Dorylaimoides malabaricus Ahmad and Jairajpuri, 1982

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 : 328-331

Dorylaimoides malabaricus Ahmad and Jairajpuri, 1982

( Figure 6 , Table 5 )

Description

Female. Slender nematode, small to medium sized, slightly ventrally curved upon fixation; body 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, 1.5–2.0 μm at midbody and 2.5–3.5 μm at tail. Outer cuticle thin, smooth; inner layer thick, finely striated. Lateral chords 6.0–8.0 μm at midbody, occupying about one-fifth to one-fourth (17–23%) of corresponding body diameter. Lateral, ventral and dorsal body pores indistinct. Lip region cap-like, continuous with body, 2.0–2.5 times as wide as high or about one-third of body diameter at neck base. Lips rounded, amalgamated; inner part slightly raised. Amphids cup-shaped, their aperture occupying an area about three-fifths to twothirds as wide as lip region diameter. Odontostyle short, asymmetrical, 0.7–0.9 times the lip region diameter long, ventral arm 4.5–5.5 μm, dorsal arm 5.5–6.5 μm, its aperture about one-fourth to one-third of the odontostyle length. Odontophore arcuate, about 1.5–1.9 times the odontostyle length. Guiding ring simple, refractive, at 0.6–0.9 times lip region diameter from anterior end. Pharynx consisting of a slender and slightly muscular anterior part, expanding abruptly into a short, cylindrical basal bulb, separated by distinct constriction, 3.1–4.1 times as long as wide, 1.5–1.9 times corresponding body diameter, occupying about 23–27% of total neck length. Pharyngeal gland nuclei often visible. Nerve ring located at 42–48% of neck length from anterior end. Cardia short, conoid, about one-sixth to one-fourth of the corresponding body diameter long. Genital system didelphic-amphidelphic. Ovaries reflexed, measuring 37–74 μm (anterior) and 52–80 μm (posterior) long; oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 45–74 μm (anterior) and 37–96 μm (posterior), consisting of a slender distal part and a well-developed pars dilatata. Oviduct-uterus junction marked by well-developed sphincter. Uterus short and tubular, measuring 41–76 μm (anterior) and 34–76 μm (posterior). Sperm cells usually present in the genital tract. Vagina cylindrical, extending inwards, 16.0–21.5 μm or about one-half to three-fifths (47–63%) of midbody diameter; pars proximalis vaginae 10–12 × 7.0–12 μm, encircled by circular muscles; pars distalis vaginae 5.0–9.0 μm with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 7.4–10.8 and rectum 1.1–1.5 times anal body diameter long. Tail long filiform, tapering gradually, its distal part bent dorsally, 10.1–13.7 times anal body diameter long, with a pair of caudal pores on each side.

Male. General morphology similar to that of female except for posterior region being more ventrally curved. Genital system diorchic, testes opposed, sperm cells spindleshaped, 5.0–6.0 μm long. In addition to adcloacal pair, situated at 9.0–12 µm from cloacal aperture, there are five to seven irregularly spaced ventromedian supplements, first one located at the level of the anterior end of the spicules, 23–30 μm from adcloacal pair. Spicules typically dorylaimoid, curved ventrad, relatively robust, 4.1–4.5 times as long as wide and 1.4–1.6 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 134–138°, head occupying 11–12% of total spicules’ length, median pieces about 10 times as long as wide, occupying 35–37% of the spicules’ maximum width, reaching the spicules’ tip, posterior end 3.5–4.0 μm wide. Lateral guiding pieces distinct, rod-like, about 7.3 times as long as wide or one-third of the spicules’ length. Prerectum 7.8–9.5 and rectum 1.7–2.0 cloacal body diameter long. Tail long filiform, tapering gradually, its distal part slightly bent dorsally, 9.7–10.6 times cloacal body diameter long, with a pair of caudal pores on each side.

Habitats and localities. Soil samples collected around the roots of (i) long grasses (unidentified) from Nagorcem , Canacona , South Goa district, Goa State , India; coordinates 15.007361°N, 74.041083°E; (ii) grasses (unidentified) from Chungathara forest , Malappuram district , Kerala State, India; coordinates 11.200111°N, 76.163250°E; (iii) bushes (unidentified) from Mudumalai National Park, Gudalur, Nilgiris district, Tamil Nadu State, India; coordinates 11.543167°N, 76.523361°E.

Remarks. Ahmad and Jairajpuri (1982) described Dorylaimoides malabaricus based on one female and three males from Kerala, India. The morphometrics of the present population conform well with the type population except in having a slightly shorter odontostyle (8.0–9.0 vs 11 μm).

Figures

Figure 6. Dorylaimoides malabaricus Ahmad and Jairajpuri, 1982 (LM photographs). (a, b) Anterior region; (c) anterior region showing amphid; (d) pharyngeal region; (e, f) expanded part of pharynx; (g) vulval region; (h) female genital system; (i, j) female posterior region; (k) male posterior region; (l, m) male posterior region showing spicules.Scale bars: a–c, e–g, l, m = 10 μm; d, h, j, k = 20 μm; i = 50 µm.