Taxonomy & naming
Microglanis oliveirai was described by Ruiz and Shibatta in 2011 in Neotropical Ichthyology, alongside a second new species, M. capixaba, from the same general survey of the upper-middle rio Araguaia basin in central Brazil. It belongs to the family Pseudopimelodidae — the bumblebee and dwarf pimelodid catfishes — within the genus Microglanis, a group of small, heavy-headed South American catfishes long confused with true Pimelodidae before being split out. The Catalog of Fishes treats Microglanis oliveirai as the valid name, and no earlier combination under another genus is documented for this species since it was described directly into Microglanis.
The genus name Microglanis combines Greek mikros ("small") and glanis (an old term for a catfish), aptly describing the genus's diminutive members. The species epithet oliveirai honors Claudio de Oliveira of the Universidade Estadual Paulista, recognizing his contributions to the study of Neotropical fish evolution. The species is distinguished from its congeners by a short lateral line and specific vertebral and fin-ray counts noted in the original description.
Morphology
Microglanis oliveirai is an extremely small catfish, known only from a holotype of 1 in standard length — among the smallest fish in the genus. Like other Pseudopimelodidae it has a broad, flattened head, a stout, tapering body, and a well-developed adipose fin set behind the dorsal fin. The pectoral fin spine is robust and heavily serrated, carrying roughly 9–13 teeth along its anterior edge and 6–10 along the posterior edge — a locking, saw-toothed spine typical of catfishes that can jab an unwary hand or snag in a net.
As in virtually all catfishes, the skin is naked and scaleless rather than armored in bony plates, which has direct consequences for medication sensitivity (see "In the aquarium"). No live color description, sexual dimorphism, or growth-beyond-holotype data has been published; the species is presently characterized almost entirely from the original type material.
Habitat
The species is known from small streams and tributaries of the rio das Mortes and rio Cristalino, within the upper-middle rio Araguaia basin of Mato Grosso, Brazil. The type locality is the rio Corrente, a right-bank tributary of the rio das Mortes, at approximately 15°29'56.3"S, 52°12'10.8"W. This places it firmly within interior Brazil's Cerrado-fringed Araguaia drainage rather than the Amazon proper.
No specific water-chemistry data — temperature, pH or hardness — was recorded in the original description or in subsequent literature, and this species has not been characterized in aquarium or field water-quality surveys. Related Microglanis species from similar habitats are typically associated with sand and mud substrates in small, well-oxygenated streams, but this cannot be stated as confirmed for M. oliveirai specifically; treat any inferred water parameters as provisional rather than measured for this exact species.
Feeding
No diet data has been published for Microglanis oliveirai. Congeners in the genus, and Pseudopimelodidae generally, are nocturnal benthic micro-predators that forage the stream bottom after dark for small invertebrates and detritus, and in the aquarium accept sinking pellets, frozen foods and other prepared foods offered once lights are out. Given the tiny adult size documented for this species (1 in SL), any prey items it takes in the wild are necessarily very small — likely micro-crustaceans, insect larvae and other tiny invertebrates — but this is inference from the genus rather than a confirmed observation for M. oliveirai itself.
Mating
No courtship or mating behavior has been documented for Microglanis oliveirai. This is an essentially unknown-in-life species outside its original taxonomic description, and no field or aquarium observations of spawning behavior have been published.
Breeding
Breeding has not been documented for Microglanis oliveirai, in the wild or in captivity — there is no record of this species having ever been bred in an aquarium, and no field data on spawning season, egg deposition or parental care exists in the literature. It is best treated honestly as a species whose reproductive biology is presently unrecorded, rather than assumed to follow any particular pattern from better-studied catfish groups.
In the aquarium
Microglanis oliveirai is not established in the aquarium trade — hobby literature covering the genus generally notes that species-specific aquarium data for M. oliveirai is unavailable, and this species is rarely if ever kept. Because it is one of the smallest catfishes on record, at roughly 1 in SL (about 1.5 in total length by some estimates), it would not require a large aquarium if ever available, but a stable, well-oxygenated setup with fine sand or soft substrate and secure hiding places would suit its bottom-dwelling, presumably nocturnal habits, mirroring the care given to other small Microglanis.
As with essentially all catfishes, its skin is scaleless and naked rather than protected by scutes, so it should be treated as medication-sensitive: copper-based treatments and many standard medications should be dosed conservatively, often at half strength, exactly as with loaches, puffers and other scaleless fishes. It also carries a robust, serrated, locking pectoral spine that can snag a net or jab a hand, so it is safer to move in a container than to net directly. Given the complete absence of husbandry records, anyone encountering this species should treat it with caution and document any observations, as almost nothing is presently known about keeping it long-term.
Conservation
The IUCN Red List has not assessed Microglanis oliveirai; its conservation status is Data Deficient in the sense that no formal Red List evaluation exists, reflecting how little is known about its population size, range extent or threats beyond the original 2011 description. It is known only from a small number of streams in the upper-middle rio Araguaia basin of Mato Grosso, Brazil, a region that has experienced substantial habitat pressure from agricultural conversion and hydrological change in recent decades, though no study has directly linked such pressures to this species.
As an apparently narrow-range stream endemic with no recorded aquarium trade presence, its conservation profile depends entirely on the health of its specific Araguaia tributaries rather than on collection pressure. Given the data gap, further field surveys — rather than assumptions — are needed before any meaningful status can be assigned.