Taxonomy & naming
Hisonotus hungy was described by Azpelicueta, Almiron, Casciotta and Koerber in 2007 in the Revue Suisse de Zoologie (volume 114, number 3), in a paper titled 'Hisonotus hungy sp. n. (Siluriformes, Loricariidae), a new species from arroyo Tirica, Misiones, Argentina'. The type series comes from arroyo Tirica, a small stream in the upper Paraná drainage of Misiones province, northeastern Argentina.
The genus Hisonotus belongs to the subfamily Hypoptopomatinae, the dwarf 'otocinclus-like' loricariids, and FishBase and the Catalog of Fishes (Eschmeyer, CAS) both list the species as valid. Hisonotus is a species-rich and taxonomically fluid genus of southern South America; its limits have been revised repeatedly, and several species once placed here have moved between genera as the group is studied.
Morphology
Hisonotus hungy is a small loricariid, reaching about 1.5 in standard length. The body is elongate and clad in the bony lateral plates characteristic of the family, with 20 to 22 plates along the lateral series. The dorsal fin has a single spine and seven branched rays; the anal fin bears five branched rays. The snout is blunt and deep, measured at roughly 45.5 to 50.9 percent of head length, and lacks a fleshy pad at its tip. The eye is moderate, about 13.4 to 17.1 percent of head length.
Diagnostic plating around the vent distinguishes the species: the area is covered by two rows of large lateral platelets together with a median, irregular series. There are no predorsal unpaired plates. Sexual dimorphism has not been documented in the available data.
Habitat
The species is known only from arroyo Tirica, a small freshwater stream in Misiones, Argentina, within the upper Paraná drainage. It is a demersal, tropical fish of flowing water. The original description noted that the stream runs through two contrasting environments along its course: reaches bordered by native vegetation, and reaches where an introduced coniferous plantation has replaced the native forest. Hisonotus hungy was recorded from the sunlit stretch where the conifer plantation exposes the brook to full sun, a detail that ties the species directly to land-use change in its catchment.
Like other members of the genus, Hisonotus is capable of facultative air-breathing, an adaptation useful in shallow, warm or oxygen-variable streams.
Feeding
No species-specific feeding study has been published for Hisonotus hungy. Members of the genus are aufwuchs grazers, rasping the film of algae, diatoms, bacteria and fine detritus that coats submerged surfaces. The ventral, sucker-like mouth and fine teeth of Hypoptopomatinae are suited to scraping biofilm from rocks, wood and plant stems rather than consuming wood as the larger panaque-group plecos do. Beyond this general expectation, dietary data for this species are sparse.
Mating
No courtship or mating behaviour has been described for Hisonotus hungy. The species is known almost entirely from preserved type material, and no aquarium observations are available.
Breeding
There are no published breeding records for Hisonotus hungy in the wild or in captivity. Reproductive mode, clutch size, spawning site and parental care are all undocumented. Many small hypoptopomatine loricariids deposit adhesive eggs on plant leaves or hard surfaces, but extending that pattern to this species would be speculation rather than reporting.
In the aquarium
Hisonotus hungy is not an aquarium fish in any meaningful sense. It is a small-range endemic known from a single stream and is not part of the ornamental trade. No husbandry data exist for it. Aquarists interested in dwarf grazing loricariids of this type generally keep more widely available Otocinclus or related Hisonotus species, which require mature, well-oxygenated tanks with established biofilm and gentle current.
Conservation
The IUCN Red List assessed Hisonotus hungy as Endangered (EN) under criterion B1ab(iii) on 28 November 2020. The listing reflects an extremely restricted range: the species is known only from arroyo Tirica, giving it a very small extent of occurrence, combined with an ongoing decline in the quality of its habitat. The original description itself flagged the threat, recording the fish from a reach where native forest had been replaced by a coniferous plantation that exposes the brook to full sun and alters its thermal and hydrological regime.
For a single-stream endemic, any further deterioration of the catchment — through continued afforestation with exotic conifers, sedimentation, water abstraction or pollution — could imperil the entire known population. There are no recorded conservation actions specific to the species, and its persistence depends on the condition of one small Misiones brook. CITES and CMS have not evaluated it.