Taxonomy & naming
The species was described by Harro Hieronimus in 1995 as Corydoras lacerdai, from the Ribeira da Terra Firme in Bahia, Brazil, and dedicated to the collector Marco T. C. Lacerda. Like all the bristle-cheeked corys it was later moved into Scleromystax Günther, 1864 — a small, well-supported genus of south-eastern Brazilian corydoradines that sits apart from Corydoras proper, distinguished by the development of patches of erectile cheek odontodes ('beards') in mature males and by a strong sexual dimorphism in colour and finnage.
The huge 2024 revision of the Corydoradinae by Dias, Tencatt and colleagues, which broke the old catch-all Corydoras into several genera (Brochis, Hoplisoma, Osteogaster, Gastrodermus and others), retained Scleromystax as a valid, ancient lineage; the Catalog of Fishes and FishBase accordingly list this fish as Scleromystax lacerdai. We keep that combination, which is also the name under which the few specialist hobbyists who keep it know the species. It is sometimes confused in collections with the more widespread S. barbatus and S. prionotos, but is geographically isolated from both, far to the north.
Morphology
This is a modestly sized Scleromystax, with males reaching about 2 in and females a little larger and broader, around 2 in in standard length. The body has the deep-chested, flat-bellied build of the tribe, clad in the usual two rows of overlapping bony scutes, with a blunt, helmet-like head and three pairs of barbels around the downturned mouth.
The ground colour is a warm tan-to-olive, heavily peppered with dark spots and short bars. The clearest sexual difference is in the dark mid-lateral marking that follows the line of the spine: in males it forms a more or less continuous dark band, while in females it is broken up into an uneven, blotchy bar pattern. Mature males, in keeping with the genus, develop bristly patches of odontodes on the cheeks and somewhat extended fins; females stay smooth-faced, larger and rounder. As with all corys the dorsal, pectoral and adipose fins are each armed with a stiff leading spine.
Habitat
Scleromystax lacerdai is endemic to a small set of coastal river systems in the state of Bahia, north-eastern Brazil, within the Atlantic Forest (Mata Atlântica) belt. The type locality is the Ribeira da Terra Firme; the species has since been recorded from the Rio Cahy near Prado and the Rio Pardo around Canavieiras, all short coastal drainages running through the remnant forest to the sea.
These are small, clear, gently flowing forest streams over sand and leaf litter. Because Bahia lies well to the north of the cool subtropical haunts of S. barbatus, this is the most thermally tolerant member of the genus, comfortable in genuinely warm water — roughly 72–77 °F — at a near-neutral, slightly acidic pH of about 6.0–7.2. The Atlantic Forest is one of the most fragmented and threatened biomes in South America, and the narrow, forest-dependent streams these fish need are exactly the habitats most exposed to clearance and degradation.
Feeding
Like all corydoradines, S. lacerdai is a benthic foraging omnivore. In its forest streams it works the sandy bottom and leaf litter, sifting substrate through its gills and using its barbels to taste out small invertebrates, insect larvae, micro-crustaceans and organic detritus. In the aquarium it takes sinking tablets and good-quality flake readily, but relishes worm foods above all — frozen bloodworm is a firm favourite, along with chopped earthworm and, used sparingly, white worm and grindal worm. A varied, protein-rich diet keeps it in spawning condition.
Mating
Reproduction follows the classic corydoradine pattern, with no pair bond and the well-known 'T-position' spawning embrace. A ripe female cleans a site, the group becomes active, and a male aligns himself at right angles to her head; she appears to take milt directly, and a few fertilised eggs at a time are clasped in a basket formed by her pelvic fins. In this species the eggs are reported to be placed high up — typically on the aquarium glass — rather than on plants or the substrate, and the sequence is repeated until the clutch is complete.
Breeding
S. lacerdai has been bred in captivity by dedicated catfish keepers, though it is far less prolific and forgiving than the common tropical corys. Spawning is encouraged by cooler, fresh water changes that imitate the rainy season. The adhesive eggs are laid in small batches, receive no parental care, and are best moved away from the adults to hatch. Newly free-swimming fry are started on liquid fry food for egg-layers, then graduate to microworm and, as they grow, crushed flake. Growth is unhurried and clean, well-oxygenated water is essential; this is a fish for the patient specialist rather than the casual breeder.
In the aquarium
This is an uncommon, collector's catfish rather than a shop staple, but it is rewarding for those who track it down. Keep it as a group of six or more in a tank with a soft sand bottom — sharp gravel abrades and infects the barbels of any cory — with leaf litter, wood and shade to echo its forest-stream origins. Unlike its cool-water southern cousins, S. lacerdai is genuinely tropical and is content in ordinary community temperatures of about 72–77 °F, with a gentle current, brisk filtration and good oxygenation. Water should be soft to medium and close to neutral. It is peaceful and retiring, best partnered with small, calm characins and other gentle community fish; avoid boisterous or large tankmates. As with all corys, handle with a cup rather than a net, since the fin spines snag easily.
Conservation
Scleromystax lacerdai has not been assessed by the IUCN, so it has no formal Red List status. That silence is itself a concern: this is a narrow-range endemic confined to a handful of small coastal drainages in Bahia, embedded in the Atlantic Forest — a biome reduced to a small fraction of its original extent and under continuing pressure from deforestation, agriculture and urban expansion. Species with such restricted distributions in heavily altered landscapes are inherently vulnerable, and the lack of an assessment reflects a data gap rather than security. Almost all aquarium specimens are wild-collected, so the species would benefit from a formal evaluation of its range and population.