Tantunema pakistanense ( Timm, 1964 ) Timm, 1964

Ahad, Sumaya & Ahmad, Wasim, 2016, Taxonomy of the genus Tantunema Siddiqi, 1982 (Dorylaimida: Tylencholaimidae) with description of one new and two known species, Journal of Natural History 50 (27), pp. 1669-1685 : 7-10

Tantunema pakistanense ( Timm, 1964) comb. nov.

( Figures 3 and 4 ; Table 2 )

Description

Female. Small-sized nematodes, slightly curved upon fixation; body cylindrical tapering slightly towards both the extremities. Cuticle with two distinct layers, 1 μm thick at midbody and 2.0 – 2.5 μm on tail. Outer cuticle smooth; inner finely transversely striated. Lateral chords occupying about one-third of midbody diameter. Lateral, dorsal and ventral body pores indistinct. Lip region cap-like, rather low, offset by slight depression, 1.6 – 2.0 times as wide as high or about one-third of the body diameter at neck base. Lips angular, labial papillae slightly raised. A weakly developed post-labial sclerotization present. Amphids small, aperture a short transverse slit. Cheilostome a truncate cone. Odontostyle slender, 1.0 – 1.2 times the lip region diameter long, its aperture about onesixth or one-fifth of the odontostyle length. Odontophore rod-like with slight basal thickening, 1.3 times the odontostyle length. Guiding ring simple, refractive, at 0.6 – 0.8 times lip region diameter from anterior end. Pharynx consists of a slender and weakly muscular anterior part, expanding gradually into a cylindrical basal expansion, occupying about 33 – 35% of total neck length. Pharyngeal gland nuclei and their orifices located as follows: DO = 71 – 73, DN = 75 – 76, DO – DN = 3.6 – 3.7, S1N1 = 80 – 83, S1N2 = 84 – 86, S2N = 92 – 93, S2O = 93 – 94. Cardia short, conoid, about one-third of the corresponding body diameter long. Nerve ring located at 44 – 45% of neck length from anterior end. Genital system mono-opisthodelphic. Ovary reflexed, measuring 37 – 41 µm long, oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally; oviduct separated from the uterus by a narrowing but no apparent sphincter seen; uterus measuring 28 – 35 µm and oviduct measuring 22 – 27 µm. Anterior genital branch completely absent. Vagina directed posteriorly; pars proximalis vaginae 5 – 6 µm long, its wall encircled by muscles; pars distalis vaginae short, 1.0 – 1.5 µm long with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 2.1 – 2.5 and rectum 0.5 – 1.0 times anal body diameter long. Tail short, rounded – conoid, 1.1 – 1.2 anal body diameter long. Caudal pores two on each side.

Male. Not found.

Habitat and locality. Soil samples around the roots of the bushy trees from Naqvi Park, Aligarh, Uttar Pradesh, India.

Remarks

Timm (1964) described Tylencholaimus pakistanensis from erstwhile East Pakistan (now Bangladesh). The nature of its lip region, the presence of small amphid with a short transverse slit-like aperture and weak post-labial sclerotization puts this species well under the generic diagnosis of Tantunema rather than Tylencholaimus . Hence, it is transferred here to Tantunema as Tantunema pakistanense ( Timm, 1964) comb. nov. The present population from India conforms well to the type population except in having higher ‘ a ’ ratio (versus ‘ a ’ = 18.0 – 19.6); odontophore without basal knobs (versus with small basal knobs, however fig. 3E of Timm shows only slight basal thickenings of the odontophore rather than distinct basal knobs). The morphology of lip region as per fig. 3E is rather unusual for a tylencholaimid and may be an error in the drawing. The tail of Indian specimens, though similar to the type, is slightly longer (c ’ = 1.1 – 1.2 versus 1.0). These minor differences could be attributed to intraspecific variations.

Tantunema pakistanense is very close to T. intermedius but differs in the shape of the lip region, shorter gradually expanded pharyngeal expansion (expanded part 33 – 35% in T. pakistanense versus expanded part 36 – 42% and pharyngeal expansion being abrupt in T. intermedius ); comparatively anterior vulva position (V = 43 – 44 versus 46 – 54). The tail shape is also distinctly different (short, rounded-conoid versus short hemispheroid).

Figures

Figure 3. Tantunema pakistanense (Timm, 1964) comb. nov. A. Entire female; B. Anterior region; C. Anterior end showing amphid; D. Pharyngeal region; E. Pharyngeal bulb; F. Female genital system; G. Female posterior region.

Figure 4. Tantunema pakistanense (Timm, 1964) comb. nov. A. & B. Anterior region; C. Anterior end showing amphid; D. Pharyngeal bulb; E. Female genital system; F. Female posterior region. A, B, C = 10 μm; D, E, F = 20 μm.