Taxonomy & naming
Corydoras reynoldsi was described in 1960 by George S. Myers and Stanley H. Weitzman, from the upper Caquetá River basin in Colombia, which remains the type locality. It was placed in Corydoras Lacépède, 1803, the huge genus of South American armoured catfishes in the family Callichthyidae. The species honours Colonel John N. Reynolds (1912–1987) of the United States Air Force, described by the authors as 'an ardent aquarist and a fine fish collector,' who helped collect the holotype.
Because Corydoras had swollen to over 170 species and was shown not to be a single natural lineage, Dias, Tencatt and colleagues split it in a 2024 phylogenetic revision of the Corydoradinae into several genera — Brochis, Hoplisoma, Osteogaster, Gastrodermus and others. Corydoras reynoldsi falls in the lineage now recognised as Hoplisoma, making its current combination Hoplisoma reynoldsi; FishBase already carries it that way. The change is recent and the hobby still says 'Corydoras reynoldsi,' so we keep that as the heading while noting the lineage placement.
Morphology
This is a small cory, reaching only about 1.5 in in standard length. It has the usual genus build: a short, deep, flat-bellied body, a blunt armoured head, and a small downturned mouth ringed by three pairs of sensory barbels. Two rows of overlapping bony plates (scutes) replace scales along each flank and meet in a ridge along the back.
Its appeal is in its pattern. The pale body carries bold dark markings — a dark band through the eye and dark saddle-like blotches over the back and onto the upper flank, a high-contrast scheme that earns it the occasional 'bumblebee' label in the trade. As in all Corydoras, the dorsal and pectoral fins are stiffened by hard, mildly venomous leading spines that can jab a careless hand or snag in a net. Females grow rounder and broader-bodied than the slimmer males, a difference clearest in conditioned fish.
Habitat
Corydoras reynoldsi is endemic, on current knowledge, to the upper Caquetá River basin in Colombia — an Andean-piedmont and lowland drainage of the western Amazon system. It is a fish of smaller streams and the shallow margins of larger watercourses, living over sand and fine substrate with leaf litter and submerged wood in the quieter reaches.
The water is warm, soft and acidic to near-neutral, broadly in the range of about 72–79 °F with a pH around 6.0–8.0 across the basin, tending softer and more acidic in the forest streams it favours. Like other Callichthyidae the species is a facultative air-breather, able to surface and take up atmospheric oxygen through a vascularised hindgut — an adaptation suited to the warm, shallow, sometimes oxygen-poor pools that form in these drainages.
Feeding
Corydoras reynoldsi is a benthic micro-omnivore and detritivore. It forages over the bottom, driving its snout and barbels into sand to taste out small invertebrates, insect larvae, worms, micro-crustaceans and organic detritus, expelling the cleaned sand through its gills. Given its small size it concentrates on correspondingly small prey and biofilm, and it is an opportunist rather than a specialist. In the aquarium it accepts small sinking granules and tablets, frozen bloodworm and brine shrimp and other small foods taken from the bottom, and like all corys does best on a varied diet of its own rather than on leftovers.
Mating
Courtship has not been documented in detail for Corydoras reynoldsi, but it is expected to follow the well-studied genus pattern. Corydoras are egg-laying shoalers with no pair bond. A ready female cleans a spawning surface and the group becomes active; a male takes up the classic 'T-position', aligning at right angles to her head. She appears to take milt directly, and the sperm is thought to pass rapidly through her gut to fertilise the few eggs she cradles in a basket formed by her pelvic fins. She presses each small batch onto the cleaned surface, and the sequence repeats until the clutch is laid.
Breeding
No widely published captive-breeding protocol is specific to Corydoras reynoldsi; expectations rest on its relatives. Spawning in the genus is generally triggered by a cool, large water change that imitates the onset of the rains. The adhesive eggs are laid in small batches on firm surfaces and given no parental care — the adults will eat them, so a breeder removes either the eggs or the parents. Eggs typically hatch in three to five days depending on temperature, and the fry take microworm, baby brine shrimp and powdered foods after absorbing the yolk sac. As a small, range-restricted and only occasionally traded species, it is bred far less often than the commercial corys.
In the aquarium
Corydoras reynoldsi is an occasional, somewhat sought-after import valued for its bold pattern, kept along standard cory lines with a lean toward soft, slightly acidic water. It is a shoaling species and is stressed when kept alone or in pairs; keep six or more and they reward you with confident, sociable foraging.
At only about 1 in it suits a modest, well-planted tank, but bottom area matters more than height. The substrate should be soft sand or very smooth, fine, rounded gravel: corys feed by sifting, and sharp or coarse gravel erodes and infects their barbels, leaving the blunted, stubby faces that mark poor husbandry. Add leaf litter and wood, keep the bottom clean, and provide gentle, well-oxygenated flow with regular water changes. Aim for warm but not hot water (about 72–79 °F), soft and slightly acidic to neutral. It is utterly peaceful and ideal with small tetras, rasboras, pencilfish and dwarf cichlids — never with anything large enough to bully it. As with all corys, use a cup rather than a net where possible, since the fin spines snag, and transport the fish carefully: a badly stressed cory can release a skin toxin that may kill the whole group in the small volume of a bag.
Conservation
The IUCN Red List assesses Corydoras reynoldsi as Data Deficient (assessment dated 2014) — meaning there is not enough information to judge its risk of extinction. The species appears to be a narrow-range endemic of the upper Caquetá in Colombia, and basic data on its distribution, abundance and trend are lacking. That uncertainty is itself a caution: a restricted-range fish in an Andean-Amazonian drainage exposed to deforestation, agriculture, mining and pollution could be more vulnerable than its quiet hobby presence suggests. Better field survey and a reassessment would be needed to know where it truly stands; for now its status is honestly unresolved rather than secure.