Tylencholaimellus sinensis, Zhang, Min, Ahad, Sumaya, Liang, Wenju & Ahmad, Wasim, 2012

Zhang, Min, Ahad, Sumaya, Liang, Wenju & Ahmad, Wasim, 2012, A new and three known species of the genus Tylencholaimellus Cobb in M. V. Cobb, 1915 (Nematoda: Dorylaimida) from Changbai Mountain, China, Zootaxa 3499, pp. 46-62 : 47-48

Tylencholaimellus sinensis n. sp.

( Figs. 1 , 2 )

Measurements: Table 1.

TABLE I. Tylencholaimellus sinensis n. sp.; all measurements in µm.

Description. Female: Medium sized nematodes, slightly curved upon fixation, tapering gradually towards the anterior end. Cuticle with two distinct layers, 3–4 μm thick at mid body and 4–5 μm on tail. Outer cuticle finely transversely straited, inner layer with distinct striations; radial refractive elements abundant. Lateral chords occupying about one-sixth of the midbody diameter. Lateral body pores 6–10 in pharyngeal region, 6–9 between pharynx and vulva and 31–41 between vulva and anus. Ventral body pore one, 11–19 μm behind the hemizonid. Dorsal pores indistinct. Lip region offset from body by constriction, 2.3–3 times as wide as high or one third of the body diameter at neck base. Lips rounded and amalgamated; labial and cephalic papillae indistinct. Amphid cupshaped with aperture located at the level of cephalic constriction and occupying about two-thirds of lip region diameter. Stoma a truncate cone. Odontostyle 1.1–1.35 times the lip region width long and provided with dorsal accessory piece covering entire dorsal arm; its aperture one-sixth of the odontostyle length. Odontophore with basal knobs; 0.3–0.4 times the odontostyle length. Guiding ring simple, refractive at 0.6–1.07 times lip region width from anterior end. Pharynx consists of a slender and weakly muscular anterior part and a short pear-shaped constricted basal bulb, which occupies about 13.8–18.4% of the total neck length. Pharyngeal glands often visible. Cardia tongue-shaped, about one-fifth of the corresponding body width long. Nerve ring located at 46–58% of the neck length. Hemizonid posterior to nerve ring, located at 96–108 μm from anterior region. Genital system monodelphic-opithodelphic. Ovary reflexed, measuring 72–149 µm long, not reaching the oviduct-uterus junction, oocytes arranged in single row except near the tip. Oviduct joining the ovary subterminally, measuring 127–296 µm, its proximal and distal parts not differentiated. Oviduct-uterus junction marked by well developed sphincter. Uterus short and tubular, measuring 54–75 µm. Sperm present throughout the genital tract. Anterior genital branch reduced to a simple sac, 0.8–1.6 midbody diameter long. Vagina cylindrical, pars proximalis vaginae 11–13 µm long, its wall encircled by muscles. Pars distalis vaginae short, 2.5–3 µm long with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 2.5–4.6 anal body diameters long. Rectum 1.02–1.2 anal body widths long. Tail short conoid, 1.03–1.2 anal body widths long.

Male: Not found.

Type habitat and locality: Mixed coniferous broad-leaved forest, Changbai Mountain, Northeast China, P.R. China (42°24ʹN, 128°06ʹE): 760m a.s.l.; annual mean temperature 2.6 ºC, annual mean precipitation 691 mm; tree species were dominated by a mixture of coniferous Pinus koraiensis , broadleaved Quercus spp. and Acer spp. on Albi-Boric Argosols.

Type specimens: Holotype female on slide Tylencholaimellus sinensis n. sp. /1; paratype females on slides Tylencholaimellus sinensis n. sp. /2–3; deposited in the nematode collection of the Department of Zoology, Aligarh Muslim University, India.

Etymology: The new species is named sinensis because of its origin in China.

Diagnosis and relationships: Tylencholaimellus sinensis n. sp. species is characterized by having a medium sized body (L = 1.1–1.3 mm); outer cuticle with fine transverse striations, inner cuticle with distinct striations; labial disc absent; lip region offset by constriction; lips rounded and amalgamated; odontostyle 18–19 µm, odontophore 7–8 µm, combined length of spear 25–27 μm; anterior uterine sac 0.8–1.6 midbody diameters long; mono-opisthodelphic female genital system with small anterior uterine sac; transverse vulva and short conoid tail.

In the presence of an offset lip region without labial disc, and comparatively long spear, the new species comes close to T. polonicus Szczygiel, 1962 ; T. pluvialis Siddiqi, 1965 ; and T. sayi Goseco et al. 1975 . However, it differs from T. polonicus in having a truncate-conical stoma not swollen in the middle (vs stoma a truncate cone slightly wider in its central portion); lip region offset by rather shallow constriction, lips more rounded with indistinct labial and cephalic papillae (vs lip region offset by very deep constriction, lips more angular with very distinct labial and cephalic papillae); both parts of pharynx separated by a constriction (vs both parts of pharynx separated by a more or less marked depression); comparatively smaller pharyngeal bulb (vs pharyngeal bulb 30–37 µm long); larger cardia (vs 3 µm Goseco et al. (1975) and 4.5–6.5 µm Peralta & Peña-Santiago, (1995), and deeper vagina (11–12 µm for Goseco et al. (1975), 12–17 µm in Peralta & Peña-Santiago (1995)).

From T. pluvialis , the new species differs in having larger body size (L= 1.10–1.25 vs 0.80–0.89 mm), in the shape and size of lip region (vs lip region 9–10 µm wide with six inner liplets around oral aperture) and comparatively longer tail (vs tail 14–26 µm long). Goseco et al. (1975) recorded few specimens of T. pluvialis from Indiana. Their specimens distinctly differ from the original description in having shorter odontostyle (14.4 vs 18 µm) and shorter prerectum (1.5 vs 3 anal body width). Although the total length of spear was same in both the populations, the ratio between odontostyle and odontophore length is distinctly different and hence the Indiana population probably represents a different species.

From T. sayi Goseco et al. 1975 , the new species distinctly differs in the shape and size of lip region (vs lip region narrow, 9 µm wide with low lips and with distinct sclerotization of the oral opening); comparatively anterior vulva (V= 27.8–31 vs 31–33); longer tail (tail 28–32 vs. 21–22 µm long, c = 36.7–42 vs 44–45) and longer prerectum (90–106 vs 40–48 µm).

Figures

FIGURE 1. Tylencholaimellus sinensis n. sp. A: Entire female. B: Anterior end. C: Anterior end showing amphid. D: Pharyngeal region. E: Expanded part of pharynx. F: Female genital system. G: Vulval region. H: Female posterior region.

FIGURE 2. Tylencholaimellus sinensis n. sp. Anterior region. B: Anterior end showing amphid. C: Expanded part of pharynx. D: Vulval region. E: Female posterior region. F: Female posterior end (scale bar A – D, F, G: 20 µm; E: 50 µm).