Taxonomy & naming
Brachychalcinus reisi was formally described by Garcia-Ayala, Ohara, Pastana & Benine in 2017 in the journal Zootaxa (4362(4):564–574). The type locality is the upper rio Curuá — a tributary of the rio Iriri in the rio Xingu drainage — on the Serra do Cachimbo plateau in Pará State, Brazil. Eschmeyer's Catalog of Fishes (CAS) records the authority as Garcia-Ayala, Ohara, Pastana & Benine 2017, and the species epithet honours the ichthyologist Roberto Esser dos Reis for his significant contributions to the systematics of the subfamily Stethaprioninae.
The genus Brachychalcinus has historically been placed within the family Characidae. FishBase assigns the genus to the subfamily Stethaprioninae; various classifications treat that group at different hierarchical levels. At the time of its description, B. reisi was the first new Stethaprioninae species to be added to the genus since a comprehensive revisionary study published around 1987, highlighting the rarity of new material from this lineage. The species is distinguished from all congeners by the combination of conspicuous dark wavy longitudinal body stripes and a reduced count of 7–8 longitudinal scale rows between the dorsal-fin origin and the lateral line (vs. 8–12 in its congeners). It also differs from B. copei, B. parnaibae, and B. retrospina in possessing 9 branched dorsal-fin rays rather than 10.
Morphology
Brachychalcinus reisi reaches a maximum recorded standard length of 2.5 in. Like other members of the genus it is a moderately deep-bodied, laterally compressed characid. Meristic counts noted in the original description include 12 dorsal soft rays and 32–35 anal soft rays — the latter count being notably high and characteristic of the genus.
The species' most striking external feature is a series of dark, wavy longitudinal stripes that run across the entire body, a pattern not found in any congener. The reduced lateral scale-row count (7–8 between the dorsal-fin origin and the lateral line, vs. 8–12 in relatives) is a supporting diagnostic character. Additional details of head proportions and fin shape follow the general Brachychalcinus bauplan, though full morphometric data remain confined to the original description; no subsequent revision has expanded the species account.
Habitat
All confirmed records of Brachychalcinus reisi come from the upper rio Curuá, a tributary of the rio Iriri within the rio Xingu basin, on the Serra do Cachimbo plateau of Pará State, northern Brazil. This is an upland stream environment in the southern Amazon region — a landscape of cerrado-transition forest overlying ancient sandstone and quartzite tableland, producing clear, typically low-conductivity waters.
Specific microhabitat data for B. reisi in the field are sparse given the limited collecting effort in the type locality since its description. FishBase characterises it as a benthopelagic freshwater species, consistent with the foraging habits typical of the genus. The restricted, upland drainage position makes the population potentially vulnerable to any land-use change or hydrological alteration in the Serra do Cachimbo headwater zone.
Feeding
No published dietary analysis specific to Brachychalcinus reisi exists in the available literature. Members of Brachychalcinus more broadly are regarded as omnivores of the mid-water zone, feeding opportunistically on small invertebrates, algae, and plant matter consistent with the general characid guild.
In captivity, fish in this genus typically accept a wide range of prepared foods — quality flake, micro-pellets, and small frozen or live invertebrates such as Daphnia and Artemia nauplii. A varied diet is advisable to maintain condition. Because the species is rarely kept and no husbandry literature specific to B. reisi exists, dietary guidance must be extrapolated from congeners.
Mating
No direct observations of mating behaviour have been published for Brachychalcinus reisi. By analogy with other characids in the subfamily Stethaprioninae and the broader family, the species is presumed to be an egg-scatterer with no parental care, broadcasting adhesive or semi-adhesive eggs among fine-leaved vegetation or over the substrate during spawning events.
Sexual dimorphism, if any, has not been formally described in the literature for this species. Aquarists have not documented courtship behaviour in B. reisi, and the species remains essentially unknown in the hobby.
Breeding
No captive breeding records for Brachychalcinus reisi are available in the published or hobbyist literature. Based on the reproductive strategy typical of free-spawning characids — open-water or plant-associated egg scattering, adhesive eggs, and no parental investment — it is reasonable to assume a similar mode for this species, but this remains undocumented.
Breeders interested in this species would be working in largely uncharted territory. Soft, slightly acidic to neutral water matching the chemistry of the Serra do Cachimbo headwaters, fine-leaved spawning substrate, and separation of adults from eggs post-spawn would be a sensible starting framework extrapolated from related genera.
In the aquarium
Brachychalcinus reisi is essentially absent from the ornamental fish trade and is not a species encountered in the hobby. Its description in 2017 was based on scientific collection material; no commercial supply route exists, and dedicated hobbyist accounts are not available.
For any aquarist obtaining specimens through scientific or specialist channels, the general requirements of the Brachychalcinus genus provide the only guidance: a well-filtered aquarium with soft to moderately hard, neutral to slightly acidic water; subdued lighting over areas of planted cover; and a peaceful community appropriate to the fish's modest size (up to about 2.5 in SL). The species' patterning — the wavy longitudinal dark stripes — would likely make it visually distinctive in the tank. Its rarity and scientific significance argue for careful documentation of any captive behaviour observed.
Conservation
Brachychalcinus reisi has not been assessed by the IUCN Red List and carries a status of Not Evaluated (NE). The species is known only from the upper rio Curuá on the Serra do Cachimbo plateau in Pará, Brazil — a narrow endemic range that, while not currently subject to documented commercial collection pressure, renders the population inherently sensitive to habitat disturbance.
The Serra do Cachimbo region sits within the broader Amazon biome and is subject to ongoing deforestation pressure from agricultural expansion and road development in Pará State. Because no population size estimate, trend data, or formal range assessment exists for B. reisi, the species' true conservation position cannot be evaluated. A formal IUCN assessment incorporating survey data from the type locality would be a valuable step in understanding whether the restricted range represents a genuine vulnerability.