Rishetia hastula (Benson, 1860)

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 : 133-134

Rishetia hastula (Benson, 1860) Figs 2D, 6

Achatina hastula B.: Benson 1860, p. 461.

Achatina (Electra) hastula Benson: Hanley and Theobald 1876, pl. 18, fig. 4.

Stenogyra (Glessula) hastula , Benson: Nevill 1878, p. 169.

G. lessula hastula (Benson): Pilsbry 1909, p. 93.

Glessula hastula Benson: Gude 1914, p. 414.

Glessula (Rishetia) hastula Benson: Godwin-Austen 1920, p.16.

Material examined.

CDZMTU059/24 shells and CDZMTU059P/5 specimens, Chitwan National Park, Central Nepal, riverine forest, opposite bank of Rapti River at Sauraha, 142-211 m, 27.571774N, 84.489514E, 8.XI.2008. CDZMTU060/6 shells, Kumrose Community Forest, 197 m, 27.556519N, 84.553028E, 21.X.2008. CDZMTU061/1 shell, Baghmara Community Forest, 201 m, 27.57750N, 84.466017E, 20.X.2008, leg. P.B. Budha. R. hastula (Benson, 1860) at NHMUK, Godwin-Austen colln. Reg. No. 3557.03.VII.1.

Type locality.

West Bengal "Pankabari (= Pankhabari), prope Darjeeling", India.

Distribution.

NE India, Nepal ( Budha et al. 2015).

Shell.

Measurements (n = 8): SH 9.5-13.6 mm, SW 3.5-4.1 mm, HA 3.3-3.6 mm, WA 2.0-2.5 mm, Wh 8.0-10.0; approx. 3 × higher than wide, slender, elongate, brownish, with dense radial riblets all over the shell. The first whorl blunt and smooth, fine riblets starting from the second whorl. Suture deep, spire rounded. Aperture ovate elliptical, nearly 2 × higher than wide, peristome thin, columellar margin calloused whitish, obliquely truncate at the base.

Genitalia

(n = 5) (Fig. 6). Flagellum very short tubular sac; there is a very short knob-like epiphallic caecum. Penis cylindrical, basal end comparatively narrow, swollen at the middle and proximal portions cylindrical. Epiphallus basally swollen and the proximal portion tapering. The penial retractor muscle far apart from the flagellum. Gametolytic sac balloon-like, separated from the gametolytic duct by a narrow neck. A mature dissected specimen contained 4-5 gelatinous eggs in the spermoviduct. Another mature specimen contained a spermatophore in the gametolytic sac. This is the first observation of a glessuline spermatophore (Fig. 6B). Vagina short, nearly half the length of the penis. Albumen gland elongate and yellowish; hermaphroditic duct thinner than the albumen gland in the observed specimens.

Remarks.

R. hastula is common in subtropical riverine floodplain forest leaf litter at lower altitudes (up to 300 m) in Chitwan National Park and the adjacent bufferzone community forests.