Taxonomy & naming
Hypostomus lima was formally described by Christian Frederik Lütken (ex Reinhardt) in 1874, in the Oversigt over det Kongelige Danske Videnskabernes Selskabs Forhandlinger, from syntypes collected in the Rio das Velhas, Ribeirão do Mato, and Lagoa Santa, Minas Gerais, Brazil. In a follow-up paper in 1875, Lütken restricted the type locality to Lagoa Santa or Ribeirão do Mato. Syntypes are distributed across five museum collections: BMNH (London), MNHN (Paris), NMW (Vienna), SMNS (Stuttgart), and ZMUC (Copenhagen). The species was originally placed in Plecostomus and later transferred to Hypostomus; the Catalog of Fishes (Eschmeyer, CAS) recognises Hypostomus lima as the valid combination.
One comparative study published in a Brazilian ichthyology journal treats H. lima as a synonym of H. wuchereri (Günther), but this synonymy is not accepted by Eschmeyer's Catalog of Fishes or FishBase, both of which continue to recognise H. lima and H. wuchereri as valid and distinct species. Until a formal revisionary treatment resolves the question, the conservative position — following CoF — is to treat H. lima as valid.
The species belongs to the large and taxonomically complex genus Hypostomus Lacepède, 1803, placed within the subfamily Hypostominae, family Loricariidae. Within the São Francisco basin, H. lima is sympatric with at least H. subcarinatus and several other congeners.
Morphology
Adults reach a maximum recorded size of 9 in standard length (SL) with a maximum weight of 312 g (FishBase). As with all loricariids, the body is encased in longitudinal rows of overlapping bony scutes that replace the scales of more derived teleosts. The mouth is positioned ventrally and furnished with a comb-toothed oral disc adapted for rasping biofilm and algae from hard substrates — the scraping dentition is consistent with a grazing rather than wood-boring feeding strategy.
Morphological adaptations to life in torrential current are well developed: the pectoral and pelvic fin spines are strongly arched, helping the fish maintain contact with cobblestone surfaces in fast-flowing water. The caudal fin is relatively large and concave, providing the short bursts of locomotion needed to reposition between grazing bouts. These characters are consistent with field observations of continuous movement over cobblestones in the main channel below Xingó dam.
Sexual dimorphism is not documented in published sources for this species. Some Hypostomus species show elongated odontodes on the pectoral spines of breeding males, but this has not been confirmed for H. lima specifically.
Habitat
Hypostomus lima is endemic to the Rio São Francisco basin of Brazil, with confirmed records extending from the upper basin in Minas Gerais — Ribeirão dos Patos, Ribeirão das Minhocas, Rio São Miguel, and the historic type localities in the Rio das Velhas drainage — downstream to the rocky torrential reaches of the main channel near Canindé do São Francisco, Sergipe, immediately below the Xingó Hydroelectric Power Dam.
The species favours torrential rocky-bottom sections of the main São Francisco channel, where it moves continuously over large cobblestones. Facultative air-breathing allows it to survive in hypoxic microhabitats that develop in the churning foam of rapids and plunge pools, where dissolved oxygen can be locally depleted despite the surface turbulence. No precise water chemistry data have been published for this species. The middle and lower Rio São Francisco is a large, warm tropical river; regional climate data suggest temperatures broadly in the range of 72–82 °F and pH values of 6.5–8.0, though these should not be applied to H. lima without species-specific measurements.
Feeding
Hypostomus lima is an algivore and periphyton grazer, using its comb-toothed oral disc to rasp biofilm, aufwuchs, and algae from cobblestone and rock surfaces. Field observations in the São Francisco main channel document individuals alternating between active grazing on cobblestones and brief surfacing events — the latter consistent with facultative air-breathing rather than deliberate feeding at the surface.
The diet broadly follows the genus-typical pattern for non-xylophagous Hypostomus: algae and periphytic vegetation dominate, with incidental ingestion of fine sediment and organic detritus. No quantitative stomach-content study specific to H. lima has been published. In general, non-wood-eating Hypostomus species occupying hard-substrate riffle habitats are considered benthic grazers rather than wood-borers, and the rasping dentition of H. lima is consistent with that dietary guild.
Mating
No reproductive behaviour data have been published for Hypostomus lima in the wild or in captivity. The genus as a whole is characterised by cave or crevice spawning with paternal brood care, and these traits are likely shared by H. lima, but this assumption has not been documented for the species specifically. Data sparse.
Breeding
No breeding data have been published or reported from captivity for Hypostomus lima. By analogy with other Hypostomus species, cave or crevice spawning with male egg-guarding is the expected mode, but this has not been confirmed. Data sparse.
In the aquarium
Hypostomus lima reaches 9 in SL — broadly comparable to many mid-sized common plecos — and would require a substantial aquarium of at least 80 US gal to be maintained comfortably as an adult. Its natural habitat in torrential rocky-bottom sections of a major river suggests a need for strong, well-oxygenated, well-filtered water with significant turnover.
No published aquarium husbandry records were found for this species, and it is not known to the hobby as an established ornamental fish. The São Francisco basin is subject to export regulations in Brazil, and Hypostomus from this drainage are not commonly traded. Any account of its captive requirements beyond basic inference from habitat data and genus biology would be speculative.
Conservation
The IUCN Red List assessed Hypostomus lima as Least Concern in November 2018, reflecting a distribution across a considerable stretch of the Rio São Francisco basin and no identified acute population threat at the time of assessment.
The Rio São Francisco is one of Brazil's most heavily managed river systems. The Xingó dam and a series of upstream hydroelectric impoundments have altered the river's flow regime, sediment transport, and thermal profile. The reach immediately below Xingó — where H. lima has been documented rasping algae from cobblestones — represents a remnant of the natural rocky-bottom habitat that once characterised more of the lower São Francisco. Ongoing dam operations and the downstream effects of impoundment represent a long-term pressure on habitat quality for riffle-dependent species throughout the basin.