Taxonomy & naming
Pseudolithoxus kelsorum was described by Nathan K. Lujan and José L. O. Birindelli in 2011, in the paper 'A new distinctively banded species of Pseudolithoxus (Siluriformes: Loricariidae) from the upper Orinoco River' (Zootaxa 2941: 38–46). The Catalog of Fishes (Eschmeyer, CAS) recognises the valid combination Pseudolithoxus kelsorum, an original combination cited without parentheses.
The genus Pseudolithoxus belongs to the subfamily Hypostominae, within the tribe Ancistrini — the bristlenose and relatives that make up much of the loricariid diversity of the Orinoco and Amazon. The genus comprises a small number of flattened, banded or spotted species adapted to fast water. Pseudolithoxus kelsorum is separated from its congeners chiefly by its colour pattern (see Morphology), the feature that gave the original description its title.
Morphology
Pseudolithoxus kelsorum reaches about 2.5 in standard length in the known material. The body is elongate and, like other members of the genus, strongly flattened in cross-section — an adaptation to clinging in current. The defining feature is colour: a dark brown to black ground crossed by 8–11 (usually 9) wide, light yellowish transverse-to-oblique bands running between the level of the orbits and the caudal fin.
This banding cleanly separates it from its congeners. Pseudolithoxus tigris carries 18 or more thin, contorted bands; P. anthrax and P. nicoi are marked with white spots on black; and P. dumus shows dark spots on a light brown ground. The bold, few, wide bands of P. kelsorum are diagnostic. No data on internal anatomy beyond the original description is summarised here.
Habitat
The species is freshwater, demersal and tropical, recorded from the Orinoco River drainage in Amazonas State, Venezuela. It is known only from a single site on the Orinoco main channel just above the Maipures rapids, roughly 37 mi south of the Atures rapids in the upper river.
Members of this genus are associated with fast-flowing, rocky, well-oxygenated water, and the rapids setting of the type locality is consistent with that ecology. Detailed water-chemistry measurements for this species have not been published in the sources consulted.
Feeding
No feeding data has been published for Pseudolithoxus kelsorum. Loricariids of fast-water habitats typically graze biofilm, algae and associated invertebrates from rock surfaces, but specific diet for this species is not documented in the sources consulted, and is left unstated rather than inferred.
Mating
No data on courtship or mating behaviour has been published for this species.
Breeding
No breeding data has been published for Pseudolithoxus kelsorum. The species is not known to have been bred in captivity, and reproductive biology is undocumented in the sources consulted.
In the aquarium
Pseudolithoxus kelsorum is not a fixture of the aquarium trade and no husbandry record is available. Its known habitat — fast, oxygen-rich, rocky water in the upper Orinoco rapids — would imply demanding conditions (strong flow, high dissolved oxygen, clean water) for any rheophilic loricariid of this type, but no species-specific husbandry guidance can be given without inventing it.
Conservation
The IUCN Red List assessed Pseudolithoxus kelsorum as Endangered (EN B1ab(iii)+2ab(iii)), with the assessment dated 22 August 2020. The listing reflects an extremely restricted range — the species is known from a single locality above the Orinoco rapids — which makes the population vulnerable to any localised habitat disturbance.
Threats to upper-Orinoco rapids habitats include changes to flow and sedimentation regimes; with the entire known range confined to one site, even a single damaging event could affect the whole documented population. Continued field survey would help clarify whether the species occurs more widely than the single recorded locality suggests.