Taxonomy & naming
Osteogaster oharai was described in 2025 by Luiz Tencatt, Carvalho, Silva and Marcelo Britto. It is a member of the so-called 'aeneus group' (lineage 7 of the Corydoradinae, the lineage whose type species is C. eques), the cluster of bronze, metallic-flanked corys that for a century were funnelled into the single name Corydoras aeneus. In the aquarium hobby the fish circulated for years under the Planet Catfish code CW068 before it was formally named.
The species is honoured with the name oharai for the ichthyologist Willian Massaharu Ohara, a friend and collaborator of the describing authors who contributed many corydoradine specimens to their work. We retain the heading Osteogaster oharai because that is how the trade and hobby will know it, but the description sits squarely within the modern reclassification: under the 2024 revision by Dias, Tencatt and colleagues the aeneus group is placed in the resurrected genus Osteogaster, so the current valid combination is Osteogaster oharai. We follow the Catalog of Fishes for the name and note the Osteogaster combination here.
This fish was long listed as Corydoras oharai; Eschmeyer's Catalog of Fishes places the species in Osteogaster, and the current combination Osteogaster oharai is followed here.
Morphology
This is a small cory, with mature females reaching roughly 1.8 in and males a little smaller at about 1.6 in — squarely in the modest size range of the aeneus group rather than the larger long-snouted corys. The build is the familiar one: a short, fairly deep, armoured body clad in two rows of overlapping bony scutes instead of scales, a blunt helmeted head, three pairs of barbels around a downturned sand-sifting mouth, and stiff leading spines in the dorsal and pectoral fins.
In overall look it is a typical 'bronze' cory — a metallic, sheened flank over a paler belly — which is exactly why fish like this were historically swept into 'C. aeneus.' Its separation from the aeneus complex rests on the fine combination of body proportions, plate counts and subtle colour and bony-plate detail set out in the original description rather than on any single dramatic field mark; in the tank it would read to most eyes as a clean, modestly sized bronze cory from a particular corner of the Tapajós system.
Habitat
Osteogaster oharai is known from the rio Aripuanã basin, its type region, with a further record from the rio Juruena basin — both part of the broader upper rio Tapajós drainage, in Mato Grosso State, Brazil. This is southern-Amazon clearwater country, the warm forest and savanna-edge streams of the Brazilian Shield headwaters.
Like its relatives it is a fish of stream and creek margins over soft sand and mud with leaf litter and submerged wood, in warm, soft, near-neutral to slightly acidic water. Detailed published water chemistry for the exact collection sites is limited, so the aquarium figures below reflect the general envelope for aeneus-group corys of this region rather than measured values for this species. As an aeneus-group fish it can be expected to share the group's hardiness and, like the bronze cory, its facultative air-breathing — gulping surface air to supplement gill respiration in warm, oxygen-poor shallows.
Feeding
Osteogaster oharai is a benthic omnivore and detritivore, as its whole group is. It works the bottom, burying snout and barbels in sand and litter to taste out small invertebrates, insect larvae, worms, microcrustaceans, fallen seeds and organic detritus, expelling cleaned substrate through the gills. No species-specific gut-content study has been published, but the aeneus-group corys are famously catholic, unfussy feeders, and there is no reason to think this one differs; in captivity its relatives take sinking pellets, frozen bloodworm and brine shrimp and anything that reaches the bottom.
Mating
No spawning has been described for Osteogaster oharai specifically, but the aeneus group is the best-studied in the whole subfamily for reproduction, and this species can be expected to follow the same pattern. These are egg-laying shoalers with no pair bond: a ready female cleans a site, a male adopts the classic 'T-position' at right angles to her head, and a small clutch is fertilised and carried in a basket of her pelvic fins to be pressed onto the cleaned surface, the sequence repeating until dozens of sticky eggs are placed. This account is inferred from close relatives such as C. aeneus rather than observed in oharai.
Breeding
There is no published captive-breeding record for Osteogaster oharai, which was named only in 2025. Its aeneus-group relatives, however, are among the easiest of all egg-laying fishes to breed: spawning is usually triggered by a cool, large water change mimicking the rains, the adhesive eggs (a clutch typically in the tens to low hundreds across the group) are laid in small batches on firm surfaces, the adults give no care and will eat the eggs, and the fry hatch in a few days to take microworm and baby brine shrimp. If oharai enters the hobby in numbers, it is reasonable to expect it will prove a similarly willing breeder, though that remains to be demonstrated.
In the aquarium
As a newly described species, Osteogaster oharai is for now more a name on the map than an established aquarium staple, though as the CW068 it has had some presence among specialist corydoras keepers. Kept as its group prefers, it would want a shoal of six or more — corys are genuinely stressed kept singly — over a soft sand bottom that protects the barbels they feed with, in a tank whose footprint matters more than its height.
Water should be warm but not hot (around 72–79 °F), clean, gently moving and well-oxygenated, soft and near-neutral, with leaf litter and wood to echo its clearwater home; aeneus-group corys tolerate a fairly broad pH and hardness range, which makes them forgiving. It is a peaceful community fish, suited to tetras, dwarf cichlids and other calm tankmates and nothing large enough to bully it. The standard cory cautions apply: the fin spines can catch in a net (a cup is safer), and a stressed cory can release a skin toxin that, in the confined volume of a transport bag, can kill a whole group — so move them gently and in small numbers.
Conservation
Osteogaster oharai has not been assessed by the IUCN and currently carries no Red List status, as is normal for a fish described only in 2025. It is so far known from a small number of sites in the rio Aripuanã and rio Juruena basins of Mato Grosso, which suggests a limited documented range — but, as with most freshly named corys, that may reflect sampling effort as much as true rarity, and the aeneus-group fishes are generally adaptable and widespread. The upper Tapajós headwaters do face real and growing pressure from agricultural expansion, deforestation and hydropower development across Mato Grosso, which is worth noting even though this species has not been formally evaluated against those threats.