Glessula orobia (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 : 130

Glessula orobia (Benson, 1860) Figs 2A, 3

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

Achatina orobia , Benson: Hanley and Theobald 1876, pl. 18, fig. 7.

Stenogyra (Glessula) orobia , Benson: Nevill 1878, p. 170.

Glessula orobia (Benson): Pilsbry 1909, p. 96.

Glessula orobia Benson: Gude 1914, p. 427.

Glessula orobia Bs.: Godwin-Austen 1920, p. 19.

Material examined.

CDZMTU055/10 shells and CDZMTU055P/2 specimens (dissected), Maipokhari, Ilam, Cryptomeria forest, 2100 m, 27.006944N, 87.93000E, 29.X.2010. leg. P.B. Budha. Glessula orobia var. major Godwin-Austen, 1920: Syntypes NHMUK, Reg. no. 1986020, 2 shells, Richila Peak, Sikkim. G. orobia (Benson, 1860): Syntypes NHMUK, Reg. no. 1946.10.16.82-83, 2 shells, Senchal, Darjeeling, India. G. orobia (Benson), RBINS (I.G. 10591), 2 shells, Darjeeling, India.

Type locality.

"Sinchul et Darjiling (alt. ped. 8500 et 7000, NE India)".

Distribution.

Nepal and NE India ( Godwin-Austen 1920, Kuznetsov and Schileyko 1997, Budha et al. 2015).

Shell. Measurements (n = 6): SH 7.0-8.5 mm, SW 4.0-4.5 mm, HA 3.0-3.5, WA 2.0-2.5, Wh 6.0-7.0; approx. 1.8 × higher than wide, thin, ovate-conic, fresh shells light yellowish, older shells straw coloured. Surface glossy, with widely spaced incised radial striations. The first whorl smooth, second whorl with 10-11distinct fine spiral lirae (Fig. 2A1), other whorls with widely spaced radial striations. Sides convex, suture impressed. Aperture nearly ovate, 1.7 × higher than wide, margin simple and thick, columellar margin abruptly truncated, columella slightly curved.

Genitalia

(n = 2) (Fig. 3). Vas deferens with a constant diameter. The flagellum hand-shaped with five “fingers”. The first “finger” is small and pear-shaped, the fifth “finger” is comparatively short and positioned apart like a thumb (Fig. 3A). Penis cylindrical, basal portion narrower than the proximal portion. The diameters of the gametolytic sac and duct of the dissected specimens were not particularly different. The vagina short, nearly 1/4th the length of the penis. The penial retractor muscle close to the flagellum. The albumen gland elongated, long, about half of the total length of the spermoviduct. The hermaphrodite duct is very thick.

Remarks.

Specimens were collected in eastern Nepal, at less than 30-40 km west of the type locality, Darjeeling, and at a similar altitude (7000 ft = 2100 m). Based on shell size Godwin-Austen (1920) distinguished var. major (SH 13.0, SW 5.2) and var. minor (SH 8.0-9.0, SW 3.75-4.0). He figured the genitalia of var. major from Damsang, Sikkim, with its hand-shaped flagellum (Fig. 3B) containing four finger-like processes, of which the first is short, while the second and the third are fused to a single finger. In contrast, the flagellum of Nepalese specimens has five distinct finger-like processes. Based on the shell size, Nepalese specimens belong to the var. minor . For the time being the taxonomic status of both varieties remains unclear.