Proleptonchus kazirangus, Ahad, Sumaya & Ahmad, Wasim, 2016

Ahad, Sumaya & Ahmad, Wasim, 2016, Three new and a known species of the genus Proleptonchus Lordello, 1955 (Nematoda: Leptonchidae) with a diagnostic compendium of the genus, Zootaxa 4189 (1), pp. 115-133 : 119-122

Proleptonchus kazirangus n. sp.

(Figs. 2, 3)

Measurements. See Table 1 .

Description. Female: Medium sized nematodes, 1.0– 1.4 mm long; body cylindrical tapering slightly towards both extremities, generally straight or slightly curved ventrally. Cuticle with two distinct layers, 3–4 µm thick at mid body and 3–5 µm on tail. Outer layer thin; inner layer with irregular outline and loose; radial refractive elements abundant. Lateral chords occupying about 28–36% of the midbody diameter. Dorsal, ventral and lateral body pores indistinct.

Lip region cap-like, offset by constriction, 2.2–2.5 times as wide as high or about one-fourth of the body diameter at neck base; lips rounded and amalgamated. Amphids cup-shaped with aperture located at the level of cephalic constriction and occupying about 0.5–0.7 of lip region diameter. Stoma inverted flask-shaped, with sclerotized walls. Odontostyle slender, attenuated, 0.6–0.8 times the lip region diameter long, with very narrow lumen and fine aperture. Odontophore slightly arcuate, 1.25–1.70 times the odontostyle length. Guiding ring simple, refractive, at 0.6–0.7 times lip region diameter from anterior end. Pharynx consists of a slender and weakly muscular anterior part, separated from basal bulb by a constriction. Pharyngeal bulb short, pear-shaped, occupying about 18–21% of the total neck length. Cardia short, rounded to hemispheroid, about one-seventh of the corresponding body diameter long. Nerve ring at 39–50% of neck length from anterior end.

Genital system monodelphic-prodelphic. Ovary reflexed, measuring 128–302 µm long, usually not reaching the oviduct-uterus junction, although in a few specimens, the ovary surpasses the oviduct-uterus junction; oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 140–254 µm, consisting of a slender portion and a well developed par dilatata, filled with sperms. Oviduct-uterus junction marked by well developed sphincter. Uterus tubular, measuring 66–80 µm, its distal end with distinctly sclerotized central lumen containing refringent apophyses (Fig. 2G, 3G, H). Posterior genital branch 1.8–2.6 times the midbody diameter long, comprised of uterus measuring 67–75 µm and distinct sphincter followed by a sac-like structure representing rudimentary oviduct. Vagina cylindrical; pars proximalis vaginae 6–13 µm long, its wall encircled by muscles; pars distalis vaginae short, 2–3 µm long with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 4.9–8.8 and rectum 0.8–1.2 anal body diameter long. Tail short, rounded-conoid, 0.6–0.8 times anal body diameter long with a pair of caudal pores on each side.

Male: General morphology similar to female except the posterior body region being comparatively more ventrally curved. Sperms spindle-shaped. In addition to ad-cloacal pair situated at 10–11 µm from cloacal aperture, there is a series of seven ventromedians supplements, located outside the range of spicules, first pair of ventromedian at 20 µm from ad-claocal pair. Spicules 1.3–1.5 times cloacal body diameter long. Lateral guiding pieces about one-third of the spicules length. Tail short, rounded-conoid, 0.8–0.9 anal body diameter long.

Type habitat and locality. Soil samples collected from the grassland of the Kaziranga National Park, Assam, India.

Type specimens. Holotype female on slide Proleptonchus kazirangus n. sp. / 1; paratype females on slides Proleptonchus kazirangus n. sp. / 2–10; and males on slides Proleptonchus kazirangus n. sp. / 11, 12; deposited with the nematode collection of the Department of Zoology, Aligarh Muslim University, India .

Etymology: The new species is named after its type locality, the Kaziranga National Park.

Diagnosis and relationship. Proleptonchus kazirangus n. sp. is characterized by having 1.08–1.45 mm long body; lip region cap-like, offset by constriction; odontostyle 7–8 µm, odontophore 10–12 µm; pharyngeal bulb short, pear-shaped, occupying about 18–21% of total neck length; female genital system mono-prodelphic; distal part of uterus with distinctly sclerotized central lumen containing refringent apophyses; posterior uterine sac 78– 112 µm, with sac-like structure representing a rudimentary oviduct; transverse vulva, short, rounded-conoid tail and males with 31–33 µm long spicules, lateral guiding pieces and seven, regularly spaced ventromedian supplements.

In the presence of refringent apophyses in the distal portion of uterus, the new species is most closely related to P. sclerouterinus Mushtaq, Naz & Ahmad, 2007 but distinctly differs from it in the shape of lip region which is caplike with rounded lips (vs lip region wider, low, flat with conoid lips); odontophore not thickened (vs odontophore distinctly thickened); stoma inverted flask-shaped, starting above the lip constriction (vs stoma inverted flaskshaped, starting at the level of the lip constriction); amphids cup-shaped, aperture about half of lip region diameter (vs amphids large with aperture about four-fifths of lip region diameter); males present and pars dilatata filled with sperms (vs males absent and sperms not present); terminal caudal pore absent (vs terminal caudal pore present); tail 17–23 µm long, rounded-conoid (vs 13.5–19 µm long, hemispheroid with a wider hyaline region).

P. orientalis Ahmad, Park, Leee & Choi, 2009 also has refringent apophyses in uterus but the new species differs from it in having larger body size (L = 1.08–1.45 vs 0.86–0.97 mm); higher b and c ratio (b = 6.4–7.9 vs 5.0– 6.0; c = 54.5–74.4 vs 45.4–55.3); longer pear-shaped basal bulb (33–41 vs 31–33 µm cylindrical bulb); presence of stronger refringent apophyses (vs refringent apophyses weak); posterior vulva position (V = 54.8–60.3 vs 53.2– 54.7); prerectal chamber absent (vs prerectal chamber present); lower c’ ratio (c’ = 0.6–0.8 vs 0.89–1.0) and more ventromedian supplements (7 vs 4–5).

The new species also comes close to P. prerectus n. sp. in the presence of pars dilatata uteri with distinctly sclerotized central lumen containing refringent apophyses, but differs in having pear-shaped basal bulb (vs cylindrical basal bulb); posterior uterine sac long, with sac-like structure representing a rudimentary oviduct (vs posterior uterine sac short, 27–36 µm, without sac-like structure representing rudimentary oviduct); prerectal chamber absent (vs present); terminal caudal pore not present (vs terminal caudal pore present); tail roundedconoid (vs rounded-hemispheriod) and smaller spicules (31–33 vs 37 µm).