Burmochlamys 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

Genus Burmochlamys Pholyotha & Panha gen. nov.

Type species.

Burmochlamys fasciola sp. nov., by original designation.

Etymology.

The name combines Burmo in reference to Burma, the historical name of Myanmar, and the Greek word chlamys meaning mantle or cloak in reference to land snail with well-developed mantle extensions. Therefore, the generic name means the Burmese land snail with the well-developed mantle extensions. The gender of the new generic name is feminine.

Diagnosis.

Shell subglobose to globose, small size, little high spire, and sculptured with spiral furrows and undulating radial lines. Snail with five well-developed mantle extensions; caudal horn raised. Genitalia with penial retractor muscle attached at tip of epiphallic caecum; gametolytic organ with rather short to moderate cylindrical duct and bulbous sac; well-developed dart apparatus; flagellum absent. Radula with large monocuspid central tooth and attached by two smaller teeth; laterals and marginals undifferentiated, large monocuspid, and at base of each tooth on outer side attached by a smaller tooth.

Description.

Shell subglobose to globose, small-sized, thin, whitish to brownish, with or without yellowish brown band on the periphery. Shell surface with distinct to faintly spiral furrows, crossed by distinct to faintly undulating radial lines. Whorls 5½ -7, regularly increasing; spire rather elevated; body whorl rounded. Aperture oblique and crescentic with simple lip. Umbilicus open, narrow to moderate, and deep.

Animal reticulated skin with pale to dark greyish or with a brown or yellow tinge. Mantle lobes or mantle extension well developed, divided into two shell lobes and three dorsal lobes, and somewhat thickened near their margins (Fig. 3A-C ). Shell lobes short to moderate, slender, finger-like, and same colour as body. Right shell lobe (rsl) rather longer and larger than left shell lobe (lsl). Dorsal lobes large, broad, normally larger than shell lobes, crescent-shaped, and same colour as body. Right dorsal lobe (rdl) larger than left dorsal lobe. Left dorsal lobe divided into anterior (ant-ldl) and posterior lobes (post-ldl). Sole tripartite and lateral foot margin present. Caudal foss (cf) and caudal horn (ch) present (Fig. 3B ).

Genitalia possess penis with thin penial sheath; penial retractor muscle varying in size and attached at tip of short and straight epiphallic caecum. Flagellum absent. Dart apparatus present. Gametolytic organ with rather short to moderate cylindrical duct and bulbous sac.

Radular teeth arranged in wide U-shaped rows. Central tooth monocuspid, large, narrow to broad spatulate shape, and with two smaller triangular-shaped teeth located at base (Fig. 3D ). Lateral and marginal teeth not differentiated, monocuspid, large spatulate shape, and with only one smaller triangular-shaped tooth located at base on outer side. From inner to outer, lateromarginal teeth gradually narrower, smaller, and rather pointed cusp (Fig. 3D, E ), and tiny inner cusp sometimes present on outermost teeth (yellow arrow in Fig. 3E ).

Constituent species.

Burmochlamys gen. nov. currently contains: B. cassidula (Benson, 1859), comb. nov., B. cauisa (Benson, 1859), comb. nov., B. perpaula (Benson, 1859), comb. nov., B. poongee (Theobald, 1859), comb. nov., B. albida sp. nov., B. fasciola sp. nov., B. moulmeinica sp. nov., B. versicolor sp. nov., and B. whitteni sp. nov.

Distribution.

Burmochlamys gen. nov. shows a remarkable degree of endemism and localisation being restricted to the limestone karsts in the south of Salween River basin, Myanmar (Fig. 1 ). The limestone formations in the region are notable for their fragmented, island-like nature, with hills, caves, and towers forming archipelagos of habitat islands and some areas are temporarily flooded during the monsoon season (Fig. 2 ).

Remarks.

Burmochlamys gen. nov. possesses a similar radular morphology (monocuspid and spatulate shape) to those of Aenigmatoconcha Tumpeesuwan & Tumpeesuwan, 2017, Chalepotaxis Ancey, 1887, and Sophina. However, the new genus is easy to distinguish from these three genera by having a microscopic shell sculpture, slender mantle extensions (left and right shell lobes) and genitalia with a well-developed dart apparatus and without a flagellum. In contrast, those three genera have a smooth shell surface and well-developed left and right shell lobes that can be enlarged and cover most of the shell. The genitalia of Sophina is more similar to that of Burmochlamys gen. nov., while Aenigmatoconcha has a small flagellum and no dart apparatus, and Chalepotaxis has neither flagellum nor dart apparatus ( Páll-Gergely et al. 2016; Sutcharit et al. 2020; Pholyotha et al. 2021b).

In addition, Burmochlamys gen. nov. is clearly discriminated from other helicarionid and ariophantid genera with or without shell lobes by the presence of the monocuspid radular teeth (see Table 1 ). In comparison, the radular morphology of most genera in these families possess bicuspid, tricuspid, or multicuspid teeth ( Stoliczka 1871; Blanford and Godwin-Austen 1908; van Benthem Jutting 1950; Solem 1966; Schileyko 2002, 2003; Páll-Gergely et al. 2016; Sutcharit et al. 2020; Pholyotha et al. 2021b).

As observed in the field, we searched after rain and found the snails climbing on the limestone walls or hiding under the slope of rocks (Fig. 4A ). Regarding the simultaneous hermaphroditism, many copulating pairs were also discovered (Fig. 4B ). Information on its natural predators and parasites remains scarce, but the carnivorous streptaxid snails were found sympatrically in some localities (Fig. 4C, D ).

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 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.