Taxonomy & naming
Aspidoras fuscoguttatus was described by the Dutch ichthyologists Han Nijssen and Isaäc Isbrücker in 1976, in the journal Bijdragen tot de Dierkunde, from material taken in the Córrego Corguinho on the road to Três Lagoas, in the upper Paraná drainage of Mato Grosso, Brazil — still the type locality. It sits in the family Callichthyidae, subfamily Corydoradinae, the group of small armoured catfishes that also contains the familiar Corydoras.
Aspidoras itself was erected by Rodolpho von Ihering in 1907 for a handful of small Brazilian callichthyids that look like miniature corys but differ in the architecture of the skull: the genus is defined by a paired (rather than single) fontanelle on the top of the head, a feature invisible without a specimen in hand but consistent enough to anchor the group. The hobby has long called these the 'false corys' for exactly that reason — they share the cory body plan but are a separate lineage.
A word on the recent upheaval is warranted. The 2024 revision of the Corydoradinae by Dias, Tencatt and colleagues split the bloated genus Corydoras into several genera — Brochis, Hoplisoma, Gastrodermus, Osteogaster and others — and reshuffled a number of species; some former Aspidoras were among the names affected. It is therefore reasonable to ask whether fuscoguttatus moved. It did not: Eschmeyer's Catalog of Fishes continues to list it as 'valid as Aspidoras fuscoguttatus Nijssen & Isbrücker 1976,' and that remains the current valid combination.
Morphology
This is one of the smallest corydoradines, reaching only about 1.5 in standard length — on the order of 1.5–2 in in total length — so that even a mature female is a thumbnail of a fish. The body is the typical cory shape but compact and slightly bulldog-blunt about the head, which has earned it the trade name 'darkspotted bulldog cory.' Like all members of the subfamily it wears bony armour rather than scales: two rows of overlapping scutes run along each flank and the head is a hard helmet, and three pairs of barbels fringe the small downturned mouth.
The colour is the source of the name. The ground is a pale fawn-to-greyish, finely peppered and blotched with dark brown spots ('fuscoguttatus' means, literally, dark-spotted) that scatter across the flanks and head and often coalesce into vague bars or a marbled pattern; the fins carry rows of dark dots. As in other corys the dorsal and pectoral fins are stiffened by spines. Sexual differences are modest and best judged from above: females grow a little larger and noticeably broader and fuller-bodied, while mature males tend to have more pointed fin tips.
Habitat
Aspidoras fuscoguttatus is an inland species of central and southeastern Brazil. It was originally known from the upper Paraná basin — the type locality lies in the Paraná drainage — and its range has since been documented to span both the upper Paraná and the upper São Francisco basins, including tributaries such as the rio Grande, rio Uberaba and rio Paraopeba systems. This is the cerrado country of interior Brazil rather than the Amazon, and the fish lives in the smaller clear streams and headwater creeks of those uplands.
The waters it favours are warm, soft and on the acid side. Aquarium and field figures put it at roughly 72–77 °F, a pH band of about 5.5–6.8 and modest hardness (around 12 °dH or less) — slightly cooler and more acidic than the broad envelope tolerated by a hardy bronze cory. It is a bottom fish of sand and fine substrate in shaded, gently flowing stream margins, where it forms loose shoals and works the sediment for small food.
Feeding
Like its relatives, fuscoguttatus is a benthic micro-omnivore that earns its living by sifting. It buries its barbels and snout in fine sand to taste out small invertebrates, insect larvae, micro-crustaceans, worms and the organic detritus and biofilm of the streambed, passing mouthfuls of sand out through the gill openings. Its small size means it specialises in correspondingly small prey. In the aquarium it takes readily to sinking pellets, granules, crushed flake and small frozen or live foods — bloodworm, Daphnia, grindal and white worm, microworm — and conditioning on live and frozen fare is the standard route to bringing a group into breeding condition. As with all sand-sifters, it should be fed foods that reach the bottom rather than left to scavenge scraps.
Mating
Aspidoras share the distinctive corydoradine courtship, and fuscoguttatus is no exception. Spawning fish are egg-layers with no pair bond: when a female is ripe the group becomes active and a male takes up the classic 'T-position,' lying at right angles across the front of the female's head while she apparently takes his milt. The few eggs she is carrying at that moment are clasped in a basket formed by her pelvic fins, and after fertilisation she swims off to press them onto a chosen surface — plant leaves, wood, stones or the aquarium glass — cleaning the site beforehand. The sequence repeats, a handful of eggs at a time. Because the fish is so small, both the eggs and the resulting fry are correspondingly tiny.
Breeding
Breeding follows the standard Aspidoras pattern and is achievable, though less casually automatic than with the bronze cory. A conditioned group, skewed towards more males than females, is typically triggered by a large, cooler water change that imitates the onset of seasonal rains, dropping the temperature a few degrees and freshening the water. The adhesive eggs are laid in small batches and scattered over firm surfaces; the adults give no parental care and will eat the spawn, so breeders move either the eggs or the parents. Eggs hatch in roughly three to five days depending on temperature, and the very small fry — once the yolk sac is absorbed — need correspondingly fine first foods: infusoria and powdered fry food at first, graduating to microworm and newly hatched brine shrimp. They are slow to grow at first simply because everything about this fish is in miniature. A clean, well-oxygenated bottom and stable, soft, slightly acid water suit the fry.
In the aquarium
This is an undemanding but genuinely shoaling fish that should be kept in groups — six or more — to see natural, confident behaviour; kept singly or in pairs it becomes shy and inactive. Its diminutive size makes it well suited to smaller, well-planted aquaria, but the priorities are the same as for any cory. First, substrate: provide soft sand or very smooth, fine rounded gravel, because these fish feed by sifting and sharp or coarse grit abrades and infects their barbels, eroding them to stubs — one of the most common signs of poor cory husbandry. Second, water: keep it warm but not hot (about 72–77 °F), soft and slightly acidic, well-filtered, well-oxygenated and clean, with a gentle current and regular changes. Shade from planting, wood or rockwork helps them settle.
It is utterly peaceful and belongs only with small, calm tankmates — small tetras, pencilfish, dwarf rasboras and the like — never with anything large enough to bully or eat a 1.5 in catfish. As with other corydoradines, two cautions apply: the fin spines can snag in a net, so a cup is safer for moving them, and a badly stressed cory can release a skin toxin that, in the small volume of a bag or bucket, can poison the whole group, so transport them with care.
Conservation
Aspidoras fuscoguttatus is assessed by the IUCN Red List as Least Concern (most recently evaluated in 2018). It is a relatively common and reasonably widespread small catfish across the upper Paraná and São Francisco headwaters, and that broad range underlies the low-concern rating. Most fish in the aquarium trade are tank-bred or come from a species that sustains collection without obvious population impact, so hobby demand is not a major pressure.
That said, the interior streams it inhabits are not pristine refuges. The cerrado headwaters of central Brazil are under sustained pressure from agricultural expansion, water abstraction, siltation, damming and pollution, all of which degrade exactly the kind of clear, soft, sandy creeks this fish needs. Least Concern is a statement about the species as a whole rather than a guarantee for any single population, and small-ranged headwater specialists like this one are precisely the fish whose status can change quietly as their habitats are altered.