Taxonomy & naming
Corydoras negro was described by the German aquarist and ichthyologist Joachim Knaack in 2004, in a paper erecting six new Corydoras species (Zoologische Abhandlungen, Staatliches Museum für Tierkunde Dresden). The type material came from eastern Bolivia — Departamento Santa Cruz, Provincia Ñuflo de Chávez, in the Río Blanco and Río Negro system of the upper Guaporé (Iténez) basin. It belongs to the family Callichthyidae, subfamily Corydoradinae.
The specific name negro ('black' in Spanish/Portuguese) refers to the river of that name from which the fish was taken, and not — despite the obvious assumption — to the great Rio Negro of the Brazilian Amazon; this is a different, much smaller Río Negro in Bolivia. In the sweeping 2024 phylogenomic revision of the subfamily by Dias, Tencatt and colleagues, C. negro falls in the long-snouted clade (Lineage 1) that retains the type species C. geoffroy, and so keeps the genus name Corydoras in the strict sense. Its valid combination after the revision therefore remains Corydoras negro.
Morphology
This is a small cory, reaching roughly 2 in standard length (FishBase) and on the order of 2.5 in total length in aquarium fish, with females the larger and fuller-bodied. The fin counts are typical of the genus: a single dorsal spine with six to seven soft rays, and an anal fin of one spine and five soft rays. As in all corys the body is armoured with two rows of overlapping bony scutes and the head is a hard helmet, with sensory barbels fringing the downturned mouth.
The specific name reflects the species' dark cast. It is reported to be variable between populations, including in snout shape — some fish having sharper, more pointed snouts and others rounder profiles — which has prompted discussion of whether more than one form is involved. As in the genus generally, the dorsal, pectoral and adipose fins carry stiff, mildly venomous spines.
Habitat
Corydoras negro is endemic, as far as is known, to the Río Blanco–Río Negro system of the upper Guaporé (Iténez) drainage in Departamento Santa Cruz, eastern Bolivia. These are warm tropical lowland waters; aquarium guidance derived from the type region gives roughly 72–79 °F and a pH of about 6.0–7.5. As a bottom-dwelling cory it favours quieter reaches over soft substrate, where it forages in sand and litter.
Like other callichthyids it is a facultative air-breather, gulping atmospheric air at the surface and absorbing oxygen through its modified, vascularised hindgut — an adaptation that suits the warm, seasonally oxygen-poor backwaters of the Bolivian lowlands. Detailed field ecology has not been published, and most of what is reported comes from the original description and from aquarists working with imported stock.
Feeding
C. negro is a benthic omnivore and detritivore in the manner of its relatives, working the bottom with snout and barbels to taste out small invertebrates, insect larvae, worms and organic detritus from sand and leaf litter. No diet study specific to the species exists, but its mouth, barbels and foraging behaviour are those of the genus. In the aquarium it accepts good-quality flake and sinking tablet foods for routine feeding, supplemented with frozen or live foods such as bloodworm and brine shrimp to keep it in condition.
Mating
Spawning in C. negro has not been formally documented, and its reproductive behaviour is presumed to follow the well-studied pattern of the genus. Corydoras are egg-laying shoalers with no pair bond and the characteristic 'T-position' courtship, in which a receptive female cleans a site, a male aligns at right angles to her head, and she carries a few adhesive eggs clasped in a basket of her pelvic fins to press onto the chosen surface, repeating the sequence until a clutch is laid. Whether and how readily C. negro performs this in captivity is essentially unrecorded.
Breeding
There are no established captive-breeding accounts for Corydoras negro; it is an uncommon species in the trade and is not bred commercially. By analogy with the genus, any clutch would consist of adhesive eggs scattered on firm surfaces and given no parental care — the adults will eat eggs, so a breeder would remove either the eggs or the parents and rear the fry on microworm, baby brine shrimp and powdered foods once the yolk sac is absorbed. Because males of this species are reported to be somewhat aggressive toward one another, a successful breeding setup would need a generous footprint and cover to spread that tension. For now the species remains essentially wild-supplied.
In the aquarium
An infrequent import, C. negro is a fish for the cory enthusiast rather than the general community keeper, though its care follows the familiar template. It is a shoaling species and should be kept in a group of six or more over soft sand, which lets it feed naturally and protects its snout and barbels; sharp or coarse gravel abrades and infects them, leaving blunted faces. Warm but not hot water (about 72–79 °F), clean and well-oxygenated with gentle to moderate flow and regular changes, suits it well.
One practical note distinguishes it from the easygoing common corys: males can be somewhat aggressive toward each other, so a larger tank with planting and hiding places helps dilute that behaviour. It is otherwise peaceful toward tankmates and pairs well with small, calm community fish such as tetras and dwarf cichlids. The standard cory cautions hold — the fin spines snag in nets, so a cup is safer, and a badly stressed fish can release a skin toxin that may prove dangerous in the small volume of a transport bag.
Conservation
Corydoras negro is assessed by the IUCN as Data Deficient (assessed 2014): too little is known of its distribution, population size and trends to evaluate its extinction risk. It appears to be narrowly distributed within the Río Blanco–Río Negro system of eastern Bolivia and is collected only in small numbers for the aquarium hobby. Narrow-range lowland fishes of this kind can be vulnerable to local habitat change — deforestation, agriculture and altered river flow — but without basic survey data its true status cannot be judged, which is precisely what the Data Deficient listing records.