Tantunema indicum, Ahad & Ahmad, 2016

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 : 10-14

Tantunema indicum sp. nov.

( Figures 5 and 6 ; Table 3 )

Description

Female. Small sized nematodes, slightly curved upon fixation; body cylindrical, tapering gradually 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 layer finely transversely striated. Lateral chords occupying about one-third of the midbody diameter. Lateral, dorsal and ventral body pores indistinct. Lip region cap-like, offset by slight constriction, 2.4 – 3.0 times as wide as high or about one-third of the body diameter at neck base. Lips amalgamated; labial papillae barely raised. Amphids small, aperture a short transverseslit. Cheilostome a truncate cone. A weak post-labial thickening present. Odontostyle slender, 1.0 – 1.1 times the lip region diameter long, its aperture one-quarter or one-fifth of the odontostyle length. Odontophore rod-like with slight swollen base, 1.2 – 1.5 times the odontostyle length. Guiding ring simple, refractive, at 0.6 times lip region diameter from anterior end. Pharynx consists of a slender and weakly muscular anterior part, expanding gradually into a cylindrical basal bulb, occupying about 35 – 41% of total neck length, with thick-walled lumen; lumen of the basal portion of expanded part distinctly widened and thickened. Pharyngeal gland nuclei and their orifices located as follows; DO = 74 – 75; DN = 78 – 79, S1N1 = 84 – 85, S1N2 = 86 – 87, S2N = 92 – 93, S2O = 93 – 94. Cardia short, conoid, about one-third of the corresponding body diameter long. Nerve ring located at 45 – 56% of neck length. Genital system mono-opisthodelphic. Ovary reflexed, measuring 31 – 61 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. 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 – 2 µm long with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 2.0 – 2.5 and rectum 0.7 – 0.8 times anal body diameter long. Tail short, hemispheroid, 0.8 – 1.1 times anal body diameter long. Caudal pores two on each side.

Male. Not found.

Type habitat and locality

Soil samples collected from around the roots of forests trees, Kaziranga National park, Assam, India.

Type specimens

Holotype female on slide Tantunema indicum sp. nov. /1; paratypes females on slides Tantunema indicum sp. nov. /2 – 7; deposited with the nematode collection of the Department of Zoology, Aligarh Muslim University, India.

Etymology

The new species is named so because it is recorded from India.

Diagnosis and relationships

Tantunema indicum sp. nov. is characterized by having small body (length 0.32 – 0.45 mm); lip region cap-like, set off by slight constriction; odontostyle 6 – 7 µm and odontophore 8 – 10 µm long; pharynx with slender anterior part, which expands gradually into cylindrical basal expansion, occupying about 35 – 41% of total neck length, lumen of posterior expanded part distinctly widened and thickened; female genital system mono-opisthodelphic, anterior genital branch absent; tail short, hemispheroid, 0.8 – 1.1 anal body diameter long.

In its body size, the presence of thick-walled lumen of the posterior part of pharyngeal expansion and tail shape, the new species comes close to Tantunema enigmatum Ahmad and Baniyamuddin, 2010 , however, it differs from it in having slightly narrow lip region (versus 6.5 – 7.2 µm); in the absence of circum oral sclerotization (versus circum oral sclerotization well developed); vulva slightly anterior (versus V = 46 – 49%); pharyngeal expansion not constricted (versus pharyngeal expansion constricted); tail slightly longer, rounded – hemispheroid (versus tail 9.6 – 10.5 µm long, hemispheroid – clavate).

It differs from T. bothriocephalum Siddiqi, 1982 in the absence of post-labial sclerotization, comparatively longer odontostyle and odontophore (versus odontostyle 4.5 – 6.5 µm; odontophore 6 – 9 µm); pharyngeal expansion gradual (versus pharyngeal expansion abrupt); basal part of lumen of pharyngeal bulb distinctly widened and thickened (versus not thickened); comparatively anterior vulva position (versus V = 45 – 51%).

The new species differs from T. pakistanense ( Timm, 1964) comb. nov. in having comparatively smaller body size (versus 0.42 – 0.54 mm), in the shape of lip region (lip region 2.4 – 3.0 times as wide as high versus 1.6 – 2.0 times), comparatively slender odontostyle, lumen of expanded part of pharynx distinctly widened and thickened (versus not thickened) and in having shorter hemispheroid tail (versus comparatively longer rounded conoid tail).

Figures

Figure 5. Tantunema indicum sp. nov. A. Entire female; B. Entire male; C. Anterior region; D. Anterior end showing amphid; E. Pharyngeal region; F. Pharyngeal bulb; G. Female genital system; H. Female posterior region; I. Male posterior region.

Figure 6. Tantunema indicum sp. nov. A. B. & C. Anterior region; D & E. Anterior end showing amphid; F. Pharyngeal bulb; G. Pharyngo-intestinal junction; H. Female genital system; I. Vulval region; J. Female posterior region. A, B, C, D, E, G, I = 10 μm; F, H, J = 20 μm.

Tables

Table 3. Measurements of Tantunema indicum sp. nov. (all measurements in µm).

Characters	Holotype female	Paratype females
n	1	6
L	371	364.3 ± 43.1 (323 – 452)
Body diameter at neck base	14	16 ± 0.8 (15 – 17)
Body diameter at mid body	16	17 ± 0.8 (16 – 18)
Body diameter at anus	12	11.8 ± 0.6 (11 – 13)
a	23.1	21.3 ± 1.8 (19.5 – 25.1)
b	3.6	3.4 ± 0.2 (3.2 – 3.8)
c	28.5	30.0 ± 2.3 (27.0 – 33.9)
c ’	1.0	1.0 ± 0.1 (0.8 – 1.1)
V	44.4	44.9 ± 1.2 (42.8 – 46.4)
G2 Lip region diameter	17.2 6	17.6 ± 2.1 (13.9 – 19.3) 6
Lip region height	2.5	2
Amphid aperture	–	–
Odontostyle length	7	6.5 ± 0.5 (6 – 7)
Odontophore length	9	9.1 ± 1.0 (8.0 – 10.5)
Guiding ring from anterior end	4	4
Nerve ring from anterior end	51	51.1 ± 5.9 (45 – 62)
Neck length	102	104 ± 8.1 (92 – 118)
Expanded part of pharynx	36	39.6 ± 4.0 (36 – 48)
Cardia length	4	4.5 ± 0.5 (4 – 5)
Posterior genital branch	63	63.8 ± 2.6 (62 – 69)
Vaginal length	10	8 ± 0.7 (7 – 9)
Vulva from anterior end	165	163.6 ± 20.6 (148 – 208)
Prerectum length	-	25.5 ± 1.5 (24 – 27)
Rectum length	10	8.8 ± 0.6 (8 – 10)
Tail length	13	12.1 ± 1.5 (10 – 15)