Aizawl: For years, a small frog found in Mizoram was mistaken for ‘Ingerana borealis’. Now, genetic and morphological evidence has established it as a distinct species, Ingerana aizawl, giving the amphibian its own scientific identity. The new species was discovered along a stream on the Mizoram University campus in Aizawl.It has been formally described as a new species, underscoring how amphibian diversity in northeastern India remains under-documented. The species, named Ingerana aizawl, was discovered by researchers from the university’s Department of Zoology under the supervision of department head Prof Hmar Tlawngte Lalremsanga.Lalremsanga told TOI that researchers from Mizoram University, Cotton University and conservation organisation Help Earth described the species in a paper published on Monday in the journal Zootaxa.The study’s authors are Lalremsanga, Manmath Bharali, Malsawm Dawngliana, Mara Duasa Hlychho, Malsawmtluanga, Rupankar Bhattacharjee, Arup Kumar Hazarika, Nilutpal Das and Jayaditya Purkayastha.The frog was discovered at Hratdawng Stream on the Mizoram University campus, about 15km west of central Aizawl. Researchers found that frogs in Mizoram historically identified as Ingerana borealis were genetically and morphologically distinct from all other recognised species in the genus.The finding was based on an integrative approach combining physical characteristics with mitochondrial 16S rRNA DNA data. Genetic analysis placed the Mizoram frogs in a strongly supported, distinct lineage within the genus Ingerana.Researchers found that the new species differed genetically from its closest relative, Ingerana occidens, by 4.8% to 6.6%. The divergence from I. borealis populations in Arunachal Pradesh was substantially higher, at 15.3% to 17.6%.The discovery also resolves a long-standing taxonomic uncertainty over the identity of the Mizoram frogs.Populations in Mizoram had been identified as I. borealis since 2009. A reassessment in 2026 established that populations in Meghalaya’s Garo and Khasi Hills belonged to a separate species, I. occidens, while true I. borealis was restricted to areas north of the Brahmaputra. The identity of the Mizoram population remained unresolved because molecular evidence was unavailable.The newly described frog is small and stout-bodied. Adult males measure between 22mm and 25.5mm in snout-to-vent length, while females measure between 24.4mm and 26mm. The frog has a distinct circular tympanum, a prominent supratympanic fold, small rounded discs at the tips of its fingers and toes, and a notably wrinkled dorsal surface.In life, it is predominantly dark brown to reddish-brown. Its darker lateral surfaces form a diffuse band extending towards the groin. The iris is dark brown to blackish, with a faint coppery tint.The species is closely associated with aquatic and forest habitats. Researchers recorded it around streams, wetlands and marshes at elevations ranging from 94 metres to 823 metres above sea level. Most individuals were encountered at night on wet rocks in or beside trickling, fast-flowing and cascading streams.During the day, the frogs shelter in rock crevices, moist leaf litter and bushes.The breeding season appears to coincide with the monsoon. Researchers recorded breeding activity between May and July, with males calling from outside the water and mating pairs found along stream margins. No eggs or larvae were recorded in the wild, and captive pairs did not lay eggs during the study.The frog’s call generally consists of 12 notes. The call analysed by the researchers lasted about 1.42 seconds and had a dominant frequency of 3,359Hz.The species name aizawl refers to Mizoram’s capital and honours the region where the type series was discovered. The holotype is an adult male collected from Hratdawng Stream on April 18, 2024. Five female paratypes were collected at the same site in June 2026. Researchers also examined two males from Khaikhy in Mizoram.The researchers said the discovery pointed to a broader pattern of hidden amphibian diversity in northeastern India. They said limited geographical sampling and a lack of molecular data had previously led to distinct populations being grouped under the same species.They also said the genus Ingerana could contain other undescribed species and called for further molecular and morphological surveys across northeastern India and adjoining regions to clarify species boundaries and the group’s evolutionary history.The discovery also has conservation implications. Mizoram’s frogs were previously considered part of the range of I. borealis, which was assessed as Least Concern by the International Union for Conservation of Nature in 2022. The newly recognised I. aizawl will require a separate assessment of its conservation status, the researchers said.The type locality also highlights the conservation value of urban and institutional green spaces. The university campus covers about 978 acres, ranges in elevation from 300 metres to 880 metres and retains relatively undisturbed forest patches, particularly on its western side.
