Taxonomy & naming
Hisonotus prata was formally described by Thiago P. Carvalho and Roberto E. Reis in 2011, as part of a revision treating a group of southern Brazilian Hisonotus from the laguna dos Patos system. The species is recognised as valid by the Catalog of Fishes (Eschmeyer, CAS) and by FishBase under the combination Hisonotus prata Carvalho & Reis, 2011.
The genus Hisonotus belongs to the subfamily Hypoptopomatinae, the dwarf suckermouth armoured catfishes within the family Loricariidae. These are among the smallest loricariids, and the genus has accumulated many species through ongoing description of regional faunas in southern and southeastern Brazil and adjacent drainages. No L-number or hobby code is associated with H. prata, which is not a fish of the ornamental trade.
Morphology
Hisonotus prata is a small, dorsoventrally flattened armoured catfish reaching about 1.5 in standard length (SL) in the largest recorded specimens. As in other Hypoptopomatinae, the body is encased in overlapping bony plates and the ventral mouth bears the rasping dentition typical of the subfamily, adapted for grazing surfaces.
Detailed colour and meristic data for this species are confined to the original description by Carvalho and Reis (2011); beyond the published maximum size, no additional morphometric information is reproduced here. Sexual dimorphism in H. prata has not been documented in the sources consulted.
Habitat
The species is restricted to the headwaters of the rio Taquari drainage within the laguna dos Patos system of Rio Grande do Sul, southern Brazil. FishBase characterises its environment as freshwater, demersal, and subtropical, consistent with the cooler streams of the southern Brazilian highlands.
Hisonotus prata is reported to be a facultative air-breather, an adaptation seen in various loricariids that lets them tolerate low-oxygen conditions. Beyond this restricted range and broad environmental classification, no detailed field data on flow, substrate, or seasonal water chemistry has been published for the species.
Feeding
No diet study has been published specifically for Hisonotus prata. Members of the genus and the wider subfamily Hypoptopomatinae are biofilm grazers, rasping the layer of algae, diatoms, microorganisms, and fine detritus (aufwuchs) that coats submerged surfaces such as plants, wood, and rock. It is reasonable to expect H. prata follows this general feeding mode, but the specifics for this species have not been documented.
Mating
No data has been published on courtship or mating behaviour in Hisonotus prata.
Breeding
No data has been published on the reproductive biology of Hisonotus prata. Maturity size, spawning mode, clutch characteristics, and any parental care all remain undescribed for the species.
In the aquarium
Hisonotus prata is not a species of the ornamental trade and no aquarium husbandry information exists for it. Any care expectations would have to be extrapolated from better-known dwarf Hypoptopomatinae, which generally need mature, well-oxygenated tanks with abundant grazing surfaces and stable water; such extrapolation is offered only as context, not as documented guidance for this species.
Conservation
The IUCN Red List assessed Hisonotus prata as Data Deficient (DD) in 2018. The species is known only from a restricted range in the upper rio Taquari of the laguna dos Patos system, and the available information is insufficient to evaluate its risk of extinction. As with many narrowly distributed southern Brazilian stream fishes, a small range can heighten vulnerability to localised habitat change, but no population trend has been established.