Taxonomy & naming
Chela macrolepis was formally described by Knight and Rema Devi in 2014, the original publication appearing in a peer-reviewed ichthyological journal. The Catalog of Fishes (Eschmeyer, California Academy of Sciences — the authority for valid names) records the valid combination as Chela macrolepis Knight & Rema Devi, 2014, with the type locality given as Chembarambakkam Lake, Coromandel floodplain, Tamil Nadu, India.
The genus Chela belongs to the cyprinid tribe Danionini and is closely allied to Laubuka — the two genera share the large-eyed, laterally compressed, surface-oriented body plan that distinguishes them from the more elongate, streamlined Danio and Devario. Members of Chela were once lumped with or confused alongside Laubuka in older literature, and the boundary between the two has been refined as more species have been described across peninsular India and Southeast Asia.
The specific epithet macrolepis is a compound of the Greek makros (large) and lepis (scale), referring to the notably large scales along the lateral line that set this species apart from its congeners and provide an immediate identification character.
Morphology
Chela macrolepis is a small, laterally compressed, almost blade-like cyprinid reaching a maximum recorded standard length of 1.5 in. The body is deep relative to its length, with the characteristic large eye and strongly upturned mouth of the genus — adaptations for surface-oriented feeding. The most striking diagnostic features are meristic: 9 dorsal soft rays; an exceptionally high anal soft-ray count of 20–24, which is unusually large for the genus; and 35–40 plus 1–3 lateral-line scales. The species is further distinguished internally by 16 precaudal vertebrae and externally by 23–24 predorsal scales.
The large scales from which the species takes its name are visible along the flanks and give the fish a slightly armoured or tiled appearance compared with the finer-scaled pattern of closely related species. Live colouration is not extensively documented in the literature; like other Chela it is likely silvery with a reflective lateral stripe, with the large scales producing a faceted, jewel-like sheen in raking light.
Habitat
The entire known range of Chela macrolepis is Chembarambakkam Lake, a substantial reservoir and irrigation tank on the Coromandel floodplain west of Chennai (formerly Madras), Tamil Nadu, India. The lake sits within a tropical monsoon climate, with water levels rising markedly during the northeast monsoon (October–January) and drawing down through the dry season. The Coromandel floodplain receives a different monsoon timing from most of peninsular India, as it lies in the rain shadow of the Western Ghats and catches the retreating northeast monsoon rather than the southwest.
Data specific to the water chemistry of Chembarambakkam Lake as it pertains to this species are sparse. Based on the habitat requirements of congeners in peninsular India (for which Seriously Fish records pH 6.5–7.5, temperature 72–82 °F, and neutral to slightly soft-moderate hardness), the species is inferred to occupy warm, seasonally variable freshwater typical of the low-gradient Coromandel tank and reservoir landscape. The lake supports marginal emergent and submerged vegetation that would provide both feeding habitat and spawning substrate for surface-oriented cyprinids.
Feeding
Like other members of the genus, Chela macrolepis is presumed to be a surface-oriented micropredator and omnivore. The upturned mouth and large eye are the principal evidence: these anatomical features are convergently associated across many distantly related fish lineages with a diet centred on insects and other invertebrates taken at or near the water surface — including fallen terrestrial insects, swarming aquatic midges and small crustaceans in the surface film.
Specific gut-content data for C. macrolepis have not been published. Congeners in comparable peninsular Indian habitats take insects, insect larvae, small crustaceans and occasional algal and plant material. In an aquarium context closely related Chela are reported to accept small live and frozen foods such as daphnia, artemia and chironomid larvae readily, along with fine-particle flake and micro-pellet foods.
Mating
No observations of courtship or spawning behaviour have been published for Chela macrolepis specifically. Based on the biology of the genus and the broader danionin tribe to which it belongs, the species is inferred to be an egg-scattering, non-guarding spawner — the mode universal among danios and their allies. In typical danionin fashion, breeding would be tied to seasonal cues such as the onset of the northeast monsoon, when rising water levels, warmer temperatures and an influx of terrestrial food trigger spawning across the Coromandel tank system.
Courtship in congeners involves persistent male pursuit of gravid females through dense vegetation, culminating in paired releases of eggs and milt into fine-leaved plants, root masses or over the substrate. There is no pair bond, no nest, and no parental involvement beyond the act of spawning itself.
Breeding
Chela macrolepis has not been bred in captivity in any documented account. The species' Endangered status, single-locality range and very recent formal description mean it has received virtually no hobbyist or aquaculture attention, and wild-caught specimens are unlikely to reach the trade.
By analogy with congeners, spawning would produce scattered, weakly adhesive eggs deposited over fine-leaved vegetation, moss or gravel, with no parental care following spawning. Adults would likely consume eggs given the opportunity. Incubation periods and fry development data are entirely unknown for this species. Any captive breeding effort would hold conservation value given the restricted wild population.
In the aquarium
Chela macrolepis is not an aquarium fish in any practical sense: it is an Endangered species known only from a single lake in Tamil Nadu, it has not been described in hobbyist literature, and it is not available in the trade. It is included here as part of a complete account of the genus and as a species whose existence — and precarity — deserves wider awareness among the aquarium community.
Were it ever to become available through conservation-backed breeding programmes, its care requirements would presumably mirror those of its congeners: a well-filtered aquarium with open surface swimming space, moderate flow, neutral to slightly soft water in the range of 72–82 °F and pH 6.5–7.5, maintained as a shoal of at least eight to ten individuals. The large anal-fin ray count and blade-like body suggest a fast, agile surface schooler that would do best with active, similarly sized companions and a diet of small live or frozen invertebrates.
Conservation
The IUCN Red List assessed Chela macrolepis as Endangered (EN) in December 2020. The assessment reflects the species' confinement to a single lake — Chembarambakkam Lake on the urban fringe of Chennai — and the intense pressures on that water body. Chennai is one of South Asia's fastest-growing metropolitan areas, and Chembarambakkam Lake, while formally a protected irrigation reservoir, sits within a landscape of encroachment, water extraction, urban runoff, sewage influx and periodic drying during drought years.
The lake achieved international attention during Chennai's catastrophic water crisis of 2019, when it and the city's other major reservoirs ran nearly dry. Such events, predicted to become more frequent under regional climate projections, pose an existential threat to a species with no other known locality. There is no documented captive population and no published conservation action plan specific to the species. The formal description of C. macrolepis in 2014 placed it immediately in the category of newly named, critically range-restricted species that India's tank and floodplain ecosystem specialists are racing to survey and protect.