Taxonomy & naming
Corydoras xinguensis was described by the Dutch ichthyologist Han Nijssen in 1972, from material collected in the upper Rio Xingu basin in central Brazil — the source of its name, the suffix -ensis simply meaning 'from' or 'belonging to' the Xingu. It was placed in Corydoras Lacépède, 1803, the large genus of South American armoured catfishes in the family Callichthyidae, and traded and written about under that name ever since.
The big change came in 2024, when Dias, Tencatt and colleagues published a phylogenetic revision of the subfamily Corydoradinae that split the unwieldy old Corydoras into several lineage genera — among them Brochis, Hoplisoma, Gastrodermus and Osteogaster. Under that scheme C. xinguensis falls into Hoplisoma, and FishBase now carries the combination Hoplisoma xinguense; the specialist site Corydoras World, which tracks the post-revision lineage classification, places it in the same genus. We keep 'Corydoras xinguensis' as the heading because that is the name the aquarium world still uses, while noting the current valid combination is in Hoplisoma. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) lists the species as valid; the genus assignment reflects the 2024 revision rather than a change in the species' validity.
Morphology
This is a small cory, with FishBase giving a maximum of about 1.5 in standard length — a genuinely diminutive fish, even by the standards of the smaller corys. The build is the familiar one for the group: a short, deep body sheathed in two rows of overlapping bony plates that meet along the back, a hard blunt-headed 'helmet', and three pairs of short barbels around the downturned, sand-sifting mouth. Females, as in the genus generally, tend to grow a little larger and rounder than males.
The colour pattern is modest rather than flashy — a pale to greyish-tan ground with darker mottling or spotting and, in many individuals, a darker marking along the flank, the kind of broken camouflage that disappears against a sandy, litter-strewn bottom. The dorsal, pectoral and adipose fins each carry the usual stiff leading spine that serves as defence and readily snags in a net.
Habitat
Corydoras xinguensis is associated with the upper Rio Xingu basin in central Brazil. The Xingu is one of the major clearwater tributaries of the Amazon, draining the Brazilian Shield from the south — characteristically warm, low-conductivity, often nutrient-poor water flowing over sand and rock. Within that system the species is a fish of shallower, quieter habitats: stream margins and slow reaches over sand with leaf litter and submerged wood.
Reported tolerances are typical of a lowland Amazonian cory — temperatures around 72–79 °F and a broad pH band from acidic to neutral or slightly above (roughly 6.0–8.0). Like all members of the subfamily it is a facultative air-breather, rising to the surface to gulp air and absorb oxygen through a vascularised hindgut, an adaptation suited to warm, oxygen-poor shallows and seasonally shrinking pools.
Feeding
Like its relatives, C. xinguensis is a benthic omnivore and detritivore that forages over the bottom, burying its snout and barbels in sand to taste out small invertebrates, insect larvae, worms, crustaceans and organic detritus and expelling the cleaned sand through the gills. It is an opportunistic feeder rather than a specialist. In the aquarium it takes sinking pellets and wafers, frozen bloodworm and brine shrimp and other small foods, and — as a small-mouthed fish — appreciates finely sized sinking food it can pick from the substrate.
Mating
There is no detailed published account of courtship for C. xinguensis specifically, but it is expected to follow the well-studied Corydoras pattern. These are egg-laying shoalers without a pair bond. A ready female cleans a spawning site and the group becomes active; a male takes the classic 'T-position' at right angles to her head, a few eggs are fertilised and held in a basket formed by her pelvic fins, and she presses them onto the cleaned surface before the sequence repeats a few eggs at a time.
Breeding
No widely circulated captive breeding account exists for Corydoras xinguensis, which is an uncommon species in the trade, so the picture is largely by analogy with better-known corys. Spawning in the genus is generally triggered by a cool, large water change simulating the onset of the rains; adhesive eggs are laid in small batches on firm surfaces and receive no parental care, with adults inclined to eat them, so breeders separate eggs from parents. Eggs hatch within a few days and the fry — small, given the adult size — take microworm, baby brine shrimp and powdered foods after the yolk sac is absorbed. These details should be confirmed first-hand for this species rather than assumed.
In the aquarium
Corydoras xinguensis is a specialist's fish rather than a common community staple, but its needs follow the standard cory template with one emphasis: it is small, so tankmates and food size should suit it. Keep it as a shoal of six or more — corys are genuinely stressed in isolation — in a tank with plenty of bottom area; a footprint of around 23.5 in or more is comfortable for a group.
Substrate is critical: soft sand or very smooth, rounded fine gravel, because these fish feed by sifting and sharp or coarse substrate erodes and infects their barbels. Keep the bottom clean and the water warm (about 72–79 °F), well-filtered and well-oxygenated with a gentle current, ideally on the soft, slightly acidic side that reflects its clearwater Xingu origins, though it tolerates a broader range. It is peaceful and best housed with similarly small, calm fish — small tetras, pencilfish, dwarf cichlids — rather than anything large or boisterous. The usual cautions apply: fin spines snag in nets, so a cup is safer, and a badly stressed cory can release a skin toxin that may prove fatal in the small volume of a transport bag, so move it with care.
Conservation
Corydoras xinguensis has not, as far as the available records show, been individually assessed by the IUCN Red List, so its status is best treated as Not Evaluated rather than assigned a category. The broader context is the Rio Xingu itself, which has been profoundly altered by the Belo Monte hydroelectric complex: damming has reshaped flow, connectivity and the seasonal dynamics of large stretches of the basin, with documented consequences for its highly endemic fish fauna. Any cory restricted to this system therefore sits in a landscape under real and ongoing pressure, which makes a proper assessment of its range and population worthwhile.