Taxonomy & naming
Corydoras pastazensis was described by the American ichthyologist Stanley H. Weitzman in 1963, in the Proceedings of the Biological Society of Washington, from Chicherata near the mouth of the Río Bobonaza, a tributary of the Río Pastaza in Pastaza Province, Ecuador. The epithet is taken from that river system. A subspecies, Corydoras pastazensis orcesi, was later named but is treated as a synonym; the species itself is valid.
The fish belongs to the family Callichthyidae, subfamily Corydoradinae. When Dias, Tencatt and colleagues published their 2024 phylogeny and revised classification — splitting the historically vast genus Corydoras into Brochis, Hoplisoma, Osteogaster, Gastrodermus, Aspidoras, Scleromystax and a restricted Corydoras — the long-snouted Pastaza cory fell within Corydoras in the strict sense (sensu stricto), the lineage built around the type species C. geoffroy. It therefore keeps the name Corydoras pastazensis under the new scheme, which is convenient: both the hobby heading and the current valid combination agree. Catalog of Fishes treats pastazensis Weitzman, 1963 as a valid species.
Morphology
This is a fairly large cory with a distinctly elongated, pointed snout — a 'long-nosed' species in hobby terms — reaching about 2.5 in in standard length, and built solidly with the deep body and twin rows of bony scutes shared by all corydoradines. The longer, more tapering head distinguishes it from the round-snouted Hoplisoma-type corys and is the kind of profile typical of restricted Corydoras.
Three pairs of barbels fringe the downturned mouth for probing the substrate, and the dorsal and pectoral fins carry the usual stiff, locking spines. The body pattern is one of dark markings on a paler ground, with the spotting and a dark dorsal-fin marking usual in the long-nosed corys. As in essentially all members of the subfamily, females grow larger and rounder than males, a difference seen most clearly from above, while mature males have more pointed fins.
Habitat
The Pastaza cory occurs in the upper Amazon system on the eastern slopes of the Andes, in the Pastaza River basin and adjacent drainages of Ecuador and Peru, including the Río Bobonaza of the type locality and the Marañón system; some references extend its range into Colombia. These are warm, lowland-to-foothill rivers and streams of the western Amazon, generally over sand and leaf litter.
FishBase gives a pH range of about 6.0–8.0 and a hardness range of roughly 2–25 dGH for the species, indicating tolerance of soft, acidic water through to moderately hard, near-neutral conditions — a broad envelope consistent with the varied chemistry of upper-Amazon tributaries. Like all corydoradines it can gulp atmospheric air and absorb oxygen through a vascularised hindgut, helping it cope with warm, low-oxygen conditions.
Feeding
There is no dedicated wild-diet study for the Pastaza cory, but it is a benthic omnivore in the corydoradine mould, working the bottom with its long snout and barbels to sift small invertebrates, insect larvae, microcrustacea, worms and organic detritus from sand and leaf litter and ejecting the cleaned substrate through the gills. Its more elongate snout suits probing into and under the substrate. In the aquarium it readily takes sinking tablets, granules and larger flake, along with live and frozen bloodworm, Daphnia, Tubifex and brine shrimp, the last especially useful for conditioning a group before spawning.
Mating
Spawning of Corydoras pastazensis is not specifically documented, but corydoradine courtship is highly conserved. They are egg-laying shoalers without a pair bond: a ripe female cleans a spawning site, the group becomes active, and a male positions himself across the front of her head in the characteristic 'T-position.' Sperm is thought to pass rapidly through the female's gut to fertilise the few eggs she holds in a basket of her clasped pelvic fins, which she then presses onto the cleaned surface, repeating the sequence a few eggs at a time until the clutch is laid.
Breeding
There is no published or registered breeding report for the Pastaza cory, so the account here is by analogy with related long-nosed corys rather than from records of this species. Spawning in such fish is generally induced by conditioning a group well and then performing a cool, large water change to imitate the rainy season; they deposit adhesive eggs on plants, wood and aquarium glass and provide no parental care, so the eggs or the parents are separated to prevent the adults eating them. A productive group, stable clean water and patience are the prerequisites; the precise figures for this species await first-hand reports.
In the aquarium
The Pastaza cory is an occasional rather than a common import, and as a larger, long-nosed cory it is kept much like its relatives, with a little extra attention to size. It is a shoaling species and should be kept in groups of six or more; it is stressed and retiring when kept alone. Being a sizeable, active fish it wants good floor space — a tank with a generous footprint rather than height — and a soft sand substrate is close to mandatory, since the long-nosed corys in particular like to bury the snout to feed and sharp or chipped gravel quickly abrades and infects their barbels.
Warm, clean, well-oxygenated water with gentle flow and regular changes suits it, and it tolerates a fairly wide pH and hardness range. It is peaceful and an excellent community fish for tetras, rasboras, dwarf cichlids and other calm species, provided tankmates are not large enough to bully it. The standard cory cautions apply: net them in a cup rather than a mesh net to avoid snagging the fin spines, and transport them with care, since a badly stressed cory can release a skin toxin that is dangerous in the small volume of a bag or bucket.
Conservation
Corydoras pastazensis is assessed by the IUCN as Least Concern, in an assessment dated 2014. It is a reasonably widespread species of the upper Amazon drainages of Ecuador and Peru, and is not subject to documented range-wide threats. As with all western-Amazon fishes it is exposed to the broad regional pressures of deforestation, agriculture, oil and mineral extraction and associated water-quality decline in the Andean-foothill rivers it inhabits, but at the species level it is currently considered of low conservation concern.