Microhyla mukhlesuri

Variation. Of the examined 10 specimens from Chittagong, the ratio of males to females was 50 %. Among these 5 males, one individual (IABHU 3879, 10 %) had a distinct black vocal sac, but this characteristic is not prominent in other males. All 5 female (50 %) specimens from Chittagong had a whitish ventral throat along with a few fine speckles along the border of the chin and base of the forelimbs. In addition, all specimens had distinct oblique bars on the hindlimbs, except for two specimens (IABHU 3957 – 8, [n = 2, 20 %]) with dim bars, even the bars were sometimes fragmented. All specimens (n = 10, 100 %), except one (IABHU 3958), had a conspicuous X mark on their back with branching at the end forming an inverse ‘ Y’ shape. However, this stripe was present on only the left side of specimen IABHU 3959, and this stripe became two spots in IABHU 3880. Natural history. Microhyla mukhlesuri was found in the grass near the bank of a pond in a calm, cold environment where soil was wet and slightly loose. Although no other Microhyla sp. were found, many Fejervarya sp. were caught in the same locality (Raozan, Chittagong) at the time of observation.

Distribution. The known occurrence of M. mukhlesuri is Raozan, Chittagong District, southeastern corner of Bangladesh (Fig. 1).

Etymology. We dedicate the species name “ mukhlesuri ” to the late Dr. Md. Mukhlesur Rahman Khan, Professor of the Department of Fisheries Biology & Genetics, Bangladesh Agricultural University (BAU), who significantly contributed to amphibian research in both Bangladesh and the international community by establishing collaborations between BAU, Bangladesh, and the Institute for Amphibian Biology, Hiroshima University, Japan. Microhyla sp. C Microhyla sp. M Microhyla fissipes M. sp. C vs. M. sp. M M. sp. C vs. M. fissipes M. sp. M vs. M. fissipes (n = 10) (n = 24) (n = 15) U P U P U P Diagnosis. The new species M. mukhlesuri is assigned to the genus Microhyla based on smooth or warty skin, absence of vomerine teeth, a narrow and elliptical tongue, hidden tympanum, and molecular phylogenetic relationships (Hasan et al. 2012; Hasan et al. unpublished data). The genus Microhyla comprises 31 species and among them, only three (Microhyla ornata, M. berdmorei and M. rubra), five (M. ornata, M. rubra, M. berdmorei, M. heymonsi and M. butleri) and seven (M. ornata, M. rubra, M. berdmorei, M. heymonsi, M. butleri, M. chakrapanii and M. sholigari) nominal species are known to occur in Bangladesh, Myanmar and India, respectively (Kabir et al. 2009; AmphibiaWeb 2013). After documentation of all available 16 S-rrn and / or cytb sequences of Microhyla species from DDBJ / EMBL / GenBank databases, it became clear that this species (M. mukhlesuri) do not fit with any other previous sequenced species of Microhyla. Further, tibiotarsal articulation and an inverse U-shaped marking on the anus, and a distinct X-shaped marking on the dorsum made it stand out from other Microhyla species. There is no available 16 S-rrn / cytb data of M. chakrapanii and M. sholigari in GenBank, but the new species differentiates from them by the absence of minute tubercle on the dorsal part of tibia and thin forelimbs (Pillai 1977; Chanda 2002) and longitudinal groove dorsally on dilated toe tips, respectively (Dutta & Ray 2000). The new species differs from M. rubra by its tibiotarsal articulation reaching eye to the tip of the snout (vs. tibiotarsal articulation reaching until the orbit in M. rubra), from M. berdmorei with no or rudimentary webbing (vs. fully webbed toes in M. berdmorei) and from M. ornata by the presence of an outer metatarsal tubercle (vs. outer metatarsal tubercle is absence in M. ornata). In addition, the new species differs from M. butleri by the projection of first finger from the palm is narrow (vs. this kind of projection is far in M. butleri) and absence of disc on finger (vs. with disc in M. butleri) (Inger 1966). The new species can be separated from M. heymonsi by the presence of X-shaped marking on the dorsum and smaller size (SVL = 16.5 – 21 mm) (vs. 22 – 26 mm in M. heymonsi) (Chanda 2002). Lastly, the new species can be distinguished from its most near congener M. fissipes by the extension of tibiotarsal articulation until eye to the tip of snout (vs. reached only until eye in M. fissipes). Microhyla inornata (Boulenger 1890) in India currently treated as Micryletta inornata based on a specimen collected by Pillai (1977) from Andaman Islands. Jerdon (1853) described two new spcies i. e. Engystoma malabaricum and E. carnaticum from “ Malabar ” (present Kerala) and “ Caranatic ” (present Karnataka), respectively. Later, Parker (1934) synonymised the former two species as a singles species M. ornata. Despite the unavailability of type specimen, it seems quite untenable to resurrect of the former two Engystoma species from the synonymy of M. ornata due to following reasons: 1) insufficient description of Engystoma species by Jerdon (“ 1853 ” 1854), 2) genetically, our new species has closer affinity with Myanmar “ M. ornata ” (Hasan et al. unpublished data) and evolutionary, its immediate ancestors likely occurred and diverged in East or Southeast Asia rather than India, 3) known occurrence of the new species reveals that the radiation of this species restricted into a particular biogeographical region, i. e. Chittagong area, and ecologically this area has some similarity with Myanmar rather than Kerala and Karnataka (Western Ghats), India. Hence, from a biogeographical point of view, the dispersal of the new species might be extending to the south-western part of Myanmar instead of Kerala and Karnataka, India. Pyxicephalus frithi Theobald (1868) described from Jessore, SW Bangladesh reported to have vinous coloration and recently it became invalid (Frost 2013). Also this nomen does not fit with our new species. Summarizing, the new species is small frog with SVL of 16.5 – 21.0 mm in males and 17.3 – 18.4 mm in females. Head length subequal head width, finger formula 1 <4 <2 <3, toe formula 1 <2 <5 <3 <4, fingers free and slender, tips of fingers and toes not widened, rudimentary web between toes and subarticular tubercles relatively prominent (Figs. 4 A, 4 B). TIL / SVL ratio was 0.54 ± 0.03, whereas this value was 0.57 ± 0.04 in M. mymensinghensis, and 0.50 ± 0.02 in M. fissipes from Taiwan. Tibiotarsal articulation reaches between the eyes to tip of snout, whereas it reaches near the eye in M. fissipes. Phylogenetically, it appears to closer to “ M. ornata ” from Myanmar plus “ M. fissipes ” from Laos and Thailand and to be sister respectively with Taiwanese topotypic M. fiissipes with significant genetic divergences (Hasan et al. 2012; Hasan et al. unpublished data; this study).

Holotype. IABHU 3956, adult female (SVL: 17.9 mm; if not otherwise specified, the following body parts are measured in mm) collected from Raozan, Chittagong (22 º 35 ′ N, 91 º 55 ′ E,> 9 m asl.), Bangladesh on 14 November 2009 by M. M. Islam (Figs. 4 A, 4 B). Paratypes. IABHU 3878, adult female (SVL: 17.3); IABHU 3879, adult male (SVL: 21.0); IABHU 3880, adult male (SVL: 19.3); IABHU 3881, adult female (SVL: 17.5); IABHU 3882, adult male (SVL: 16.5); IABHU 3957, adult female (SVL: 18.4); IABHU 3958, adult female (SVL: 17.3); IABHU 3959, adult male (SVL: 16.5); and IABHU 3960, adult male (SVL: 16.6) collected from Raozan, Chittagong, Bangladesh on 14 November 2009 by M. M. Islam.