Taxonomy & naming
Planaltina myersi was described by James E. Böhlke in 1954. The type locality is the córrego Sarandi, a tributary of the ribeirão Mestre-d'Armas, itself a tributary of the rio Corumbá in the rio Paranaíba drainage — upper rio Paraná basin — near what is now the Federal District of Brasília, Brazil. Eschmeyer's Catalog of Fishes recognises the valid name as Planaltina myersi Böhlke, 1954, in the family Characidae.
The genus Planaltina is a small characid lineage endemic to the highland interior of Brazil, associated with the Cerrado plateau — the word planalto means 'high plain' or 'plateau' in Portuguese, and the name directly references this landscape. Molecular phylogenetic work published in PLOS ONE (2018) has re-examined the relationships within Planaltina, confirming that P. myersi is diagnosable from congeners by morphological characters including the single, very elongate scale that forms the dorsal margin of the caudal pouch opening, a character absent or differently developed in related species.
The species epithet myersi is a patronym, almost certainly honouring the eminent American ichthyologist George Sprague Myers (1905–1985), who made foundational contributions to Neotropical freshwater ichthyology during the mid-twentieth century and whom Böhlke's contemporaries frequently honoured in new descriptions.
Morphology
Planaltina myersi is a small, slender characid. Published measurements from molecular-phylogenetic surveys record females from the rio Paranaíba population at up to 1.5 in standard length (SL) and males at up to 1.5 in SL — effectively the same maximum size between sexes in that drainage. Fish from the rio São Francisco basin reach slightly larger sizes, with females recorded to 1.5 in SL; a male from the same drainage measured 1 in SL, suggesting that São Francisco males may be smaller relative to females than in the Paranaíba population, though sample sizes in the literature are limited.
The body is fusiform and laterally compressed in the typical characid fashion, with the rounded profile and relatively large eyes characteristic of small, visually oriented stream fishes. Colouration in life is not elaborately documented in the available literature; the species lacks the vivid pigmentation of popular aquarium characids and is described primarily on meristic and morphological grounds. The diagnostic feature noted in the literature is the single, markedly elongate scale at the dorsal margin of the caudal pouch opening, which distinguishes it from congeners. As with many small Cerrado characids, sexually mature females are likely deeper-bodied than males when gravid, though specific dimorphism data are sparse for this species.
Habitat
Planaltina myersi inhabits the headwater streams and small tributaries of the Brazilian Cerrado, occupying the upper rio Paraná and upper rio São Francisco river basins in Brazil's interior highlands. The type locality, córrego Sarandi, is a small, shaded stream draining into the ribeirão Mestre-d'Armas and thence to the rio Corumbá and rio Paranaíba — the kind of clear, often shallow, seasonally variable watercourse that characterises the gallery-forest creeks of the Cerrado savanna.
The Cerrado's headwater streams are generally well-oxygenated and clear, with substrates of sand or fine gravel, often shaded by riparian vegetation. Water chemistry in undisturbed Cerrado streams tends toward soft and mildly acidic to circumneutral conditions, reflecting the deep weathered soils of the plateau, though local geology can push values somewhat. Seasonal fluctuation in flow, temperature, and turbidity is a feature of these systems. The species' occurrence across two distinct major drainages — Paraná and São Francisco — separated by the watershed divide on the Planalto Central implies some tolerance for the variable conditions encountered in different headwater catchments.
Feeding
Specific dietary data for Planaltina myersi in the wild have not been published in the sources available. Based on its small size, slender build, and the general ecology of small characids in Cerrado gallery-forest streams, it is presumed to feed opportunistically on small invertebrates — microcrustaceans, aquatic insect larvae, and terrestrial invertebrates falling onto the water surface — together with any available algae or organic detritus. This generalist insectivore–omnivore strategy is typical of comparably sized characids in similar habitats across the Neotropics.
In an aquarium context, small live or frozen foods such as Daphnia, micro-worms, and newly hatched brine shrimp would address the invertebrate component of the natural diet and help maintain condition in captive specimens. Fine-particle prepared foods are likely acceptable. As a small and presumably active fish in a structurally complex environment, it would benefit from multiple small feedings rather than a single large daily meal.
Mating
No dedicated behavioural studies of mating in Planaltina myersi appear in the published literature. The species is expected to follow the open-water egg-scattering strategy typical of small characids in its lineage: sexually motivated adults scatter adhesive or semi-adhesive eggs among fine-leaved aquatic plants or submerged vegetation, without nest construction or territory defence, and with no parental investment beyond the spawning act itself.
In Cerrado streams, spawning activity in small characids is often correlated with the onset of the wet season, when rising water levels, increased food availability, and longer photoperiod cue reproductive readiness. Whether P. myersi shows a pronounced seasonal breeding pulse or spawns more continuously under stable conditions is not documented. Males of small characids often develop breeding tubercles on the snout or pectoral fin rays when in reproductive condition, though whether this occurs in P. myersi specifically is unrecorded in the available sources.
Breeding
Published breeding accounts for Planaltina myersi in captivity are absent from the literature available for this species. By analogy with small, egg-scattering characids of similar ecology, spawning would likely involve the scattering of small adhesive eggs over fine-leaved plants or spawning mops, with incubation at ambient water temperature and no parental care — adults should be considered likely to consume eggs and should be separated from the spawning substrate promptly.
Given the Cerrado stream environment of the type locality — soft to moderately soft, circumneutral water, modest temperatures — conditioning water for captive breeding attempts would logically follow those parameters. Fry of small characids typically require very fine first foods (infusoria, rotifers, or commercial micro-fry preparations) immediately after the yolk sac is absorbed, graduating to newly hatched brine shrimp nauplii as they grow. Detailed captive-breeding notes for this species remain to be published.
In the aquarium
Planaltina myersi is essentially unknown as an aquarium fish; it does not appear in hobby trade catalogues or husbandry guides and is encountered only in the ichthyological literature. Should specimens become available — through collection associated with scientific surveys or specialist importation — the appropriate approach would be to treat it as one would any small, delicate Cerrado characid: a well-planted aquarium with soft, lightly acidic to neutral water, subdued lighting, and peaceful tankmates of comparable size.
The species' small maximum size (under 1.5 in SL) means it is suitable for modest-sized aquaria, but its rarity in the trade means that practical husbandry notes are almost entirely absent. Any aquarist keeping this species would be contributing genuinely novel information to the hobby's knowledge base. Water quality stability and a varied diet of small live and frozen invertebrate foods would be the starting priorities.
Conservation
Planaltina myersi is assessed as Least Concern (LC) on the IUCN Red List. The assessment reflects the species' presence across a reasonably broad area spanning both the upper rio Paraná and upper rio São Francisco basins in the Brazilian interior, and the absence of evidence of rapid population decline sufficient to trigger a threatened category.
Nonetheless, the Cerrado biome — the world's most biodiverse savanna — has suffered severe and ongoing habitat loss, with estimates suggesting that well over half of its original extent has been converted to agriculture, principally soybean farming and cattle pasture. Headwater streams, the preferred habitat of Planaltina myersi, are among the most degraded components of the Cerrado landscape: channelisation, siltation from agricultural runoff, removal of riparian gallery forest, and water abstraction for irrigation all degrade the small, clear streams these fishes depend on. The LC assessment should not be read as indicating that the species faces no threats, but rather that its current distribution and abundance have not yet declined to thresholds that trigger listing.