Burmochlamys albida 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 albida Pholyotha & Panha sp. nov.

Figs 1 , 2C , 5D , 7A, B , 8G-I , 9C , 11C

Material examined.

Type material. Holotype: CUMZ 14211 (Fig. 7A ; width 4.5 mm, height 3.7 mm). Paratypes: Same locality as holotype: CUMZ 14212 (Fig. 7B ; width 4.4 mm, height 3.2 mm), NHMUK (two shells).

Type locality.

Limestone outcrop at Waiponla Monastery, Hpa-An, Kayin State, Myanmar (16°56'07.4"N, 97°42'56.8"E).

Diagnosis.

Shell globose and milky-white with a yellow tinge, rarely with a faintly yellowish brown peripheral band. Animal pale fleshy grey with brown or yellow tinge and five mantle extensions. Genitalia with rather short epiphallic caecum attached by a very large and thick penial retractor muscle and rather short vagina.

Description.

Shell (Figs 7A, B , 8G-I ). Shell globose, small (width up to 4.5 mm, height up to 3.7 mm), thin, semi-translucent. Colour milky-white with a yellow tinge and without or rarely with faintly yellowish brown band above periphery. Protoconch and teleoconch surface with similar sculpture. Surface of body whorl with little distinct spiral furrows at regular intervals, crossed by very faintly undulating radial lines (Fig. 8G-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. 9C ). Atrium (at) rather short. Penis (p) moderate, cylindrical, and with penial sheath covering more than half of its length. Epiphallus (e1+e2) ca. three-sevenths of penis length; e1 cylindrical and small diameter smaller than penis and e2; e2 bulbous and ca. half of e1 length. Epiphallic caecum (ec) rather short, cylindrical, and with very large and thick penial retractor muscle (prm) attached at tip. Vas deferens (vd) thin tube. Dart apparatus large, long cylindrical, and located on atrium close to genital orifice. Vagina (v) rather short, cylindrical-shaped. Gametolytic sac (gs) bulbous; gametolytic duct (gd) cylindrical, moderate, ca. half of penis length. Free oviduct (fo) ca. one-quarter of penis length, cylindrical, and encircled with thick tissue near vagina.

Radula (Fig. 11C ). Generally resembles B. cassidula . Teeth arranged in wide U-shaped rows, each row consisting of ~ 55 teeth. Central tooth monocuspid, large, and ovate spatulate shape; with two smaller triangular-shaped teeth. Laterals and marginals not differentiated, monocuspid, large spatulate shape and then gradually become narrower, elongate, rather more pointed cusp, and with one smaller triangular-shaped tooth. Some outermost teeth with a small, pointed cusp at the inner side.

External appearance (Fig. 5D ). Living animal with reticulated skin, pale freshy-grey with a brown or yellow tinge. Five well-developed mantle extensions, with similar colour to body. Sole divided into three parts longitudinally; caudal foss and caudal horn well developed, similar colour to body.

Etymology.

The specific epithet albida is from the Latin word albidus meaning white. It refers to the whitish shell, which characterises this species.

Distribution.

Burmochlamys albida sp. nov. is endemic to a limestone outcrop at Waiponla Monastery. The surrounding paddy fields usually become flooded during the monsoon season (Figs 1 , 2C ). In addition, this new species is also sympatric with the limestone karst-restricted species, Sophina salweenica Sutcharit & Panha, 2020.

Remarks.

Among the whitish-shelled species (see Table 2 ), B. albida sp. nov. has a very indistinctly narrow yellowish brown peripheral band, whereas B. cassidula has a wide yellowish brown peripheral band, B. fasciola sp. nov. has a narrow yellowish brown peripheral band, and B. versicolor sp. nov. has yellowish brown body whorl near the aperture and wider umbilicus than the other preceding species. Anatomically, B. albida sp. nov. has a large and thick penial retractor muscle, rather slender vagina, and simple at the tip of dart apparatus. In comparison, B. cassidula has a thin penial retractor muscle, large and short vagina, and soft at the tip of dart apparatus, while B. fasciola sp. nov. has a thin penial retractor muscle, very short vagina, and solid at the tip of dart apparatus. In addition, B. versicolor sp. nov. has a thin penial retractor muscle, rather slender vagina, and relatively smaller dart apparatus with soft at the tip.

Burmochlamys albida sp. nov. differs from the remaining Burmochlamys species by having a milky-white shell. While most other species have a pale to dark brownish shell without a peripheral band (see Table 2 ). Regardless of the shell colour and genitalia, this new species differs from B. cauisa and B. perpaula by spire, body whorl, and aperture. In comparison, B. cauisa has slightly elevated spire, well-rounded last whorl, and rather broad crescent-shaped aperture, while B. perpaula has slightly elevated spire, rather more convex body whorl, and narrower crescent-shaped aperture.

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 2. Habitat of some species of Burmochlamys gen. nov. in the karst basin of Hpa-An, Kayin State, Myanmar. A type locality of B. fasciola sp. nov. at Bardai Mountain and microhabitat structure of the karst wall B newly discovered locality of B. poongee at Kaw Ka Thaung Cave C type locality of B. albida sp. nov. at Waiponla Monastery D type locality of B. moulmeinica sp. nov. at Lun Nya Pagoda E type locality of B. versicolor sp. nov. at Bayin Nyi Cave. Photos by Ruttapon Srisonchai.

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 7. Shells of Burmochlamys species A, B B. albida sp. nov. A holotype CUMZ 14211, and D paratype CUMZ 14212 C, D B. fasciola sp. nov. C holotype CUMZ 14213 D paratype CUMZ 14214 E, F B. moulmeinica sp. nov. E holotype CUMZ 14216 F paratype CUMZ 14217.

Figure 8. Representative SEM images of the shell of Burmochlamys species A-C B. cassidula specimen CUMZ 14209 A protoconch B body whorl C zoom-in view of body whorl D-F B. poongee specimen CUMZ 14210 D protoconch E body whorl F zoom-in view of body whorl G-I B. albida sp. nov. paratype CUMZ 14212 G protoconch H body whorl I zoom-in view of body whorl J-L B. fasciola sp. nov. paratype CUMZ 14214 J protoconch K body whorl L zoom-in view of body whorl.

Figure 9. General view of the genital system of Burmochlamys species A B. cassidula specimen CUMZ 14209 B B. poongee specimen CUMZ 14210 C B. albida sp. nov. paratype CUMZ 14212. White arrow indicates the end of the penis. Red-dotted line indicates vas deferens missing.

Figure 11. Representative SEM images of the radula of Burmochlamys species A B. cassidula specimen CUMZ 14209 B B. poongee specimen CUMZ 14210 C B. albida sp. nov. paratype CUMZ 14212 D B. fasciola sp. nov. paratype CUMZ 14214. Central tooth indicated by ' C'; yellow colour indicates central tooth row.