Taxonomy & naming
Apareiodon davisi was described by the American ichthyologist Henry Weed Fowler in 1941, from material collected in the Rio Jaguaribe near Russas, Ceará, in northeastern Brazil. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) lists it as a currently valid species in the genus Apareiodon, family Parodontidae — the "scrapetooths" or "toothed headstanders," a small Neotropical family of algae-grazing characiforms distinguished by their distinctive scraping dentition.
Parodontidae sits apart from the better-known Serrasalmidae (piranhas, pacus, silver dollars) and Hemiodontidae (hemiodus) within Characiformes, though all three are loosely grouped here under the "Hemiodus & minor characins" umbrella as small-to-modest river characins that are not piranhas, pacus or silver dollars. Apareiodon is a moderately large genus of similar-looking, speckled, bottom-grazing species scattered across South American drainages, and A. davisi is one of the geographically restricted members, distinguished from its congeners by a combination of meristic counts and its specific river-basin distribution — details that fall outside what the available sources document for a general-audience account.
Morphology
FishBase records a maximum size for Apareiodon davisi of just 2.5 in standard length, making it one of the smaller characins covered in this atlas — a genuinely tiny river fish, not a scaled-down piranha or pacu. Like other Apareiodon species, it has an elongate, torpedo-shaped body suited to holding position in flowing water, and a small, subterminal mouth equipped with specialised scraping teeth used to rasp algae and biofilm from hard surfaces rather than to bite or shear flesh.
Detailed colouration, fin counts and other diagnostic morphology for this specific species are not documented in the sources available for this account; readers should treat any photograph offered as A. davisi with caution; small Apareiodon species are frequently confused with one another and are rarely photographed or catalogued outside taxonomic literature.
Habitat
Apareiodon davisi is known from the Jaguaribe and Paraíba river basins of northeastern Brazil, with its type locality at the Rio Jaguaribe near Russas, in the state of Ceará. FishBase lists it as a benthopelagic freshwater species, consistent with the genus's habit of holding near the bottom in flowing sections of river where algae and biofilm accumulate on rock, wood and submerged debris.
Detailed water chemistry data — temperature range, pH, hardness — is not available in the sources consulted for this account, and it should not be assumed to match the soft, acidic blackwater conditions often generalised for Amazonian characins; the Jaguaribe and Paraíba systems drain a markedly different, more seasonal northeastern Brazilian landscape. Data is sparse; prospective keepers or researchers should treat any specific water parameters offered for this species as inference from congeners rather than direct measurement.
Feeding
Apareiodon davisi is not directly documented for diet in the sources available, but its family and genus placement is informative: Parodontidae are specialised algae- and biofilm-grazers, using their scraping dentition to rasp periphyton from rock and wood surfaces in flowing water, and related Apareiodon species such as A. affinis are reported to combine that algae-scraping habit with some opportunistic feeding on small bottom-dwelling invertebrates.
On that basis A. davisi is best treated as a grazing omnivore leaning strongly toward algae and biofilm rather than a predatory or detritivorous feeder, but no stomach-content study specific to this species is cited in the available sources, so this should be read as an inference from its relatives rather than a confirmed account.
Mating
No courtship or spawning behaviour has been documented for Apareiodon davisi in the sources consulted for this account. The species does not appear in aquarium hobby literature, and no breeding records — in the wild or in captivity — were found. Data is sparse; nothing further can be stated responsibly.
Breeding
There are no known aquarium breeding records for Apareiodon davisi, and no wild reproductive biology has been documented in the sources available. Unlike the true piranhas of this atlas, which are established substrate-nest spawners bred commercially and in the hobby, or the pacus and Prochilodus, which are migratory farm-bred food fish, A. davisi has essentially no presence in aquaculture or aquarium literature at all — it should be treated as an unbred species on current evidence, not assigned a breeding mode by inference from other characins.
In the aquarium
Apareiodon davisi is not an established aquarium fish. No specific care data, tank recommendations or hobbyist accounts were found for this species in the sources consulted, and it does not appear to be present in the ornamental trade. Its very small adult size — under 2.5 in — and grazing habits suggest it would, in principle, suit a modest, well-oxygenated, flowing-water setup alongside other small river characins, but this is an inference from its genus and family rather than a documented recommendation.
Anyone encountering A. davisi in the trade (most likely mislabelled or mixed in with other small South American characins) should treat identification with real caution, since small Apareiodon species are easily confused, and should not assume care information for a better-known relative such as A. affinis transfers directly to this narrowly distributed, poorly documented species.
Conservation
Apareiodon davisi has not been formally assessed by the IUCN Red List and carries a status of Not Evaluated. Its known range — the Jaguaribe and Paraíba basins of northeastern Brazil — lies in a region under substantial and growing pressure from damming, water abstraction and the area's naturally seasonal, drought-prone hydrology, all of which are relevant long-term watch items for a narrowly distributed river endemic, even though no formal risk assessment exists to confirm or quantify that pressure for this species specifically.
Given the complete absence of an IUCN assessment and the sparse documentation available generally, this account deliberately says less rather than guessing at a conservation status or trend that has not actually been established for A. davisi.