Taxonomy & naming
Hisonotus vespuccii was described by Roxo, Silva and Oliveira in 2015 in ZooKeys number 498, pages 127-143 (description on page 128, figures 1-2a, 3). The type locality is in Minas Gerais State, municipality of Pirapora, in the rio São Francisco at approximately 17°21'00"S, 44°57'08"W, Brazil. The Catalog of Fishes (Eschmeyer, CAS) recognises Hisonotus vespuccii as a valid name; the authority carries no parentheses, reflecting that the species has remained in its original genus, and no synonyms are recorded.
The species belongs to the subfamily Hypoptopomatinae, the group of small, slender suckermouth catfishes that includes Otocinclus and its relatives. Hisonotus is a speciose genus of these dwarf loricariids distributed across eastern and southern South American river systems.
Morphology
Hisonotus vespuccii is a small, elongate loricariid. Males and unsexed specimens reach about 1 in standard length (SL), while females grow somewhat larger, to roughly 1.5 in SL. The body is slender with a low caudal peduncle (depth only 6-8% of SL) and 21-23 lateral median plates.
The species is diagnosed by a distinctive caudal-fin coloration: a single black spot extending from the fin origin to the ventral lobe, plus two dark spots at the tips of the lobe rays. Additional diagnostic features include odontodes arranged in longitudinally aligned rows, a functional V-shaped spinelet, and a single rostral plate. Beyond the larger body size of females, no other sexual dimorphism is detailed in the accessible literature.
Habitat
Hisonotus vespuccii is endemic to the rio São Francisco basin of Brazil, occurring in the main river and in three of its tributaries: the rio das Velhas, the rio Paraopeba, and the rio Formoso. It is a freshwater, demersal, tropical species and is reported as abundant throughout the basin.
In life it is associated with marginal vegetation along river and stream banks — the dense aquatic and overhanging plant growth that provides cover, grazing surfaces, and shelter for many small hypoptopomatines. Specific water-chemistry figures for the species are not published in the accessible sources.
Feeding
Hisonotus vespuccii is an algivore and detritivore, occupying a low trophic level (estimated at about 2.3). Like other dwarf suckermouth catfishes, it grazes the biofilm — algae, diatoms, and fine organic detritus — coating submerged surfaces, plants, and marginal vegetation. Its small ventral mouth and rasping dentition are suited to scraping these films from leaves, stems, and substrate.
Mating
No courtship or mating behaviour has been documented for Hisonotus vespuccii. As with many recently described hypoptopomatines, the species is known chiefly from its formal description and distributional records, and its reproductive behaviour remains unstudied.
Breeding
No breeding report exists for Hisonotus vespuccii. Its spawning mode, clutch size, egg deposition site, and any parental care are unknown. Many small Hypoptopomatinae are egg-scatterers or plant-spawners, but this has not been confirmed for the species, and no captive-breeding data are available.
In the aquarium
Hisonotus vespuccii has no established presence in the aquarium hobby; it is known almost entirely from scientific collections in the rio São Francisco basin. As a small, peaceful algae grazer of the Otocinclus-like group, it would in principle suit a well-established planted aquarium with abundant biofilm, gentle flow, and clean, well-oxygenated water — the genus is also noted for facultative air-breathing — but no husbandry record exists for this particular species, and any guidance would be extrapolated from its close relatives rather than documented for it.
Conservation
The IUCN Red List assessed Hisonotus vespuccii as Least Concern (LC), with the assessment dated 1 December 2020. The listing reflects its wide distribution across the rio São Francisco basin and its several tributaries, together with reports that the species is abundant throughout that range — no significant population decline or imminent threat has been identified. The broader rio São Francisco system nonetheless faces pressures from damming, water abstraction, and pollution, which warrant ongoing monitoring of its fish communities.