Taxonomy & naming
Hemigrammus tupebas was described by Antônio Henrique Alves Esguícero and Mário César Cardoso de Castro in 2017. The description was published in Copeia, volume 105, issue 4, pages 753–764. The species is placed in Hemigrammus, one of the largest and most species-rich genera of Neotropical characiform fishes, which has traditionally been accommodated within the family Characidae. Recent phylogenomic work on characiform classification — including a broad analysis of Characidae and allied families — has evaluated the deep relationships within this hyper-diverse lineage, though Hemigrammus itself remains in Characidae under current usage.
The species is diagnosed relative to its nearest congeners by the combination of conical teeth in the premaxilla and dentary (rather than the tricuspid teeth found in Hemigrammus apiaka) and four longitudinal scale rows between the base of the dorsal fin and the lateral line (versus five in H. apiaka). These subtle but consistent characters are the principal basis on which H. tupebas was recognised as distinct.
The epithet tupebas is a toponym honouring the Tupebas, an indigenous ethnic group associated with the lower rio Solimões region including the rio Tefe drainage, which encompasses the type locality. ETYFish records this derivation directly from the original description.
Morphology
Hemigrammus tupebas is a small tetra with the body plan typical of the genus: slender to moderately compressed, with a fully scaled lateral line, the dorsal-fin origin above or slightly behind the mid-body, and an adipose fin present. Congeners in the genus commonly fall in the range of 0.5–1 in standard length, and H. tupebas is expected to be similar in scale, though precise maximum size data are sparse in the available literature.
The key diagnostic characters are dental: the teeth of the premaxilla and dentary are conical, a condition that separates H. tupebas from H. apiaka (which bears tricuspid teeth) and aligns it with a subset of Hemigrammus species bearing simple conical dentition. The count of four longitudinal scale rows between the dorsal-fin base and the lateral line provides a complementary meristic marker. Coloration in life has not been described in detail in the accessible literature; like many small Amazonian characids, it is likely silvery with subdued lateral markings.
Habitat
The type locality of Hemigrammus tupebas lies within the lower rio Solimões system of Amazonas state, Brazil, in the rio Tefe tributary. This is classic western Amazonian blackwater and whitewater country — a mosaic of seasonally flooded várzea, igapó gallery forest, and main-channel tributaries draining into the Solimões (upper Amazon) before it reaches Manaus.
Broad Hemigrammus habitat preferences, consistently documented across the genus in the Amazon Basin, are for shallow, calm marginal areas: densely vegetated banks, submerged leaf litter, submerged wood, and flooded forest margins. Water is typically soft and acidic, with pH values around 5.0–6.5 and temperatures in the range of 75–82 °F (75–82 °F), reflecting the tannin-stained blackwater conditions characteristic of many western Amazonian tributaries. No habitat data specific to H. tupebas beyond the type locality are available from the sources reviewed.
Feeding
No feeding data specific to Hemigrammus tupebas appear in the literature consulted. The genus as a whole is composed of opportunistic micro-predators and omnivores that feed on small invertebrates — insect larvae, microcrustaceans, and zooplankton — as well as algae and fine plant matter, typically taken in the water column and at the surface.
In the aquarium, congeners are routinely maintained on a varied diet of good-quality micro-pellets or crushed flake supplemented with small live and frozen foods such as Daphnia, baby brine shrimp, and micro-worms. Given H. tupebas's likely small size, appropriately small food items are essential. As with most small tetras, colour and condition benefit from a mixed diet rather than exclusively prepared foods.
Mating
No published mating behaviour data exist for Hemigrammus tupebas specifically. The genus follows the general characid reproductive pattern: egg-scattering open spawning with no parental care. Males typically become more intensely coloured and actively pursue females during spawning events, driving them into fine-leaved vegetation or other substrate where eggs are deposited and fertilised.
Adhesive or semi-adhesive eggs are scattered among fine-leaved aquatic plants or deposited into leaf litter and root tangles in the wild. Because the adults do not guard the eggs or fry, the eggs are left to develop unattended and are equally at risk of being eaten by the spawning adults themselves.
Breeding
No captive-breeding records for Hemigrammus tupebas are known from the sources reviewed, and it does not appear to have entered the aquarium trade in any quantity. Based on general Hemigrammus husbandry, breeding would be expected to follow the standard small-tetra protocol: soft, slightly acidic water (pH 5.5–6.5) at 77–81 °F (77–81 °F), a heavily planted spawning tank or one furnished with fine-leaved artificial mops, and conditioned adult pairs or trios.
Eggs in comparable congeners are small and adhesive, hatching in 24–48 hours depending on temperature, with fry becoming free-swimming a few days later. First foods for fry of species this size are typically infusoria or commercial liquid fry foods, followed by rotifers and newly hatched brine shrimp nauplii. Adults should be removed after spawning to prevent egg predation.
In the aquarium
Hemigrammus tupebas has not been documented in the aquarium hobby and is not known to be commercially available as of 2026. It was described from scientific specimens rather than from aquarium imports, and no care accounts appear in hobby literature.
Should it become available, husbandry for the genus would apply: a well-filtered, softwater aquarium with gentle flow, dark substrate, some floating plants or surface cover to diffuse light, and the warm temperatures of its Amazonian origins (75–82 °F / 75–82 °F). Small Hemigrammus are shoaling fish that should be kept in groups of six or more; they are peaceful community residents compatible with other small, soft-water tetras and dwarf cichlids. Their small size makes them incompatible with larger, predatory tankmates.
Conservation
Hemigrammus tupebas has not been assessed by the IUCN Red List as of the date of this article; its status is Not Evaluated (NE). As a species described only in 2017 from a restricted set of type specimens in the lower rio Solimões drainage, its distribution extent and population status remain unstudied.
The lower Solimões and its tributaries, including the rio Tefe catchment, face ongoing pressures from deforestation, agricultural expansion, and associated water-quality changes across the Brazilian Amazon. The true range of H. tupebas — whether it is genuinely restricted to the type locality or more widespread across the Solimões drainage — is unknown. Given the pace of description of new small Amazonian characids, many such species remain poorly surveyed even after their formal description, and formal IUCN assessment is likely years away.