Tylencholaimus shamimi, 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 : 81-85

Tylencholaimus shamimi sp. nov.

urn:lsid:zoobank.org:act:8EA31D0A-727E-44BD-923C-364BB928F60E

Figs 9–10 , Table 7

Diagnosis

Tylencholaimus shamimi sp. nov. is characterized by having 0.57–0.71 mm long body; lip region offset by constriction, lips slightly elevated; odontostyle 6.0–7.0 μm, odontophore 8.5–9.5 μm with basal thickening, total stylet length 14.5–16.0 μm; pharynx with slightly muscular anterior part, expanding gradually into the cylindrical basal bulb occupying about 38–44% of total neck length; female genital system amphidelphic; vulva a transverse slit; tail short, convex-conoid with bluntly rounded terminus and males with 19–23 μm long spicules, lateral guiding pieces and two to three spaced ventromedian supplements.

Etymology

The new species is named after Prof. Mohammad Shamim Jairajpuri in recognition of his contribution to nematode taxonomy.

Material examined

Holotype INDIA • 1 ♀; Kerala State, Idukki, Kudyathoor ; 9º49′37.2″ N, 76º47′45.6″ E; 5–15 cm depth; 31 Oct. 2017; roots of grasses (unidentified); slide reference number AMU/ZD/NC/ Tylencholaimus shamimi /1. Paratypes INDIA • 4 ♀♀, 2 ♂♂; same collection data as for holotype; slides reference number AMU/ZD/NC/ Tylencholaimus shamimi /2–4 • 1 ♀, 1 ♂; same collection data as for holotype; slides reference number AMU/ZD/NC/ Tylencholaimus shamimi /5–6, nematode collection of the Zoological Survey of India, Kolkata, India .

Other material

INDIA • 6 ♀♀; Karnataka State, Uttara Kannada district, Yellapur ; 14º58′12.00″ N, 74º43′12.00″ E; 5–15 cm depth; 29 Oct. 2018; roots of grasses and shrubs (unidentified); slides reference number AMU/ ZD/NC/ Tylencholaimus shamimi /7–9 .

Type habitat and locality

Soil sample collected from around the roots of grasses (unidentified) from Kudyathoor, Idukki district, Kerala State.

Other habitat and locality

Soil sample collected from around the roots of grasses and shrubs (unidentified) from Yellapur, Uttara Kannada district, Karnataka State.

Description

Female

Slender, small sized nematodes, slightly curved ventrad upon fixation; body cylindrical, tapering gradually towards both extremities. Cuticle with two distinct layers, 1.0–1.5 μm thick at anterior region, 1.5–2.0 μm at midbody and 2.5–3.0 μm on tail. Outer cuticle thin, finely striated; inner layer thick, loose, its outline irregular, with radial refractive elements. Lateral chords occupying about 23–32% of the midbody diameter. Dorsal, ventral and lateral body pores indistinct. Lip region narrow, cap-like, offset by constriction, 2.0–2.6 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 short, cylindrical, 0.8–0.9 times the lip region diameter long, its aperture about ¼ to ⅓ of the odontostyle length. Odontophore simple rod-like, with basal thickening, 1.3–1.5 times the odontostyle length. Guiding ring simple, refractive, at 0.6–0.9 times lip region diameter from anterior end. Pharynx consisting of a slightly muscular anterior part, expanding gradually into a cylindrical basal bulb, with thickwalled lumen, occupying about 38–44% of total neck length. Pharyngeal gland nuclei and their orifices are located as follows: DO = 60–63, DN = 62–65, DO–DN = 1.6–2.3, S1N1 = 75–77, S1N2 = 80–83, S2N = 89–90, S2O = 91–92. Nerve ring located at 38–42% of neck length from anterior end. Cardia rounded to conoid, about ¼ to 2/5 of the corresponding body diameter long.

Genital system didelphic-amphidelphic. Ovaries reflexed, measuring 43–89 μm (anterior) and 36–54 μm (posterior) long, not reaching the oviduct-uterus junction; oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 42–74 μm (anterior) and 33–66 μm (posterior) long, consisting of a slender distal portion and a well developed pars dilatata. Oviduct-uterus junction marked with well-developed sphincter. Uterus short and tubular, measuring 28–41 μm (anterior) and 26–45 μm (posterior). Sperm cell rarely present in the genital tract. Vagina cylindrical, extending inwards for 10–13 μm or about ½ (48–54%) of midbody diameter; pars proximalis vaginae 8.0–10 × 4.0–6.0 μm, encircled by circular muscles; pars distalis vaginae 3.0–3.5 μm with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 3.2–5.6 and rectum 0.8–1.4 anal body diameter long. Tail short, convex-conoid, 0.8–1.0 times anal body diameter long, with a pair of caudal pores on each side and a distinct terminal pore.

Male

General morphology similar to that of female, except for posterior region being more ventrally curved. Genital system diorchic, testes opposed, sperm cell spindle-shaped, 8.0–9.0 μm long. In addition to adcloacal pair, situated at 5.0–6.0 µm from cloacal aperture, there are two to three spaced ventromedian supplements, located outside the range of spicules; first one at 32–36 μm from adcloacal pair, second at 23–35 μm from first and the third (n = 1) at 20 μm from second ventromedian supplement. Spicules typically dorylaimoid, curved ventrad, relatively slender, 4.6–4.8 times as long as wide and 1.4 times as long as cloacal body diameter, dorsal contour regularly convex, ventral contour bearing a moderately developed hump and hollow, curvature 128–131º, head occupying about 10–13% of total spicules length, median pieces 10.5–14.3 times as long as wide, occupying about 30–40% of the spicules maximum width, reaching the spicules tip, posterior end 1.5–2.0 μm wide. Lateral guiding pieces distinct, rod-like, 4.3–4.6 times as long as wide or about ⅓ of the spicules length. Prerectum 3.9–5.5 and rectum 1.5–1.6 cloacal body diameter long. Tail short, convex-conoid, with rounded terminus, 0.9–1.0 times cloacal body diameter long, with a pair of caudal pores on each side and a distinct terminal pore.

Taxonomic remarks

By its small body size; gradual pharyngeal expansion and amphidelphic female genital system, the new species comes close to T. innebus Ahmad & Jairajpuri, 1979 ; T. congestus Loof & Jairajpuri, 1968 ; T. mongolicus Andrássy, 1967 and T. suryawanshii Ali & Chisty, 1972 , but differs from the former in having a cap-like lip region with rounded, amalgamated lips (vs lip region expanded, broad and labial papillae elevated); smaller amphidial aperture (⅓ vs ⅔ of the lip region diameter); odontostyle with narrow lumen (vs wide lumen); shorter expanded part of pharynx (38–44 vs 36–37% of the total neck length); differently shaped cardia (rounded to conoid vs hemispheroid); longer prerectum (53–86 vs 26–50 μm); differently shaped tail (convex-conoid vs hemispheroid) and presence of male (vs absent).

The new species differs from T. congestus in having a shorter body size (0.57–0.71 vs 0.72–0.83 mm); smaller amphidial aperture (⅓ vs ½ of the lip region diameter); shorter pharynx and its expansion (166– 172 vs 230 μm, 64–75 vs 80 μm) and presence of male (vs absent).

The new species differs from T. mongolicus in having a longer body size (0.57–0.71 vs 0.52–0.57 mm); narrower lip region (7.0–8.0 vs 11–12 μm); higher c (36–63 vs 21–30) and slightly lower c’ (0.8–1.0 vs 1.0–1.2) ratios; comparatively posterior vulva position (V = 58–63 vs 52–55) and presence of male (vs absent).

The new species differs from T. suryawanshii in having a narrower lip region (7.0–8.0 vs 9.0 μm); smaller amphidial aperture (⅓ vs ⅔ of the lip region diameter); shorter odontostyle (6.0–7.0 vs 8.5 μm) and odontophore (8.5–9.5 vs 12 μm); longer prerectum (53–86 vs 30 μm) and presence of male (vs absent).

In the presence of gradual pharyngeal expansion, the new species also comes close to T. sinensis Li et al., 2008 and T. teres Thorne, 1939 but differs from the former in having a smaller body size (0.57– 0.71 vs 0.76–0.93 mm); smaller amphidial aperture (2.0–3.0 vs 4.0–5.0 μm); comparatively posterior vulva position (V = 58–63 vs 57.0–57.5); longer pharyngeal expansion (38–44 vs 35–36% of total neck length); shorter prerectum (53–85 vs 100–105 μm) and shorter spicules (23–24 vs 32 μm).

The new species differs from T. teres in having a smaller body size (0.57–0.71 vs 0.75–1.2 mm), slightly smaller amphidial aperture (2.0–3.0 vs 3.0–4.0 μm); shorter pharynx and its expansion (166–172 vs 184–247 μm, 65–74 vs 76–115 μm); shorter prerectum (53–85 vs 105–202 μm, 3.2–5.6 vs 6.8–9.5 times corresponding body diameter); shorter (23–24 vs 28–37 μm) and differently shaped spicules (robust vs slender, 4.6–4.8 vs 6.2 times as long as wide).

Figures

Fig. 9. Tylencholaimus shamimi sp. nov. A, G. Paratype 5, ♀ (slide 4). B, I–K. Paratype 6, ♂ (slide 5). C–F, H. Holotype, ♀ (AMU/ZD/NC/Tylencholaimus shamimi/1). A. Entire female. B. Entire male. C. Female anterior region. D. Female anterior region showing amphid. E. Female expanded part of pharynx. F. Female pharyngeal region. G. Female genital system. H. Female posterior region. I. Male posterior region. J. Spicule. K. Lateral guiding piece.

Fig. 10. Tylencholaimus shamimisp. nov. (LM photographs). A, C, E, F–H. Holotype, ♀ (AMU/ZD/NC/ Tylencholaimus shamimi/1). B, D, I. Paratype 5, ♀ (slide 4). J–K. Paratype 6, ♂ (slide 5). A–B. Female anterior region. C. Female anterior region showing amphid. D. Female pharyngeal region. E. Female expanded part of pharynx. F–G. Female genital system. H. Vulval region. I. Female posterior region. J. Male posterior region. K. Male posterior end. Scale bars: A–C, E–K = 10 μm; D = 20 μm.