Basirotyleptus minutus Khan, 1987

Islam, Md Niraul & Ahmad, Wasim, 2022, Description of five new and six known species of the genus Basirotyleptus Jairajpuri, 1964 (Nematoda: Dorylaimida: Tylencholaimoidea) from the Western Ghats, India, European Journal of Taxonomy 791 (1), pp. 1-57 : 20-24

Basirotyleptus minutus Khan, 1987

Figs 6–7 , Table 6

Basirotyleptus minutus Khan, 1987: 177–179 .

Material examined

INDIA – Karnataka State • 2 ♀♀; Kodagu district, Bhagamandala ; 12º23′29.1″ N, 75º31′50.0″ E; 5–15 cm depth; 8 Nov. 2016; soil samples collected from around the roots of shrubs and forest trees (unidentified); slides reference number AMU/ZD/NC/ Basirotyleptus minutus /1 .

Description

Female

Small sized nematodes, slightly curved ventrad upon fixation; body cylindrical, tapering gradually towards both extremities but more so towards the anterior end. Cuticle with two distinct layers, 1.0 µm thick at anterior region, 1.5 µm at midbody and 2.0–2.5 μm on tail. Outer cuticle thin, with fine transverse striations; inner layer thick, finely striated, loose, with radial refractive elements. Lateral chords occupying about 26–30% of midbody diameter. Lateral, dorsal and ventral body pores indistinct. Lip region cap-like, offset by constriction, 2.3 times as wide as high or about one-third of the body diameter at neck base. Lips rounded, amalgamated, slightly angular; inner part slightly elevated. Amphids duplex, cup-shaped, their aperture about one-half to three-fifths as wide as lip region diameter. Stoma a long, slender truncate cone, slightly sclerotized in the perioral region. Odontostyle slender, solid, needlelike, 1.4 times the lip region diameter long. Odontophore simple, sclerotized, with basal flanges, about 1.3–1.4 times the odontostyle length. Guiding ring simple, refractive, at 1.3 times the lip region diameter from anterior end. Pharynx consisting of a slender anterior part, expanding abruptly into a short pyriform bulb, with a perceptible thickening at the posterior part of its inner lining, occupying about 18% of total neck length. Nerve ring at 52–55% of neck length from anterior end. Cardia rounded to hemispheroid, about one-fourth of the corresponding body diameter long.

Genital system monodelphic-opisthodelphic. Ovary reflexed, measuring 43–59 μm; oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 55–84 μm, consisting of a slender distal portion and a well-developed pars dilatata. Oviduct-uterus junction marked by distinct sphincter. Uterus a short tube with wide lumen, measuring 27–30 μm. Anterior genital branch reduced to a very small sac, about one-fifth midbody diameter long. Sperm cell absent. Vagina cylindrical, extending inwards, 10.0–10.5 μm or about one-half (50–55%) of midbody diameter; pars proximalis vaginae 6.5 × 4.5–5.0 μm, encircled by circular muscles; pars distalis vaginae 4.0 μm with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 3.1–3.2 and rectum 0.9–1.0 times anal body diameter long. Tail short, rounded to conoid, 0.8 times anal body diameter long, with a pair of caudal pores on each side.

Male

Not found.

Remarks

Khan (1987) described Basirotyleptus minutus from Tamil Nadu, India. The morphometrics of present specimens conform well with the type population except in having differently shaped amphids (duplex, cup-shaped vs simple, stirrup-shaped) and slightly longer pharyngeal bulb (19–20 vs 16 µm). In original description of B. minutus , the size of odontostyle (10–14 µm) and odontophore (8.0–10.0 µm) does not correspond with the figure ( Khan 1987: fig. 2b, e). The figure depicts the odonotostyle as shorter than the odontophore which is generally true with other Basirotyleptus species. There might be error in his measurements. In our present specimens the length of odontostyle (10 µm) is shorter than odontophore (13–14 µm) with a combined length of 23–24 µm, which overlaps with type population (18–24 µm). However, in the other characters the present population agrees well with the type population.

In the presence of flanged odontophore, this species closely resembles Basirotyleptus nindei Siddiqi, 1970 except in having slightly differently shaped lip region (lips slightly angular and labial papillae not distinct vs lips more angular and labial papillae distinct); differently shaped amphids (duplex, cupshaped vs simple, stirrup-shaped) and comparatively shorter tail (10.0 vs 11.0–13.5 µm, c’ = 0.8 vs 1.0–1.2).

Figures

Fig. 6. Basirotyleptus minutus Khan, 1987, ♀ (AMU/ZD/NC/Basirotyleptus minutus/1). A. Entire specimen. B. Anterior region showing amphid. C. Anterior region. D. Pharyngeal bulb. E. Pharyngeal region. F. Genital system. G. Posterior region.

Fig. 7. Basirotyleptus minutus Khan, 1987, ♀ (AMU/ZD/NC/Basirotyleptus minutus/1) (LM photographs). A–B. Anterior region. C. Anterior region showing amphid. D. Pharyngeal region. E–F. Pharyngeal bulb. G. Vulval region. H. Genital system. I. Posterior region. J–K. Posterior end. Scale bars = 10 µm.