Taxonomy & naming
Corydoras evelynae was described in 1963 by the German aquarist and ichthyologist Fritz Rössel, from the upper Solimões (the Brazilian name for the upper Amazon mainstem) in Amazonas, Brazil. The epithet evelynae is a patronym — a Latinised genitive honouring a woman named Evelyn — so it is invariant and does not change with the gender of the genus. For decades it was carried as Corydoras evelynae within Lacépède's vast genus Corydoras (family Callichthyidae).
That genus had grown to well over 170 species and molecular work showed it was not a single natural lineage. In 2024 Dias, Tencatt and colleagues published a large phylogenomic revision (Zoological Journal of the Linnean Society) that split Corydoradinae into several genera — among them Brochis, Hoplisoma, Gastrodermus, Osteogaster, Aspidoras and Scleromystax. Under that scheme Evelyn's cory falls within the short-snouted Hoplisoma lineage (the resurrected genus Hoplisoma Agassiz, 1846), giving the valid combination Hoplisoma evelynae. The change is recent and not yet universally adopted, and the hobby still says 'Corydoras evelynae,' so we keep that as the heading while noting the current combination.
Morphology
This is a small, fairly stocky, short-snouted cory reaching roughly 1.5–2 in, with females growing larger and rounder than males. It has the standard Corydoras armour — a hard, blunt, helmet-like head, a downturned mouth fringed with three pairs of sensory barbels, and two overlapping rows of bony scutes down each flank in place of scales — with the rounded face typical of the short-snouted Hoplisoma corys.
The ground colour is a pale tan to greyish, densely covered in small dark spots and reticulations over the head and body, with a dark band associated with the eye and spotting carried into the dorsal and caudal fins. As in all corys, the first ray of the dorsal, pectoral and adipose fins is a stiff spine — a mildly venomous defence that can jab a careless hand and snag in a net. It is a tidy, finely peppered fish rather than a boldly marked one.
Habitat
Corydoras evelynae comes from the upper Solimões and Rio Negro drainages of Amazonas, Brazil — the heart of the central Amazon. This is a region where black water (the tannin-stained, soft, acidic Negro) meets the silt-laden white water of the Solimões, and the cory inhabits the quieter, shallower margins of these systems.
It is a fish of the shallow, sandy edges — slow stream and river margins over fine sand, with submerged wood and fallen leaf litter. These are warm, soft waters, slightly to markedly acidic depending on how much black-water influence there is. Like other corys it is a facultative air-breather, darting to the surface to gulp air and absorb oxygen across a vascularised hindgut, an adaptation suited to the warm, oxygen-poor shallows it favours.
Feeding
Evelyn's cory is a benthic omnivore and detritivore. In the wild it works the sandy bottom continuously, burying its snout and barbels to taste out small invertebrates, insect larvae, worms, micro-crustaceans and the organic film of detritus, sieving cleaned sand back out through the gill openings. It is an opportunist, and that broad diet is part of what makes corys hardy. In the aquarium it readily takes good-quality sinking dried foods alongside small live and frozen items — bloodworm, brine shrimp, chopped earthworm — and should be offered a varied diet rather than left to scavenge whatever its tankmates drop.
Mating
Corydoras are egg-laying shoalers with no pair bond and a distinctive, well-studied courtship that Evelyn's cory is expected to share. When a female is ready she cleans a site and the group becomes active; a male positions himself at right angles to her head in the classic 'T-position,' and she appears to take his milt directly. The sperm is thought to pass rapidly through her gut to fertilise the small number of eggs she clasps in a basket formed by her pelvic fins, which she carries to a cleaned surface — a leaf, a stone, the glass — and presses into place, the sequence repeating a few eggs at a time.
Breeding
Little is published on the deliberate captive breeding of Corydoras evelynae specifically; it is an uncommon, collector-grade species rather than a commercially farmed cory. It is expected to breed along standard Corydoras lines: a group skewed to more males than females, spawning triggered by a large, cooler, soft water change that mimics the onset of the rains, with adhesive eggs scattered onto plants, wood and glass. The eggs receive no parental care — adults will eat them, so breeders remove either the eggs or the parents — and typically hatch in three to four days, the fry taking microworm and baby brine shrimp once the yolk sac is absorbed.
In the aquarium
Evelyn's cory is an attractive, finely spotted species best suited to keepers who can give it clean, soft, well-managed water rather than to absolute beginners. It is a shoaling fish and is genuinely stressed when kept alone or in pairs — keep six or more, and they reward you with constant, confident foraging.
Substrate matters: provide soft sand or very smooth, fine rounded gravel, because corys feed by sifting and sharp or coarse gravel erodes and infects their barbels, leaving the stubby, blunted faces that signal poor husbandry. Coming from warm, soft central-Amazon water, it does best in soft, slightly acidic conditions (about 73–81 °F), well-filtered and well-oxygenated with gentle flow and regular changes; tannin-stained set-ups with leaf litter and wood suit it well. It is utterly peaceful and suits a community of small tetras, pencilfish, rasboras, dwarf cichlids and other calm fish — never anything large enough to bully it. Two standard cautions: the fin spines can catch in nets (a cup is safer), and a distressed cory can release a skin toxin that, in the confined volume of a bag, can kill the whole group, so transport with care.
Conservation
Corydoras evelynae has not been assessed by the IUCN Red List, so it carries no formal conservation status. It is a localised species of the central Amazon, and as with other narrow-range Amazonian fishes that limited distribution is worth noting: the broad pressures on Amazonian freshwaters — deforestation, agricultural and mining run-off, damming and changes to water chemistry — could degrade the soft, sandy shallows it depends on. There is no evidence the aquarium trade threatens it, but a localised black-and-white-water species is the kind of fish whose status would be worth assessing on its own terms rather than assuming it is secure.