Taxonomy & naming
Weber described the species in 1907 as a New Guinea sole, and the Catalog of Fishes treats Brachirus villosus as the valid name with the authority in parentheses, showing it was first placed in another genus. It belongs to Soleidae, the true soles, a family that is almost entirely marine; a handful of species live in fresh water in Asia, Australasia and Africa.
Morphology
A flatfish with both eyes on one side of the head, as in all soles. FishBase gives a maximum of 4 in SL for males or unsexed fish. Colour and fin details are not recorded in the sources available to the atlas.
Habitat
FishBase lists it as a freshwater, demersal fish of the tropics, known only from central-southern New Guinea between about 4°S and 10°S. It inhabits turbid main river channels and swampy backwaters, where it lies on the bottom.
Feeding
The diet is not documented for this species. Freshwater soles in general feed on small bottom invertebrates such as worms and crustaceans.
Mating
Courtship has not been described for this species.
Breeding
Breeding has not been documented for this species, and FishBase records no reproduction data.
In the aquarium
Sold by partner stores as a rarity among freshwater flatfish. A bare or fine-sand bottom, subdued light and live bottom foods suit a freshwater sole. FishBase gives no temperature, pH or hardness range for the species, and the atlas records none. Flatfish need a clear sand surface to rest on and do not compete well with active tank mates at feeding time.
Conservation
The IUCN Red List classes Brachirus villosus as Least Concern, assessed in June 2020. It is known only from southern New Guinea, a region where the large rivers remain comparatively intact.