Dorylaimellus (Dorylaimellus) hulqus, Ahmad & Naz, 2010

Ahmad, Wasim & Naz, Tabbasam, 2010, Two new and two known species of the family Belondiridae Thorne, 1939 (Nematoda: Dorylaimida) from Singapore, Journal of Natural History 44 (41 - 42), pp. 2465-2479 : 2472-2477

Dorylaimellus (Dorylaimellus) hulqus sp. nov.

( Figures 3A–H, 4A–F ; Table 2)

Description

Female. Body curved ventrad upon fixation, tapering towards both extremities. Cuticle with fine transverse striations, 1.0–1.5 µm thick at mid body and 2.0–3.0 µm on tail. Lateral chords about one-quarter to one-third as wide as body width at mid body. Lateral, dorsal and ventral body pores indistinct. Lip region offset, about one-third as wide as body width at neck base. Four cuticularized pieces present around oral opening. Peri-oral disc absent. Amphids cup-shaped, their aperture 0.8–1.0 times as wide as lip region width. Odontostyle 1.0–1.2 times lip region width long, its aperture about one-third of its length. Odontophore rodlike with basal flanges, 1.8–2.2 times the odontostyle length. Nerve ring at 24–27% of neck length from anterior end. Pharyngeal expansion abrupt; expanded part occupying about 60–73% of total neck length, enclosed in a thick sheath of dextrally spiral muscles. Cardia short, conoid, about one-third of the corresponding body width long. Genital system amphidelphic; both the sexual branches almost equally developed. Ovaries reflexed, measuring 17–19 µm (anterior) and 16–23 µm (posterior) with oocytes arranged in a single row except near tip. Oviduct undifferentiated, joining ovary subterminally, measuring 15–17 µm (anterior) and 10–16 µm (posterior) long. Sphincter indistinct at oviduct–uterus junction. Uterus a small tube, measuring 10–12 µm (anterior) and 12–14 µm (posterior). Vulva longitudinal. Vagina extending inward, about one-half of corresponding body width; pars proximalis vaginae 6–7 µm with convex walls encircled by circular muscles; pars refringens vaginae absent; pars distalis vaginae 1.5 µm with rounded walls. Pre-rectum 4.1–5.0 times anal body width long. Rectum about as long as anal body width. Tail hemispheroid, 0.9–1.4 times anal body width long. Caudal pores two on each side.

Male. Not found.

Type habitat and locality

Soil around the roots of forest trees from Kent Ridge Park, near the National University of Singapore, Singapore.

Diagnosis and relationships

Dorylaimellus (D.) hulqus sp. nov. is characterized by having 0.4–0.5 mm long body; offset lip region; 5 µm long odontostyle; expanded part of pharynx 59–73% of neck length; longitudinal vulva; amphidelphic gonad; pre-rectum four to five times anal body width long and hemispheroid tail.

In having an offset lip region without peri-oral disc, longitudinal vulva and amphidelphic gonad, the new species belongs to the subgenus Dorylaimellus Cobb, 1913 . In this group, because of its small body size, long expanded part of pharynx and short tail, it is most similar to Dorylaimellus (D.) meridionalis Jordan and Heyns, 1984 and Dorylaimellus (D.) tenuidens Thorne, 1939 . However, from the former, the new species differs in having a shorter body (L: 0.4–0.5 vs 0.7–1.1 mm); longer pharynx (b: 1.9–2.7 vs 3.6–4.8); posterior vulva (V: 59–69 vs 47–53), and in the shape and size of the tail (hemispheroid vs convex conoid; c: 27.6–35.2 vs 31–42, c′: 0.9–1.4 vs 1.3–1.7).

From D. (D.) tenuidens , the new species differs in having a slightly shorter odontostyle (5 vs 6.1 µm), longer expanded part of pharynx (60–73% vs 41% of neck length), slightly posterior vulval position (V: 59–69 vs 56), longer prerectum (four to five times vs twice anal body width long), and differently shaped tail (hemispheroid vs convex conoid).

In having a long expanded part of pharynx, the new species is also similar to D. (Axodorylaimellus) parvulvus Thorne, 1939 ; D. (A.) catarcticus Andrássy, 1968 and D. (A.) deviatus Baqri and Jairajpuri, 1969 but differs from them in the absence of a perioral disc (vs presence) and in having a longitudinal vulva (vs transverse vulva). Mohilial et al. (2000) describe Dorylaimellus himilis from Manipur, India, characterized by having body 0.4–0.5 mm long; odontostyle 6.4–8.8 µm long; transverse vulva and pre-rectum eight times anal body width. As per their illustrations, the odontostyle is about 5 µm; odontophore about 15 µm; vulva appears to be longitudinal and prerectum about 4.5 times anal body width long. Though the description of the above species is not reliable, it still appears very similar to present populations. However, the specimens from Singapore distinctly differ from D. himilis in their tail shape (hemispheroid vs convex conoid).

Etymology

The species name is derived from the Arabic and Urdu word hulq meaning throat and refers to the characteristically long pharynx.

Figures

Figure 4. Dorylaimellus hulqus sp. nov. (A,B) anterior region, (C,D) junction between two parts of pharynx, (E) female genital system, (F) female posterior region. Scale bars A–F, 10 µm.