Burmochlamys whitteni Pholyotha & Panha, 2022

Pholyotha, Arthit, Sutcharit, Chirasak, Lin, Aung & Panha, Somsak, 2022, Uncovering local endemism from southeastern Myanmar: description of the new karst-associated terrestrial snail genus Burmochlamys (Eupulmonata, Helicarionidae), ZooKeys 1110, pp. 1-37 : 1

Burmochlamys whitteni Pholyotha & Panha sp. nov.

Figs 1 , 5G , 12C, D , 13G-I , 14 , 15C

Material examined.

Type material. Holotype: CUMZ 14221 (Fig. 12C ; width 5.8 mm, height 5.0 mm). Paratypes: Same locality as holotype: CUMZ 14222 (Fig. 12D ; width 5.6 mm, height 5.0 mm), NHMUK (two shells).

Type locality.

Limestone outcrop at Htaung Wee Cave, Hpa-An, Kayin State, Myanmar (16°50'31.1"N, 97°37'18.4"E).

Diagnosis.

Shell globose and pale to dark brownish. Animal pale grey with five mantle extensions. Genitalia with slender epiphallus, rather short epiphallic caecum attached by a thick and short penial retractor muscle, and gametolytic part and free oviduct entirely encircled by connective tissue.

Description.

Shell (Figs 12C, D , 13G-I ). Shell globose, small (width up to 5.8 mm, height up to 5.0 mm), rather thin, and semi-translucent. Colour pale to dark brownish. Protoconch and teleoconch surface with similar sculpture. Surface of body whorl with distinct spiral furrows at regular intervals, cut by undulating radial lines (Fig. 13G-I ). Whorls 6- 6½, increasing regularly; suture shallowly impressed; spire much elevated; last whorl well-rounded. Aperture obliquely crescent-shaped; peristome simple. Columellar margin simple, slightly reflected near umbilicus. Umbilicus open, narrow, and deep.

Genital organs (Fig. 14 ). Atrium (at) short. Penis (p) rather long, cylindrical and with penial sheath. Epiphallus (e1+e2) ca. five-eighths of penis length; e1 cylindrical and smaller diameter than penis and e2; e2 bulbous and ca. two-third of e1 length. Epiphallic caecum (ec) rather short, cylindrical, and with thick and short penial retractor muscle (prm) attached at tip. Vas deferens (vd) thin tube. Dart apparatus large, long cylindrical, and located on atrium at vagina and penis junction. Vagina (v) very short and cylindrical. Gametolytic sac (gs) bulbous; gametolytic duct (gd) cylindrical, moderate, ca. three-eighths of penis length; thin connective tissue encircled entire gametolytic organ and free oviduct (Fig. 14A, B ). Free oviduct (fo) as long as gametolytic duct.

Radula (Fig. 15C ). Resembles B. cassidula . Teeth arranged in wide U-shaped rows with each row consisting of ~ 55 teeth; central tooth monocuspid, large and ovate spatulate shape and attached at both sides of its base with two smaller triangular-shaped plates; lateromarginals monocuspid, large and ovate spatulate shape and then gradually smaller, narrower, and rather more pointed cusp; each lateromarginal tooth with one smaller triangular-shaped plate attached at base outwards. Some outermost teeth with a small and pointed cusp at inner side.

External appearance (Fig. 5G ). Living animal with reticulated skin, pale grey body, slightly paler on foot sole and darker colour on caudal horn. Mantle extensions with two shell lobes and three dorsal lobes, similar colour to body.

Etymology.

The specific epithet whitteni is named in honour of the late Dr. Tony Whitten (1957-2017) of Fauna & Flora International, who invited our team to explore the land snails in southern Myanmar during 2015 to 2016.

Distribution.

Burmochlamys whitteni sp. nov. is known only from the type locality (Fig. 1 ). This isolated limestone of Htaung Wee Cave is situated close to the east-bank of the Thanlwin River and is surrounded by paddy fields that are temporarily flooded during the monsoon season.

Remarks.

Among the brownish-shelled species (see Table 2 ), B. whitteni sp. nov. can be distinguished from B. poongee and B. moulmeinica sp. nov. by the presence of the connective tissue encircled entirely at the gametolytic part and free oviduct, whereas in the latter two species this tissue is absent. In addition, B. whitteni sp. nov. has a thick penial retractor muscle, relatively long epiphallus, and rather short at the base of dart apparatus. In contrast, B. poongee has a thin penial retractor muscle, relatively long epiphallus, and very long at the base of dart apparatus, while B. moulmeinica sp. nov. has a thin penial retractor muscle, relatively short epiphallus, and rather short at the base of dart apparatus.

Figures

Figure 1. Map of the Salween River basin (known as Thanlwin River) in the southeastern Myanmar showing the sampling sites. Coloured triangles indicate the localities recorded for each Burmochlamys species. White circles indicate the localities recorded for Sophina species. White squares indicate the sampling localities with no records of both Sophina and Burmochlamys species.

Figure 5. Living snails of Burmochlamys species A B. fasciola sp. nov. paratype CUMZ 14214 showing left and right lateral views B B. cassidula specimen CUMZ 14209 C B. poongee specimen CUMZ 14210 D B. albida sp. nov. paratype CUMZ 14212 E B. moulmeinica sp. nov. paratype CUMZ 14217 F B. versicolor sp. nov. paratype CUMZ 14219 G B. whitteni sp. nov. paratype CUMZ 14222.

Figure 12. Shells of Burmochlamys species A, B B. versicolor sp. nov. A holotype CUMZ 14218, and D paratype CUMZ 14219 C, D B. whitteni sp. nov. C holotype CUMZ 14221, and D paratype CUMZ 14222.

Figure 13. Representative SEM images of the shell of Burmochlamys species A-C B. moulmeinica sp. nov. paratype CUMZ 14217 A protoconch B body whorl C zoom-in view of body whorl. D-F B. versicolor sp. nov. paratype CUMZ 14219 D protoconch E body whorl F zoom-in view of body whorl G-I B. whitteni sp. nov. paratype CUMZ 14222 G protoconch H body whorl I zoom-in view of body whorl.

Figure 14. Genital system of Burmochlamys whitteni sp. nov. paratype CUMZ 14222 A general view of the genital system B a part of gametolytic organ (duct and sac) and free oviduct after the connective tissue is removed. White arrow indicates the end of the penis. Yellow arrow indicates the connective tissue surrounding the gametolytic organ and free oviduct.

Figure 15. Representative SEM images of the radula of Burmochlamys species A B. moulmeinica sp. nov. paratype CUMZ 14217 B B. versicolor sp. nov. paratype CUMZ 14219 C B. whitteni sp. nov. paratype CUMZ 14222. Central tooth indicated by ' C'; yellow colour indicates central tooth row.