Taxonomy & naming
The Guaporé cory was described by Gerhard Knaack in 1961 from the main stream of the upper Río Guaporé, in Rondônia, Brazil — the same year and the same river that produced the tail-spot cory. It was catalogued for decades as Corydoras guapore, in the small armoured catfish genus (family Callichthyidae). The species was redescribed in detail by Tencatt and Pavanelli in 2015, who documented its midwater habits and the morphological adaptations that go with them.
The genus Corydoras had grown unwieldy — well over 170 species — and molecular work showed it was not a single natural group. In June 2024 Dias, Tencatt and colleagues published a large phylogenomic revision (Zoological Journal of the Linnean Society, zlae053) that split the old Corydoras into several genera, including Aspidoras, Scleromystax, Osteogaster, Brochis, Hoplisoma and the resurrected Gastrodermus Cope, 1878. Under that scheme the Guaporé cory falls in the Gastrodermus lineage — the group with the shortest head profile, also containing the elegans and pygmy-type corys — and becomes Gastrodermus guapore; the epithet, an invariable noun, does not change form. The change is recent and not yet universal, so we keep the familiar 'Corydoras' heading while noting the current valid name. The species belongs to a distinct lineage alongside C. mamore and C. paucerna, and is often confused with C. caudimaculatus, C. ourastigma and C. similis.
Morphology
This is a small cory, reaching only about 1.5–2 in in standard length, and it does not look quite like its relatives. Where most corys are flat-bellied bottom huggers, C. guapore is notably high-bodied and more symmetrical from top to bottom, with a warm golden-brown to tan body overlaid with a fine dark reticulation and a soft metallic sheen. Like all members of the group it is armoured rather than scaled: two rows of overlapping bony plates run down each flank, and three pairs of short barbels fringe the mouth.
The telling features are the ones tied to its mid-water life. The eye is relatively large, the mouth sits in a more terminal (forward-facing) position than the strongly down-turned mouth of a typical sand-sifter, the caudal fin is more deeply and strongly forked, and the whole body is more evenly fusiform — all changes that suit a fish which hangs and manoeuvres in open water rather than ploughing the substrate. The dorsal, pectoral and adipose fins each still carry the stiff, mildly venomous spine characteristic of the group.
Habitat
Corydoras guapore is endemic to the Río Guaporé drainage — the Iténez on the Bolivian side — in the upper Madeira basin, where the river forms the border between western Brazil and northeastern Bolivia. The Guaporé here is an acidic, tannin-stained but relatively clear, warm-water river, and the species occurs in loose aggregations in the water column over sandy substrates with wood and leaf litter.
These are warm, soft, acidic waters. The species sits in a tropical envelope — temperatures of roughly 72–82 °F (FishBase narrows the core to about 70–75 °F), a pH band that runs distinctly acidic to neutral (about 5.0–7.0) and soft to moderately hard water. Like other corys it is a facultative air-breather, surfacing to gulp air and absorb oxygen through a modified, vascularised hindgut — useful insurance in the warm, oxygen-poor shallows of its range.
Feeding
The Guaporé cory is a foraging omnivore, but its diet reflects its unusual lifestyle. As well as taking the small invertebrates, worms, insect larvae and detritus that all corys sift from the bottom, it is partly adapted to feeding on drifting zooplankton in the water column — a pelagic habit unusual in the genus. In the aquarium it accepts sinking dried foods, frozen and live bloodworm and Tubifex, but it does noticeably better when offered small live and frozen suspended foods such as Daphnia and Artemia that it can chase in open water, which suit both its terminal mouth and its mid-water habits.
Mating
Corydoras are egg-laying shoalers with no pair bond and a distinctive, well-studied courtship. When a female is ready she cleans a site — a leaf, a stone, the aquarium glass — 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 into her mouth. Sperm is then thought to pass rapidly through her gut and out to fertilise the few eggs she clasps in a basket formed by her pelvic fins, which she carries to the cleaned site and presses into place. The sequence repeats, a few eggs at a time, until a clutch of sticky eggs is distributed across the chosen surfaces.
Breeding
The Guaporé cory is only rarely bred in captivity, and it has a reputation as a more delicate, less prolific spawner than the workhorse corys. Where it does spawn, the trigger is the familiar one: a large (50–70%) water change with cooler, well-oxygenated water that mimics the rainy season, with a group skewed to more males than females (around two males per female). The adhesive eggs are laid on glass and plants and receive no parental care — the adults will eat them, so breeders move the eggs or the parents. Eggs hatch in about three to four days, and the fry, after absorbing the yolk sac, take microworm and Artemia nauplii. Because captive breeding is uncommon, most fish in the trade are wild-caught from the Guaporé.
In the aquarium
The Guaporé cory is a prized but slightly more demanding aquarium fish than the beginner corys, and its mid-water nature changes how it should be kept. It is an emphatically social, shoaling species — keep eight or more rather than the usual minimum of six, because a larger group brings out the confident, hovering, schooling behaviour that is the whole point of the fish; in small numbers it skulks. A group is comfortable in a tank of around 20 US gal or more, and because it uses the water column as well as the floor, open swimming space matters as much as bottom area.
Substrate should still be soft sand or very smooth, rounded fine gravel, since the fish does sift the bottom: sharp or coarse gravel erodes and infects the barbels, leaving blunted faces — a common sign of poor husbandry. Provide soft, warm (about 72–82 °F), acidic, well-filtered and well-oxygenated water with a gentle current, ideally tinted by leaf litter and wood in the manner of its home river, plus planting and structure to give the shoal security. It is utterly peaceful and suits a quiet community of small tetras, pencilfish, rasboras and dwarf cichlids — never anything large or boisterous. Two cautions worth knowing: the fin spines can catch in nets (a cup is safer), and a distressed cory can release a toxin from its skin that, in the confined volume of a bag or bucket, can kill the whole group, so transport them with care.
Conservation
Corydoras guapore was assessed by the IUCN as Least Concern in 2020. It is reasonably widespread within the Guaporé drainage and there is no evidence that aquarium collection threatens the wild population. That said, it is a narrow-range endemic of a single river system rather than a continent-spanning generalist, and the broad pressures on Amazonian headwaters — deforestation, agricultural run-off, gold-mining sediment and damming in the upper Madeira — all degrade the warm, soft, tannin-stained habitats it depends on. A mid-water specialist tied to clear, structured water may also be more sensitive to siltation than its bottom-grubbing relatives, so it is a species worth watching as land-use change accelerates in Rondônia and the Bolivian Iténez.