Taxonomy & naming
Microglanis carlae was described in 2008 by Vera Alcaraz, da Graça & Shibatta from the arroyo Yacaré, a left-bank tributary in the Río Paraguay basin of Paraguay; the holotype (MNHNP 3667, 1.5 in SL) and the original description were published in the Brazilian journal Neotropical Ichthyology. It belongs to the family Pseudopimelodidae, the bumblebee catfishes and their relatives, a group that was long lumped into Pimelodidae before being recognised as its own family. The Catalog of Fishes treats Microglanis carlae as the valid name, with no synonyms noted in the cached sources.
The genus Microglanis combines Greek mikros ("small") with glanis, an old name for a catfish, a fitting label for a genus of diminutive bottom-dwellers rarely exceeding a few centimetres. The species epithet carlae honours Dr. Carla Simone Pavanelli, a Brazilian ichthyologist, following the common taxonomic practice of naming a species after a colleague.
Morphology
Microglanis carlae is a genuinely tiny catfish: the maximum recorded size is just 1.5 in SL, making it one of the smallest species in a genus already known for small members. Like other pseudopimelodids it has the compact, broad-headed, big-eyed build typical of the bumblebee catfish group, with three pairs of barbels used to sense food on the bottom in low light.
As with virtually all catfishes, the skin is scaleless (naked), which matters directly for medication — dose copper-based treatments and many other medicines conservatively, as this species has no scales to buffer chemical exposure. It also carries the stiff, small locking spines typical of the order at the leading edge of the pectoral and dorsal fins; while nowhere near as formidable as in larger catfish, they can still snag in a net, so it is best scooped with a container rather than netted.
Habitat
The species is known from the Río Paraguay basin in Paraguay, where it has been collected in moderately flowing stream sections with dark, tannin-stained water over sand and mud bottoms, typically sheltering under floating vegetation at depths of roughly 5–7 ft. This dark-water, structurally complex habitat gives the fish cover during the day and a rich supply of small invertebrates at night.
The cached sources do not give precise pH or hardness figures for the type locality; general Microglanis care notes describe the genus as tolerant of a wide range of water chemistry, with soft, slightly acidic water more often recommended specifically to encourage breeding rather than as a strict survival requirement.
Feeding
Microglanis carlae is a nocturnal benthic micro-predator and opportunist, foraging along the bottom after dark for small invertebrates and other food items its tiny mouth can manage. In the aquarium it readily accepts standard ornamental fish foods — sinking pellets and shrimp pellets sized appropriately for its small mouth — along with live or frozen blackworms when available.
Because it is most active at night, feeding is best timed after the lights go out, or at least at dusk, so this small, retiring catfish is not out-competed by more active tankmates for food that sinks to the bottom.
Mating
Specific field observations of courtship in Microglanis carlae are not recorded in the cached sources. For the genus generally, males reach sexual maturity at a very small size — around 1 in excluding the tail fin — and spawning in captivity, where it has been achieved, follows no elaborate courtship ritual beyond a receptive pair or group coming together over vegetation.
Breeding
Breeding is rarely attempted or reported for Microglanis in the aquarium, and no detailed breeding account specific to Microglanis carlae exists in the cached sources — treat this species' captive breeding as effectively undocumented. General genus notes describe spawning as possible but uncommon: eggs are deposited among aquatic plants rather than gathered into a nest, and the parents provide no brood care afterward, leaving the tiny eggs and fry to fend for themselves among the vegetation.
Given the lack of species-specific data, aquarists should not expect this to be an easily home-bred fish; soft, slightly acidic water is the condition most often cited as favourable if breeding is attempted, but successful spawns appear to be incidental rather than routinely reproducible.
In the aquarium
At a maximum of just 1.5 in, Microglanis carlae is a genuine nano-aquarium fish and is marketed as such, comfortable in small, well-planted tanks rather than needing anything like the space larger catfish demand — but its size also means it is easily outcompeted or even eaten by larger tankmates, so stock with other small, peaceful nano species. Provide fine leaf litter, driftwood and dense planting to mimic the floating-vegetation cover it uses in the wild, and expect it to hide by day and forage after dark.
As with all scaleless catfish, treat this species as medication-sensitive: use copper-based and other treatments at reduced, conservative doses. Its small locking fin spines can still catch in fine aquarium nets, so moving it in a cup or container is gentler than chasing it with a net. Sources describe the genus as otherwise undemanding regarding water parameters, tolerating ordinary tap water, which makes this species more about tank mates and cover than exacting water chemistry.
Conservation
The IUCN Red List assesses Microglanis carlae as Least Concern. It is known from the Río Paraguay basin in Paraguay, and the cached sources do not report any specific population threats or major pressures on the species.
As a small-range South American stream species, its long-term status is nonetheless tied to the condition of its home streams — water quality, flow and the floating-vegetation habitat it depends on — even though no elevated conservation concern is currently recorded.