Microhyla rubra, the red narrow-mouthed frog, is a small stout microhylid frog with fossorial habits.Thurston (1888) and Boulenger (1890) originally described it from lowland peninsular India and Sri Lanka, but more recent work indicates that the population in Sri Lanka is in fact a distinct species, M. mihintalei, based on call, morphology, and genetics (Wijayathilaka 2016).The range of M. rubra has been extended since to Bangladesh and western Myanmar (Wogan et al. 2008). An abundant species, it inhabits dry areas including forests, brushlands and agricultural lands.By day adults burrow under soil, leaves, in rubble piles and other ground cover, including elephant dung (Campos‐Arceiz 2009).It is able to withstand disturbance, and is found living close to humans and urbanized environments. The cryptic, nocturnal and burrowing nature of M. rubra contributes to its poorly known biology, ecology and distribution, despite the fact that it is abundant and wide-spread near human habitation Bowatte and Meegaskumbura (2011).
A smooth-skinned frog, M. rubra has a reddish dorsal surface, and darker sides.A dark stripe runs from its rounded snout through its eyes and back to its hind legs. Its legs have a banded pattern, and there is a dark brown mark across the thigh.Its belly is creamy white, sometimes with brown markings on the throat. Male snout-vent length is 20-28 mm, females are slightly larger at 20-30 mm (Thurston 1888; Boulenger 1890)
Microhyla rubra reproduces in still ephemeral pools and rice paddies.Adults breed during monsoon season, producing flat, transparent egg masses. Bowatte and Meegaskumbura (2011) characterized the larval stages of “Microhyla rubra” in Sri Lanka. As stated above, Sri Lankan populations are now considered to be a new, closely related species, M. mihintalei.It would be interesting to compare the biology of tadpoles from peninsular India.Sri Lankan tadpoles swim close to the water surface, feeding on plankton and suspended particles.They develop in 77 days. Bowatte and Meegaskumbura (2011) found that in Sri Lanka these tadpoles were not found in any rice paddies, only in ephemeral pools.
Microhyla rubra is also known as the Guangdong rice frog and Jerdon’s narrow-mouthed frog (Frost 2016).
Habit stout. Snout rounded, a little shorter than the diameter of the orbit ; interorbital space broader than the upper eyelid. Fingers moderate, first much shorter than second ; toes moderate, one-third webbed ; tips of fingers and toes not swollen ; subarticular tubercles very distinct ; two rather large, oval, compressed, very prominent metatarsal tubercles, outer somewhat larger than inner. The tibio-tarsal articulation reaches somewhat beyond the shoulder, never to the eye. Skin smooth. Reddish brown above, sides darker; a dark brown line from the tip of the snout through the eye along the side of the back to the groin ; a dark brown mark across the thigh, beginning on the loin ; limbs with more or less distinct dark cross bars ; sometimes a dark X-shaped marking on the anterior portion of the back, commencing between the eyes ; beneath whitish, immaculate or with a few brown dots on the throat. Male with a subgular vocal sac, and the throat black.
From snout to vent 1.2 inches. Habitat is distributed from Southern India and Sri Lanka. Some adults have been observed dwelling in elephant dung.
The tadpole of Microhyla rubra has a transparent body with a long, tapering whip like tail. In dorsal view, body clearly differentiated into two parts, a longer and wider anterior region and a narrower posterior region. Anterior region almost twice as long and wide as posterior region. Eyes small and snout rounded. Head and body posterior to eyes with sides parallel to each other. Eyes directed slightly dorsolaterally, bulbous, and entire eye visible through epidermis due to dearth of pigmentation. Nares closed, narial depressions visible, located immediately anterior to two small concentrated patches of pigment, anterodorsolaterally directed, and closer to snout tip than to pupils. Nasolacrimal duct apparent. Mouth narrow, superior, lower and upper-lips both visible. Tail long, tapering, with a whip-like flagellum.
Tadpoles of Microhyla rubra lack keratinized mouth parts and have a dorsoterminal mouth. They have six papillae (scallops) on the lower lip but number varies with developmental stage.
The preferred habitats of M. rubra tadpoles are ephemeral pools which have less aquatic predators. Since the ephemeral pools dry rapidly after the rainy period tadpoles have to adapt to this condition by having a rapid growth rate. M. rubra tadpoles live in water close to the surface and feed on plankton and suspended food particles.