Taxonomy & naming
Corydoras orphnopterus was described by Weitzman and Nijssen in 1970, on the basis of specimens collected in Ecuador from the lower Río Bobonaza between Montalvo and Chicherota, in the province of Pastaza — within the Pastaza River drainage of the upper Amazon, and still the type locality. The specific name comes from Greek orphnos ('dark, dusky') and pteron ('wing, fin'), referring to dark markings in the fins. For half a century it was carried as Corydoras orphnopterus, a long-snouted member of the great armoured-catfish genus Corydoras Lacépède, 1803 (family Callichthyidae).
That genus had grown past 170 species and was shown by molecular work not to be a single natural lineage. The 2024 revision by Dias, Tencatt and colleagues split it into several genera — Brochis, Hoplisoma, Gastrodermus, Osteogaster and others — and the Catalog of Fishes now lists this species in Brochis: the valid combination is Brochis orphnopterus (Weitzman & Nijssen 1970). The change is recent and not yet universally adopted, and the trade still says 'Corydoras orphnopterus,' so we keep that heading while recording the new combination. The fish is sometimes confused with other dotted long-snouts of the Ecuadorian and Peruvian upper Amazon.
Morphology
The rabbit cory is a long-snouted species of modest size, reaching about 2.5 in standard length. The snout is elongated and pointed and the head angular, in the manner of the long-nosed corys rather than the blunt community species.
The colour pattern is distinctive. The ground colour is whitish to pale, overlaid with a pattern of relatively small dark dots; on the caudal peduncle these dots line up into about three parallel rows, and the pale gaps between them read as light bands along the rear body. A dark band masks the eye. The most conspicuous mark is a black blotch in the dorsal fin, most intense along the front edge of the centre of the fin, and the caudal fin carries roughly six or seven thin dark bars that break up into rows of spots — the dusky fin markings that give the species its name (orphnos, 'dusky'; pteron, 'fin'). As in all corys the body is armoured with two rows of overlapping bony scutes, the mouth is downturned with three pairs of barbels, and the dorsal and pectoral fins bear stiff, mildly venomous leading spines.
Habitat
Corydoras orphnopterus is a fish of the upper Amazon in Ecuador and Peru. Its type locality is the lower Río Bobonaza in the Pastaza province of Ecuador, within the Pastaza River basin, and it ranges into the adjacent upper-Amazon drainages including the Napo system. It belongs to the quiet-water guild of the genus — slow tributaries, forest streams and creek margins over soft sand and leaf litter, in the foothill and lowland waters draining the eastern Andes.
These are warm, soft, slightly acidic to neutral waters. Reported aquarium-relevant figures are on the cooler side — around 68–75 °F, reflecting its upper-Amazon, foothill-influenced range — with a pH band of roughly 6.0–8.0 and soft to moderately hard water (about 2–25 dH). Like the rest of the subfamily it is a facultative air-breather, surfacing to gulp air and absorb oxygen through a vascularised hindgut, which lets it cope with warm, oxygen-poor backwaters.
Feeding
The rabbit cory is a benthic omnivore and detritivore. It forages over the bottom, driving its long snout and barbels into sand and leaf litter to taste out small invertebrates, worms, insect larvae, micro-crustaceans, fallen organic matter and detritus, expelling cleaned substrate through the gill openings as it sifts. The long, pointed snout suits probing into and under the substrate. In the aquarium it takes sinking pellets and tablets, frozen and live bloodworm, blackworm and brine shrimp, and other sinking foods; as with all corys it should be fed deliberately rather than left to scavenge whatever its tankmates drop.
Mating
Corydoras are egg-laying shoalers with the conserved 'T-position' courtship and no pair bond, and the rabbit cory follows the family pattern. A ripe female cleans a spawning site, the group becomes active, and a male presses crosswise against her head to form the characteristic T as she takes his milt; the eggs are clasped in a pelvic-fin basket, carried to the cleaned surface and pressed into place a few at a time until the chosen spots carry sticky eggs. Specific spawning observations for orphnopterus are limited, but there is no reason to think it departs from this conserved corydoradine sequence.
Breeding
Aquarium breeding of C. orphnopterus is not commonly documented; it is an uncommon, largely wild-collected import rather than a mass-bred staple, and as a long-snouted upper-Amazon species it is regarded as a more demanding subject than the easy community corys. Guidance is mostly extrapolated from related long-snouts: a cool, large water change mimicking the rainy season triggers activity, adhesive eggs are laid in small batches on firm surfaces and the glass, and the adults give no parental care and may eat the eggs, so a breeder removes the eggs or the parents. Fry hatch in a few days and take microworm, baby brine shrimp and powdered foods once the yolk sac is absorbed. A mature group in cool, soft, clean water gives the best chance; repeatable published spawning reports for orphnopterus specifically remain scarce.
In the aquarium
The rabbit cory is a peaceful, shoaling fish and should be kept in groups of six or more — kept singly or in pairs it becomes stressed and withdrawn. As a long-snouted species it appreciates a tank with a generous footprint (around 23.5 in / 20 US gal or more for a group) and open swimming area. Substrate is critical: soft sand or very fine, smooth, rounded gravel only, because the long feeding snout is precisely what coarse or sharp grit erodes and infects, leaving the blunted faces that mark a badly kept fish.
Water should be on the cooler side for a cory (about 68–75 °F), soft to moderately hard, slightly acidic to neutral, clean and well-oxygenated with gentle current and regular changes. Its fine-dotted, dusky-finned pattern shows best over dark sand with leaf litter and subdued light. It is peaceful with calm community fish — tetras, rasboras, dwarf cichlids — and should never share a tank with anything large enough to bully it. The usual cory cautions apply: the fin spines snag in nets (use a cup), and a badly stressed cory can release a skin toxin lethal in the small volume of a bag, so transport with care.
Conservation
Corydoras orphnopterus is assessed by the IUCN Red List as Least Concern (assessment dated 2020). It occupies the upper-Amazon drainages of Ecuador and Peru and is not currently considered threatened, with aquarium collection at modest levels. As with all fishes of the Andean-foothill Amazon, the regional pressures — deforestation, agriculture, oil and extractive activity in the Ecuadorian and Peruvian Amazon, run-off and habitat alteration — bear on the tributaries and creeks it inhabits, but the species itself is not presently flagged as at risk. Its restriction to the upper-Amazon headwater drainages nonetheless means it merits closer monitoring than a continent-wide generalist.