Taxonomy & naming
Exastilithoxus hoedemani was described by Isbrücker and Nijssen in 1985. The Catalog of Fishes (Eschmeyer, CAS) recognises the valid combination Exastilithoxus hoedemani as the original combination, written without parentheses because the species has never been moved to another genus.
The genus belongs to the Lithoxus group within the tribe Ancistrini, part of the subfamily Hypostominae as currently circumscribed. These are small, dorsoventrally flattened, fringe-lipped catfishes adapted to life among stones in flowing water — a body plan quite distinct from the larger wood-eating and algae-grazing plecos more familiar to hobbyists. The principal modern reference treating the species is Fisch-Muller's 2003 account of the Loricariidae-Ancistrinae in the Checklist of the Freshwater Fishes of South and Central America.
Morphology
Exastilithoxus hoedemani is a small loricariid, reaching about 2 in in standard length in the largest measured specimens. Like other members of the Lithoxus group it has a strongly depressed, flattened body suited to clinging to stone surfaces in current, and the fringed, papillose lips that give the group its 'fringe-lipped' description.
Detailed published colour and meristic descriptions beyond the original 1985 account are sparse, and no reliable data on sexual dimorphism in this species has been published.
Habitat
The species is recorded from the Rio Marauiá (also spelled Maurauiá), a tributary within the upper Rio Negro drainage in Amazonas State, Brazil. It is a freshwater, demersal, tropical fish of stony, fast-flowing water — the rheophilic habitat typical of the Lithoxus group, where small loricariids cling to rock surfaces in well-oxygenated current.
Facultative air-breathing has been reported for the genus, an adaptation consistent with shallow, turbulent stream habitats. Precise field measurements of temperature, pH, and conductivity for this species are not published.
Feeding
No detailed dietary study has been published for Exastilithoxus hoedemani. By analogy with other small fringe-lipped Lithoxus-group loricariids of stony fast water, it is presumed to graze biofilm — the aufwuchs of algae, micro-invertebrates, and detritus coating submerged rocks — using its papillose lips and fine teeth. This should be treated as inference from the group rather than documented fact for this species.
Mating
No data on courtship or mating behaviour has been published for this species.
Breeding
No breeding reports or reproductive data have been published for Exastilithoxus hoedemani, in the wild or in captivity.
In the aquarium
Exastilithoxus hoedemani is essentially absent from the ornamental trade, and reliable aquarium husbandry data is sparse. As a small rheophilic loricariid from cool, swift, oxygen-rich upper-Rio-Negro tributaries, it would in principle demand strong flow, high oxygenation, scrupulously clean soft acidic water, and a stony biofilm-covered substrate — conditions that make fringe-lipped Lithoxus-group fishes challenging specialist subjects rather than community fish. In practice it is a species known to science more than to the hobby, and any keeping recommendations remain inferential.
Conservation
The IUCN Red List assessed Exastilithoxus hoedemani as Least Concern, with the assessment dated 7 November 2018. The species occupies fast-water habitat in the upper Rio Negro drainage; as with other narrowly distributed rheophilic loricariids, any future alteration of its stony stream habitat would warrant reassessment, but at present it is not considered threatened.