Microhyla mymensinghensis

Variation. The Sylhet population has a longer head than the Mymensingh population (HL / SVL: 0.39 vs. 0.29, HL / HW: 1.17 vs. 0.91), the differences being highly significant. Dorsal pattern is variable among individuals from the Mymensingh population (Figs. 6 A, 6 B), but Netrokona, Sylhet and Sunamganj specimens follow the dorsal pattern noted in Fig. 6 A. Usually, the dorsal color of Mymensingh population is reddish to yellowish, while a few individuals have a browner dorsal color (Fig. 6 B). Of the 15 specimens examined from Mymensingh, 9 individuals (60 %) have a whitish ventral throat while 6 individual (40 %) have a slightly ash ventral throat, along with a few speckles from their chin to base of forelimbs and rarely between the bases of forelimbs, not correlated with the male vocal sac. Of the examined 14 specimens from Sylhet, 12 individuals (86 %) have two parallel small dark lines at the terminus of their X-shaped distinct pattern, located near the crescent-shaped markings on the anus, but the remaining two individuals (IABHU 3945 and 3950) lacked these lines. These lines are irregular in the Mymensingh population. Chromosomes. Microhyla mymensinghensis has 2 n = 24 chromosomes (Fig. 7). The frogs of genus Microhyla from Southeast Asia have been reported to possess 2 n = 24 or 2 n = 22 chromosomes (King 1990; Kuramoto 1990; Kuramoto & Yong 1992). M. okinavensis (Ryukyu Archipelago, Japan), M. fissipes (China) and M. berdmorei (Thailand) have 2 n = 24 chromosomes. Joshy & Kuramoto (2011) suggested that the 2 n = 24 and 2 n = 22 karyotypes derive from the 2 n = 26 karyotype of the Indian M. ornata and M. rubra. The karyotype of M. mymensinghensis supports a close relationship with M. fissipes. Natural history. Microhyla mymensinghensis is sympatric with M. berdmorei, in the northeastern part of Bangladesh. We observed M. mymensinghensis either in grass under large trees (locally called “ Lendi Korui ”) or in open fields with some vegetation and slightly wet and loose soil. After dissection, we found many small insect parts, as well as some sand in the gut. Their breeding season is likely June-July, as we caught several females in June from Bangladesh Agricultural University Campus (BAUC) just after light rains, which contained about 40 – 50 mature ova in the ovaries. Each ovum is very small, approximately 650 µm in diameter.

Diagnosis. The new species M. mymensinghensis is allocated to genus Microhyla due to its smooth or warty skin, absence of vomerine teeth, hidden tympanum, and sister relationships with other microhylid frogs (Hasan et al. 2012; Hasan et al. unpublished data). Comparison of the 16 S-rrn and / or cytb sequences of the new species with its congeners in DDBJ / EMBL / GenBank databases from South and Southeast Asia including Bangladesh, India and Myanmar, denotes that any known microhylid frogs do not correspond to this new species and merits its distinctness. Considering the molecular analyses and morphological characters i. e. a crescent-shaped marking on the anus, an X-shaped marking on the dorsum and the tibio-tarsal articulation of the new species deduct it from all of the known Microhyla species from South and Southeast Asia, particularly from Bangladesh and its neighbor countries; but make confusion with only M. mukhlesuri, M. fissipes, M. heymonsi and M. ornata. However, the new species differs from M. ornata by the presence of an outer metatarsal tubercle (vs. outer metatarsal tubercle is absence in M. ornata) and from M. heymonsi by smaller size (SVL = 14.2 – 21.3 mm) (vs. 22 – 26 mm in M. heymonsi) (Chanda 2002) and presence of X-shaped marking on the dorsal (this kind of marking absence in M. heymonsi). 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). Most importantly, the new species differs from M. mukhlesuri by smaller body size, SVL = 16.5 ± 1.8 mm (vs. SVL = 17.8 ± 1.4 mm in M. mukhlesuri), higher forearm width, FAW = 0.9 ± 0.1 mm (vs. FAW = 0.7 ± 0.1 mm in M. mukhlesuri) (see Table 1), and presence of crescent shape marking on the anus (vs. this marking looks “ U ” shape in the M. mukhlesuri). Further, like with M. mukhlesuri, none of the old nomina of Microhyla corresponds to this new species. In conclusion, this new species is small frog with SVL of 14.2 – 17.6 mm in males and 15.2 – 21.3 mm in females. Head length subequal head width, finger formula 1 <4 <2 <3, toe formula 1 <5 <2 <3 <4, fingers free and slender, tips of fingers and toes not widened, rudimentary web between toes and subarticular tubercles distinct (Figs. 4 G, 4 H). TIL / SVL ratio was 0.57 ± 0.04, whereas this value was 0.54 ± 0.03 in M. mukhlesuri, and 0.50 ± 0.02 in M. fissipes from Taiwan. Tibiotarsal articulation extends from between the eyes to the tip of the snout, while it reaches near the eye in M. fissipes and in front of the shoulders in M. ornata. Phylogenetically, it shows sister relationship with M. mukhlesuri plus M. fissipes with high genetic divergences (Hasan et al. 2012; Hasan et al. unpublished data; this study).

Distribution. The known occurrence of M. mymensinghensis includes the Mymenisngh, Netrokona, Sylhet and Sunamganj districts in the in the central and northeastern regions of Bangladesh (Fig. 1).

Etymology. The specific name refers to Mymensingh, the type locality of this species.

Holotype. IABHU 4116, adult female (SVL: 21.3 mm, if not otherwise specified, the following body parts are measured in mm) collected from Bangladesh Agricultural University Campus (24 º 44 ′ 50 ″ N, 90 º 24 ′ 24 ″ E,> 18 m asl.), Mymensingh, Bangladesh on June 25, 2012 by M. Hasan (Figs. 4 E, 4 F). Paratypes. IABHU 4004, adult male (SVL: 14.8); IABHU 4117, adult female (SVL: 20.2); and IABHU 4120, adult female (SVL: 20.5) collected from Bangladesh Agricultural University Campus, Mymensingh, Bangladesh on 9 June 2011 and 25 June 2012 by M. Hasan. IABHU 3947, adult male (SVL: 17.6); IABHU 3948, adult male (SVL: 17.3); and IABHU 3899, adult female (SVL: 16.7) collected from Golapganj, Sylhet on 6 June 2011 by M. M. R. Khan.