Basirotyleptus constrictus, Islam & Ahmad, 2022

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 : 30-34

Basirotyleptus constrictus sp. nov.

urn:lsid:zoobank.org:act:D3AB632D-0286-4577-9A83-78E61A57225E

Figs 10–11 , Table 8

Diagnosis

Basirotyleptus constrictus sp. nov. is characterized by having 0.38–0.49 mm long body; lip region caplike, offset by constriction; lips rounded, inner part elevated, forming a perioral disc; odontostyle 9.5– 10 μm long, odontophore 14–15 μm long, total stylet length 23.5–25.0 μm; pharynx slender with slightly muscular anterior part, expanding abruptly into a short pear-shaped basal bulb separated by constriction, occupying about 15–17% of total neck length; female genital system monodelphic-opisthodelphic; anterior genital branch absent or rarely a very small sac, 4.0–6.0 µm or one-fourth to one-third midbody diameter long, tail short, with conoid to bluntly rounded terminus, 1.1–1.4 times anal body diameter long.

Etymology

The new species is named Basirotyleptus constrictus sp. nov. because of its pharyngeal bulb separated by constriction.

Material examined

Holotype INDIA • ♀; Karnataka State, Kodagu district, Bhagamandala ; 12º23′29.1″ N, 75º31′50.0″ E; 5–15 cm depth; 8 Nov. 2017; roots of shrubs and forest trees (unidentified); slide reference number AMU/ZD/ NC/ Basirotyleptus constrictus /1.

Paratypes INDIA • 8 ♀♀; same collection data as for holotype; slides reference number AMU/ZD/NC/ Basirotyleptus constrictus /2–5 .

Type habitat and locality

Soil samples collected from around the roots of shrubs and forest trees (unidentified) from Bhagamandala, Kodagu, Karnataka State.

Description

Female

Small sized nematodes, slightly curved ventrad or open C-shaped upon fixation, tapering gradually towards both extremities but more so towards anterior end. Cuticle with two distinct layers, 1.0–1.5 µm thick at anterior region, 1.5–2.0 µm at midbody and 2.0–2.5 μm on tail. Outer cuticle thin, with fine transverse striations; inner layer thick, finely striated, loose, its outline irregular, with distinct radial refractive elements. Lateral chords occupying about 25–30% of midbody diameter. Lateral, dorsal and ventral body pores indistinct. Lip region cap-like, offset by constriction, 1.8–2.1 times as wide as high or about two-fifths to one-half of the body diameter at neck base. Lips rounded, amalgamated; inner part elevated, forming a perioral disc-like structure. Labial and cephalic papillae clear but not interfering with labial contour. Amphids stirrup-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, needle-like, 1.2–1.3 times the lip region diameter long. Odontophore simple with basal flanges, about 1.4–1.6 times the odontostyle length. Guiding ring simple, refractive, at 1.0–1.2 times the lip region diameter from anterior end. Pharynx consisting of a slender and slightly muscular anterior part, expanding abruptly into a short, pear-shaped basal bulb, with a perceptible thickening at the posterior part of its inner lining, occupying about 15–17% of total neck length, two parts separated by constriction. Nerve ring at 56–60% of neck length from anterior end. Cardia short, rounded to conoid, about one-fifth to one-third of the corresponding body diameter long.

Genital system monodelphic-opisthodelphic. Ovary reflexed, measuring 51–71 μm; oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 29–54 μm, consisting of a slender distal portion and a poorly developed pars dilatata. Oviduct-uterus junction marked by weak sphincter. Uterus short and tubular, measuring 21–27 μm. Anterior genital branch absent or sometimes reduced to small sac (n = 3), 4.0–6.0 µm or about one-fifth to one-third midbody diameter long. Sperm cell absent. Vagina cylindrical, extending inwards, 8.5–10.0 μm or about two-fifths to one-half (43–53%) of midbody diameter; pars proximalis vaginae 5.0–7.0 × 3.0–4.0 μm, encircled by circular muscles; pars distalis vaginae long, 3.0–4.0 μm with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 2.2–3.7 and rectum 0.9–1.3 times anal body diameter long. Tail short, conoid with bluntly rounded terminus, 1.1–1.4 times anal body diameter long, with a pair of caudal pores on each side.

Male

Not found.

Remarks

In the presence of a distinct labial disc, the new species comes close to B. discinus Siddiqi, 1995 ; B. ethiopicus Siddiqi, 1970 and B. nemoralis Siddiqi, 1970 but differs from B. discinus in having longer odontophore (14–15 vs 9.5–10 µm), with distinct basal flanges (vs odontophore with poorly developed basal flanges); longer total stylet length (23.5–25 vs 18.5–19.5 µm); pharyngeal bulb separated by constriction (vs without constriction); anterior genital branch either absent or rarely present but very short (about 0.2–0.3 vs one anal body diameter long), lower c (24–30 vs 35) ratio and absence of male (vs present).

From B. ethiopicus , the new species differs in having its odontophore with distinct basal flanges (vs odontophore without flanges); pharyngeal bulb separated by constriction (vs without constriction); posterior vulva position(V =51–56 vs 38–48) and in the size and shape of tail (tail conoid vs comparatively short, rounded to hemispheroid, c = 24–30 vs 46–77, c’ = 1.1–1.4 vs 0.50–0.80).

From B. nemoralis , the new species differs in having odontophore with distinct basal flanges (vs odontophore without flanges), pharyngeal bulb separated by constriction (vs without constriction); posterior vulva position (V = 51–56 vs 43–50) and longer tail (15–18 vs 11.0 µm, c = 24–30 vs 45–58, c’ = 1.1–1.4 vs 1.0).

Figures

Fig. 10. Basirotyleptus constrictus sp. nov., ♀ (AMU/ZD/NC/Basirotyleptus constrictus/2–5). A. Paratype 3. B, H. Paratype 1. C–E, I. Paratype 5. F. Paratype 4. G. Paratype 2. A. Entire specimen. B–C. Anterior region. D. Anterior region showing amphid. E. Pharyngeal region. F. Pharyngeal bulb. G–H. Genital system. I. Posterior region.

Fig. 11. Basirotyleptus constrictus sp. nov., ♀ (LM photographs). A, C–F, H–I, K. Paratypes (AMU/ ZD/NC/Basirotyleptus constrictus/2–5). B, G, J. Holotype (AMU/ZD/NC/Basirotyleptus constrictus/1). A. Paratype 5. C. Paratype 7. D–E. Paratype 5. F. Paratype 2. H. Paratype 1. I, K. Paratype 3. A–B. Anterior region.C. Anterior region showing amphid. D. Pharyngeal region. E–F. Pharyngeal bulb. G–H. Genital system. I–J. Posterior region. K. Posterior end. Scale bars = 10 µm.