Oospira bulbus (Benson, 1863)

Man, Nem Sian, Lwin, Ngwe, Sutcharit, Chirasak & Panha, Somsak, 2023, Further notes on the taxonomy of the land snail family Clausiliidae Gray, 1855 (Stylommatophora, Helicina) from Myanmar with description of two new species, ZooKeys 1160, pp. 1-59 : 1

5 Oospira bulbus (Benson, 1863)

Figs 3C , 7D-F , 8D-F , 18E

Clausilia bulbus Benson, 1863: 321. Type locality: "ad ripas fluvii Attaran, non procul ab urbe Moulmein" [banks of Attaran River, Mawlamyine, Mon State, Myanmar]. Pfeiffer 1868: 409. Hanley and Theobald 1870: 12, pl. 24, fig. 5. Sowerby 1875: Clausilia pl. 6, species 51.

Clausilia (Oospira) bulbus - Blanford 1872: 206, pl. 9, fig. 16. Gude 1914: 332.

Clausilia [ Phaedusa (Oospira) ] Phaedusa bulbus - Boettger 1878: 56.

Oospira (Oospira) bulbus - Nordsieck 2002b: 86. Nordsieck 2007: 23. Preece et al. 2022: 162, fig. 72e.

Oospira bulbus - Szekeres et al. 2021a: 168, fig. 5c, d.

Material examined.

Sanbel Cave , Mawlamyine Township, Mon State, Myanmar (16°22'26.0"N, 97°46'22.6"E): CUMZ 13042 (15 shells; 7D-F), CUMZ 13043 (3 specimens in ethanol), JG-C2882 (1 shell) .

Description.

Shell oblong-ovate, translucent, and brownish; spire rounded and almost flatted to apex. Shell surface with fine and distinct striations; suture wide and distinct. Whorls 5- 5½; penultimate whorl rapidly growing and largest; last whorl compressed and narrower. Aperture obliquely pear-shaped, basis rounded and narrowing towards parietal sinus; peristome detached, thickened, slightly expanded, and not reflexed. Superior lamella sharp, oblique, continuous with spiralis, and low at transition to spiralis. Inferior lamella steeply ascending, distant from superior lamella and ending at peristome. Subcolumellaris emerged and invisible in oblique view. Principalis running along lateral-dorsal side and anterior end visible through oblique apertural view. Palatal plicae lateral, five: first plica longest; following four plicae parallel, equal in length and spacing, and slightly reduced towards anterior. Clausilium plate lateral side and narrow.

Genitalia (n = 2). Atrium (at) short and slender; penis (p) muscular and cylindrical. Epiphallus (ep) muscular, cylindrical, ca. same length and half diameter of penis, and broadest at middle part. Penial retractor muscle (pr) attaches proximally to epiphallus. Vas deferens (vd) slender, and shortly bounded at atrium and penis junction (Fig. 8D ). Internal sculpture of penis consists of two parts: region near atrium and ~ 1/2 of penis length with series of irregular transverse folds, chevron-shaped; region near epiphallus becoming smooth, with 5-7 slightly wavy longitudinal folds (Fig. 8E ). Internal sculpture of epiphallus with elevated papillae arranged in oblique rows (Fig. 8F ).

Vagina (v) thick and short, ~ 1/2 of free oviduct (fo) length. Distal part of pedunculus (dpb) large and long; diverticulum (db) long, ~ 2 × in length and slightly smaller in diameter than dpb; proximal part of pedunculus (ppb) slender, ca. equal in length to diverticulum and bursa copulatrix (bb) with distinct ovate shape (Fig. 8D ).

Distribution.

Oospira bulbus has only been reported from Myanmar and is possibly endemic in the limestone hills along the lower course of Attaran River. The specimens examined herein were collected near the type locality.

Remarks.

Oospira ovata can be separated from this species by its a smoother striated shell, attenuated spire and usually seven plicae. In terms of the genital organs, the male internal sculpture of O. ovata has longer V-shaped folds in the region near the atrium and rounded papillae in epiphallus than this species. Although O. bulbus has a similar shell form to Atractophaedus pyknosoma (Gittenberger & Vermeulen, 2001) from Vietnam, A. pyknosoma has a narrower spire, visible subcolumellaris in frontal view, peristome reflected with nearly double lip and first palatal plicae shorter than the following plicae (see Gittenberger and Vermeulen 2001: figs 1-10).

Figures

Figure 3. Living snails A Phaedusa shanica from Pyinyaung Village, Mandalay Region (SH ~ 14 mm) B Oospira philippiana from Kayon Cave, Mon State (SH ~ 22 mm) C Oospira bulbus from Sanbel Cave, Mon State (SH ~ 19 mm) D Oospira ovata from Pathein Mountain, Mon State (SH ~ 16 mm) E Oospira gouldiana from Kaw Ka Thuang Cave, Kayin State (SH ~ 26 mm) F Oospira shanensis from Nanthe Cave, Shan State (SH ~ 25 mm).

Figure 7. Shell and clausilial apparatus of A-C Oospira philippiana A possible syntype SMF 62294 / 1 from Burma B clausilial apparatus, specimen CUMZ 13040 from Pha Boang Cave, Mon State C shell, specimen CUMZ 13037 from Saddan Cave, Mon State and D-F Oospira bulbus, specimen CUMZ 13042 from Sanbel Cave, Mon State D clausilial apparatus E, F shells. White arrow indicates principalis.

Figure 8. Genital anatomy of A-C Oospira philippiana, specimen CUMZ 13039 A whole reproductive system B internal sculpture of penis C internal sculpture of epiphallus and D-F Oospira bulbus, specimen CUMZ 13043 D whole reproductive system E internal sculpture of penis F internal sculpture of epiphallus. Yellow arrows indicate approximate transitional position from penis to epiphallus.

Figure 18. Synoptic view of the clausiliid species recorded from Myanmar A Indonenia admirabilis, holotype NHMUK 20200185 B Oospira andersoniana, specimen CUMZ 13054 C Oospira arakana, lectotype NHMUK 1888.12.4.1037 D Cylindrophaedusa bacillum, specimen NHMUK 1906.2.2.345 E Oospira bulbus, possible syntype NHMUK 1903.7.1.1278 F Phaedusa burmanica, holotype NHMUK 1888.12.4.1058 G Oospira decollata, paratype ZISP H Indonenia excellens, specimen NHMUK 20200189 I Oospira fusiformis, holotype NHMUK 1906.2.2.380 J Oospira gouldiana, lectotype NHMUK 196548 K Oospira gracilior, lectotype NHMUK 1907.12.30.243 L Oospira insignis, lectotype USNM 117120 M Phaedusa kazueae, holotype NHMUK 20200187 N Phaedusa lemani (after Gude, 1914: fig. 107) O Oospira limborgi, holotype NHMUK 1903.7.1.1266, and P Oospira luneainopsis sp. nov., holotype CUMZ 13062.