Taxonomy & naming
Xyliphius anachoretes was described by Figueiredo & Britto in 2010, one of several Xyliphius species erected or reviewed around that time as South American banjo catfishes received closer taxonomic attention. It belongs to the family Aspredinidae, the banjo catfishes, within the genus Xyliphius — a group of small, flattened, mostly poorly known river-bottom catfishes found across northern and central South America.
The genus name Xyliphius is of Greek derivation referencing the flattened, wood-like body shape typical of the genus. The species epithet anachoretes is Greek/Latin for "hermit" or "recluse", chosen because the species was known from only a very small number of original specimens — a fitting name for a fish that has been collected so seldom. As with much of Aspredinidae, the Catalog of Fishes treats Xyliphius anachoretes as the currently valid combination; no historical placement under another genus is documented for this species.
Morphology
Xyliphius anachoretes is small, reaching a maximum recorded size of only about 3.5 in standard length. Like other banjo catfishes it has a strongly flattened, disc-like head and forebody tapering to a slender tail, giving the family its "banjo" silhouette, and it lacks scales, instead carrying naked or lightly plated skin typical of the family.
Distinctive features noted for the species include highly reduced eyes — an adaptation to a benthic, often turbid or low-light existence — toothless premaxillae, and a row of fleshy papillae along the lower lip, likely sensory or feeding structures used to detect food on or in the substrate. As in other catfishes, any fin spines should be treated as potentially capable of locking and snagging a net; the skin is naked, so the species should be assumed medication-sensitive like other scaleless catfish.
Habitat
The species is known from the Rio Tocantins-Araguaia system in Brazil, a major river system of central and northeastern South America. It is described as rare, consistent with the handful of specimens on which the species was based, and consistent with the reclusive habits implied by its name.
Specific temperature and pH data have not been documented for this species. As a South American river-bottom catfish it can be assumed to prefer warm, tropical freshwater typical of the Tocantins-Araguaia basin, but exact parameters are not established in the available literature and should not be guessed at precisely.
Feeding
Detailed dietary data for Xyliphius anachoretes has not been documented. Aspredinids in general are nocturnal, benthic micro-predators and scavengers, using barbels and sensory papillae — like the fleshy lower-lip papillae noted in this species — to locate small invertebrates, detritus and other food items on or within the substrate after dark.
In the near-total absence of a hobby record for this species, feeding guidance can only be inferred from its family: a bottom-feeding diet of small live or frozen invertebrate foods offered after lights-out would suit its build and toothless, papillae-fringed mouth, but this is inference from Aspredinidae generally rather than a documented fact about this species.
Mating
No mating behaviour has been documented specifically for Xyliphius anachoretes. In several banjo catfishes (Aspredinidae), the female is known to carry fertilised eggs attached to the skin of her belly via fleshy stalks called cotylephores, brooding them in shallow water until they hatch — a reproductive mode documented for some genera in the family. Whether Xyliphius anachoretes follows this pattern has not been specifically confirmed, so it should be taken as a plausible family trait rather than an established fact for this species.
Breeding
Breeding of Xyliphius anachoretes is essentially undocumented, and the species has no known aquarium-breeding history. Given the belly-carrying reproductive strategy reported in other Aspredinidae, any eggs produced would likely be tended by the female rather than scattered or guarded by a male, but this cannot be stated as confirmed for this species specifically.
With only a small number of specimens ever recorded and no aquarium trade presence, there is no record of captive spawning, and none should be expected — this is a wild, poorly studied species rather than an aquarium-adapted one.
In the aquarium
Xyliphius anachoretes is not an aquarium fish in any meaningful sense — it is not known to be traded, and almost nothing about its husbandry has been documented. Anyone who did encounter it should still respect the basics that apply across banjo catfishes and catfish generally: the naked, scaleless skin means it should be treated as sensitive to copper-based medications and dosed conservatively if treatment is ever needed, and it should be moved in a container rather than netted to avoid tangling any spines.
At a maximum of around 3.5 in SL this is a small fish by catfish standards, so the size trap that catches keepers of larger catfish is not the concern here — rather, the concern is that its needs (rare, reclusive, likely nocturnal and benthic, with undocumented water chemistry preferences) are simply not established well enough to responsibly recommend keeping it.
Conservation
The IUCN Red List currently lists Xyliphius anachoretes as Data Deficient, reflecting how little is known about its distribution, population size and trends beyond the original small series of specimens from the Rio Tocantins-Araguaia system.
As a narrow-range, rarely collected species restricted to a single South American river system, it would benefit from further field surveys before its conservation status can be meaningfully assessed. Any pressures on the Tocantins-Araguaia basin — damming, sedimentation, water quality changes — are relevant to its future even though they have not been specifically quantified for this species.