Dorylaimoides leptura Siddiqi, 1965

Islam, Md Niraul & Ahmad, Wasim, 2022, Description of two new and six known amphidelphic species of the genus Dorylaimoides Thorne and Swanger, 1936 (Nematoda: Dorylaimida: Tylencholaimoidea) from the Tropical Rainforest, Western Ghats, India, Journal of Natural History 56 (5 - 8), pp. 311-347 : 324-327

Dorylaimoides leptura Siddiqi, 1965

( Figure 5 ; Table 4 )

Description

Female. Slender, large nematode, 2.1 mm long, slightly curved ventrad to open C-shaped upon fixation; tapering gradually towards anterior end, posteriorly narrowing to form a long filiform tail. Cuticle with two distinct layers, 1.0–1.5 μm thick at anterior region, 2.5–3.0 μm at midbody and 3.5–4.0 μm at tail. Outer cuticle thin, with fine transverse striations; inner layer thick, distinctly striated. Lateral chords 10 μm at midbody, occupying about one-fourth (23–25%) of corresponding body diameter. Lateral, ventral and dorsal body pores indistinct. Lip region cap-like, offset by constriction, 2.0–2.2 times as wide as high or about one-fourth of the body diameter at neck base. Lips slightly projected, amalgamated, labial and cephalic papillae slightly protruding. Amphids cupshaped, their aperture occupying about one-half to two-thirds of lip region diameter. Odontostyle short, robust, asymmetrical, anterior tip acute, beak-like, 1.1–1.2 times the lip region diameter long, ventral arm 5.5–6.0 μm and dorsal arm 7.5–8.0 μm, its aperture about one-fourth of the odontostyle length. Odontophore arcuate, about 1.5–1.6 times the odontostyle length. Guiding ring simple, refractive, at 0.7–0.8 times lip region diameter from anterior end. Pharynx consisting of a slender and slightly muscular anterior part, expanding gradually into a cylindrical basal bulb, 5.3–6.1 times as long as wide, 2.1– 2.2 times corresponding body diameter long, occupying about 28–29% of total neck length. Pharyngeal gland nuclei barely visible. Nerve ring located at 40–43% of neck length from anterior end. Cardia short, conoid, about one-fourth of the corresponding body diameter long. Genital system didelphic-amphidelphic. Ovaries reflexed, measuring 44–55 μm (anterior) and 53 μm (posterior) long; oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 79–97 μm (anterior) and 69– 78 μm (posterior), consisting of a slender distal part and a well-developed pars dilatata. Oviduct-uterus junction marked by well-developed sphincter. Uterus long and tubular, measuring 98–132 μm (anterior) and 121–130 μm (posterior). Sperm cells absent. Vagina cylindrical, extending inwards, 22.5–24.5 μm or about one-half to three-fifths (52–63%) of midbody diameter; pars proximalis vaginae 14–15 × 9.0–10 μm, encircled by circular muscles; pars distalis vaginae long 9.0–10 μm with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 12.9–14.1 and rectum 1.5–1.7 times anal body diameter long. Tail long filiform, tapering gradually, its distal part dorsally bent, 9.4–10.7 times anal body diameter long, with a pair of caudal pores on each side.

Male. General morphology similar to that of female but body slightly longer than female and posterior region being more ventrally curved. Genital system diorchic, testes opposed, sperm cells spindle-shaped 8.0 μm long. In addition to adcloacal pair, situated at 8.0 µm from cloacal aperture, there are eight regularly spaced ventromedian supplements, first one located within the range of spicules, 16 μm from adcloacal pair. Spicules typically dorylaimoid, curved ventrad, relatively robust, 4.3 times as long as wide and 1.6 times as long as body diameter at level of cloacal aperture, dorsal contour regularly convex, ventral contour bearing a moderately developed hump and hollow, curvature 124°, head occupying 17% of total spicules’ length, median pieces 13 times as long as wide, occupying 37% of the spicules’ maximum width, reaching the spicules’ tip, posterior end 3.5 μm wide. Lateral guiding pieces distinct, rod-like, about 8.6 times as long as wide or one-third of the spicules’ length. Prerectum 13.3 and rectum 1.5 cloacal body diameter long. Tail long filiform, tapers gradually, its distal part slightly dorsally bent, 6.0 times cloacal body diameter long, with a pair of caudal pores on each side.

Habitat and locality. Soil sample collected around the roots of grasses (unidentified) from forest near Kaas Pond, Satara district, Maharashtra State, India; coordinates 17.722361°N, 73.811639°E .

Remarks. Siddiqi (1965) described Dorylaimoides leptura based on seven females from Maharashtra, India. Goseco et al. (1976), in their revision of the genus Dorylaimoides , made a detailed study of the type population as well as one population comprising three females and one male from Venezuela. Jana and Baqri (1981) reported this species from West Bengal, India. The morphometrics of the present population conforms well with the type population except in having a slightly longer and less slender body (L = 2.1 vs 1.9– 2.0, a = 48–55 vs 59–65), slightly higher b value (7.2–7.6 vs 6.8–7.2), slightly more anterior vulva position (V = 37–39 vs 40–42), longer prerectum (12–14 vs 8.7 times anal body diameter), longer tail (213–220 vs 175 μm) and presence of male (vs male absent). The morphometrics of the present population also conforms well with the West Bengal population described by Jana and Baqri (1981) except in having a longer body (L = 2.1 vs 1.7–1.8), slightly posterior vulva position (V = 37–39 vs 35–36), slightly longer tail (213– 220 vs 180–198 μm) and presence of male (vs absent). The present population also conforms well with the Venezuela population except in having a lower b value (7.2–7.6 vs 8.3–9.3), more anterior vulva position (V = 37–39 vs 42–45), longer pharyngeal bulb (78–83 vs 70 μm), longer tail (213–220 vs 147–188) and longer spicules (46 vs 35 μm).

The morphometrics of the present population completely overlapped the type population as well as those of other Indian populations described by Jana and Baqri (1981), but it cannot be conspecific with the Venezuelan population because of its lower b (6.8–7.6 vs 8.3–9.3) and c (9.0–11.0 vs 11–15) ratios, more anterior vulva position ( V = 35–42 vs 42–45) and longer spicules (46 vs 35) . These significant differences can support a separate species, and as a consequence, further study of the Venezuelan population is necessary.

Figures

Figure 5. Dorylaimoides leptura Siddiqi, 1965 (LM photographs). (a, b) Anterior region; (c) anterior region showing amphid; (d) pharyngeal region; (e) expanded part of pharynx; (f, g) female genital system; (h) vulval region; (i) female posterior region; (j) male posterior region; (k) male posterior region showing spicules. Scale bars: a–c, e–h, k = 10 μm; d, i, j = 20 μm.