Large sized nematode, 1.3–1.4 mm long body. Cuticle dorylaimoid, outer cuticle thin with very fine transverse striation, inner layer thicker than the outer, distinctly striated. Lateral chords narrow. Lip region cap-like, offset by constriction, 8.0 μm wide or one-fourth of the body diameter at pharyngeal base, labial papillae raised, lips slightly separated. Cheilostom a truncate cone. Amphidial fovea cup-shaped, aperture slit-like, occupying about one-half as wide as lip region diameter. Odontostyle short, robust, spindle-shaped, 8.0–9.0 μm long, 1.0–1.1 times lip region diameter. Odontophore simple, rod-like, 10.5–11.5 μm long with thickening or minute knobs-like structure at the base. Guiding ring simple. Pharynx consists of a slender and weakly muscular anterior part expanding abruptly into a cylindrical basal bulb, separated by constriction, occupying about two-fifths to one-half (42–50%) of the total pharyngeal length. Female genital system monodelphic-opisthodelphic with anterior uterine sac. Vulva pore-like. Tail long, elongated with a slight dorsally curved tip. Male not known.

Tahamina indica gen. nov., sp. nov.

In the presence of a short odontostyle with a distinct lumen, odontophore with minute knobs-like structure and longer pharyngeal expansion, the new genus well fits under the subfamily Tylencholaiminae Filipjev, 1934 of the family Tylencholaimidae (Tylencholaimoidea).

Tahamina indica gen. nov. can be separated from Tylencholaimus de Man, 1876 in having a dorylaimoid cuticle, radial elements absent (vs. tylencholaimoid cuticle, radial elements present); vulva pore-like (vs. vulva transverse); differently shaped tail (tail long, elongated vs. tail short, rounded to conoid). The new genus differs from the Heynsnema Peňa-Santiago, Guerrero & Ciobanu, 2008 in having female genital system mono-opisthodelphic (vs. amphidelphic); vulva pore-like (vs. vulva transverse) and differently shaped tail (tail long, elongated vs. tail short, rounded to conoid).

Based on the shape and size of the odontostyle and odontophore, the expanded part of the pharynx and tail, the new genus comes close to Discomyctus Thorne, 1939 and Wasimellus Bloemers & Wanless, 1996 but differs from the former in having the inner cuticle dorylaimoid (vs. tylencholaimoid); labial disc absent and labial papillae raised (vs. labial disc present and labial papillae not raised); odontophore with thickened base or minute basal knobs-like structure (vs. odontophore with distinct large basal knobs); female genital system mono-opisthodelphic (vs. mono-prodelphic); vulva pore-like (vs. transverse) and tail elongated (vs. tail elongated to tail long filiform). It differs from Wasimellus in having a guiding ring single (vs. guiding ring double), the expanded part of the pharynx comparatively long (42–49 vs. 35–42% of total neck length), pharyngeal expansion abrupt (vs. gradual expansion); vulva pore-like without sclerotized pieces (vs. vulva transverse, with sclerotized pieces); female genital system mono-opisthodelphic (vs. amphidelphic), tail elongated (vs. tail filiform).

In the presence of a dorylaimoid cuticle, narrow lateral chord, and weakly muscular expanded part of the pharynx, the new genus resembles Dorylaimoides Thorne & Swanger, 1936, which belongs to the family Mydonomidae but differs in having a differently shaped odontostyle (odontostyle spindle-shaped, symmetrical vs. odontostyle simple, asymmetrical) and odontophore (odontophore simple rod-like with basal thickening or very minute knobs-like structure vs. odontophore angular or arcuate without basal thickening or knobs); longer pharyngeal expansion (about two-fifths to one-half vs. one-fifth to one-third of total neck length); and vulva pore-like (vs. vulva transverse).

Based on the shape of the stylet, lip region and tail pattern, the new genus is comparable to two non-tylencholaimid members Mitoaxonchium Yeates, 1973 and Hulqus Siddiqi, 1981, both belonging to the subfamily Hulqinae of the family Qudsianematidae (Dorylaimoidea) but it differs from the former in having a longer body size (L = 1.3–1.4 vs. 0.46–0.61 mm); shorter pharynx (b = 4.9–5.2 vs. 2.4–3.2); the position of dorsal esophageal gland nuclei more anteriorly (12–16 vs. 30% of expanded part of pharynx from its expansion), female genital system mono-opisthodelphic (vs. amphidelphic) and differently shaped vulval opening (pore-like vs. transverse). The new genus differs from Hulqus in having a longer body (L = 1.3–1.4 vs. 0.86–1.10 mm); shorter pharynx (b = 4.9–5.2 vs. 2.4–3.0); the position of dorsal esophageal gland nuclei more anteriorly (12–16 vs. 35–41% of expanded part of pharynx from its expansion), pharyngeal expansion abrupt, separated by constriction (vs. expansion gradual, without constriction) and differently shaped vulval opening (pore-like vs. transverse).

Seven females and two juveniles from Yaraganalu, Shivamoga District, Karnataka State, India; 13°48'04.3"N 75°34'23.4"E; 17 November 2018. Female holotype (slide number AMUZDNC Tahamina indica gen. nov. sp. nov. /1), six female paratype specimens (slide numbers AMUZDNC Tahamina indica gen. nov. sp. nov. /2–5) and two juveniles (J2) (slide number AMUZDNC Tahamina indica gen. nov. sp. nov. /6) are deposited with the nematode collection in the Department of Zoology, Aligarh Muslim University, India.

See Table 1.

Female . Slender nematodes of large sized, 1.3–1.4 mm long body, slightly curved ventrally upon fixation; body cylindrical, tapering gradually towards at the anterior end and posteriorly narrowing to form an elongated tail. Cuticle with two distinct layers, 1.0–1.5 μm thick at anterior region, 2.0–2.5 μm at midbody, and 3.0–4.0 μm on the tail. The outer cuticle is thin, with fine transverse striation, the inner layer is thicker than outer, distinctly striated. Lateral chord 5.0–7.0 μm at midbody, occupying about one-sixth to one-four (18–24%) of corresponding body diameter. Lateral, dorsal and ventral body pores are indistinct. Lip region cap-like, offset from the body by constriction, 2.0–2.2 times as wide as high or about one-fourth of the body diameter at the pharyngeal base. Under SEM (Fig. 3A), lips are rounded, and slightly separated, inner portion somewhat amalgamated forming a hexagonal disk-like structure, offset from the rest of the lip region; labial and cephalic papillae button-like, slightly protruding over the lip surface. Amphidial fovea cup-shaped, aperture slit-like, 4.0–5.0 μm wide or occupying about one-half to three-fifths of lip region diameter. Stoma a truncate cone. Odontostyle short, robust, spindle-shaped with a wide lumen, 1.0–1.1 times the lip region diameter long or 0.54–0.63% of total body length, it’s aperture about one-fourth of the odontostyle length. Odontophore simple, rod-like with slightly thickened base or minute knobs-like structure (Fig. 1B, C), 1.2–1.4 times the odontostyle length. Guiding ring simple refractive, at 0.7–0.8 times lip region diameter from anterior end. Pharynx consisting of a slender and weakly muscular anterior part, expanding abruptly into a cylindroid bulb, separated by slight constriction, occupying about 42–49% of total pharyngeal length. Dorsal pharyngeal gland nuclei located at 12–16% of expanded part of pharynx from its expansion. Pharyngeal gland nuclei and their orifices are located as follows: DO=58–60, DN=60–62, DO–DN=1.5–2.5, S1N1=74–76, S1N2=79–81, S2N2=88–90, S2O=90–91. Nerve ring at 34–35% of the pharyngeal length from anterior end. Cardia is short, conoid, about one-fifth to one-fourth of the corresponding body diameter long.

Figure 1. 

Tahamina indica gen. nov., sp. nov. female: A entire B, C anterior region (arrow showing knobs-like structure) D anterior region showing amphid E pharyngeal region F expanded part of pharynx (arrow showing dorsal pharyngeal gland nuclei) G pharyngo-intestinal junction. Scale bars: 100 µm (A); 10 µm (B–D, F–G); 20 µm (E).

Figure 2. 

Tahamina indica gen. nov., sp. nov. female: A entire B anterior region C anterior region showing amphid D pharyngeal region E pharyngeal expansion F genital system G Vulval region H posterior end.

Figure 3. 

Tahamina indica gen. nov., sp. nov. female (SEM): A anterior region frontal view B anterior region lateral view C, D posterior end showing anal opening. Scale bars: 1 µm (A); 2 µm (B); 10 µm (C, D).

Figure 4. 

Tahamina indica gen. nov., sp. nov. female: A, B genital system C, D vulval region E arrow showing genital primordia in juvenile F posterior region G posterior end. Scale bars: 20 µm (A, F); 10 µm (B–D, E–G).

Genital system mono-opistho-ovarian, didelphic. Ovary reflexed, measuring 50–78 μm long, not reaching oviduct-uterus junction; oocytes arranged in a single row except the near tip. Oviduct joining the ovary subterminally, measuring 57–82 μm, its consisting of a slender distal portion and a well-developed pars dilatata. Oviduct-uterus junction marked by the well-developed sphincter. Uterus long well differentiated, tripartite, proximal part short well-developed muscular, median part long, convoluted tube and distal part short, somewhat spheroid, measuring 96–109 μm. The anterior genital branch reduced to a simple sac, 34–69 μm or about 1.0–2.2 times midbody diameters long. Vagina cylindrical, extending inwards, 13.5–14.5 μm or about one-half (45–48%) midbody diameter; pars proximalis vaginae 10–12 × 6.0–8.0 μm, its wall encircled by circular muscles; pars distalis vaginae 2.5–3.5 μm with slightly curved walls; pars refringens absent. Vulva pore-like. Sperm cell absent. Prerectum long, 7.3–10.0 and rectum 1.1–1.4 anal body diameter long. Tail elongated, tapering gradually and its distal part slightly bent dorsally with a rounded terminus, 4.3–5.8 times anal body diameter long with a pair of caudal pores on each side.

Male. Not found.

Juvenile (J2). General morphology is similar to that of adults, but with the following differences. Medium sized nematodes, 1.0 mm long. Lip region cap-like, 2.1–2.3 times as broad as high or about one-third (29–34%) of body diameter at the pharyngeal base. Functional odontostyle 0.90 times the lip region diameter long, 0.80 times the replacement odontostyle length. Replacement odontostyle 1.0 times the lip region diameter long, with its base located at 45–48 μm from the anterior end. Position of odontostyle forming cell nucleus at 48–49 μm from the anterior end and at 26–28 μm from the odontophore base. Odontophore simple, rod-like, 1.5–1.6 times of functional odontostyle length. Guiding ring simple and refractive, at 0.7 times the lip region diameter from the anterior end. Pharyngeal expansion occupying 45–46% of the total pharyngeal length. Nerve ring at 33–34% of the total pharyngeal length from anterior end. Genital primordia 18–19 µm or 0.8–0.9 times the corresponding body diameter long, located at 442–445 μm or 41–43% of body length from the anterior end.

Soil samples collected around the roots of grasses (Cynodon dactylon L.) from Yaraganalu, Shivamoga District, Karnataka State, India.

The new genus and new species named after first author mother’s Tahamina and its type locality India.