Taxonomy & naming
Corydoras difluviatilis was described in 2002 by Marcelo Britto and Cláudio de Pinna (often cited as Britto & Castro through later FishBase usage; the describing authors are Britto & Pinna) from the upper rio Paraná and upper rio São Francisco basins of Brazil — material that placed a single small species across two of the continent's major drainages. The epithet difluviatilis is Latin for 'of two rivers,' a direct reference to that double-basin distribution.
What made the fish notable was not its modest appearance but its phylogenetic position. The describers argued, on osteological grounds, that difluviatilis retains a suite of plesiomorphic (ancestral) character states relative to the assemblage made up of Brochis and most Corydoras species, which would put it at or near the very base of that lineage — effectively a living approximation of what an early corydoradine looked like. In the large 2024 revision of the subfamily by Dias, Tencatt and colleagues (DOI 10.1093/zoolinnean/zlae053), which split the old super-genus Corydoras into Brochis, Hoplisoma, Osteogaster, Gastrodermus and others, this species falls within the resurrected genus Brochis, and its current valid combination is Brochis difluviatilis. The aquarium world overwhelmingly still writes 'Corydoras difluviatilis,' so we keep that as the heading while noting the new genus.
Morphology
This is a small, stocky, rather plain Corydoras-type catfish, reaching about 2 in in standard length. Like all members of the subfamily it is armoured rather than scaled: two longitudinal rows of overlapping bony plates run along each flank, the head is a hard bony helmet, and three pairs of barbels fringe the downturned, sucker-like mouth used to sift the substrate. The body is robust and the snout moderately rounded rather than elongated.
The species is distinguished from its relatives by technical osteological features rather than by flashy colour: among them, posterior pectoral-spine serrations restricted to the proximal half of the spine, and reduced parapophyses on the fourth free vertebra that remain separate rather than fusing into a haemal arch. The colour pattern is unremarkable — a pale to greyish-brown ground with scattered darker mottling — which is part of why it has never become a trade staple. As in all corys the dorsal, pectoral and adipose fins each bear a stiff locking spine.
Habitat
Corydoras difluviatilis is known from the upper rio Paraná and the upper rio São Francisco systems of central and southeastern Brazil — clear-to-turbid headwater and upland streams of the Brazilian Shield, generally over sand and gravel with some leaf litter and submerged structure. These are the cooler, faster, higher-altitude waters near the drainage divides rather than the warm lowland floodplains where most familiar corys are caught.
Detailed wild water-chemistry data for this species are scarce, and FishBase does not publish a measured temperature or pH envelope for it; like other corys of the upland Paraná and São Francisco it can be expected to occupy moderately soft to moderately hard, near-neutral water in the broad 68–79 °F range, but those figures should be read as inference from the region rather than as recorded values for difluviatilis itself. As a callichthyid it is a facultative air-breather, gulping air at the surface and absorbing oxygen across a vascularised hindgut.
Feeding
Like other corydoradine catfishes, Corydoras difluviatilis is a benthic omnivore and detritivore. It works the bottom, burying snout and barbels in sand and fine gravel to taste out small invertebrates, insect larvae, micro-crustaceans and the organic film of detritus, expelling cleaned substrate through the gill openings. No diet study specific to this species has been published, so this account is the standard corydoradine feeding mode applied to it; there is no evidence it is a dietary specialist.
Mating
No spawning of Corydoras difluviatilis has been documented in the aquarium or described from the wild, and it is essentially absent from the ornamental trade, so its courtship is unrecorded. By strong inference from its close relatives, it is an egg-laying shoaler with no pair bond that uses the characteristic corydoradine 'T-position': a male positions himself at right angles to a receptive female, who clasps a few adhesive eggs in a basket formed by her pelvic fins and presses them onto a cleaned surface, the sequence repeating until the clutch is laid. This should be treated as the expected pattern rather than an observed one for this particular species.
Breeding
There is no published breeding record for Corydoras difluviatilis. It is not commercially bred and only rarely, if ever, reaches aquarists, so clutch size, egg development and fry-rearing are unknown for the species. If it follows its relatives — and there is no reason to expect otherwise — it would lay a modest clutch of adhesive eggs in small batches with no parental care, the adults taking no part beyond spawning and likely eating unguarded eggs. Until someone keeps and spawns it, all of this remains inference from the genus rather than fact about difluviatilis.
In the aquarium
Corydoras difluviatilis is effectively unknown in the hobby: it is not commercially bred, not a regular import, and there is no body of aquarist experience with it. Any keeper who did obtain wild specimens should treat it as a typical upland-stream cory — a shoaling species to be kept in groups of six or more, over soft sand to protect the barbels, in clean, well-oxygenated, gently flowing water that is cooler rather than tropical-hot (its headwater origins argue against high temperatures). It would be a peaceful community fish among small, calm tankmates. None of this is established practice for the species; it is the sensible default for a cory of this provenance, and the honest position is that its captive requirements have not been worked out.
Conservation
Corydoras difluviatilis is assessed by the IUCN Red List as Least Concern, in an assessment dated 7 November 2018. Despite its restricted, headwater distribution across the upper Paraná and upper São Francisco, it was judged not to face threats severe enough to warrant a higher category at the time of assessment. That said, the upland streams of southeastern and central Brazil are under real and growing pressure from agriculture, water abstraction, damming and pollution, and a small-bodied fish tied to clear headwaters can be vulnerable to local habitat degradation even when the species as a whole is secure. Its negligible presence in the aquarium trade means collection is not a meaningful pressure on wild populations.