Taxonomy & naming
Hisonotus dinizae was described by Ribeiro-Silva, Silva, Venere, da Silva and Roxo in 2020, in Zootaxa (volume 4860, number 4, pages 553–562). The type material was collected in the rio Araguaia basin of central Brazil. The Catalog of Fishes (Eschmeyer, CAS) recognises the name as valid.
The species belongs to Hisonotus, a genus of small suckermouth catfishes placed in the subfamily Hypoptopomatinae of the family Loricariidae. Hisonotus is one of several genera of the diminutive armoured catfishes that Brazilian aquarists call 'cascudinhos'. Diagnostic features separating H. dinizae from its congeners include a V-shaped spinelet, yellowish teeth, the absence of unpaired platelets in the region typically occupied by an adipose fin, a hyaline caudal fin crossed by three transverse dark bars, a single series of abdominal median plates, and an oval body cross-section.
Morphology
Hisonotus dinizae is a very small loricariid, reaching a maximum recorded size of about 1 in standard length. The body is armoured with the overlapping bony plates characteristic of the family, and its cross-section is oval rather than strongly flattened.
The described diagnostic characters are largely osteological and meristic: a V-shaped spinelet at the dorsal-fin origin, yellowish teeth, and a single series of median plates along the abdomen. There is a distinctive absence of unpaired platelets in the area where an adipose fin would normally sit. The caudal fin is hyaline (translucent) and bears three transverse dark bars. No published account of in-life coloration beyond the original description is available, and detailed sexual dimorphism for this species has not been documented in the literature consulted.
Habitat
Hisonotus dinizae is known from the rio Araguaia basin in central Brazil. It is a freshwater, demersal species recorded at shallow depths of roughly 0–7 ft in a tropical climate.
The original description characterises its habitat as small, shallow streams with clear, swift-flowing water around 2–7 ft deep, fringed with marginal aquatic vegetation. These are the well-oxygenated headwater conditions typical of many small Hypoptopomatinae, where the fish cling to submerged surfaces in moderate to fast current.
Feeding
Like other members of Hisonotus and the broader Hypoptopomatinae, H. dinizae is a small grazing catfish that rasps biofilm — the layer of algae, microorganisms and fine detritus that coats submerged plants, stones and wood. FishBase gives an estimated trophic level of 2.7, consistent with a diet dominated by aufwuchs and associated micro-organisms rather than animal prey.
No direct gut-content study specific to this species has been published in the sources consulted; the feeding profile is inferred from its anatomy and from the well-established ecology of related cascudinhos.
Mating
No data on the courtship or mating behaviour of Hisonotus dinizae has been published. Reproductive behaviour for the species is undocumented in the literature consulted.
Breeding
No reproductive data — spawning mode, clutch size, egg deposition or parental care — has been published for Hisonotus dinizae. Many small Hypoptopomatinae deposit adhesive eggs on plant leaves or hard surfaces, but no breeding account specific to this species exists in the sources consulted, and the details should not be assumed.
In the aquarium
Hisonotus dinizae is a recently described species with no established presence in the ornamental trade, and no aquarium husbandry account is available. Any keeping notes would have to be extrapolated from related cascudinhos, which generally require clean, well-oxygenated water, gentle to moderate flow, and abundant biofilm and algae to graze.
Given the absence of published husbandry data, no specific parameters or care recommendations can be responsibly stated for this species.
Conservation
Hisonotus dinizae has not been evaluated by the IUCN Red List (status Not Evaluated, per FishBase IUCN Red List status, version 2025-2). As a small, recently described species known from a restricted area of the rio Araguaia basin, its population status and any threats remain unassessed.
The Araguaia and the wider Tocantins–Araguaia system face pressures from agricultural expansion, sedimentation and hydrological alteration, but no species-specific conservation assessment exists, and no claims about its threat status can be made.