Taxonomy & naming
Corydoras amapaensis was described by the Dutch ichthyologist Han Nijssen in 1972, from a holotype taken in Cachoeira Creek on the right bank of the Rio Amapari, a few kilometres downstream of Casa do 7, in Amapá State, Brazil. The species epithet is geographic, formed straightforwardly from the name of that Brazilian state. It sits in the family Callichthyidae, subfamily Corydoradinae — the South American armoured or 'mailed' catfishes whose bodies are clad in two rows of bony plates rather than scales.
For more than half a century it has been carried as Corydoras amapaensis, and that remains the name in the Catalog of Fishes today. The genus Corydoras had, however, swollen to well over 170 species and was shown by molecular work to be unnatural, so in 2024 Dias, Tencatt and colleagues published a wide revision (DOI 10.1093/zoolinnean/zlae053) that split it into several genera, resurrecting Brochis for the deep-bodied, many-plated 'long-finned' corys and erecting or revivifying Hoplisoma, Gastrodermus, Osteogaster and others. It would be easy to assume a long-snouted fish like this went to Brochis — but it did not. Dias et al. (2024:23) retained amapaensis within Corydoras in the strict sense, so the heading and the current valid combination are one and the same: Corydoras amapaensis Nijssen 1972. We note the revision here because its genus reshuffles touch so many of this fish's relatives.
Morphology
This is one of the long-snouted corys: the head tapers to a noticeably elongate, pointed muzzle, quite unlike the blunt 'pig-nosed' profile of the common bronze and peppered species. The body is comparatively slim and reaches roughly 3 in in standard length, females growing a little larger and deeper-bodied than males. As in all members of the subfamily, the flanks are protected by two overlapping series of bony scutes that meet along the dorsal ridge, the head is a hard helmet of bone, and three pairs of barbels fringe the small, downturned, sucker-like mouth.
The colour pattern is its most useful field mark. A clean dark longitudinal stripe runs along the midflank from behind the gill cover to the tail base, and a separate dark bar crosses the head through the eye in the classic cory 'mask'. The ground colour is a pale tan-to-cream, and the fins are largely clear. The dorsal, pectoral and adipose fins each bear a stiff leading spine — a defensive feature shared across Corydoras that can deliver a sharp, mildly venomous jab and readily snags in a net.
Habitat
Corydoras amapaensis is restricted to the Oyapock (Oiapoque) and Amapari river drainages of Amapá State in Brazil and adjacent French Guiana — the band of Guiana Shield rivers that drain north and east to the Atlantic. It is a fish of the upper reaches: it is recorded specifically from small creeks with flowing, well-oxygenated water and sandy bottoms, in the headwater sections upstream of the first rapids, rather than in the larger lowland channels.
These clear forest streams are warm and soft. Reported husbandry parameters span a temperature range of about 72–79 °F, a pH from acidic to slightly alkaline (roughly 6.0–8.0) and soft to moderately hard water. Like other corys it is a facultative air-breather, periodically darting to the surface to gulp atmospheric air and absorb oxygen across a vascularised section of the hindgut — an adaptation that buffers it against the low-oxygen conditions of shrinking, sun-warmed dry-season pools. In its native creeks it is recorded living alongside the short-snouted Corydoras solox.
Feeding
Like its relatives, C. amapaensis is a benthic omnivore and detritivore. Its elongate snout is a feeding tool: long-nosed corys are thought to specialise in driving the muzzle deeper into sand and soft sediment than the blunt-faced species can, rooting out buried insect larvae, small crustaceans, worms and other invertebrates along with organic detritus and fallen plant material. Sand taken up in the process is sifted and expelled through the gill openings. In the aquarium the species takes the usual cory fare — sinking pellets and wafers, frozen bloodworm and brine shrimp, and anything edible that settles to the bottom — but it should never be relegated to subsisting on tankmates' leftovers.
Mating
No detailed account of spawning specific to Corydoras amapaensis appears in the literature, and what follows is the well-documented general pattern of the genus, to which it can be expected to conform. Corydoras are egg-laying shoalers with no pair bond. When a female is gravid the group becomes active and she cleans a spawning site; a male then takes up the characteristic 'T-position', aligning his body at right angles to the female's head. She appears to take milt into her mouth, sperm passing rapidly through the gut to fertilise the small clutch of eggs she clasps in a basket formed by her pelvic fins. She carries the eggs to the cleaned surface and presses them into place, and the sequence repeats a few eggs at a time.
Breeding
There is no published, species-specific breeding report for C. amapaensis, and as a long-snouted species from clear, flowing Guiana Shield creeks it is likely to be more demanding than the easy bronze and peppered corys. By analogy with the genus, spawning would be expected to follow a substantial cool water change that mimics the onset of the rains, with the adhesive eggs scattered on firm surfaces and given no parental care — adults will eat their own spawn, so a breeder removes either the eggs or the parents. Eggs typically hatch in a few days, and the fry take microworm, baby brine shrimp and powdered foods once the yolk sac is absorbed. Conditions closer to the wild — clean, well-oxygenated, gently flowing soft water and a fine sand bed — would give the best chance of success. Most fish offered for sale are wild-caught rather than commercially bred.
In the aquarium
Corydoras amapaensis is an occasional rather than a staple import, sometimes appearing among mixed shipments of Guianese corys. It is a peaceful shoaling fish and should be kept in a group of six or more; kept singly or in pairs it becomes withdrawn and stressed. A group needs a tank with a generous footprint — bottom area matters far more than height — furnished with soft sand, because long-snouted corys in particular are vulnerable to barbel erosion and infection on sharp or coarse gravel, which leaves them blunt-faced and unable to feed properly.
Given its headwater-creek origins, it appreciates clean, well-oxygenated water with gentle flow, warm but not hot temperatures (around 72–79 °F), and regular water changes. Provide shade from wood, rock or plants and an open sand area for foraging. It is utterly peaceful and suits a community of small, calm tankmates such as tetras, pencilfish and dwarf cichlids. The usual cory cautions apply: the fin spines tangle in nets, so a cup is safer for moving them, and a badly stressed cory can release a skin toxin that, in the confined volume of a transport bag, may kill the whole group.
Conservation
Corydoras amapaensis was assessed by the IUCN in 2020 and listed as Least Concern. Although its range is comparatively small and concentrated in the Oyapock and Amapari headwaters, those rivers drain relatively intact, sparsely populated forest, and no major, range-wide threat has been identified. The species is collected for the aquarium trade in modest numbers rather than intensively exploited. The broader risks to Guiana Shield freshwaters are real, however — small-scale and illegal gold mining in particular brings sedimentation and mercury contamination to exactly the kind of clear headwater creeks this fish depends on — so a narrowly distributed clear-water specialist of this sort warrants ongoing attention even under a Least Concern listing.