Taxonomy & naming
Auchenipterus brachyurus was described by the American palaeontologist and naturalist Edward Drinker Cope in 1878. It belongs to the family Auchenipteridae, the driftwood catfishes, within the genus Auchenipterus, and the Catalog of Fishes treats it under this combination.
As with much of Siluriformes, older literature and some historical combinations for driftwood catfishes have shuffled species among genera over the decades; Auchenipterus brachyurus has remained in its describing genus. Data on the species is comparatively sparse — it is a lesser-known member of a family better represented in the hobby and literature by genera such as Trachelyopterus and Tatia.
Morphology
Auchenipterus brachyurus reaches a maximum of about 6.5 in standard length, a modest size for a catfish and one that keeps it comfortably within reach of a home aquarium. Like other driftwood cats it has a compressed, laterally flattened, elongate body built for holding position in open water rather than the squat, bottom-hugging shape typical of many catfishes.
The skin, as in all catfishes, is scaleless — this matters directly for medicating the fish (see "In the aquarium"). Barbels and the small adipose fin typical of the family are present, along with the stiff, often serrated pectoral spines characteristic of catfishes generally, which can lock erect and should be handled with care.
Habitat
The species is native to the upper Amazon River basin in South America, where it occupies benthopelagic habitat — meaning it ranges through open water in the water column as readily as near the bottom, rather than being a strict substrate-dweller. This matches the broader ecology of driftwood catfishes, many of which shoal in mid-water around fallen timber, root tangles and slower river margins.
Detailed water-chemistry data for this species is not documented in the sources consulted here; as an upper Amazonian river fish it can be assumed to come from warm, soft, tropical freshwater typical of the region, but specific temperature and pH figures are not confirmed and should not be guessed at.
Feeding
FishBase records a trophic level of 3.4 for Auchenipterus brachyurus, consistent with an omnivorous-to-carnivorous benthic and mid-water forager. Like most driftwood catfishes it is presumed to be most active after dark, taking invertebrates, small prey and organic material as it moves through the water column and along the bottom.
In the aquarium, driftwood cats of this size typically accept sinking pellets, frozen foods and other prepared foods readily, but because they forage mostly at night, offering food after the lights go out helps ensure a nocturnal feeder is not out-competed by faster, diurnal tankmates.
Mating
Auchenipterus brachyurus shares the family Auchenipteridae's remarkable reproductive strategy: internal fertilisation, one of the few such cases among catfishes. The male's anal fin is modified into an intromittent organ used to transfer sperm directly to the female during mating, rather than the external egg-and-milt release typical of most fish.
Following internal insemination, the female stores sperm within her body and can lay fertile eggs some time after mating has occurred — the exact interval is not documented for this species, but related auchenipterids are known to carry stored sperm and mature eggs for extended periods before spawning. This decoupling of mating from egg-laying is rare among catfishes and worth stating plainly rather than assuming the more familiar external-fertilisation pattern.
Breeding
Because fertilisation in Auchenipterus brachyurus is internal, breeding does not follow the egg-scattering or nest-building patterns seen elsewhere in Siluriformes. Eggs are laid externally by the female sometime after internal mating has taken place, but details of spawning site, clutch size and any parental care specific to this species are not documented in the available sources.
Parental care after laying is not confirmed for this species; data is sparse. Given the general pattern in Auchenipteridae, sustained brood-guarding by either parent is not typical, though this should not be stated as certain for A. brachyurus specifically. The species is not established as a regularly home-bred aquarium fish.
In the aquarium
At a modest maximum of 6.5 in, Auchenipterus brachyurus stays within reach of a reasonably sized home aquarium, avoiding the size trap that catches keepers of larger catfish species — but it should still be given adequate swimming space given its open-water, shoaling habits rather than treated as a strict bottom-dweller. As with any catfish, its scaleless skin makes it more sensitive than scaled fish to copper and many medications; dose conservatively, often at half the labelled rate.
Handle it with the same caution due any catfish carrying pectoral spines — move it in a container rather than a net to avoid tangling and injury to both fish and keeper. Being most active after dark, it benefits from cover during the day and feeding after lights-out. Specific temperature and pH requirements are not confirmed in the sources available here, so new keepers should default to stable, warm tropical conditions typical of Amazonian river fish and avoid extremes.
Conservation
The IUCN Red List assessed Auchenipterus brachyurus as Least Concern in 2020. FishBase also notes the species has high resilience, with a population doubling time under fifteen months, and lists it as harmless to humans.
As an upper Amazon basin species it is not currently flagged as facing significant range-wide pressure, though like many South American river fishes its long-term status is tied to the health of Amazonian freshwater habitats generally, including deforestation, damming and water-quality pressures across the basin.