Taxonomy & naming
Danio htamanthinus was described by Sven O. Kullander and Michael Norén in 2016 in Zootaxa (vol. 4178(4): 535–546). The Catalog of Fishes (Eschmeyer, CAS) records it as a valid species in the genus Danio, and no subsequent revision has moved it to another genus. The parentheses are absent from the authority because Kullander and Norén placed it directly in Danio at the time of description.
The species is part of the glowlight danio complex, a group of closely related, small, vertically barred danios from upland Myanmar streams. Its congeners D. choprae (the original glowlight danio) and D. flagrans have been in the hobby for decades, but D. htamanthinus was only formally distinguished in 2016 on the basis of colouration differences and molecular divergence. COI barcode p-distances of 4.3% from D. choprae and 7.5% from D. flagrans support its status as a distinct species. The species has occasionally been referred to in hobbyist media as a miniature glowlight danio variant, but it is a full species, not a morph of D. choprae.
Morphology
Danio htamanthinus is among the smallest members of its genus: the holotype, a male, measured 1 in standard length, and the range of known specimens at the time of description was 0.5–1 in SL. Like the other members of the glowlight complex, the body is slender and elongate, with the slightly upturned mouth typical of surface-oriented danios.
The colour pattern features dark vertical bars on a pale background, with a reddish interstripe on the posterior half of the body — the feature that originally united the glowlight complex. The critical distinction from D. choprae and D. flagrans is the absence of the P+1 stripe (the stripe immediately above the principal lateral stripe), giving the flank a cleaner, less densely barred appearance. Fin colouration and precise meristics are detailed in the original description; insufficient specimens have been studied since to characterise intraspecific variation or full range of pigmentation.
Habitat
The type series was collected from small, shallow streams in the vicinity of Htamanthi, a town in Sagaing Region of northern Myanmar, within the middle Chindwin River drainage. The Chindwin is a major tributary of the Irrawaddy system, draining mountainous terrain in northern Myanmar before joining the Irrawaddy in the west of the country.
The collection sites were small upland streams with clear water, low banks margined by low vegetation, and — importantly — also flooded cleared areas with stagnant clear water over grasses. This dual habitat suggests the species uses both flowing and temporarily inundated standing water. Associated fishes collected from the same sites include Paracanthocobitis cf. rubidipinnis, Channa gachua, Pethia meingangbii, Pethia thelys, Badis sp., Dario sp. and Esomus sp. — a community characteristic of small upland Myanmar watercourses. Water chemistry parameters for the Chindwin headwaters are not recorded in the original description; the clear, likely soft-to-moderately hard water of small forested Myanmar hill streams is the presumed context.
Feeding
No feeding study specific to Danio htamanthinus has been published. Like other small danios from clear upland streams, it almost certainly feeds on small aquatic and terrestrial invertebrates — insect larvae, small crustaceans and whatever drifts into the water column or lies at the surface. Its small mouth and upturned angle suggest a surface-to-midwater micropredator rather than a bottom feeder.
In the aquarium, closely related glowlight danios such as D. choprae accept a standard variety of small foods: finely crushed flakes, micro-pellets, and small live or frozen items such as daphnia, baby brine shrimp, micro-worms and bloodworm. D. htamanthinus can be expected to have similar requirements, with small particle size particularly important given its miniature body.
Mating
Danio htamanthinus is an egg-scattering, non-guarding spawner, consistent with all members of the genus Danio. No specific courtship study of this species exists, but the pattern seen across the glowlight complex involves an active male pursuing a gravid female through vegetation or over substrate, with eggs and milt released in brief pressing contacts. There is no pair bond, no nest construction and no preparation of a spawning site.
Spawning in upland Myanmar danios is likely cued by seasonal changes in water temperature and volume associated with the monsoon, when streams rise and marginal vegetation is inundated — the same cue used by most South and Southeast Asian danios. The presence of stagnant flooded grassy areas in the type locality habitat suggests the species may use both stream-edge and inundated terrestrial habitat for reproduction during high water.
Breeding
No captive breeding of Danio htamanthinus has been documented in the published literature. As a member of the glowlight danio complex, its reproductive biology is expected to follow the pattern of D. choprae: scattered adhesive or weakly adhesive eggs released over fine plants, moss or gravel substrate, with no parental care and a tendency for adults to consume eggs if not separated after spawning.
Given the species' very small body size (under 1 in SL), egg numbers per spawning are likely modest. Fry would be correspondingly tiny at hatching and would require infusoria-grade first foods before graduating to newly hatched brine shrimp. In the aquarium hobby, D. htamanthinus is essentially unknown in the trade as of the time of description, and practical captive-breeding observations are lacking. Techniques developed for D. choprae — conditioning on live foods, a separate shallow spawning tank with fine-leaved plant cover, and prompt removal of adults — are the logical starting point.
In the aquarium
Danio htamanthinus is not established in the aquarium trade and had not been imported as a recognised species at the time it was described. Its close relatives in the glowlight complex, particularly D. choprae, are well known in specialist circles as peaceful, active nano-tank inhabitants, and D. htamanthinus can be expected to share many of those qualities while being even smaller.
For any keeper who obtains this species, a small species-only or nano community tank with other miniature, non-aggressive fishes would be most appropriate. Soft to moderately hard, clear, well-oxygenated water reflecting the clear-stream conditions of the Chindwin uplands is recommended — avoid the organically stained blackwater conditions more appropriate for Sundaland species. A gentle current, fine-leaved plants or moss, and a darker substrate to bring out the species' colour pattern would complete a suitable setup. As with all small shoaling danios, a group of at least six individuals is preferable to encourage natural behaviour and reduce individual stress.
Conservation
Danio htamanthinus has not been assessed by the IUCN Red List. It was described in 2016 and, as a recently named species known only from the vicinity of Htamanthi in the middle Chindwin River, it qualifies as a Myanmar endemic with a very restricted known range — factors that would warrant conservation attention under standard IUCN criteria.
The Chindwin basin and northern Myanmar's upland streams are subject to increasing pressure from deforestation, agricultural expansion and infrastructure development. While the species has not been formally evaluated, the combination of a small, fragmented range, clear-water habitat dependency, and the general degradation of freshwater ecosystems in the region suggests that a future IUCN assessment would likely find cause for concern. No targeted collection for the aquarium trade has been documented, and the species is not known to be commercially available. Monitoring of the Htamanthi area streams and any additional populations in the Chindwin drainage would be valuable for establishing the species' true range and abundance.