Taxonomy & naming
Devario sondhii was described by Hora and Mukerji in 1934, originally placed in the genus Danio. It was subsequently transferred to Brachydanio — a genus used for smaller, fewer-rayed danios that was long maintained by some authors — where it appeared in the older literature as Brachydanio sondhii. The modern reclassification came with Kullander's revision in 2001, which assigned the species to Devario, the genus now used for the larger, more elongate danionins of South and Southeast Asia. The Catalog of Fishes (Eschmeyer, CAS) records the valid combination as Devario sondhii (Hora & Mukerji, 1934), with the parenthetical authority marking the change from the original generic placement.
The species epithet honours the collector or associate referenced in the original description. The common name 'fireline danio' circulates in the hobby and trade, a reference to the vivid lateral stripe coloration that is characteristic of the Devario group.
Morphology
Devario sondhii is a slender, elongate cyprinid reaching a maximum recorded standard length of approximately 2.5 in, placing it at the smaller end of the Devario size range. Like other members of the genus it has a streamlined, laterally compressed body suited to active life in flowing or well-oxygenated water, a slightly upturned mouth indicative of surface and mid-water feeding, and the horizontal stripe patterning typical of the danionins.
Sexual dimorphism follows the pattern seen in allied species: females are deeper-bodied and become noticeably rounder when gravid; males are more torpedo-shaped and typically slimmer. Precise colour descriptions from wild material are sparse in the available literature, but the 'fireline' trade name suggests a prominent, vivid lateral stripe.
Habitat
Devario sondhii is known from the vicinity of Ho Pong (Hopong) in the Shan Plateau of Myanmar, where it occupies shallow wetland pools — recorded at depths of up to approximately 12 in — with dense growth of submerged aquatic vegetation including Elodea and other plants. The water is described as well-oxygenated and the substrate as rocky or sandy, consistent with highland pool conditions at elevation on the Shan Plateau.
This is an interior Myanmar highland species, not a lowland river fish. The Shan Plateau sits at considerable elevation compared with the surrounding lowlands, and its pool and stream systems reflect that: the water is likely cooler, well-aerated and soft to moderately hard. The dense vegetation in which the species is recorded suggests calm to gently circulating water rather than turbulent current, despite the upland setting.
Feeding
Devario sondhii is omnivorous in the broad sense typical of danionin cyprinids. Field data for this species specifically are sparse, but the guild of small pool-dwelling Devario are generalised opportunists, taking small invertebrates — aquatic insect larvae, crustaceans, worms — from the water column and surface, supplemented by plant material, algae and organic detritus associated with the dense vegetation of their habitat.
In aquarium settings, the species accepts a wide range of prepared and live or frozen foods: quality flake and small pellets form a workable staple, with bloodworm, daphnia, cyclops and brine shrimp providing the protein variety and colour-conditioning appropriate for a cyprinid in good condition.
Mating
Devario sondhii is an egg-scattering, non-guarding spawner. There is no nest, no pair bond beyond the act of spawning, and no parental investment in the eggs or fry. Courtship follows the standard danionin pattern: a ready male drives a gravid female through vegetation, the pair pressing close as eggs and milt are released simultaneously among plants or over the substrate.
The eggs are adhesive to weakly adhesive and fall among vegetation or settle to the bottom, where the spawning adults will eat them readily if given access. Spawning in the wild is likely tied to seasonal cues — temperature shifts and rainfall patterns associated with the highland wet season — though direct field observations for this species are not documented in the available literature.
Breeding
In the aquarium Devario sondhii is reported to spawn within approximately 24 hours when placed in a prepared breeding setup, and fry are said to reach sexual maturity in roughly three months — a fast reproductive cycle consistent with its small cyprinid biology. The standard approach for egg-scattering danios applies: a shallow tank with fine-leaved plants, spawning mops, or a mesh or marbled bottom to protect eggs from being eaten by the adults after spawning.
A conditioned group or selected pair is introduced; spawning typically occurs at first light. Adults should be removed promptly after spawning. Eggs hatch in two to three days at appropriate temperatures and the larvae become free-swimming shortly after, initially taking infusoria or similarly fine live foods before graduating to newly hatched brine shrimp and microworm. No parental care is given at any stage.
In the aquarium
Devario sondhii is an active, shoaling fish that should be kept in groups — a minimum of six individuals is advisable to maintain natural schooling behaviour and reduce individual stress. Its upland Myanmar origins suggest an affinity for cool, well-oxygenated water: a temperature range of 68–79 °F (68–79 °F) is recommended, with a pH between 6.0 and 7.5 and soft to moderately hard water matching the character of its Shan Plateau home pools.
A longer tank with open swimming space, some planting for structure and cover, and good surface agitation or filtration to maintain oxygen levels suits the species well. It is compatible with other peaceful, similarly sized fish that tolerate its active temperament. The fireline danio is not among the most commonly encountered Devario in the trade but is appreciated by hobbyists who seek out the less familiar members of the genus.
Conservation
Devario sondhii is assessed as Data Deficient (DD) on the IUCN Red List, with the assessment dated January 2010. The DD designation reflects the limited survey data available for this species and its restricted, apparently narrow range in the Ho Pong area of Myanmar's Shan Plateau, rather than a confident determination that it is either threatened or secure.
The highland wetland pools it occupies are potentially vulnerable to agricultural water extraction, drainage for cultivation, and general degradation of upland catchments — pressures that affect interior Myanmar wetlands broadly. The species' apparently restricted natural range (known from a single general locality) means that any significant habitat change in that area could affect the whole known population. Further field surveys to define its distribution, abundance, and the condition of its habitat would be needed to assign a more precise threat category.