Taxonomy & naming
Corydoras zawadzkii was described in 2016 by Luiz Tencatt and Willian Ohara, from the Rio Madeira basin in Brazil. It belongs to the long-snouted group of Corydoras — fish with an elongated mesethmoid producing a drawn-out, slightly beaked profile — and was diagnosed in part by that well-developed snout and by one to two longitudinal black stripes along the flanks. The patronym honours the ichthyologist Cláudio Zawadzki.
The species was described as a member of Corydoras Lacépède, 1803, and the Catalog of Fishes (Eschmeyer, California Academy of Sciences) lists Corydoras zawadzkii Tencatt & Ohara, 2016 as a valid species. When Dias, Tencatt and colleagues split the old, oversized Corydoras into several lineage genera in their 2024 revision, zawadzkii was retained in Corydoras in the strict sense rather than moved into Hoplisoma, Brochis, Osteogaster or another of the new genera — the combination FishBase and the Catalog of Fishes currently carry. As a recently described species from a well-studied revision team, its placement is reasonably secure, though the genus-level classification of the subfamily as a whole remains in flux.
Morphology
This is a medium-sized, long-snouted cory, reaching about 2 in standard length. Its defining external features, set out in the original description, are the elongated snout — the product of a long mesethmoid with a well-developed anterior tip — and one to two longitudinal black stripes running along the flanks. In life the body shows an iridescent greenish-yellow cast, photographed in freshly caught specimens, over the usual cory armour of two rows of overlapping bony plates meeting along the back.
The head is the hard, helmeted structure typical of the group, and the long-snouted profile gives the fish a more pointed, probing look than the blunt-faced 'short-snout' corys. Three pairs of barbels fringe the mouth. As in all Corydoras, the dorsal, pectoral and adipose fins carry stiff leading spines used in defence; females are expected to grow somewhat larger and deeper-bodied than males, the usual pattern in the genus.
Habitat
Corydoras zawadzkii is known from the Rio Madeira basin — the largest tributary of the Amazon, draining the eastern slopes of the Andes and the Bolivian and Peruvian lowlands before joining the main river in Brazil. According to the type material it was collected in small clearwater streams roughly 7–10 ft wide and a half to under two metres deep, over sandy substrate with leaf litter.
That habitat — shallow, clear, gently flowing forest streams over sand — is characteristic of the long-snouted corys, which probe the sand for food. Water in such streams is warm and soft, and the species' tolerances are expected to match: temperatures around 72–79 °F and a pH on the acidic-to-neutral side. Like all members of the subfamily it is a facultative air-breather, gulping atmospheric air at the surface and absorbing oxygen through a vascularised hindgut, which helps it cope with warm, low-oxygen shallows.
Feeding
Corydoras zawadzkii is a benthic omnivore and detritivore, and its long snout is a feeding adaptation: it lets the fish probe more deeply into sand and between leaf litter to extract small invertebrates, insect larvae, worms and organic matter than the blunt-faced corys can reach. It works the bottom continuously, sifting substrate through the gills. In the aquarium it would be expected to take sinking pellets and wafers, frozen bloodworm and brine shrimp and similar foods, foraged from a soft, sandy bottom that suits its probing style.
Mating
Courtship has not been described specifically for C. zawadzkii, but it is expected to follow the standard Corydoras pattern. These are egg-laying shoalers with no pair bond. A ready female cleans a spawning surface and the group becomes active; a male adopts the classic 'T-position' at right angles to her head, a few eggs are fertilised and clasped in a basket formed by her pelvic fins, and she presses them onto the cleaned site, repeating the sequence a few eggs at a time until the clutch is laid.
Breeding
There is no published captive breeding account for Corydoras zawadzkii, which is a recently described species rarely seen in the trade, so what can be said is by analogy with the genus. Spawning in Corydoras is typically triggered by a cool, large water change mimicking the onset of the rains; the adhesive eggs are laid in small batches on firm surfaces and receive no parental care, adults being inclined to eat them, so breeders move eggs or parents. Eggs hatch in a few days and the fry take microworm, baby brine shrimp and powdered foods once the yolk is absorbed. These specifics should be verified directly for this species rather than assumed from the genus.
In the aquarium
Corydoras zawadzkii is rarely available and is a fish for the dedicated cory keeper rather than the general community, but its care follows the standard template with attention to its long-snouted feeding style. Keep it in a shoal of six or more — corys are stressed alone — in a tank with generous bottom area, around 23.5 in of footprint or more for a group.
Substrate matters more for a long-snouted cory than almost any other detail: provide soft, fine sand, because these fish probe and sift, and coarse or sharp substrate quickly erodes and infects the barbels and snout. Keep the bottom clean and the water warm (about 72–79 °F), well-filtered and well-oxygenated with a gentle current, on the soft, slightly acidic side that reflects its clearwater stream origins. It is peaceful and suits calm tankmates such as small tetras, pencilfish and dwarf cichlids. The usual cautions apply: fin spines snag in nets, so use a cup, and a badly stressed cory can release a skin toxin that may kill the group in the confined volume of a transport bag, so move it carefully.
Conservation
Corydoras zawadzkii has not, on the available records, been individually assessed by the IUCN Red List, so its status is best given as Not Evaluated rather than assigned a category. As a recently described species known from a restricted part of the Rio Madeira basin, its true range and population size are still poorly understood, which is itself a reason for caution. The Madeira system faces real pressures — large hydroelectric dams on the main river, deforestation and mining in its catchment — that degrade exactly the kind of small clearwater forest streams this species inhabits, so a proper assessment of its distribution and status would be valuable.