Taxonomy & naming
Hyphessobrycon mapinguari was formally described in 2025 by Pastana, Dutra, Ohara, Teixeira, and Menezes in Ichthyology & Herpetology 113(2):301–312. The holotype is MZUSP 130000, a male measuring 1.5 in standard length, collected from the Rio dos Couros, a tributary of the Rio Acari in the Rio Madeira drainage, near Apuí, Amazonas, Brazil. Eschmeyer's Catalog of Fishes (Catalog of Fishes) is the authority for the valid name, which stands as Hyphessobrycon mapinguari Pastana, Dutra, Ohara, Teixeira & Menezes, 2025.
The genus Hyphessobrycon Durbin, 1908 is one of the largest and most species-rich genera in the order Characiformes. A 2024 phylogenomic study reassigned many members of the traditional family Characidae — including Hyphessobrycon — to a revised family Acestrorhamphidae; FishBase now lists the species under Acestrorhamphidae. The top-level family field on this site follows the currently most widely applied catalogue placement; the broader systematic context is discussed here for transparency.
The species epithet mapinguari refers to the Mapinguari, a fearsome creature of Amazonian indigenous oral tradition — a giant, ground-sloth-like forest guardian. The choice reflects both a sense of place and an implicit conservation statement: the type locality in the Apuí region of Amazonas sits within one of the most heavily deforested stretches of the Brazilian Amazon.
Morphology
H. mapinguari is a small tetra reaching a maximum of approximately 1.5 in standard length in males. The body plan is that of a typical small Hyphessobrycon: laterally compressed, moderately deep, and fusiform, with the proportions varying subtly between the sexes.
The species is strongly sexually dichromatic. Adult males are red to orange across much of the body, with dark pigmentation concentrated in the dorsal-fin rays and interradial membranes — a conspicuous black blotch in the dorsal fin that contrasts sharply against the warm body colour. The dorsal-fin rays are elongated in mature males, producing a flagging display structure absent in females and immatures. Females and juveniles are pale yellow with muted markings. Both sexes lack the dark caudal-peduncle blotch present in related species, which is one of the meristic characters used in the original description to distinguish H. mapinguari from congeners. The inner premaxilla series carries six or seven teeth; dorsal soft rays number 8–9 and anal soft rays 23–27. Adult males lack the fin hooks reported in some other Hyphessobrycon species.
Habitat
The type locality is the Rio dos Couros, a tributary of the Rio Acari within the Rio Madeira basin near the municipality of Apuí in southern Amazonas state, Brazil. The Rio Madeira is the Amazon's largest right-bank tributary, and the Apuí region represents one of its upper drainages in a zone of extraordinary, and ongoing, deforestation.
FishBase characterises the species as inhabiting streams with slow-flowing, clear water and minimal riparian vegetation, specifically noting marginal grasses rather than the dense overhanging forest cover typical of more intact Amazonian streams. This riparian simplification is consistent with the heavily impacted landscape around the type locality. The species is described as benthopelagic — associated with the lower water column and substrate — in freshwater tropical environments. No precise water-chemistry data for the type locality are published in the available sources, so temperature and pH ranges cannot be stated with confidence.
Feeding
No dedicated dietary study of H. mapinguari has been published. As a small Hyphessobrycon in a stream environment, it is reasonable to infer — consistent with the broader genus — an opportunistic invertivore diet: small aquatic insects, microcrustaceans, worms, and organic detritus, supplemented by whatever surface-fallen prey enters the stream.
In the aquarium, Hyphessobrycon species of comparable size are generally undemanding feeders that accept quality micro-pellets, finely crushed flake, and small live or frozen foods such as Artemia nauplii, micro-worms, and Daphnia. A varied diet supports the best colouration in the males.
Mating
H. mapinguari has not been observed spawning in the wild or described in any published breeding account. Based on the family-level biology of Hyphessobrycon and its immediate relatives, the species is expected to be an egg-scattering open spawner: males court females with fin-flaring displays, driving them into fine-leaved vegetation or other dense cover where adhesive eggs are deposited.
The pronounced sexual dichromatism — and particularly the elongated dorsal-fin rays and vivid red-orange colouration of males — suggests that male display plays a significant role in mate choice or male–male competition. The absence of fin hooks in adult males, noted in the original description, distinguishes this species from those Hyphessobrycon in which hooks are used in physical male–male contact.
Breeding
No captive breeding records for H. mapinguari have been published as of 2026. The species was only described in 2025 and has not, to our knowledge, entered the mainstream aquarium trade.
By analogy with other small Hyphessobrycon, aquarists who obtain specimens should expect egg-scattering over fine-leaved plants or synthetic spawning mops, with the adults showing no parental care and actively eating their own eggs if left in the breeding tank. A separate, well-planted or mop-furnished breeding vessel, slightly warmer water to trigger spawning, and removal of adults after eggs are laid would be the standard approach. Fry are likely very small at hatching and would require fine first foods — infusoria or commercial liquid fry food — before being weaned onto Artemia nauplii.
In the aquarium
H. mapinguari is unlikely to be available in the hobby in the near term; it was described in 2025 and there are no known commercial imports or breeding programmes as of mid-2026. Aquarists who encounter it should treat it as a specialist species.
If kept, standard small-tetra husbandry applies: a well-planted aquarium with soft, slightly acidic to neutral water, subdued or dappled lighting, and a peaceful community of similarly sized fish. The vivid male colouration suggests it would be visually rewarding in a species tank or a biotope aquarium representing the Rio Madeira drainage. Given the species' origin in impacted habitat with marginal riparian cover, it may prove more tolerant of modest water parameters than pristine soft-water specialists — but this is inference, not confirmed data.
Conservation
H. mapinguari has not been assessed on the IUCN Red List as of 2026 — it was only described in 2025 and formal assessments take time. The original description, however, notes that the type locality in the Apuí region of Amazonas lies within one of the most severely deforested zones of the Brazilian Amazon, a region the authors characterise as greatly impacted. The Rio Madeira basin has experienced rapid and extensive land-use change driven by agriculture, cattle ranching, and infrastructure development.
A stream-dwelling tetra with what appears to be a localised distribution in already-disturbed habitat faces real, if as yet unquantified, risk. The authors' choice to name the species after the Mapinguari — a mythic forest guardian — reads as a deliberate act of attention-drawing: the region is under pressure, and the species may be too. Until a formal IUCN assessment is completed, its conservation status should be treated as unknown but potentially precarious.