Rishetia nagarjunensis Budha & Naggs

Budha, Prem B., Naggs, Fred & Backeljau, Thierry, 2017, Conchological differentiation and genital anatomy of Nepalese Glessulinae (Gastropoda, Stylommatophora, Subulinidae), with descriptions of six new species, ZooKeys 675, pp. 129-156 : 136

Rishetia nagarjunensis Budha & Naggs sp. n. Figs 2G, 9, 13E

Material examined.

Holotype: CDZMTU067P/1, Nagarjun Forest, Balaju-Jamacho trail, Nagarjun-Shivapuri National Park, Kathmandu, Nepal, 1850 m, 27.745997N, 85.287240E, 24.I.2009, leg. P.B. Budha, R. Devkota, S. Khatiwara and S. Khanal. Paratypes: CDZMTU067/9 shells and CDZMTU068P/1 specimen from the type locality (same data as holotype). Paratypes: CDZMTU069P/1 specimen (dissected), Phulchowki Hill, mixed Rhododendron forest, 2324 m, 27.578317N, 85.396885E, 03.V.2007, leg. P.B. Budha.

Distribution.

Nagarjun-Shivapuri National Park and Phulchowki Hill, Central Nepal.

Etymology.

The name is derived from the type locality Nagarjun Forest.

Shell.

Measurements (n = 4): SH 33.2-38.4 mm, SW 10.6-11.9 mm, HA 10.2-10.8 mm, WA 5.5-6.2 mm, Wh 10-11.0; holotype: SH 38.0 mm, SW 12.0 mm, HA 10.5 mm, WA 6.3 mm, Wh 11; approx. 3.3 × higher than wide, elongately turreted, thick, reddish-brown or dark chestnut colour. Surface striated with obliquely raised riblets on the first 2-3 whorls, later whorls with comparatively thin and dense sculpture. The first whorl smooth, rounded. Sides rather flat, suture shallow. Aperture ovate, 1.8 × longer than wide, peristome thin, inner side of the aperture thickened and whitish, columella slightly truncate at the base.

Radula

(Fig. 13E). Central tooth very small, lacks cusps, lateral teeth shouldered.

Genitalia

(n = 2) (Fig. 9). All specimens have a long vas deferens. Flagellum and epiphallic caecum are reduced to two very short knobs (Fig. 9A). Penis cylindrical, with a nearly constant diameter in its proximal half, distally it rapidly expands into a bulbous section before the diameter contracts to somewhat less than the proximal penis, narrowing slightly distally. The penial retractor muscle far apart from the flagellum. The inner surface contains weakly convoluted folds (Fig. 9B). Epiphallus length about 1/3 of penis length. Vagina nearly as long as the penis. Gametolytic duct cylindrical, ends into a simple gametolytic sac. Hermaphroditic duct is loosely convoluted and connected at the middle of the albumen gland.

Remarks.

The shell of R. nagarjunensis sp. n. is similar in size and shape to that of sympatric R. kathmandica sp. n. However, the shell of R. kathmandica sp. n. is more slender and has more whorls than R. nagarjunensis sp. n. Conversely, R. nagarjunensis sp. n. has a wider body whorl, a comparatively more robust shell, and stronger radial ribs than R. kathmandica sp. n. The genitalia of both species are consistently different due to the reduced knob-like flagellum and epiphalic caecum in R. nagarjunensis sp. n., as well as by the inner surface of the penis, which in R. nagarjunensis sp. n. shows three loosely convoluted folds, whereas in R. kathmandica sp. n. it shows distinct rectangular zigzag folds (Fig. 7A1).