Taxonomy & naming
This species was described in 1980 by Han Nijssen and Isaäc Isbrücker as Aspidoras virgulatus, a plated catfish from Espírito Santo, Brazil. Aspidoras and Scleromystax are closely related corydoradine lineages, and subsequent phylogenetic work transferred virgulatus into Scleromystax Günther, 1864 — the genus of south-eastern Brazilian corys distinguished by the erectile cheek odontodes ('bristles') of breeding males. That reassignment is now reflected in the major databases.
The 2024 revision of the Corydoradinae by Dias, Tencatt and colleagues — best known for dismantling the old super-genus Corydoras into Brochis, Hoplisoma, Osteogaster, Gastrodermus and others — retained both Aspidoras and Scleromystax as valid genera, and the Catalog of Fishes and FishBase list this fish as Scleromystax virgulatus. We follow that combination, noting honestly its Aspidoras origin. The Latin epithet virgulatus, 'striped with little rods', refers to the slender dark streaks along the body.
Morphology
Scleromystax virgulatus is among the smallest members of the genus, with a maximum recorded length of only about 1.5 in in standard length. It has the compact, armoured, deep-bellied build shared by all corydoradines — two rows of bony scutes down each flank, a blunt helmeted head and three pairs of barbels around the mouth.
Its pattern sets it apart: rather than the heavy spotting or marbling of some relatives, the body carries fine, slender dark streaks, the feature its name records. Reflecting its origin in the Aspidoras-like group, its sexual dimorphism is less extreme than in the spectacular bearded corys such as S. barbatus, and the cheek-odontode development of males is correspondingly modest. The dorsal, pectoral and adipose fins each bear the usual stiff cory spine.
Habitat
The species is restricted to coastal river systems in the state of Espírito Santo, in south-eastern Brazil, within the Atlantic Forest belt. This places it toward the northern end of the range of Scleromystax, in clear, generally warm coastal streams running over sand and leaf litter through remnant forest.
It is a tropical freshwater, bottom-dwelling fish of these small coastal drainages. Detailed field water chemistry is sparse, but conditions typical of the region — moderately warm temperatures, soft to medium and acidic-to-neutral water — apply. As with all the genus's coastal-stream endemics, clear, well-oxygenated water is important, and the surrounding Atlantic Forest of Espírito Santo is among the most fragmented in Brazil.
Feeding
Like all corydoradines, S. virgulatus is a benthic foraging omnivore. In its coastal streams it works sand and leaf litter, using its barbels to taste out small invertebrates, insect larvae, micro-crustaceans and organic detritus and venting cleaned substrate through the gills. In the rare event of its being kept, it would be expected — like its relatives — to take sinking dried foods and small live and frozen items such as bloodworm and Tubifex, doing best on a varied diet.
Mating
No specific spawning account has been published for this seldom-kept species, but reproduction can be expected to follow the corydoradine pattern: an egg-scattering shoaler with no pair bond and the characteristic 'T-position' embrace, in which a male aligns at right angles to a ripe female's head, a few eggs are fertilised, and the female carries them in the basket of her pelvic fins to a cleaned surface, repeating until the clutch is laid. Given the species' modest sexual dimorphism, the exaggerated male ornament seen in the bearded Scleromystax is unlikely to feature strongly here.
Breeding
Scleromystax virgulatus is essentially absent from the aquarium hobby, and there is no established captive-breeding record for it. By analogy with related corydoradines it would be expected to lay small batches of adhesive eggs on firm surfaces with no parental care, the eggs best separated from the adults, after a trigger such as a cool, fresh water change mimicking seasonal rain. The fry would need clean, well-oxygenated water and small live foods. This remains inference from its relatives rather than documented practice.
In the aquarium
This is a rarely seen fish of interest chiefly to corydoradine specialists rather than a trade species, and reliable aquarium experience with it is limited. Should it be kept, the standard small-Scleromystax template applies: a group of six or more over soft sand, with leaf litter, wood and gentle, well-oxygenated flow, and soft, near-neutral water. Being small, peaceful and unobtrusive, it would suit a quiet species set-up or company of similarly small, calm fish, away from boisterous tankmates. The usual cory precautions hold — smooth substrate to protect the barbels and a cup rather than a net for handling.
Conservation
Scleromystax virgulatus has been assessed by the IUCN as Least Concern (assessed 7 November 2018). That said, it is an Atlantic-Forest endemic confined to coastal rivers in a single Brazilian state, Espírito Santo, where forest cover is heavily fragmented and small streams are exposed to deforestation, agriculture and development. A Least Concern listing reflects the absence of evidence of major decline rather than wide range or large numbers, and ongoing habitat loss across coastal Espírito Santo means its status is worth keeping under review.