: Tylencholaimus singaporensis n. sp. is characterised by having 0.35–0.47 mm long body; distinctly offset, cap-like lip region; 4.5–5.5 µm long, slender odontostyle; simple rod-like odontophore with small but distinct basal knobs; pharynx consists of a slender and weakly muscular anterior part which expands abruptly into a cylindrical basal bulb; mono-prodelphic female genital system with no post uterine sac, two rod-shaped thickening in vagina, and short hemispheroid tail with distinct terminal caudal pore.

In the Tylencholaimus De Man, 1876 species group with mono-prodelphic female genital system, absence of perioral disc and anterior part of pharynx weakly muscular and expanding abruptly into basal bulb, the new species closely resembles T. rumjhumi Khan & Laha, 1983 but differs in having smaller and robust body (vs L= 0.48–0.65 mm; a= 21.5–26.5); smaller amphid (vs 1/3 lip region width wide); shorter odontostyle (vs odontostyle 6–7 µm); comparatively shorter pharynx (vs b=3.1–3.5); longer expanded part of pharynx (vs 41%), presence of rod-shaped thickening in vagina (vs absence), and in having rounded tail with terminal caudal pore (vs tail dorsally convex conoid without terminal caudal pore).

The new species is also close to T. vigil Andrássy, 1959 but differs in having smaller body (vs 0.57–0.61 mm); smaller amphids (vs 30–40% of corresponding body width wide), shorter odontostyle+odontophore length (vs odontostyle+odontophore length 14–15 µm); smaller expanded part of pharynx (vs 56–60%); more posterior vulva position (vs V= 67.8–68.5); presence of clear thickening in vagina (vs no thickening in vagina); shorter prerectum (vs prerectum 3.2 anal body widths long) and differently shaped tail (vs tail conoid without terminal caudal pore).

Etymology: The species epithet singaporensis refers to Singapore.