Taxonomy & naming
Corydoras carlae was described in 1983 by Han Nijssen and Isaäc Isbrücker, the Dutch duo responsible for naming a great many South American corys, in the Revue française d'Aquariologie et Herpétologie. The type locality is a small left-bank tributary of the Río Iguazú in Misiones Province, Argentina, in the Paraná drainage above the Iguazú Falls. The species honours a 'Carla', in the affectionate dedicatory style typical of these authors.
For 150 years 'Corydoras' had absorbed almost every short-bodied callichthyid catfish, but the genus proved not to be a single natural group. The 2024 phylogenetic revision by Dias, Tencatt and colleagues (DOI 10.1093/zoolinnean/zlae053) split it into several genera and resurrected Hoplisoma Blyth, 1860 for a large clade of the short-snouted species. Under that classification Carla's cory becomes Hoplisoma carlae, the placement followed by the specialist site Corydoras World and now reflected in FishBase. The change is recent and the aquarium world still says 'Corydoras carlae,' so we keep that as the heading while recording the current combination.
Morphology
Carla's cory is a small, short-snouted species reaching about 2 in in standard length, with the deep, flat-bellied, bony-plated body shape characteristic of the genus: two rows of overlapping scutes down each flank, a hard helmeted head, and three pairs of barbels around the downturned mouth. Females, as usual in Corydoras, grow larger and rounder than males.
The pattern is a network of dark reticulation and spotting over a pale ground — a marbled or 'masked' look that has caused it to be confused with several similar Paraná-basin corys. The dorsal, pectoral and adipose fins each bear the stiff locking spine of the family, and the body has the same iridescent sheen under good light that gives many small corys their appeal. It is a tidy, modestly sized fish rather than a showy one.
Habitat
Corydoras carlae is endemic to the upper Río Iguazú system in Misiones Province, northeastern Argentina — a subtropical drainage of the Paraná basin, restricted to smaller tributaries above the famous Iguazú Falls, the great cataract that isolates the upper river from the lower. This is not the warm, muddy backwater habitat of the bronze cory.
Field images and accounts describe relatively clear, fast-flowing, shallow streams with thick riparian forest along the banks and patches of submerged plants such as Echinodorus uruguayensis. The substrate is sand and fine gravel. Because the fish comes from clean, flowing, well-oxygenated subtropical water, it experiences cooler temperatures and more current than the typical lowland Amazon cory — a key point for anyone trying to keep it. Its restriction to a single drainage above a major waterfall makes it a genuinely endemic, narrow-range species.
Feeding
Like all corys, C. carlae is a foraging benthic omnivore. In its clear Iguazú streams it works the sandy and gravelly bottom, using its barbels to taste out small invertebrates, insect larvae, microcrustaceans and the organic film of detritus, processing mouthfuls of substrate as it goes. There are no detailed dietary studies of the wild fish, but its niche is the familiar one of a sand-sifting stream cory. In captivity it would take the standard cory fare — sinking dried foods plus small live and frozen items such as bloodworm and Tubifex — but, given its origins, in cleaner, cooler, more oxygenated water than most.
Mating
No spawning has been documented specifically for Carla's cory, but the genus is highly conservative in its reproduction. Corydoras are egg-laying shoalers with no pair bond and the well-known 'T-position' courtship: the male presents himself crosswise to the female's head, she appears to take his milt, and a few adhesive eggs are clasped in a basket of her pelvic fins and pressed onto a cleaned leaf, stone or pane. The sequence repeats, a few eggs at a time. C. carlae is expected to follow this pattern, though it has not been observed in detail.
Breeding
Carla's cory is not a fish with an established breeding record, and no clutch sizes or fry data are published for it. The expectation, by analogy with related Hoplisoma/Corydoras, is a clutch of adhesive eggs laid in small batches on hard surfaces, no parental care (adults will eat the eggs, so a breeder removes eggs or parents), and fry that take microworm and baby brine shrimp after the yolk sac is absorbed. The practical complication is its origin: a cool, clean, flowing subtropical stream. Successful breeding would likely hinge on soft, well-oxygenated water and a genuine cool-water change to simulate seasonal cues, rather than the warm conditions that trigger lowland species.
In the aquarium
Corydoras carlae is an uncommon, somewhat specialist aquarium fish rather than a staple, and the literature is explicit that it is not a beginner's cory: because it comes from pristine, flowing water it needs stable, clean conditions and should never be added to a young, biologically immature tank.
Keep it as a shoal of six or more — corys are stressed alone or in pairs — over fine sand (rounded gravel only if kept scrupulously clean, to protect the barbels), with cover for security. It wants cooler, well-oxygenated water with gentle current and very good maintenance, closer to a subtropical stream than a tropical community tank, so avoid keeping it warm. Tankmates should be small, peaceful subtropical or temperate-leaning species. The standard cory cautions apply: the fin spines snag in nets (use a cup), and a stressed cory can shed a skin toxin that can wipe out a group in the confined volume of a bag, so transport with care.
Conservation
Corydoras carlae was assessed by the IUCN as Least Concern in 2018. That status reflects the absence of evidence of decline rather than a wide, secure range: the species is a single-drainage endemic of the upper Río Iguazú, and narrow-range endemics in heavily developed subtropical river systems warrant ongoing attention. The upper Iguazú basin faces deforestation, agriculture and the cumulative effects of dams across the wider Paraná system, all of which degrade exactly the clear, forested, flowing streams this fish depends on. For now it is judged not threatened, but its limited distribution means its fortunes are tied closely to the health of one river above one great waterfall.