Taxonomy & naming
Paralithoxus jariensis was formally described by Silva, Covain, Oliveira and Roxo in 2017 in Zootaxa (volume 4347, number 1, pages 151-168), originally placed in the genus Lithoxus. The Catalog of Fishes (Eschmeyer, CAS) treats the species as valid. It belongs to the Lithoxus group of subfamily Hypostominae, within the tribe Ancistrini of the family Loricariidae.
The species is diagnosed from its relatives by a combination of characters: the presence of an adipose fin, three dark caudal-fin bands, five branched anal-fin rays, fourteen branched caudal-fin rays, the absence of light body spots, and medial premaxillary teeth bearing an enlarged, widened cusp (with five to eight dentary teeth). The specific epithet refers to the type locality.
No aquarium L-number has been assigned to this species, and it is essentially unknown in the ornamental trade.
Morphology
Paralithoxus jariensis reaches approximately 2.5 in standard length in the largest measured specimens. The body is elongated and dorsoventrally flattened in the manner typical of the Lithoxus group — a profile that allows the fish to press tightly against rock surfaces in strong current.
The fin formula given in the original description is two dorsal spines and seven dorsal soft rays, with one anal spine and five anal soft rays. The caudal fin carries fourteen branched rays and is marked with three dark bands. An adipose fin is present. The body lacks the light spotting seen in some congeners, and the medial premaxillary teeth bear an enlarged, widened cusp.
No information on sexual dimorphism has been published for this species.
Habitat
The species is known from the Rio Jari basin in Amapá State, Brazil — a large tributary of the Amazon draining the Brazilian Guiana shield. At the genus level, Paralithoxus inhabits the bottoms of fast-flowing, clear-water rivers of medium to large size, over substrates of small-to-large rocks, loose stones and sand.
The fish is a freshwater, demersal, tropical species. Like other members of the Lithoxus group, it is a facultative air-breather, an adaptation that suits the well-oxygenated but variable rocky-river environments it occupies. No specific field measurements of temperature, pH or hardness for this species have been published.
Feeding
No specific diet study has been published for Paralithoxus jariensis. Members of the Lithoxus group are bottom-dwelling rasping loricariids that graze the biofilm — algae, microorganisms and fine detritus — coating the rocks and loose stones of their fast-flowing habitats. A comparable grazing ecology can reasonably be inferred for this species, but the particulars remain undocumented.
Mating
No data on courtship or mating behaviour have been published for this species.
Breeding
No data on reproduction, spawning mode or parental care have been published for Paralithoxus jariensis. It is not known to have been bred in captivity.
In the aquarium
Paralithoxus jariensis is not established in the aquarium hobby, and no husbandry experience has been documented for it. Its known ecology — fast, clear, well-oxygenated rocky rivers — implies that, were it ever kept, it would require strong current, high oxygenation, clean water and a substrate of stones and sand, much like other rheophilic Lithoxus-group plecos. Any keeping recommendations beyond this would be speculation.
Conservation
Paralithoxus jariensis has not been evaluated by the IUCN Red List, and its conservation status is therefore unknown. It is also Not Evaluated under CITES and CMS. As a species described only in 2017 from a single shield-river basin, its range and population trends remain poorly characterised. The rivers of the Brazilian Guiana shield are broadly subject to pressures from mining, deforestation and sedimentation, but no species-specific threat assessment exists.