Taxonomy & naming
Hemigrammus durbinae was described by Renata P. Ota, Flávio C.T. Lima, and Carla S. Pavanelli in 2015, in a paper published in Zootaxa (3948(2): 218–232). The type series was collected from the middle rio Solimões/Amazonas, tributaries of the upper and middle rio Madeira, and the rio Paraná-Paraguai drainage. The valid name as governed by Eschmeyer's Catalog of Fishes is Hemigrammus durbinae Ota, Lima & Pavanelli, 2015.
The species belongs to the large and species-rich genus Hemigrammus, a core group within the family Characidae whose members are found throughout tropical South America and are among the most familiar aquarium fishes in the world. Within this genus, H. durbinae is most similar to H. marginatus, from which it is distinguished by the conspicuous dark patches on the caudal-fin lobes (occupying most of each lobe, except the tips), two dark narrow stripes along the anal-fin base, and a small number of pored lateral-line scales (5–8), among other meristic characters.
Morphology
Hemigrammus durbinae is a small, slender characin with a maximum recorded standard length of 1 in. The body is laterally compressed in the typical Hemigrammus form, with a somewhat elongate profile and a forked caudal fin. Meristic data from the original description give 10–11 dorsal soft rays, 20–25 anal soft rays, and 32–34 vertebrae.
The species' most distinctive feature is its caudal-fin colour pattern: each lobe of the caudal fin carries a bold dark pigment patch that covers most of the lobe, fading only toward the outer tips — a mark that functions as the primary character for distinguishing H. durbinae from related species. Two dark narrow stripes run along the base of the anal fin. The lateral line is incomplete, with only 5–8 pored scales. A humeral spot, present in some Hemigrammus species, is absent in H. durbinae.
Habitat
Hemigrammus durbinae inhabits freshwater lowland environments across a broad range of the central South American river system. It is recorded from large floodplain lakes associated with the middle and upper rio Madeira, the lower rio Purus, the middle rio Solimões and main-stem Amazonas, and the lower rio Tapajós in Brazil, as well as from the rio Paraguai and rio Paraná drainages extending into Paraguay. FishBase characterises it as benthopelagic and tropical, consistent with a floodplain lake lifestyle in slow or still waters of the várzea.
The distribution across several major drainages is notable for a species described as recently as 2015, and likely reflects both genuine broad occurrence and the relatively late scrutiny given to small, cryptic Hemigrammus. Its stomach contents indicate that it feeds at or near the water surface in habitats where terrestrial insects fall into the water, a pattern typical of floodplain fish that exploit the forest-water interface seasonally.
Feeding
Stomach-content data from wild specimens show that terrestrial insects form the dominant component of the diet of Hemigrammus durbinae — a pattern common among small characins inhabiting floodplain lakes and forest-edge waters, where insects falling from overhanging vegetation or flooded forest floor are an abundant and seasonally reliable food source. The species is likely an opportunistic surface and mid-water feeder rather than a specialist.
In the aquarium, closely related Hemigrammus species of similar size do well on small live and frozen invertebrates — Daphnia, brine shrimp, micro-worms, and finely crushed insect-based flake foods — supplemented with high-quality small-particle prepared diets. A varied diet that includes live or frozen invertebrates would best match the natural feeding habits suggested by the field data.
Mating
No specific mating observations have been published for Hemigrammus durbinae. Based on the biology of the genus, H. durbinae is expected to be an open, egg-scattering spawner in the characin mould: no pair bond, no territory, and no parental investment beyond the spawning act itself.
In related Hemigrammus species, spawning typically involves a brief, active pursuit and embrace among fine-leaved aquatic vegetation or plant litter, with adhesive or semi-adhesive eggs scattered across the substrate and plants. Males often display lateral flashing to prospective females before spawning. In floodplain environments, spawning activity in many characins is triggered by seasonal cues — rising water levels, temperature shifts, and increased food supply — though the precise cues for H. durbinae are undocumented.
Breeding
No captive breeding records for Hemigrammus durbinae have been published, and the species is not currently established in the aquarium hobby. Based on genus-level biology, it would be expected to breed after the typical Hemigrammus pattern: egg-scattering among fine-leaved plants or over a gravel substrate, adhesive eggs, no parental care, and adults that will consume eggs and newly hatched fry if not removed.
Incubation in related species at tropical temperatures typically spans 24–48 hours, with free-swimming fry appearing within a further day or two. Fry are small and require infusoria or commercially prepared liquid fry foods in early stages before progressing to newly hatched brine shrimp. Given the species' size — under 1 in — any breeding setup would need to be scaled accordingly, with very fine spawning media and careful attention to water quality during the fry stage.
In the aquarium
Hemigrammus durbinae is not an established aquarium fish, and specimens are unlikely to be encountered in the trade under this name. Its small size (under 1 in SL), peaceful characin temperament, and tropical freshwater habitat suggest it would be suited to a nano or species tank, or a community of small peaceful fishes in soft, warm, slightly acidic to neutral water — consistent with the soft, warm lowland Amazonian and Pantanal waters it inhabits in the wild.
Should specimens become available, care would likely follow the well-documented pattern of other small Hemigrammus: a planted aquarium with subdued lighting and a dark substrate to enhance coloration, gentle filtration, water temperatures in the mid-to-upper 20s Celsius, slightly soft and acidic to neutral pH, and a diet of small live and frozen invertebrates supplemented with prepared foods. The bold caudal-fin markings would likely show best against a dark background and in calm water.
Conservation
Hemigrammus durbinae has not been assessed by the IUCN Red List and carries no formal conservation status. As a species described in 2015 from multiple major river basins in Brazil and Paraguay, it is not considered threatened at present, and its documented occurrence across several large drainage systems — the Madeira, Purus, Solimões/Amazonas, Tapajós, Paraguai, and Paraná — suggests a range broad enough to buffer localised pressures.
The species inhabits floodplain lakes and lowland river systems, habitats that face ongoing threats from deforestation, agricultural run-off, hydroelectric dam construction, and altered flood regimes across South America. None of these pressures has been assessed specifically for H. durbinae, and detailed population data are lacking. Continued inventory work on small characins in these river systems will be important for understanding whether the apparent broad range reflects genuine abundance or patchy occurrence that was missed prior to formal description.