Dorylaimellus tropicus, Kumar & Ahmad, 2024

Kumar, Sumit & Ahmad, Wasim, 2024, Description of five new and four known species of Dorylaimellus Cobb, 1913 with perioral disc (Nematoda: Belondiroidea) from the Western Ghats of India, European Journal of Taxonomy 925 (1), pp. 1-45 : 36-41

Dorylaimellus tropicus sp. nov.

urn:lsid:zoobank.org:act:AAEDDB89-DF85-48CA–B151-D1FAF000710E Figs 14–15 , Table 9

Diagnosis

Dorylaimellus tropicus sp. nov. is characterized by having a 0.6–0.7 mm long body; lip region rounded, offset with prominent perioral disc, cuticularized pieces distinct around oral opening; odontostyle 4–5 µm long, odontophore 8–10 µm long; hemizonid present at level of nerve ring; expanded part of pharynx 43–52% of neck length; female genital system amphidelphic; vulva post-equatorial (V= 52–56); prerectum 3.6–6.3 times as long as anal body diameter; tail elongate-filiform, sudden tapering ending with rounded tip.

Etymology

The new species is named Dorylaimellus tropicus because of its distribution in tropical rain forests.

Material examined

Holotype

INDIA • 1 ♀; Karnataka State, Shimoga district, Dummalli village ; 13°55′53.65″ N, 75°34′4.48″ E; 10–15 cm deep; October 26, 2018; roots of grasses (unidentified); slide reference number AMU/ZD/ NC / Dorylaimellus tropicus /1.

Paratypes

INDIA • 13 ♀♀; same collection data as for holotype; slide reference number AMU/ZD/NC / Dorylaimellus tropicus /2–9 .

Type habitat and locality

Soil samples collected from around the roots of the grasses (unidentified) from village Dummalli, district Shimoga, Karnataka, India.

Description

Female

Body straight to slightly curved ventrad upon fixation, 0.6–0.71 mm long. Cuticle with distinct transverse striations, about 1 µm thick throughout length of body. Lateral chords 3–6 µm, about one-sixth to one-third (17–30%) of body diameter at mid-body, glandular bodies distinct in some specimens, about 29–35 in number; 7–9 in pharyngeal region, 7–11 from pharyngeal base to vulva, 13–14 from vulva to anal region and 2 in caudal region. Ventral body pores distinct, about 31–42 in number; 8–13 in pharyngeal region, 9–10 from pharyngeal base to vulva, 13–18 from vulva to anal region and 1–2 in caudal region; lateral and dorsal body pores indistinct. Hemizonid present at level of nerve ring. Lip region cap-like, offset by deep constriction, 1.8–2.0 times as wide as high, or about two-sevenths to two-fifths (28–38%) of body diameter at neck base. Lips amalgamated, perioral disc prominent. Cheilostome a truncate cone with refractive walls and distinct cuticularized pieces near oral aperture. Amphids fovea cup-shaped, their aperture occupying about 0.6–0.7 times lip region diameter, fusus almost at level of odontophore base. Guiding ring weakly developed, at 0.8–1.0 times lip region diameter from anterior end. Odontostyle 4–5 times as long as wide, or about 0.7–0.8 times lip region diameter, its aperture occupying about one-third of its length. Odontophore with weakly developed basal flanges, 1.8–2.5 times as long as odontostyle. Nerve ring encircling anterior slender part of pharynx at 30–37% of neck length from anterior end. Pharyngeal expansion abrupt; expanded part 7–11 times as long as wide, or about 4.1–5.8 times body diameter at neck base, occupying about 43–52% of total neck length, enclosed in a spiral muscular sheath. Only dorsal pharyngeal gland and orifice visible: DO = 53–60; DN =55–62; DO–DN =1.7–3.5. Cardia oblong, 1.0–1.5 times as long as wide, occupying about one-fourth to two-fifths (25–40%) of corresponding body diameter.

Genital system amphidelphic, anterior genital branch slightly longer than posterior. Ovaries reflexed, reaching oviduct-uterus junction, measuring 32–75 µm (anterior) and 32–55 µm (posterior) long with oocytes arranged in single row except near tip. Oviduct joining ovary subterminally, anterior 25–40 µm or 1.3–2.1 times and posterior 28–38 µm or 1.4–2.0 times as long as mid-body diameter, consisting of a long slender part with prismatic cells and a slightly wider pars dilatata; oviduct-uterus junction marked with sphincter. Uterus a small tube, anterior 12–25 µm or 0.6–1.2 times and posterior 11–19 µm or 0.6–1.0 times as long as corresponding body diameter; sperm not observed. Vulva longitudinal. Vagina extending inward about two-fifths to one-half (40–53%) of corresponding body diameter; pars proximalis vaginae longer than wide, 4–7×3–4 µm, with convex walls, pars refringens absent; pars distalis 2 µm. Prerectum 3.6–6.3 and rectum 1.0–1.5 times as long as anal body diameter. Tail suddenly tapering, elongate-filiform with finely rounded terminus. Caudal pores two on each side.

Male

Not found.

Taxonomic remarks

Dorylaimellus tropicus sp. nov. comes close to Dorylaimellus vietnamensis Ahmad & Sturhan, 2000 ; D. afer Andrássy, 1969 ; and D. salimi Siddiqi, 1966 but differs from the former in having a well-developed hemizonid almost at the level of the nerve ring (vs hemizonid absent), a ventral body pore present (vs absent), a comparatively robust body (a=32–36 vs 39–42), a narrower lip region (5–6 vs 7–8 µm), a shorter tail (c =13–17 vs 10.5–12.2; c′ =3.1–4.3 vs 4.5–5.3) and in the tail shape (sudden tapering, elongate-filiform ending with rounded tip vs gradual tapering, elongate-filiform ending with finely rounded tip).

From D. afer Andrássy, 1969 , the new species differs in having a shorter body length (0.6–0.7 vs 0.88 mm); presence of a hemizonid (vs absent), in having a longer tail (c= 13–17 vs 20–22) and also in the tail shape (vs bends slightly ventrally first, then quickly narrows like a finger and curved slightly dorsally, ending with finely rounded terminus).

From D. salimi Siddiqi, 1966 the new species differs in having a comparatively shorter and robust body (L=0.6–0.7 vs 0.7–0.8 mm; a= 32–36 vs 43–53), distinct hypodermal glandular bodies (vs obscured), an odontostyle comparatively robust with distinct lumen and aperture (vs slender with indistinct aperture), a longer odontophore (8–10 vs 7 µm), a longer pharynx (b = 3.2–3.9 vs 4.7), a longer expanded part (43–52 vs 40% of total neck length) and in the tail shape (sudden tapering to a elongate-filiform vs regularly tapering to a finely rounded terminus) and in the absence of male (vs present).

Figures

Fig. 14. Dorylaimellus tropicussp. nov. A–B, F. Paratype 1, ♀ (slide 2). C, E, G–H. Paratype 3, ♀ (slide 4). D. Paratype 2, ♀ (slide 2). A. Entire. B. Anterior region.C. Anterior end showing amphid. D. Neck region. E. Vulva. F. Genital system. G. Posterior end showing prerectum. H. Female posterior end.

Fig. 15. Dorylaimellus tropicus sp. nov. (LM photographs). A, D–E, G, I. Paratype 1, ♀ (slide 2). B–C, F, H. Paratype 3, ♀ (slide 4). A. Anterior region, arrow indicating cuticularized pieces. B. Arrow indicating odontostyle. C.Anterior end showing amphid.D. Arrow indicating hemizonid.E. Expanded part of pharynx. F. Vulva. G. Female genital system. H. Tail. I. Hypodermal glandular bodies. Scale bars: A–I = 10 µm.