Burmochlamys versicolor 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 versicolor Pholyotha & Panha sp. nov.

Figs 1 , 2E , 4B, C , 5F , 10C , 12A, B , 13D-F , 15B

Material examined.

Type material. Holotype: CUMZ 14218 (Fig. 12A ; width 6.0 mm, height 4.2 mm). Paratypes: Same locality as holotype: CUMZ 14219 (Fig. 12B ; width 5.9 mm, height 4.5 mm), NHMUK (two shells).

Other material.

Limestone outcrop at Golden valley, Hpa-An, Kayin State, Myanmar (16°51'02.3"N, 97°36'26.1"E): CUMZ 14220 .

Type locality.

Limestone outcrop at Bayin Nyi Cave, Hpa-An, Kayin State, Myanmar (16°58'10.1"N, 97°29'30.6"E).

Diagnosis.

Shell subglobose, whitish yellow and then gradually turned yellowish brown near aperture opening, and umbilicus somewhat narrow and very deep. Animal dark greyish with five mantle extensions. Genitalia with very short epiphallic caecum attached by thin penial retractor muscle, rather short vagina, and small, slender, rather short gametolytic duct.

Description.

Shell (Figs 12A, B , 13D-F ). Shell subglobose, small (width up to 6.3 mm, height up to 4.9 mm), thin, semi-translucent. Colour whitish yellow and then gradually turned yellowish brown on body whorl near aperture opening. Protoconch and teleoconch surface with similar sculpture. Surface of body whorl with indistinct spiral furrows without radial lines (Fig. 13D-F ). Whorls 5½ -6, increasing regularly; suture shallowly impressed; spire rather elevated; last whorl broad and well-rounded. Aperture obliquely crescent-shaped; peristome simple. Columellar margin simple, slightly reflected near umbilicus. Umbilicus open, moderate, and very deep that show preceding whorl.

Genital organs (Fig. 10C ). Atrium (at) very short. Penis (p) moderate, cylindrical and with penial sheath. Epiphallus (e1+e2) ca. one-third of penis length; e1 cylindrical and its slightly smaller diameter than penis and e2; e2 bulbous and slightly longer than e1. Epiphallic caecum (ec) very short, small, bulbous with thin penial retractor muscle (prm) attached at tip. Vas deferens (vd) thin tube. Dart apparatus rather small, long cylindrical, and located on atrium at vagina and penis junction. Vagina (v) rather short and cylindrical. Gametolytic sac (gs) rather large, elongate bulbous; gametolytic duct (gd) small, slender, and rather short ca. half of penis length. Free oviduct (fo) cylindrical, very long ca. half of penis length, and encircled with thick tissue near vagina.

Radula (Fig. 15B ). Teeth arranged in wide U-shaped rows, each row consisting of ~ 40 teeth. Central tooth monocuspid, large and oblong spatulate plate, and attached at both sides of its base by two smaller triangular-shaped teeth. Laterals and marginals not differentiated and monocuspid; each tooth with large and oblong spatulate plate attached by one smaller triangular-shaped tooth on outer side of its base. Outermost teeth shorter and smaller than inner teeth.

External appearance (Figs 4B , 5F ). Living animal with reticulated skin and pale to dark greyish body. Mantle extensions well developed, divided to three dorsal lobes and two shell lobes; same colour as body. Foot margin and caudal horn well-developed, dark greyish.

Etymology.

The specific epithet is the Latin word versicolor meaning of various colours. It refers to the two distinct shell colours which characterise this species.

Distribution.

Burmochlamys versicolor sp. nov. is confirmed from two localities in the south of Salween River basin (Fig. 1 ). Bayin Nyi Cave is surrounded by paddy fields that are temporarily flooded during the monsoon season (Fig. 2E ), while Golden valley is a small limestone outcrop located close to the Thanlwin River (= Salween River). Occurrence of the new species between the two limestone areas is expected. A living snail was found climbing up a limestone wall and many mating pairs were also discovered at Bayin Nyi Cave (Fig. 4B ), where the carnivorous snail Carinartemis sp. was also found sympatrically (Fig. 4C ).

Remarks.

Burmochlamys versicolor sp. nov. is easy to distinguish from all known species by having (i) a whitish yellow shell with yellowish brown colour on ca. one-fourth of body whorl near the aperture, (ii) shell sculpture as only shallow spiral lines, and (iii) much wider and larger umbilicus that shows the preceding whorl. In comparison, all other congeneric species have (i) a brownish or whitish shell colour, with or without peripheral band, (ii) a shell surface with both impressed spiral lines and undulating radial lines, and (iii) a small umbilicus (see Table 2 ).

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 4. A adult of B. moulmeinica sp. nov. while climbing slowly on the karst wall after raining at Lun Nya Pagoda B mating pairs of B. versicolor sp. nov. on the karst wall at Bayin Nyi Cave C B. versicolor sp. nov. eaten by the carnivorous snail Carinartemis sp. on the karst wall at Bayin Nyi Cave D B. cassidula eaten by the carnivorous snail Haploptychius sp. on the karst wall at Kaw Gon Cave.

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 10. General view of the genital system of Burmochlamys species A B. fasciola sp. nov. paratype CUMZ 14214 B B. moulmeinica sp. nov. paratype CUMZ 14217 C B. versicolor sp. nov. paratype CUMZ 14219. White arrow indicates the end of the penis. Yellow arrow indicates the solid at the tip of dart apparatus. Red-dotted line indicates vas deferens missing.

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 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.