Taxonomy & naming
Apareiodon tigrinus was described by Carla Simone Pavanelli and Heraldo Antonio Britski in 2003, in a paper in the journal Copeia titled "Apareiodon (Eigenmann, 1916) (Teleostei: Characiformes) from the Tocantins-Araguaia Basin," which erected three new species in the genus from headwater streams of that Brazilian river system. It belongs to the family Parodontidae — the scrapetooths — a small group of Neotropical characiform fishes distinguished from the piranhas, pacus and silver dollars of Serrasalmidae by their specialised, spatulate, close-set teeth adapted for scraping algae and biofilm from rocks and wood in current.
The genus Apareiodon currently holds several dozen species distributed across South American river systems, many of them, like A. tigrinus, narrow-range headwater endemics described only in the last few decades. Full taxonomic detail on A. tigrinus — its precise diagnostic characters and type locality — sits behind the paywalled original description; the species has not yet accumulated the secondary literature, FishBase account or common name that better-known aquarium characins have.
Morphology
As a member of Parodontidae, Apareiodon tigrinus can be expected to share the family's general body plan: a slender, fusiform body, a subterminal, downturned mouth armed with the closely packed, blade-like teeth used for scraping periphyton, and paired fins suited to holding station against current on stream substrate. The species epithet "tigrinus" (tiger-striped) points to a banded or blotched patterning, though a precise, sourced description of its colouration and maximum size is not available in the cache used for this article — the original description would hold those details, but they are not accessible here.
Given the data gap, no maximum length figure is asserted for this species. Congeners in the genus are uniformly small stream fish, typically well under 6 in, and there is no reason from the available sources to expect A. tigrinus to differ substantially, but this article does not state a specific size in the absence of a documented figure.
Habitat
Apareiodon tigrinus is known from headwater streams of the Tocantins-Araguaia Basin in Brazil, a large river system draining central and northern Brazil to the Amazon's eastern margin. Parodontids as a family are specialists of fast-flowing, well-oxygenated water — rapids, riffles and rocky or pebble-and-leaf-litter stream beds — rather than the sluggish floodplain lakes and backwaters that many other Neotropical characins favour, and there is no indication in the sources that A. tigrinus departs from that pattern.
A closely related congener, A. affinis, is documented tolerating roughly 61–82 °F with a nominal preference around 72–79 °F in fast, oxygen-rich water over pebble and leaf substrate; this is offered here only as a plausible guide for a related species in the same genus, not as a measured figure for A. tigrinus itself, whose specific water chemistry has not been located in the sources reviewed.
Feeding
Parodontidae are periphyton grazers: their scraping dentition is built to rasp algae, biofilm and associated microfauna from submerged rock and wood surfaces in current, and the family is generally treated as herbivore-detritivore in diet. No stomach-content or diet study specific to Apareiodon tigrinus was found in the sources used here, but this feeding mode is a well-established family trait shared across the genus, including the related Tocantins-Araguaia species described alongside it.
In practical terms this makes A. tigrinus, and Apareiodon generally, unlike the omnivorous-to-predatory reputation of piranhas or the fruit-and-seed diet of larger pacus — it is a grazer of the biofilm layer, a role more comparable to an otocinclus or a plecostomus than to its more famous serrasalmid relatives.
Mating
No courtship or spawning behaviour has been documented for Apareiodon tigrinus in the sources reviewed for this article. The species was described from museum specimens collected in headwater surveys rather than from long-term field or aquarium observation, and reproductive biology for most Apareiodon species remains essentially unstudied.
Breeding
There is no documented breeding record for Apareiodon tigrinus, in the wild or in captivity, in the sources available for this article. Unlike the substrate-nesting true piranhas or the farmed, hormone-induced spawning of commercial pacus and prochilodontid migrators, this is a narrow-range headwater endemic with essentially no aquarium trade presence and no known captive-breeding history to report. Rather than assign a breeding mode by inference from more familiar characins, this account states plainly that the species' reproductive biology is unknown from available sources.
In the aquarium
Apareiodon tigrinus is not an established aquarium fish — it does not appear on FishBase and no aquarium-trade or hobbyist care literature for the species was found. As a small Parodontidae stream-grazer it would, in principle, need what the family generally requires: strong current, high dissolved oxygen, a hard or rocky substrate carrying a healthy biofilm to graze, and cool-to-moderate, well-oxygenated water rather than a warm, still community tank. This is inference from family biology, not a documented care record for this exact species, and it should be read that way.
Because it has essentially no presence in the trade, prospective keepers are unlikely to encounter A. tigrinus for sale; this article does not manufacture stocking or tank-size guidance for a species with no aquarium history to draw on.
Conservation
Apareiodon tigrinus has not been assessed by the IUCN Red List and carries no formal conservation status; it is treated here as Not Evaluated. As a narrow-range headwater endemic of the Tocantins-Araguaia Basin, it shares the general exposure of small-range Brazilian stream fishes to damming, deforestation-driven sedimentation and water-quality change, but no species-specific population or threat data is available to characterise its status further. Its obscurity is itself informative: this is a scientifically described but largely unstudied fish outside its original taxonomic paper, with no evidence of commercial or aquarium-trade collection pressure.