Taxonomy & naming
Apareiodon cavalcante was described in 2003 by Carla Pavanelli and Heraldo Britski in Copeia, alongside two other new Apareiodon species, as part of a revision showing that the diversity of the family Parodontidae in the Rio Tocantins-Araguaia basin had been underestimated. It belongs to the genus Apareiodon (Eigenmann, 1916), a member of Parodontidae — the parodontids or "darter-characins," a small family of characiform fishes distinct from the pacus and true piranhas of Serrasalmidae despite sharing the broader order Characiformes.
The genus Apareiodon is characterised by an elongated, laterally compressed body, a small subterminal mouth adapted for scraping algae and biofilm from rocks and wood, and a distinctive dentition of close-set, multicuspid teeth restricted to the premaxilla. As with many recently described, range-restricted parodontids, Apareiodon cavalcante has not been reassessed or revised since its original description, and no synonyms or alternate combinations are documented in the sources available for this article.
Morphology
Apareiodon cavalcante is a small fish, with a maximum recorded standard length of just 2 in — modest even by the standards of a genus that runs small throughout. The body is elongated with an oval cross-section, the classic darter-characin silhouette built for holding position and grazing in flowing headwater streams rather than for open-water shoaling.
Fin counts recorded in the description include 10-11 soft rays in the dorsal fin and 7-8 soft rays in the anal fin. The species carries a midlateral stripe formed by a line of dark chromatophores running along the flank, a pattern shared with a number of its Apareiodon relatives and one of the characters used to distinguish it from its Tocantins-Araguaia congeners. Beyond these description-level details, no further morphological or colour-pattern data is available in the sources consulted for this article.
Habitat
Apareiodon cavalcante is known from headwater streams of the Rio Tocantins-Araguaia basin in Brazil, one of three new Apareiodon species Pavanelli and Britski described from that system in 2003. Like other members of its genus, it is presumed to occupy flowing, well-oxygenated stream habitat where it grazes algae and biofilm from submerged rocks and wood — the ecological role the genus's scraping dentition is built for — though no habitat-specific field data beyond the original description is available in the sources consulted.
General parodontid care literature places the family in water around pH 6.0-7.5 and 72–79 °F, consistent with the clear, moving headwater streams the group typically inhabits, but these figures come from Parodontidae generally rather than from field measurements taken specifically for Apareiodon cavalcante. Data on this species' precise range extent, elevation and specific stream conditions is sparse.
Feeding
Apareiodon cavalcante has not been the subject of a dedicated dietary study, but its genus-typical dentition — a row of close-set, multicuspid teeth on a small, subterminal, downward-facing mouth — is built for scraping algae, biofilm and associated microinvertebrates from rock and wood surfaces in flowing water, the standard feeding mode for Apareiodon and the wider family Parodontidae. General accounts of parodontid care describe a diet supplemented with tiny invertebrates such as insect larvae and small crustaceans picked up while grazing.
No aquarium feeding record exists for this species specifically. Any captive diet would reasonably follow the genus pattern: a base of algae wafers or spirulina-based foods to match its grazing habit, supplemented with small live or frozen invertebrate foods, but this is inference from genus biology rather than a documented account for Apareiodon cavalcante.
Mating
No courtship or spawning behaviour has been documented for Apareiodon cavalcante. Sexual dimorphism is not described in the original species account, and no source consulted for this article reports a way to visually distinguish males from females in this species. Data is sparse to the point that nothing further can be responsibly stated.
Breeding
There is no confirmed aquarium or field breeding record for Apareiodon cavalcante. General parodontid aquarium literature describes the family as egg-scatterers with no parental care, consistent with the reproductive mode reported across most small stream-dwelling characiforms, but this is a genus-level inference rather than a documented account for this species — no source reviewed confirms this species has been spawned in captivity or that its reproductive behaviour has been observed in the wild. This account should be read as: breeding mode unconfirmed, likely egg-scattering by genus pattern, but not established for Apareiodon cavalcante specifically.
In the aquarium
Apareiodon cavalcante has no established presence in the aquarium hobby, and no keeper accounts, import records or care guides specific to this species were found. It is not a food fish or commercial aquaculture species either, unlike many of its larger Serrasalmidae relatives in this atlas group.
Were it ever to appear in the trade, its small adult size (around 2 in SL) and grazing habit suggest it would suit a modest, well-oxygenated, flow-rich aquarium set up to mimic a clearwater stream, with algae growth encouraged as a food source and other small, peaceable stream fish as tankmates — the general approach hobbyists use for other small Apareiodon species. That said, this is speculative extrapolation from genus biology, not a documented care record, and this species should not be assumed available or suitable for the hobby on the strength of this article alone.
Conservation
Apareiodon cavalcante has not been formally assessed by the IUCN Red List and currently carries no conservation status — it is Not Evaluated. This is unsurprising for a small, recently described (2003) headwater species known from a single river basin, where formal assessment work has not yet reached many range-restricted Neotropical stream fishes.
No specific threats to this species are documented in the sources consulted. As with many small-range Tocantins-Araguaia basin endemics, plausible long-term pressures would include damming, deforestation-linked sedimentation and water-quality change affecting headwater streams in the basin, but no source reviewed for this article ties a specific threat to Apareiodon cavalcante, so none is asserted here beyond this general watch-item context.