Taxonomy & naming
Pethia macrogramma was described by Kullander and Fang in 2008. The species was placed in the genus Pethia, which was formally established by Pethiyagoda, Meegaskumbura, and Maduwage in 2012 to accommodate a cluster of small South and Southeast Asian barbs previously lumped under the sprawling catch-all genus Puntius. Under the Catalog of Fishes (Eschmeyer, CAS — the authority for valid names) the valid combination is Pethia macrogramma (Kullander & Fang, 2008), with the parenthetical authority indicating the original description was made under a different genus before its current placement was recognised.
FishBase places the species within the Puntius conchonius group, a loose assemblage of Pethia and related barbs sharing broadly similar body plans. The epithet macrogramma most likely refers to a prominent marking — macro (large) and gramma (line or mark) in Greek, probably alluding to the humeral mark or the lateral-line scale row, though the original description should be consulted for the authors' stated intent.
Morphology
Pethia macrogramma is a short and deep-bodied barb with a maximum recorded standard length of 2 in. The species lacks barbels entirely — a key distinguishing feature within Pethia. The lateral line is complete or nearly complete, and a minute humeral mark sits on the lateral-line scale at position 3, just behind the gill cover.
Fin formula data from FishBase give: dorsal fin iii,8 (occasionally iv,8); anal fin iii,5; pectoral fin i,12–i,13; pelvic fin i,7–i,8. The transverse scale count is recorded as ½4/1/4½. No detailed colour description from fresh specimens is available in the published literature accessible to date; colour in preservative and any in-life pattern distinctive to the species remain incompletely documented.
Habitat
The species is known only from streams in the vicinity of Myitkyina, the capital of Kachin State in northernmost Myanmar. This region is characterised by hilly to montane terrain drained by tributaries of the upper Ayeyarwady (Irrawaddy) River system. Streams at these latitudes and elevations tend to be cool, fast-flowing, and well-oxygenated relative to lowland tropical rivers, though specific physico-chemical measurements from the type locality have not been published.
FishBase classifies the species as benthopelagic and freshwater, consistent with the generalised barb life-style of moving near the bottom and through the mid-water in flowing streams. No temperature range, pH values, or substrate preferences have been formally recorded for the species. Given the montane northern Myanmar setting, water is likely cool and near-neutral to slightly alkaline, but keepers should treat these parameters as informed inference rather than confirmed data.
Feeding
No specific dietary information has been published for Pethia macrogramma. By analogy with the broader genus Pethia and the Puntius conchonius group, the species is almost certainly an opportunistic omnivore, feeding on small aquatic invertebrates, algae, diatoms, and fine organic matter picked from the substrate and the water column.
In an aquarium context, if the species were ever available, standard small-barb fare — quality flake or micro-pellets supplemented with frozen bloodworm, daphnia, and brine shrimp — would be a reasonable starting point. Any keeper fortunate enough to work with this species should document feeding observations for the scientific record.
Mating
No mating behaviour has been described for Pethia macrogramma in the wild or in captivity. As with all members of the genus Pethia and the wider barb lineage, the species is expected to be an egg-scattering, non-guarding spawner with no nest construction and no pair bond extending beyond the act of spawning itself.
In egg-scattering barbs generally, a ripe male pursues a gravid female through vegetation or across the substrate, the pair pressing together briefly to release eggs and milt simultaneously. No territory is held, and spawning may involve multiple males attending a single female. All courtship activity is inferred from congeners; direct observation of P. macrogramma has not been recorded in the available literature.
Breeding
Breeding in captivity has not been documented for Pethia macrogramma. The species is not known to be established in the aquarium trade, and information on captive reproduction is absent from the available literature.
Based on the biology of the genus, a small spawning tank with fine-leaved plants or a spawning mop over a mesh or marbled bottom — to protect scattered adhesive eggs from adult predation — would be the standard approach if the species were to become available. Adults should be removed after spawning, as barbs give no parental care and readily consume their own eggs and larvae. Any successful captive breeding of this rarely encountered species would be of genuine scientific and conservation value.
In the aquarium
Pethia macrogramma is not a species encountered in the ornamental fish trade. It is known from a single locality in northern Myanmar and has not been collected for the hobby. No aquarium husbandry data — water parameter targets, tankmate compatibility, group size requirements, or diet preferences — have been formally published.
Should the species become available, the general guidance for small montane Pethia would apply: a species tank or quiet community with other small, similarly-sized fishes; clean, well-oxygenated water cooler than typical tropical aquarium temperatures; neutral to slightly alkaline pH; and a mixed diet of small live, frozen, and prepared foods. Given its extremely restricted known range and Data Deficient conservation status, any specimens entering the trade should ideally originate from documented captive-bred stock.
Conservation
Pethia macrogramma is assessed as Data Deficient (DD) on the IUCN Red List, with the assessment recorded in 2010. The Data Deficient category does not imply that the species is not at risk; rather, it reflects that insufficient information exists to make a reliable determination of its threat status. Given that the species is known only from streams near Myitkyina in Kachin State, northern Myanmar, its effective range is extremely narrow.
Kachin State has experienced significant environmental pressures in recent decades, including logging, small-scale gold mining in river channels, agricultural expansion, and the broader impacts of conflict and reduced environmental oversight in border regions. Any of these activities could affect stream quality and continuity in the type locality. The absence of subsequent collections or detailed surveys since the original description is itself a cause for caution. Formal resurveys of the Myitkyina stream system to clarify the species' current status and population size would be a priority for freshwater conservation in the region.