Serina prostoma (Ancey, 1884)

Wu, Min & Xu, Qin, 2013, Serina Gredler (Gastropoda, Stylommatophora: Enidae), the continuous-peristomed mountain snails endemic to the eastern slope of the Qinghai-Xizang Plateau, Zootaxa 3620 (1), pp. 43-66 : 51-53

4. Serina prostoma (Ancey, 1884)

Figs. 1 , 2 K– O, 4, 9, 10; Tables 1–3 , 6

Bulimus prostomus Ancey, 1884: 395 .

Bulimus prostomus var. leucochila Ancey, 1884: 396 (Type locality: Yerkalo).

Buliminus (Serina) prostoma— Kobelt, 1902: 933, pl. 131, figs. 8–10.

Buliminus (Holcauchen) tubios Annandale, 1924: 394 , pl.16, figs. 6, 6a (Type locality: Gorges in the Yangtsa district of the Upper Mekong).

Ena (Serina) prostomus— Yen, 1938: 442.

Serina prostoma –Yen, 1939: 87, pl. 8, fig. 24. Yen, 1942: 255. Chen, Zhou, Luo & Zhang, 2003: 442.

Serina deqenensis Chen, Zhou & Luo, 2003: 444 , figs. 1–4 (Type locality: Meilishi Town).

Type locality. Tsé-kou (Xizang Autonomous Region).

Material examined. HBUMM-04287: 16 fma (all measured and 1 dissected) and 1 juv.; Deqing County, Yunnan, 2003–VIII–28, colln. KS. HBUMM-04296: 171 fma (20 measured and 2 dissected) and 15 juv.; eastern bank of Lancangjiang River, western to Yanjing Town, Mangkang County, Xizang Autonomous Region, 2583 m a.s.l., 29º02ʹ0 0.0ʹ N, 098º36ʹ22.9ʹ E), red Sandstone + sandy loam, bushes and grass, 2002–VII–11, colln. AW & MW ( Fig. 10 in this work). NHM-1920.8.10.38 Reg.: 1 full matured shell. Mekong, Thibet. NHM- 1912.6.27.69–71 Reg.: 3 fms, all measured. Mekong (imprecise locality), Upper Yangtze, Tibet. NHM: 1 fms. Mekong, Ancey, Thibet. Trechmann Acc. No. 2176. NHM-1923.5.24.17–36: paratypes of Buliminus (Holcauchen) tubios , numerous fms; 5 measured. Gorge of Mekong above Yangtsa; alt. 2134 m to 2286 m, arid. SMF-42050: Paratype, measured. Dshy-kow (unrecognised locality belonged to Xizang Autonomous Region today), Szechwan, China (Ancey in Slg. Möllendorff—see Yen, 1939: 87).

Distribution. Xizang Autonomous Region (type locality, Mangkang, Mekong), Yunnan (Deqing).

Diagnosis. Shell with the most swollen part occurred at penultimate whorl. Whorls with a narrow, defined zone below the suture. Last whorl descending in front; straight or concaved at periphery. Aperture not duplicate; separated from body whorl; not armed.

Shell. Turrited, or fusiform; dextral; apically more or less abruptly pointed; opaque (except apical 4 whorls slightly semitransparent); more or less glossy; with the most swollen part occurred at penultimate whorl; height 11.2–13.3–14.9, diameter major 3.4–4.5–5.5, ratio of height /diameter major 2.53–2.96–3.50. Growth lines fine and clear. Whorls 7 7/8–8 1/2–9 1/4, convex (except ultimate two whorls); with a narrow, defined zone below the suture. Embryonic shell 1 5/8–1 7/8+–2 1/8 whorls. Postnuclear whorls smooth. Last whorl slightly descending in front; slightly concaved or straight at periphery; abaperturally with a rugate region with crowded and/or thickened growthlinelike folds. Aperture almost in a plane and straight; ovate; rather oblique; separated from body whorl; not armed; height 3.2–3.9–4.5, width 2.8–3.5–3.9, ratio of shell height /apertural height 2.99–3.41–4.02. Aperture not duplicate. Peristome and parietal callus almost completely fusing except for a channel at upper insertion of peristome. Reflexed part of peristome straight and not curved backward. Abapertural peripheral depression on body whorl spirally extending for ca. 1 whorl. Columellar margin reflexed. Columella oblique. Umbilicus widely open. Apical four whorls reddish brown; subsequent whorls white with a few streaks in light brown; bandless. Aperture white. Apical whorls differently tinted. Measured specimens: NHM- 1912.6.27.69-71, NHM- 1923.5.24.17-36, HBUMM-04287, HBUMM-04296, SMF-42050: 45 shells.

Genitalia. Vas deferens proximally swollen; entering epiphallus laterally with distinct demarcation. Epiphallus short; straight; cylindrical and of uniform thickness. Epiphallic caecum blunt apically; located in middle of epiphallus. Flagellum short; tubular; proximally normal; with tip blunt. Penis clavate; evenly thick; laterally entering epiphallus; thin-walled. Longitudinal pilasters more than two; not fused at epiphallic pore; forming 2 Vshaped structures. V-shaped pilaster with proximal free end approaching at penial retractor insertion; without papilla formed by fused distal pilasters. Penial process absent. Penial appendix short; branched off from penis at some distance from atrium; with A-1 fused with A-2, A-3 distinct, and A-4 fused with A-5. A-1 long; without verge toward penial chamber. A-2 internally with longitudinal pilasters; near A-3 internally with a ring of papilla. A-3 opening into A-2 by a long needle-like papilla. A-5 short; straight. Penial retractor biramous; with arms arising from diaphragm separately, or with arms arising from diaphragm closed to each other; with penial branch attaching to proxmal penis; with appendical branch attaching to A-1+A-2. Atrium short; with weak atrial retractor. Free oviduct moderately long; subequal to vagina in length. Vagina moderately long; not swollen; straight; unpigmented. Bursa copulatrix duct moderately long; proximally straight. Bursa copulatrix in normal size; well defined; with stalk; without apical ligament; with long neck. Diverticle longer than or subequal to reservoir in length; unexpanded. Bursa copulatrix and diverticle distinguishable; forked more distally from their base. Measurement of genitalia: See Table 2 (HBUMM-04287–specimen 1 and HBUMM-04296–specimen 21 are measured).

Taxonomic remarks. Buliminus (Holcauchen) tubios is a obvious synonym of Serina prostoma . Bulimus prostomus leucochila , was established by the diagnosis “ Testa minore, exiliore, pallid caerulea; apice corneo; aperture intus subcornea; peristomate albido;-alt. 12 millim ” (Ancey 1884). Such shell size and main coloration feature is also observed in the specimens HBUMM-04287 of which 16 shells have the white aperture and with shell height range 11.2–12.7–14.0 mm. Therefore it is insufficient to be distinguished from S. prostoma . Since no reliable diagnosis of Serina deqenensis was given by Chen, et al. (2003), this taxon is here regarded as a synonym of S. prostoma .

Ecological remarks. This species dwells in the very arid environment near the bank of Langcangjiang River (Yanjing) ( Fig. 10 A). In the same season, as observed by the first author at the locality situated nearby, another enid snail Holcauchen sp. inhabits a relatively wet environment characterized by the rich coverage of periodically hydrophilous moss, algae and lichen. This slightly indicates there might be different habitat preference by these two genera/species.

Figures

FIGURE 1. Distribution of Serina species. S. soluta inflata Yen, 1939 is also indicated although synonymized in this paper. S. soluta stenochila (Möllendorff, 1901) is not mapped due to imprecise locality information.

FIGURE 10. Habitats of Serina prostoma (Ancey, 1884). Eastern bank of Lancangjiang River, western to Yanjing Town, Mangkang, Xizang Autonomous Region, 2583 m a. s. l., (29 º 02 ’ 00.0 ’’ N, 098 º 36 ’ 22.9 ’’ E), red sandstone and sandy loam, bushes and grass; 2002 – VII – 11, HBUMM- 04296. A. Landscape of Yanjing. B. Habitat. Photos by MW.

FIGURE 2. A. Serina belae (Hilber, 1883), SMF- 42069, paratype, Bangda. B, C. Serina cathaica Gredler, 1898: B. SMF- 42046, between Yue-lin-kuan and Wen-hsien. C. NHM- 1902.5.13.19. D. Clausiliopsis szechenyi (Böttger, 1883), syntype of B. sobrina Preston, NHM- 1912.3.26.9, Gansu. E – J. Serina egressa Sturany, 1900. E. NHM- 1902.5.13.21, Gansu. F. HBUMM- 05426 – specimen 21, Wenxian. G. HBUMM- 05426 – specimen 23, Wenxian. H. SMF- 42038 (from type locality, between Yuelin-kuan and Wen-hsien). I. HBUMM- 5673 – specimen 22, Lianghekou. J. HBUMM- 5673 – specimen 23, Lianghekou. K – O. Serina prostoma (Ancey, 1884). K. NHM- 1912.6.27.69 – 71. L. A paratype of Buliminus (Holcauchen) tubios Annandale, 1924, NHM- 1923.5.24.17 – 36, Gorge of Mekong above Yangtze. M. SMF- 42050, paratype, Dshy-kow. N. HBUMM- 04296 – specimen 25, Yanjing. O. HBUMM- 04296 – specimen 24, Yanjing.