Taxonomy & naming
Rhinopetitia myersi was described by Jacques Géry in 1964 and simultaneously became the type species of the new genus Rhinopetitia, which Géry erected to accommodate it. The valid name is recorded as Rhinopetitia myersi Géry, 1964 in Eschmeyer's Catalog of Fishes; because the species was described directly in Rhinopetitia, no parenthetical authority is used.
For several decades Rhinopetitia remained monotypic, known only from the original material collected in the Rio Araguaia system. A major systematic revision published in Zootaxa in 2019 (Netto-Ferreira et al.) redescribed R. myersi from modern specimens and expanded the genus to five species, with the four newly described forms from the Tocantins, Tapajós, and Xingu drainages. The revision placed Rhinopetitia within the subfamily Stevardiinae of the family Characidae, and identified a suite of characters — including reduced, fewer gill rakers — that diagnose the genus within that diverse subtropical and tropical South American clade.
Morphology
Rhinopetitia myersi is a small, slender characid reaching a maximum recorded standard length of 1 in. Like other stevardiine characids it has the typical compressed, fusiform body plan of a small stream tetra, with the modest adipose fin characteristic of the family. FishBase records a trophic level of approximately 2.9, consistent with feeding low in the food web on small invertebrates and organic detritus.
Detailed morphological information for R. myersi as a living aquarium subject remains sparse in the published and hobby literature. The 2019 Netto-Ferreira et al. revision characterised the genus by rudimentary and reduced gill rakers, distinguishing it from related stevardiines, but colour pattern and soft-tissue details of the living fish are not widely documented outside the original and revision literature. It is a small, unassuming fish in overall appearance; no common name has become established in either the scientific or the hobby community.
Habitat
Rhinopetitia myersi is endemic to the Rio Araguaia drainage in Brazil, with the original type locality in the Ilha do Bananal area of what is now the state of Tocantins. The Ilha do Bananal is the world's largest fluvial island, formed by two channels of the Araguaia, and hosts a range of seasonally inundated habitats including gallery forest streams, flooded savannahs, and backwater channels with dense marginal vegetation.
The Araguaia–Tocantins system drains the central Brazilian cerrado and transitions into Amazonian forest in the north. Stream habitats in this region typically offer warm, soft, slightly acidic to near-neutral water with abundant leaf litter and submerged woody debris. The 2019 revision confirmed occurrence of the genus across the Araguaia, Tocantins, Tapajós, and Xingu basins, though R. myersi itself is currently known primarily from Araguaia records. Specific water-chemistry data from its precise collection sites have not been widely published.
Feeding
FishBase records Rhinopetitia myersi as a benthopelagic species with a trophic level of 2.9, placing it among lower-level consumers that subsist mainly on small invertebrates, microcrustaceans, zooplankton, and organic detritus — the typical feeding guild of small characids in South American streams.
No detailed dietary studies specific to this species appear in the accessible literature. By analogy with ecologically similar small stevardiine tetras from the same river system, it likely forages in the lower and mid-water column over sandy or leaf-littered substrates, exploiting whatever small prey items are seasonally available. In an aquarium setting, small live and frozen foods such as microworms, Daphnia, and baby brine shrimp would be expected to be accepted readily, along with suitably fine prepared foods.
Mating
No published mating observations specific to Rhinopetitia myersi are available in the accessible scientific or hobby literature. By analogy with other small stevardiine and characid tetras from similar South American stream habitats, the species is presumed to follow the characteristic egg-scattering strategy of the family: brief courtship chases, with pairs or groups spawning among fine-leaved aquatic plants or submerged roots, depositing small adhesive eggs that sink or attach loosely to vegetation.
Sexual dimorphism, if present, has not been described in available sources. Spawning seasonality in wild populations would likely be tied to the pronounced wet-dry cycle of the cerrado Araguaia region, with peak reproductive activity coinciding with rising water levels at the onset of the wet season, when flooded marginal habitat and food availability expand dramatically. This is speculative, as no field reproductive data have been published for this species.
Breeding
Rhinopetitia myersi has not been reported as bred in captivity in any accessible hobby or scientific source. Given the species' near-absence from the ornamental fish trade and its restricted wild range, captive stocks almost certainly do not exist outside of specialist Brazilian research collections.
Should the species ever become available to aquarists, a breeding approach suited to small, subtropical stevardiine characids would be the logical starting point: a dedicated breeding tank with fine-leaved plants or spawning mops, soft to moderately hard slightly acidic water, and separation of adults after spawning to prevent egg predation. The adhesive eggs of related genera typically hatch within two to three days at warm temperatures, with fry requiring very fine first foods. These are inferences from the broader family pattern — no species-specific breeding data are documented.
In the aquarium
Rhinopetitia myersi is essentially unknown in the ornamental fish trade. The species has not been commercially collected or bred at any scale, and no established husbandry literature exists for it. Hobbyists are unlikely to encounter it outside of rare wild-caught imports or specimens obtained through specialist scientific exchange.
Were it to become available, the husbandry baseline for small stevardiine tetras from Brazilian cerrado streams would apply: a well-filtered, well-planted aquarium, warm soft to slightly acidic water in the range typical of central Brazilian drainages, peaceful tankmates no larger than the fish itself, and a varied diet of small live, frozen, and prepared foods. Its 1 in adult size makes it a candidate for nano or planted aquaria, but its scarcity means that such husbandry guidance remains entirely theoretical at present.
Conservation
Rhinopetitia myersi is assessed as Data Deficient (DD) by the IUCN Red List, based on an evaluation completed on 7 November 2018. The Data Deficient designation reflects the absence of adequate distribution and population data to make a reliable determination of extinction risk — not an assurance of security. A species endemic to a defined stretch of one river drainage, with sparse survey records and no known trade population, may face pressures that simply have not been documented.
The Araguaia basin and the Ilha do Bananal region have experienced substantial land-use change associated with agricultural expansion in the Brazilian cerrado, including wetland drainage, sedimentation from cattle grazing, and altered river hydrology. The 2019 Netto-Ferreira et al. revision clarified that Rhinopetitia comprises five species spread across four river systems rather than a single species, which may indicate that individual species have smaller effective ranges than previously assumed. Renewed field surveys targeting the genus across its revised range would be necessary to move any of these species beyond a Data Deficient assessment.