Taxonomy & naming
Puntius viridis was formally described by Plamoottil and Abraham in 2014 in the Journal of Research in Biology (volume 3, issue 7), based on eight specimens from the Manimala River at Kallumkal, Kottayam district, Kerala. The genus Puntius was established by Hamilton in 1822 and long served as a catch-all for South and Southeast Asian barbs; a major revision by Pethiyagoda et al. in 2012 split out numerous lineages into new genera, but P. viridis, described two years later, was placed directly in the residual Puntius as currently recognised under the Catalog of Fishes.
The species epithet viridis is Latin for 'green', referring to the greenish colouration of the living fish. The type series was collected at a single locality, and the species has not since been reported from rivers outside the Manimala basin, giving it a very small known distribution within the Western Ghats biodiversity hotspot.
Morphology
Puntius viridis reaches a maximum recorded length of 3 in SL. The body is moderately elongate and laterally compressed, with a terminal, protrusible mouth well suited to picking invertebrates from the substrate. The dorsal fin carries 8 branched rays and the anal fin 5 branched rays (8 anal-fin rays total); the lateral line runs through 25–26 scales, and there are 9 pre-dorsal scales. Four-and-a-half to five-and-a-half scales separate the lateral line from the dorsal-fin base.
The distinguishing features that separate this species from closely related Indian barbs are threefold: a greenish ground colour on the body and fins; a band of dark, elongated spots arranged in a single row along the middle of the dorsal fin; and a patch or band of dark spots situated outer to the operculum. The eyes are notably visible from below the ventral surface, and the depth of the head is proportionally lesser than in congeners of similar size. Scale coverage is moderate on the breast region. These characters were diagnostic in the original description, which was based on comparison with other Puntius then known from peninsular India.
Habitat
The only confirmed locality for Puntius viridis is the Manimala River at Kallumkal in Kerala, within the Manimala River Basin (MMRB) of the southern Western Ghats. This is a tropical mountainous catchment where the river rises in the hills and descends through forest and agricultural land before joining the Vembanad backwaters. The basin experiences strong monsoon seasonality that drives marked fluctuations in flow, temperature, and chemistry.
The hill streams of this region drain granitic and metamorphic substrate, and the water is typically soft to moderately hard with a near-neutral to slightly acidic pH. Fast-flowing, well-oxygenated conditions prevail in the reaches where such barbs are collected, and water temperatures in the cooler upland portions are substantially lower than in the lowland rivers of the peninsula. FishBase lists P. viridis as a benthopelagic, tropical freshwater fish, consistent with the substrate-associated feeding habits typical of small Indian barbs.
Feeding
No direct stomach-content study has been published for Puntius viridis. FishBase assigns it a trophic level of approximately 2.6, estimated from the closest relatives, placing it firmly in the category of benthic omnivores and insectivores. This is consistent with the guild of small Indian hill-stream barbs that forage along the bottom and among submerged vegetation, picking up aquatic insect larvae, small crustaceans, organic detritus, and algal films.
The terminal, protrusible mouth seen in the original description supports this mode of feeding — it allows the fish to take prey precisely from the substrate and from among plant material rather than pursuing it in open water. In captivity, barbs of this ecological type generally accept live and frozen invertebrate foods as well as quality flake and small pellets.
Mating
Puntius viridis has not been studied in courtship or spawning, but as a member of the family Cyprinidae it is expected to follow the egg-scattering, non-guarding reproductive mode universal among barbs. In cyprinids of this guild, readiness to spawn is typically triggered by seasonal cues — rising temperature, increasing water flow, or improved condition following the monsoon — and there is no lasting pair bond or defended territory.
Courtship in small Indian barbs typically involves an active male driving a gravid female through aquatic vegetation or over the substrate, with eggs and milt released in brief bursts of contact. The adhesive eggs settle among plants or onto the riverbed, and neither parent returns to them. The Manimala River's strong monsoon hydrology may well serve as the spawning trigger in the wild, as it does for many hill-stream cyprinids of peninsular India.
Breeding
No captive breeding of Puntius viridis has been documented in the aquarium literature, and the species is not present in the commercial trade in any significant numbers. Based on the biology of comparable small Indian Puntius, captive spawning would likely require soft, near-neutral, well-oxygenated water at a moderate temperature, with fine-leaved plants or a spawning mop to receive the scattered adhesive eggs.
As with all egg-scattering barbs, parents would need to be removed immediately after spawning to prevent egg predation. Clutch size and egg development times are unknown for this species. The very limited wild population and absence from the trade mean that any captive work with P. viridis would be scientifically significant rather than routine.
In the aquarium
Puntius viridis is not established in the aquarium hobby and is unlikely to appear through normal commercial channels given its restricted known range and the absence of any trade collection from the Manimala system. It is a species of scientific interest rather than a practical aquarium subject at present.
If it were to become available, its care requirements would be expected to mirror those of other small hill-stream barbs from the Western Ghats: a well-filtered, well-oxygenated aquarium with moderate flow, soft to moderately hard water of near-neutral pH, a temperature in the low-to-mid twenties Celsius reflecting the cooler upland conditions of its native river, and a diet of live or frozen invertebrate foods supplemented with prepared foods. A species tank or a biotope setup evoking Indian hill-stream conditions would be most appropriate.
Conservation
Puntius viridis has not been formally assessed by the IUCN Red List and carries a status of Not Evaluated (NE) as of 2026. Its known range is limited to a single locality — the Manimala River at Kallumkal, Kerala — based on the eight type specimens collected in 2014. This extreme range restriction, combined with the pressures facing Western Ghats freshwater ecosystems, makes the species a genuine conservation concern even in the absence of formal evaluation.
The Manimala River Basin is listed in Kerala's threatened animals database as harbouring species of conservation concern, and the Western Ghats as a whole face ongoing pressure from dam construction, water extraction for agriculture and industry, and pollution from shifting land use. Many of the small-range barbs described from peninsular India in recent decades have been found to be localised in a single river or even a single reach, making them disproportionately vulnerable to any change in their catchment. Formal survey and IUCN assessment of P. viridis would be a priority for any herpetology or ichthyology programme working in the Manimala basin.