Taxonomy & naming
Corydoras spilurus was described by the British ichthyologist John Roxborough Norman in 1926, in the Annals and Magazine of Natural History, from material taken in Iponcin Creek, a tributary of the Approuague River in French Guiana (the type locality). It was placed in Corydoras Lacépède, 1803, the large genus of South American armoured catfishes (family Callichthyidae). The lectotype and paralectotypes are held in the Natural History Museum, London, and the Amsterdam museum collections.
The 2024 phylogenetic revision of the Corydoradinae by Dias, Tencatt and colleagues split the overgrown genus Corydoras into several lineages — reviving Brochis, Hoplisoma, Gastrodermus and Osteogaster among them — but retained a core of species in Corydoras in the strict sense, and C. spilurus is one of them: it stays Corydoras spilurus under the new classification, and FishBase still lists it under Corydoras. The epithet spilurus, from the Greek spilos ('spot') and oura ('tail'), refers to a dark marking at the base of the tail.
Morphology
This is a small cory, reaching about 2.5 in in standard length, with the usual compact corydoradine build: a hard, helmet-like head, a body sheathed in two rows of overlapping bony scutes, three pairs of barbels around the downturned mouth, and stiff leading spines in the dorsal, pectoral and adipose fins.
The pattern is a pale ground with a darker dorsal region and the dark caudal-base marking that gives the species its name; the underside and throat carry the pinkish flush behind the hobby name 'pinkthroat corydoras.' Females, as in most corys, grow somewhat larger and noticeably broader and deeper-bodied than males when in spawning condition. Exact meristics rest on Norman's original description and later Guiana-Shield revisions, since several similar small corys occur in the same drainages.
Habitat
Corydoras spilurus is a Guiana-Shield fish, recorded from the Approuague River basin in French Guiana and the Suriname River basin in Suriname. FishBase reports it as very abundant in the upper reaches of rivers, where it frequently occurs over sandy bottoms swept by strong currents and is often found schooling alongside related corys — a rheophilic habit somewhat unusual among the more sedate members of the genus.
These are warm, soft, clear-to-stained shield waters. The species is a facultative air-breather, gulping surface air and absorbing oxygen through a vascularised modified hindgut, the standard corydoradine adaptation. Reported figures sit at roughly 72–79 °F and a pH band of about 6.0 to 8.0; given its preference for current it does best with well-oxygenated, flowing water.
Feeding
Corydoras spilurus is a benthic omnivore and detritivore. It works the sandy bottoms of upper-river reaches, sifting the substrate for small invertebrates, insect larvae, micro-crustaceans, worms and organic detritus and venting cleaned sand through the gill openings. It is an opportunist rather than a specialist. In the aquarium it readily takes sinking pellets and tablets, frozen bloodworm and brine shrimp, and other small foods worked from the bottom.
Mating
No detailed spawning account specific to C. spilurus is widely published, but it follows the standard corydoradine courtship. These are egg-laying shoalers with no pair bond: a ready female cleans a spawning site, a male takes the classic 'T-position' at right angles to her head, she appears to take milt into her mouth, and sperm passes quickly through the gut to fertilise the few eggs she carries in a basket of her clasped pelvic fins before pressing them onto the cleaned surface. The cycle repeats a few eggs at a time.
Breeding
C. spilurus is not among the commonly bred corys, and there is no large body of published fry data for it specifically. By analogy with related Guiana-Shield species, spawning would be expected to follow a cool, soft water change that mimics the rains, with a small clutch of adhesive eggs scattered on plants, wood and glass and given no parental care — adults will eat the eggs, so a breeder removes either the eggs or the parents. Eggs of similar corys hatch in roughly three to five days, and the fry take microworm, baby brine shrimp and fine prepared foods once the yolk is absorbed. A well-oxygenated tank with gentle flow suits this current-loving species.
In the aquarium
C. spilurus is a peaceful, active shoaling catfish that should be kept in a group of six or more; it is stressed and listless when kept alone or in pairs. Provide a tank with a generous footprint and a soft sand substrate — corys feed by sifting, and sharp or coarse gravel erodes and infects the barbels, leaving them blunted, a common sign of poor husbandry.
Because it comes from fast, sandy upper reaches, it appreciates more current and oxygenation than the average cory: clean, well-filtered, soft and slightly acidic water with a brisk turnover and regular water changes shows it at its best. It is an ideal companion for small tetras, pencilfish, dwarf cichlids and other calm soft-water fish, and should never be kept with anything large enough to bully it. The usual corydoradine cautions apply: the fin spines can catch in a net, so a cup is safer for moving the fish, and a badly stressed cory can release a skin toxin that may kill the whole group in the small volume of a bag, so transport it with care.
Conservation
Corydoras spilurus is assessed by the IUCN as Least Concern (assessment published in 2021). It is reported as very abundant across its Guiana-Shield range, which spans the Approuague basin of French Guiana and the Suriname basin, and the shield's freshwaters remain comparatively well preserved, so no major range-wide threat has been identified. As with all shield endemics, localised pressures — gold-mining sedimentation, deforestation and creek pollution — could affect particular populations, but the species as a whole is in no apparent danger.