Tylencholaimus tamiliensis, Islam & Ahmad, 2021

Islam, Md Niraul & Ahmad, Wasim, 2021, Five new and five known species of the genus Tylencholaimus de Man, 1876 (Nematoda: Dorylaimida: Tylencholaimoidea) from Western Ghats of India, European Journal of Taxonomy 774 (1), pp. 58-105 : 97-102

Tylencholaimus tamiliensis sp. nov.

urn:lsid:zoobank.org:act:90F61B5B-B85A-4BD0-823F-76A964973D92

Figs 15–16 , Table 10

Diagnosis

Tylencholaimus tamiliensis sp. nov. is characterized by its small slender body, 0.51–0.58 mm long; lip region cap-like, offset, lips elevated; odontostyle slender 5.5–6.0 μm, odontophore 6.0–6.5 μm, total stylet length 11.5–12.5 μm; pharynx with slightly muscular anterior part, expanding gradually into the cylindrical basal bulb occupying about 40–43% of total neck length; female genital system monodelphicprodelphic; posterior genital branch reduced to a simple sac, 1.3–2.0 times midbody diameter long; vulva a transverse slit and tail short, rounded to conoid with sunken terminus.

Etymology

The new species is named Tylencholaimus tamiliensis sp. nov. because of its type locality Tamil Nadu.

Material examined

Holotype INDIA • 1 ♀; Tamil Nadu State, Nilgiris district, Naduvattum ; 11º28′37.8″ N, 76º32′36.7″ E; 5–15 cm depth; 15 Nov. 2016; roots of shrubs(unidentified); slide reference number AMU/ZD/NC/ Tylencholaimus tamiliensis /1.

Paratypes INDIA • 6 ♀♀; same collection data as for holotype; slides reference number AMU/ZD/NC/ Tylencholaimus tamiliensis /2–3 • 3 ♀♀; same collection data as for holotype; slide reference number AMU/ZD/NC/ Tylencholaimus tamiliensis /4, nematode collection of the Zoological Survey of India, Kolkata, India .

Type habitat and locality

Soil samples collected from around the roots of shrubs (unidentified) from forest near Naduvattum, Nilgiris district, Tamil Nadu State.

Description

Female

Moderately 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, 1.5– 2.0 μm thick at midbody and 2.5–3.0 μm on tail. Outer cuticle with fine transverse striations; inner layer thick, its outline loose irregular, with distinct radial refractive elements. Lateral chords occupying about 22–31% of midbody diameter. Lateral body pores indistinct, dorsal body pores one at odontostyle- odontophore region, 1–2 in neck region, one between pharyngeal base to vulva and one at post-vulval region; ventral body pores: 1–2 in neck region, and 2 in post-vulval region. Lip region cap-like, offset by deep constriction, 2.0–2.3 times as wide as high or about ⅓ of the body diameter at neck base. Lips rounded, amalgamated, inner part slightly elevated. Labial and cephalic papillae distinct but not interfering with the labial contour. Amphids small, cup-shaped, their aperture occupying about ⅓ of lip region diameter. Stoma a truncate cone. Odontostyle 0.7–0.9 times the lip region diameter long, its aperture about ¼ to 1/5 of the odontostyle length. Odontophore rod-like, with minute basal knobs, about 1.0–1.1 times the odontostyle length. Guiding ring simple, refractive, at 0.6–0.8 times the lip region diameter from anterior end. Pharynx consisting of a slightly muscular anterior part, expanding gradually into a cylindrical basal bulb, with thick-walled lumen, occupying about 40–43% of total neck length. Pharyngeal gland nuclei and their orifices are located as follows: DO = 58–62, DN = 61–64, DO–DN = 2.1–3.5, S1N1 = 74–77, S1N2 = 77–82, S2N = 87–89, S2O = 89–92. Nerve ring located at 37–41% of neck length from anterior region. Cardia rounded conoid, about ⅓ to 2/5 of the corresponding body diameter long.

Genital system monodelphic-prodelphic. Ovary reflexed, measuring 48–70 μm long; oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 52–83 μm, consisting of a slender distal part and well developed pars dilatata. Oviduct-uterus junction marked by welldeveloped sphincter. Uterus short, tubular, measuring 32–43 μm. Posterior genital branch reduced to a short uterine sac, 1.3–2.0 times the corresponding body diameter. Sperm cell not present in the genital tract. Vagina cylindrical, 10–12 μm or about 2/5 to ½ (44–53%) of midbody diameter; pars proximalis vaginae 7.0–8.0 × 5.0–6.5 μm, its wall encircled by circular muscles; pars distalis vaginae 3.0–4.0 μm with slightly curved walls; pars refringens absent. Vulva a transverse slit. Prerectum 3.0–5.4 and rectum 1.0–1.3 times anal body diameter long. Tail short, rounded to convex-conoid with sunken terminus, 0.7–0.9 times anal body diameter long, with a dorsal pore at level of anal opening and a pair of subdorsal caudal pores.

Male

Not found.

Taxonomic remarks

In the absence of labial disc, gradual pharyngeal expansion, presence of posterior uterine sac and short tail with sunken terminus, the new species comes close to T. australis Yeates, 1979 ; T. orientalis Li et al., 2008 ; T. maritus Loof & Jairajpuri, 1968 and T. loofi Dhanachand, 1994 but differs from the former in having a distinctly offset lip region, with elevated, angular and slightly separate lips (vs not elevated, flat, rounded and amalgamated), slightly higher lip region (3.0–3.5 vs 2.5–3.0 μm); body pores distinct (vs indistinct), slightly higher c (39.7–48.8 vs 36–40), lower c’ (0.7–0.9 vs 1.0–1.1) ratios and presence of three caudal pores (vs two caudal pores).

It differs from T. orientalis in having a slightly smaller pharyngeal expansion (40–43 vs 44–45% of total neck length); longer post-uterine sac (30–44 vs 10–27 μm); tail short, rounded to conoid with sunken tip (vs rounded tip) and presence of three caudal pores (vs two caudal pores).

The new species differs from T. maritus in having a comparatively posterior vulva position (V = 68– 72 vs 63–66); longer post-uterine sac (30–44 vs 6.0–9.5 μm); lower c’ ratio (0.7–0.9 vs 1.0–1.3); tail short, rounded to conoid with sunken tip (vs rounded tip); caudal pores three (vs two) and absence of male (vs present).

The new species differs from T. loofi in having a shorter total stylet length (11.5–12.5 vs 22.4–25.6 μm); slightly posterior vulva position (V = 68–72 vs 65.0–67.5); longer post-uterine sac (30–44 vs 10 μm); longer prerectum (42–80 vs 24–25 μm) and tail with sunken tip (vs conoid tip).

The new species also comes close to T. chathami Yeates, 1979 but differs in having a comparatively shorter body length (0.51–0.58 vs 0.6–0.8 mm); shorter pharynx and its expansion (156–179 vs 192– 223 μm, 64–76 vs 84–103 μm); longer post-uterine sac (1.3–2.0 vs 0.25 times the corresponding body diameter long); tail with sunken tip (vs rounded tip) and three caudal pores (vs two).

Figures

Fig. 15. Tylencholaimus tamiliensis sp. nov., ♀. A, C–F. Paratype 5 (slide 3). B. Paratype 2 (slide 2). G–H. Holotype (AMU/ZD/NC/Tylencholaimus tamiliensis/1). A. Entire specimen. B. Anterior region. C. Anterior region showing amphid. D. Pharyngeal region. E. Pharyngeal expansion. F. Genital system. G–H. Posterior region.

Fig. 16. Tylencholaimus tamiliensis sp. nov., ♀ (LM photographs). A, F. Paratype 1, (slide 2). B, G, J. Paratype 2 (slide 2). C. Paratype 5 (slide 3). D, I. Paratype 4 (slide 3). E. Paratype 8 (slide 4). H. Paratype 6 (slide 3). K–L. Holotype (AMU/ZD/NC/Tylencholaimus tamiliensis/1). A–B. Anterior region. C. Anterior region showing amphid. D. Pharyngeal region. E. Expanded part of pharynx. F–G. Pharyngo-intestinal junction. H–I. Genital system. J. Vulval region. K. Posterior region. L. Posterior end. Scale bars: A–C, E–G, I–L = 10 μm; D, H = 20 μm.