Taxonomy & naming
Corydoras oiapoquensis was described by the Dutch ichthyologist Han Nijssen in 1972, from material taken in the rio Oyapock (Oiapoque) drainage; the type locality is a creek on the left bank of the Oyapock in French Guiana. The epithet is geographic, formed from the river's name. For half a century it has been known as Corydoras oiapoquensis, and that is the heading we keep, because it is how the fish is traded and discussed.
It belongs to a tight knot of similar 'panda-faced' corys — most notably C. condiscipulus, which shares the Oyapock and is so alike that the two are mainly told apart by snout length (condiscipulus has the longer snout). With the 2024 revision of the Corydoradinae by Dias, Tencatt and colleagues, which broke the old super-genus Corydoras into several lineage genera, this species is placed in the resurrected genus Hoplisoma; the current combination is therefore Hoplisoma oiapoquense. We follow the Catalog of Fishes for the name and note the new combination here.
Morphology
This is a small, short-bodied cory, reaching about 2 in in standard length, with females tending to grow a little larger than males. It has the standard genus architecture: armour of two rows of overlapping bony plates rather than scales, a blunt helmeted head, three pairs of barbels around a downturned mouth, and stiff leading spines in the dorsal and pectoral fins.
The pattern is the draw. The body is pale with the 'panda' essentials — a dark mask through the eye and a dark saddle on the back beneath the dorsal fin — but, crucially, it lacks the bold black spot on the caudal peduncle that defines the true panda cory. In its place the tail fin carries a series of wavy, broken dark bars, the 'flag' that gives the fish its trade name. It is this combination — panda face, no tail-base spot, barred caudal — that distinguishes it at a glance from C. panda, while the very similar C. condiscipulus is separated chiefly by its longer snout.
Habitat
Corydoras oiapoquensis is, as far as is known, endemic to the rio Oyapock basin straddling the French Guiana–Brazil border, and within that river it has only been found in the upper reaches, above the first rapids — it has not turned up downstream or in neighbouring drainages. That gives it a genuinely small known range.
Its habitat is the slower water of the system: gently flowing streams, the margins of larger rivers, marshland and ponds, typically over sand with leaf litter and wood. These are warm, soft, slightly acidic Guiana-Shield waters. In the aquarium literature the species is associated with well-oxygenated water with some surface movement, which fits a fish of clear, flowing forest streams. Reported maintenance ranges sit around 73–82 °F, a pH of roughly 6.0–7.2 and soft to moderately soft water.
Feeding
Like all corys, Corydoras oiapoquensis is a benthic omnivore that forages over the bottom, sifting sand and leaf litter with its barbels for small invertebrates, insect larvae, worms, microcrustaceans and organic detritus. In the aquarium it readily takes sinking dried foods along with small live and frozen items such as bloodworm, brine shrimp and chopped earthworm. As with the whole genus, it should not be expected to live on tankmates' leftovers; a varied sinking diet keeps it in good condition and, in breeders' hands, in spawning trim.
Mating
Corydoras oiapoquensis follows the courtship pattern shared across the genus. These are egg-laying shoalers with no pair bond: when a female is ready the group becomes active, she cleans a spawning site, and a male takes up the classic 'T-position' at right angles to her head. A small clutch of eggs is fertilised and clasped in a basket formed by her pelvic fins, then carried to the cleaned surface — leaf, stone or glass — and pressed into place, the sequence repeating until the eggs are distributed across several sites.
Breeding
The flag-tailed panda has been bred in captivity and reproduces much as other small corys do, though it is considered a little less prolific and more demanding than the easiest species. Conditioning on varied live and frozen foods and a cooler water change to simulate the rains will prompt spawning, typically with the group kept warm (around 77 °F). The adhesive eggs are laid in small batches on firm surfaces and receive no parental care — the adults will eat them, so breeders remove the eggs or the parents. Eggs hatch in roughly three to four days, and the fry take microworm, baby brine shrimp and powdered foods once the yolk sac is absorbed. It is a satisfying but not beginner-trivial cory to raise.
In the aquarium
Corydoras oiapoquensis is a long-known but never common aquarium fish, prized by cory enthusiasts for its tidy panda-meets-flag-tail looks. It wants what its relatives do, with a couple of emphases. Keep it in a shoal of six or more — it is a sociable species that is stressed kept singly — over soft sand that will not abrade the barbels it feeds with. Give it clean, well-oxygenated water with gentle flow and some surface movement, reflecting its clear-stream origins, and decorate with fine sand, smooth rounded stones, wood and planting.
Warm but not hot water (about 73–82 °F), soft and slightly acidic to neutral, suits it. It is utterly peaceful and makes an excellent companion for small tetras, rasboras, dwarf cichlids and other calm community fish, never anything large enough to harass it. The familiar cory cautions apply: the fin spines can tangle in a net, so catch it with a cup, and a badly stressed cory can release a skin toxin that, in the small volume of a transport bag, can kill the whole group — so move them gently and in small numbers.
Conservation
Corydoras oiapoquensis has been assessed by the IUCN as Least Concern. Within its single river system it is reported to be quite abundant, which underpins that rating, even though its overall range is small and apparently confined to the upper Oyapock above the first rapids. A narrowly distributed but locally common fish like this is secure as long as its one river stays healthy; the flip side is that a species restricted to a single drainage is inherently more exposed to any localized threat — pollution, deforestation in the catchment, or changes to flow — than a continent-spanning cory such as the bronze. For now, though, it is in no recognised danger.