Burmochlamys cassidula (Benson, 1859) Pholyotha & Sutcharit & Lin & 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 cassidula (Benson, 1859) comb. nov.

Figs 1 , 3C , 4D , 5B , 6A, B , 8A-C , 9A , 11A

Helix cassidula Benson, 1859: 186. Type locality: ad Moulmein, nee raro [Mawlamyine, Mon State, Myanmar].

Hyalinia cassidula - Tryon, 1886: 177, pl. 53, fig. 68.

Material examined.

Type material. Moulmein: probable syntype UMZC I.104235.

Other material.

Kaw Gon Cave , Hpa-An, Kayin State, Myanmar (16°49'22.2"N, 97°35'08.9"E): CUMZ 14209 (Fig. 6A, B ) .

Diagnosis.

Shell globose, milky white with yellow tinge, and with wide yellowish brown band. Animal greyish with five mantle extensions. Genitalia with very short epiphallic caecum attached by thin penial retractor muscle, very short and large vagina, and short and large gametolytic duct.

Description.

Shell (Figs 6A, B , 8A-C ). Shell globose, small (width up to 7.8 mm, height up to 6.3 mm), rather thin, semi-translucent. Colour milky-white with yellow tinge with wide yellowish brown band above periphery. Protoconch and teleoconch surface with similar sculpture. Surface of body whorl with distinct spiral furrows at regular intervals, cut by distinctly undulating radial lines (Fig. 8A-C ). Whorls 6- 6½, increasing regularly; suture impressed; spire much elevated; varix usually present; last whorl rounded on periphery, and little convex below. Aperture obliquely crescent-shaped; peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus open, narrow, and deep.

Genital organs (Fig. 9A ). Atrium (at) very short. Penis (p) rather short, cylindrical, and with a penial sheath. Epiphallus (e1+e2) ca. three-quarters of penis length; e1 cylindrical and its diameter smaller than penis and e2; e2 bulbous and ca. half of e1 length. Epiphallic caecum (ec) very short, cylindrical and with thin penial retractor muscle (prm) attached at tip. Vas deferens (vd) thin tube. Dart apparatus large, rather long cylindrical, and located on atrium at vagina and penis junction. Vagina (v) large, very short, and cylindrical. Gametolytic sac (gs) bulbous; gametolytic duct (gd) short, ca. one-quarter of penis length, cylindrical, and very enlarged near vagina. Free oviduct (fo) as long as penis, cylindrical, and encircled with thick tissue near vagina.

Radula (Fig. 11A ). Teeth arranged in wide U-shaped rows with each row consisting of ~ 75 teeth. Central tooth monocuspid, large and ovate spatulate shape, with two smaller triangular-shaped teeth located at base of central tooth. Laterals and marginals not differentiated, monocuspid, large spatulate shape then gradually become narrower, elongated and rather pointed cusp. One smaller triangular-shaped tooth located at base on outer side of each tooth, and then gradually reduced in size outwards. Some outermost teeth with tiny inner cusp.

External appearance (Figs 3C , 5B ). Animal with reticulated skin, pale creamy grey to greyish body. Five well-developed mantle extensions same colour as body; right shell lobe (rsl) larger and longer than left shell lobe (lsl); right dorsal lobe (rdl) larger than both anterior left dorsal lobe (ant-ldl) and posterior left dorsal lobe (post-ldl). Sole divided into three parts longitudinally. Caudal foss and caudal horn present.

Distribution.

Burmochlamys cassidula is known only from Kaw Gon Cave in Myanmar (Fig. 1 ). The isolated limestone outcrop is surrounded by paddy fields and temporary wetlands (flooded in the monsoon season). We searched after rain and found them on the surface of limestone walls. The carnivorous snail Haploptychius sp. was also found sympatrically at this locality (Fig. 4D ).

Remarks.

Burmochlamys cassidula is easy to distinguish from all other recognised congeners by its unique shell colour pattern: milky-white with a yellow tinge and with one wide yellowish brown peripheral band.

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 3. Synoptic illustration of mantle extensions, body terminology and radular morphology of Burmochlamys gen. nov. A right and left shell lobes of B. fasciola sp. nov. B mantle extensions (shell lobes and dorsal lobes) and posterior body of B. poongee C dorsal view of mantle extensions (shell lobes and dorsal lobes) of B. cassidula D, E representative SEM images of radula showing monocuspid central tooth (yellow) and lateromarginal teeth (blue) attached by the smaller triangular-shaped teeth (red). White arrow indicates pneumostome or breathing pore. Yellow arrow indicates a tiny cusp on outermost lateromarginal teeth.

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 6. Shells of Burmochlamys species A, B B. cassidula specimen CUMZ 14209 C B. cauisa specimen NHMUK 1888.12.4.465 - 466 D B. perpaula specimen NHMUK 1903.7.1.533 E, F B. poongee E specimen NHMUK 1888.12.4.23 - 6 F specimen CUMZ 14210.

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.