Tylencholaimellus cinctus Orr & Dickerson, 1965

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 : 58-59

Tylencholaimellus cinctus Orr & Dickerson, 1965

( Figs. 7 , 8 )

Measurements: Table 4.

Description. Female: Moderately slender nematodes of small size, slightly curved upon fixation, tapering gradually towards the anterior end. Cuticle with two distinct layers, 2 μm thick at mid body and 3 μm on tail. Outer cuticle with fine transverse striations, inner layer with distinctly striated with abundant radial refractive elements. Lateral chords occupying about 22% of the midbody diameter. Lateral body pores distinct, 8 in pharyngeal region, 5 between pharynx to vulva, 23 between vulva to tail; dorsal and ventral body pores indistinct.

Lip region cape-like, offset from body by a less marked constriction, about twice as wide as high or one-third as wide as body diameter at neck base. Lips rounded and amalgamated; labial and cephalic papillae indistinct. Amphid cup-shaped with aperture located at the level of cephalic constriction and occupying about two-thirds of lip region diameter. Stoma truncate cone, weakly sclerotized. Odontostyle 1.5 times the lip region width long and provided with dorsal accessory piece covering the entire dorsal arm; its aperture one-seventh of odontostyle length. Odontophore with basal knobs; 0.5 times the odontostyle length. Guiding ring simple, refractive, at about one lip region width from anterior end. Pharynx consists of a slender and weakly muscular anterior part and a short pearshaped constricted basal bulb, which occupies about 14.6% of the total neck length. Pharyngeal gland often visible. Cardia hemispherical, about one-fourth of the corresponding body width long. Nerve ring located at 61% of the neck length. Genital system monodelphic-opithodelphic. Ovary reflexed, measuring 137 µm long, not reaching the oviduct-uterus junction, oocytes arranged in single row except near the tip. Oviduct joining the ovary subterminally and consisting of a slender distal part and a well developed pars dilatata. Oviduct-uterus junction marked by poorly developed sphincter. Uterus short and tubular. Sperms present throughout the genital tract. Anterior genital branch reduced to a simple sac, 1.15 mid body diameters long. Vagina cylindrical, pars proximalis vaginae 10 µm long, its wall encircled by muscles. Pars distalis vaginae short, 1.5 µm long with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 3 anal body diameter long. Rectum 0.95 anal body width long. Tail short, 0.9 anal body width long, rounded-conoid.

Male: General morphology similar to female but the posterior body region is more ventrally curved. Diorchic with opposed testes. Sperms spindle-shaped. Apart from the adcloacal pair only one ventromedian supplement is present, located outside the spicule range and separated from adcloacal pair by slightly more than two times the distance of the adcloacal pair to the anus. Spicules 1.6–1.8 times anal body width long. Lateral guiding pieces onefifth of the spicule length. Tail slightly shorter than that of the female and with a more concave ventral side.

Habitat and locality: Mixed coniferous broad-leaved forest, Changbai Mountain, Northeast China (42°24ʹN, 128°06ʹE): 760m a.s.l.; annual mean temperature 2.6ºC, 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.

Remarks: Orr & Dickerson (1965) described this species from Kansas, USA. Goseco et al. (1975) provided a redescription of this species based on the study of type material. Peralta & Peña-Santiago (1996) recorded this species from several localities in Spain and provided a redescription. The present specimens from China conform well to the earlier descriptions. Peralta & Peña-Santiago described the pharyngeal bulb as expanding abruptly whereas in our specimens as well as the earlier description of Orr & Dickerson (1965) and Goseco et al. (1975) it has been indicated as offset by constriction. In our single female specimen, the vulva is slightly anterior compared to earlier descriptions (V= 28.5 vs 31–41). These minor differences could be considered as geographical variations.

Figures

FIGURE 7. Tylencholaimellus cinctus Orr & Dickerson, 1965. A: Entire female. B: Entire male. C: Anterior end. D: Anterior end showing amphid. E: Pharyngeal region. F: Expanded part of pharynx. G: Female genital system. H: Female posterior region. I: Male posterior region.

FIGURE 8. Tylencholaimellus cinctus Orr & Dickerson, 1965. A: Anterior region. B: Anterior end. C: Anterior end showing amphid. D – E: Expanded part of pharynx. F: Vulval region. G: Female genital system. H – I: Female posterior region. J – K: Male posterior region (scale bar: 20 µm).