Taxonomy & naming
This species was first described in 2015 by Pablo Lehmann A., Luiz J. Schvambach and Roberto E. Reis as Parotocinclus variola, in Neotropical Ichthyology (volume 13, number 1, pages 47–52), in a paper introducing a new armoured catfish of the subfamily Hypoptopomatinae from the Amazon basin in Colombia. In 2022, Reis and Lehmann erected the genus Rhinotocinclus and transferred the species into it, producing the valid combination Rhinotocinclus variola.
The Catalog of Fishes (Eschmeyer, CAS) records the species under this current combination. By the rules of zoological nomenclature, the authority is written in parentheses — (Lehmann A., Schvambach & Reis, 2015) — precisely because the species is no longer in the genus (Parotocinclus) in which it was originally described; the parentheses signal that the generic placement has changed since the original 2015 description, while the original describers and date are retained. The earlier combination Parotocinclus variola is therefore a former combination of the same fish, not a distinct species.
Rhinotocinclus belongs to the Hypoptopomatinae, the subfamily of small biofilm-grazing armoured catfishes. The 2022 revision moved several species out of the broadly defined Parotocinclus into Rhinotocinclus, of which R. variola is one.
Morphology
Rhinotocinclus variola is a small, elongate loricariid reaching about 1 in standard length. The original description records a dorsal fin with 1 spine and 7 soft rays and an anal fin with 6 soft rays.
Its most distinctive feature is its coloration: conspicuous dark dots, each smaller than the pupil, are broadly distributed across both the dorsal and ventral body surfaces — the pattern that inspired the epithet variola (smallpox). The describers also noted a Y-shaped light mark on the snout as a diagnostic character. Dentition is well developed for a fish of this size, with 38–46 teeth on each premaxilla and 39–46 on each dentary. No data on sexual dimorphism have been published for this species.
Habitat
Rhinotocinclus variola is known from Quebrada Tacana, a blackwater creek that is a tributary of the Amazon River in Colombia. The type-locality habitat is a sandy-bottomed blackwater stream. The describers reported an average rainfall of about 3,15.5 in per year for the area and an average water temperature of around 78 °F, consistent with the warm, soft, acidic and tannin-stained conditions typical of Amazonian blackwater drainages.
The species is a freshwater, demersal fish associated with this creek system; no broader distribution beyond the type locality is recorded in the sources consulted here.
Feeding
No dedicated diet study has been published for Rhinotocinclus variola. FishBase assigns it a trophic level of about 2.5, in line with the herbivore-detritivore feeding ecology general to the dwarf Hypoptopomatinae, which graze biofilm — algae, diatoms, microbes and fine detritus — from submerged surfaces using their suckermouth oral disc. Members of the genus are noted as facultative air-breathers, able to take atmospheric oxygen when conditions warrant. Specific feeding observations for this species are not available.
Mating
No courtship or mating behaviour has been documented for Rhinotocinclus variola. The species is known from its original description and subsequent taxonomic transfer; reproductive behaviour was not reported.
Breeding
No breeding data have been published for Rhinotocinclus variola. There is no documented record of captive spawning, and no information on spawning mode, clutch size, egg deposition or parental care is available for the species.
In the aquarium
Rhinotocinclus variola is not an established aquarium species, and no husbandry guidance specific to it has been published; it is known essentially as a wild taxon from a single Colombian blackwater creek rather than as a trade fish.
Were it ever to be kept, its blackwater origin (warm water around 77–79 °F, soft and acidic) and biofilm-grazing ecology would suggest care broadly similar to other dwarf suckermouths, but in the absence of direct husbandry observation this remains inference rather than guidance.
Conservation
Rhinotocinclus variola has not been evaluated by the IUCN Red List. Known only from a single blackwater creek in Colombian Amazonia, it has a narrowly documented range, and its population size and trends are unstudied.
No species-specific threats have been identified, though small-range Amazonian fishes can be vulnerable to localised habitat change from deforestation and watershed disturbance.