Dorylaimellus (Fillidorylaimellus) khasianus, Ahmad & Naz, 2012

Ahmad, Wasim & Naz, Tabbasam, 2012, Four new and six known species of the genus Dorylaimellus Cobb, 1913 (Nematoda: Belondiridae) from India, Journal of Natural History 46 (45 - 46), pp. 2787-2828 : 2801-2805

Dorylaimellus (Fillidorylaimellus) khasianus sp. nov.

( Figures 7 and 8 ; Table 4)

Description

Female. Body curved ventrad upon fixation, tapering towards both extremities. Cuticle finely striated, 1.5–2.0 µm thick at mid body and 1.5–2.0 µm on tail. Lateral chords about one-third as wide as body width at mid body. Lateral, dorsal and ventral body pores indistinct. Lip region offset, about twice as wide as high or about one-third as wide as body width at neck base; lips amalgamated. Amphids stirrup-shaped, their aperture about 0.8–0.9 times as wide as lip region width. Cheilostome a truncate cone with refractive walls and distinct cuticularized plates slightly behind oral aperture. Odontostyle about 0.7–0.8 times lip region width long, its aperture about one-third of its length. Odontophore with distinct basal flanges, 2.0–2.5 times the odontostyle length. Nerve ring at 43–46% of neck length from anterior end. Pharyngeal expansion abrupt; expanded part occupying about 31–35% of total neck length, enclosed in a thick sheath of dextrally spiral muscles. Cardia short, tongue-like, about one-third of the corresponding body width long. Genital system amphidelphic; both the sexual branches almost equally developed. Ovaries reflexed, measuring 77–95 µm (anterior) and 77–100 µm (posterior) with oocytes arranged in a single row except near tip. Oviduct joining ovary subterminally, measuring 80–100 µm (anterior) 80–100 µm (posterior) long. Sphincter present at oviduct–uterus junction. Uterus a wide tube filled with spermatozoa, measuring 66–100 µm (anterior) and 62–100 µm (posterior). Vulva longitudinal. Vagina extending inward, about half of corresponding body width; pars proximalis vaginae cylindrical with almost straight walls, 14–16 µm long, encircled by circular muscles; pars refringens vaginae absent; pars distalis vaginae 5–6 µm with rounded walls. Prerectum 4.2–4.7 times anal body width long. Rectum about one anal body width. Tail elongate conoid gradually tapering to a finely rounded terminus, 3.1–3.8 times anal body width long. Caudal pores two on each side.

Male. Similar to female in general morphology, except for posterior region being more curved because of presence of copulatory muscles. Supplements, an adcloacal pair and nine irregularly spaced ventromedians. Spicules cylindrical, about 1.3 times cloacal body width long. Lateral guiding pieces about one-third of spicules length. Prerectum 4.2–4.7 times cloacal body width long. Rectum about as long as cloacal body width. Tail similar to female, 2.9 times cloacal body width long, with a pair of caudal pores on each side.

Type habitat and locality

From soil around the roots of forest trees near Norgrim village, Cherapunji , East Khasi hills, Meghalaya; 25 ◦ 41 ′ 0 ′′ N, 91 ◦ 21 ′ 0 ′′ E, altitude 1484 m from sea level .

Type specimens

Holotype female on slide Dorylaimellus (F.) khasianus sp. nov. / 1; paratype females and males on slides Dorylaimellus (F.) khasianus sp. nov. / 2–5; deposited with the nematode collection of the Department of Zoology, Aligarh Muslim University, India. A paratype female deposited with the nematode collection of the Universidad de Jaén, Spain.

Etymology

The species name D. (F.) khasianus sp. nov. is derived from Khasi Hills, the type locality of the species.

Diagnosis and relationships

Dorylaimellus (F.) khasianus sp. nov. is characterized by having 1.2–1.4 mm long body; offset lip region with amalgamated lips; 6–7 µm long odontostyle; odontophore with well developed flanges; pharyngeal bulb short, occupying about 31–35% of neck length; a longitudinal, pre-equatorial vulva; amphidelphic genital system; elongate conoid, more or less cylindriod tail ending in a finely rounded terminus and males with slender spicules and nine irregularly spaced ventromedian supplements.

In the presence of long tail, longitudinal vulva, amphidelphic gonad and in absence of peri-oral disc the new species fits under the subgenus Filidorylaimellus Jairajpuri and Ahmad, 1980 and comes close to Dorylaimellus jonsoni Jordan and Heyns, 1984; Dorylaimellus spicatus Loof, 1964 and Dorylaimellus dorylaimoidurus Siddiqi, 1966 but differs from the former in having larger body size (L = 1.2–1.4 vs 0.8–1.03 mm), shorter pharynx (b = 7.2–8.3 vs 3.3–4.2), pre-equatorial vulva (V = 44.5–46 vs 51–61), differently shaped spicule (cylindrical vs robust) and more ventromedian supplements (9 vs 4).

From D. spicatus , the new species differs in having larger body size (L = 1.2–1.4 vs 0.73–0.82 mm), smaller pharynx (b = 7.2–8.3 vs 2.7–3.2), pre-equatorial vulva (V = 44.5–46.3 vs 51–56) and in the presence of male (vs absence).

From D. dorylaimoidurus , it differs in having longer body size (L = 1.2–1.4 mm vs 0.84 mm), shorter pharynx (b = 7.2–8.3 vs 5), slightly posteriorly located vulva (V = 44.5–46.3 vs 42.6), longer and differently shaped spicule (30 µm long, very slender spicule vs 17 µm long, robust spicule), more ventromedian supplements (9 vs 4) and shorter tail (c = 15.7–19.2 vs 10.5, c′ = 3.1–3.8 vs 5.5).

Figures

Figure 7. Dorylaimellus (Fillidorylaimellus) khasianus sp. nov. (A) Entire female, (B) entire male, (C) anterior region, (D) anterior end showing amphid, (E) pharyngeal region, (F) expanded part of pharynx, (G) female genital system, (H) vulval region, (I) female posterior region, (J) male posterior region, (K) spicule.

Figure 8. Dorylaimellus (Fillidorylaimellus) khasianus sp. nov. (A) Anterior region, (B) anterior end showing amphid, (C,D) expanded part of pharynx, (E,F) vulval region, (G) female posterior region, (H) male posterior region showing spicules, (I) male posterior region. Scale bars: A–I = 20 µm.