Taxonomy & naming
Neoplecostomus granosus was described by Achille Valenciennes in the fifteenth volume of Cuvier and Valenciennes' Histoire Naturelle des Poissons (1840, pages 490–491), making it one of the oldest formally described species in the genus and in Neoplecostominae as a whole. The Catalog of Fishes (Eschmeyer, CAS) recognises the valid combination Neoplecostomus granosus (Valenciennes, 1840), with the authority in parentheses reflecting the original description under a different generic placement subsequently revised.
The genus Neoplecostomus Miranda Ribeiro, 1908 is placed in subfamily Neoplecostominae by the primary systematic literature, including Ferraris (2003). Some classification databases assign the genus to Hypoptopomatinae, reflecting an alternative higher-level arrangement; the Neoplecostominae treatment is followed in the primary references cited here.
The specific epithet granosus derives from the Latin granum ('grain'), likely applied in reference to the granular texture of the bony scute surfaces visible in museum specimens — a descriptive tradition common among the early nineteenth-century ichthyologists working with preserved Loricariidae.
Morphology
Neoplecostomus granosus reaches a maximum recorded standard length of 3.5 in, as reported in Ferraris (2003). The body plan follows the general neoplecostomine pattern: robust, dorsoventrally depressed, and heavily armoured with interlocking bony scutes bearing a granular surface texture — consistent with the species epithet. The mouth is ventral and adhesive, suited to clinging to rocky substrate in current.
Beyond the summary data available in FishBase and Ferraris (2003), detailed morphological descriptions of N. granosus are found in Valenciennes (1840) and in the broader genus revision literature, which are not fully reproduced in secondary sources accessible for this account. No published data on sexual dimorphism are available, and the species has not been characterised in captive settings.
Habitat
Neoplecostomus granosus occurs in Brazil, in freshwater river systems of the Atlantic coastal slope. Precise drainage-level records are not reproduced in accessible secondary sources; FishBase lists distribution as 'South America: Brazil' without specifying individual drainages, and the IUCN assessment page was not renderable in the research pass. The original Valenciennes material was almost certainly collected in south-eastern Brazil, in keeping with the Atlantic-slope distribution of all other Neoplecostomus species, but the exact localities from the 1840 material are not confirmed here.
By microhabitat analogy with congeners, N. granosus is expected to occupy fast-flowing, well-oxygenated, clear streams or rivers with rocky bottoms and preserved riparian cover — the habitat type characteristic of the genus across its range. The common name Anhã, retained in FishBase, indicates the species is or was recognisable to local communities, suggesting it was once encountered in accessible river reaches.
Feeding
No feeding study specific to Neoplecostomus granosus has been published. The species' ventral mouth and scute-armoured body are consistent with benthic grazing on periphyton, diatoms, and fine organic biofilm coating hard substrates — the dietary mode shared by other small neoplecostomines occupying rocky rheophilic microhabitats. No aquarium feeding observations exist.
Mating
No mating behaviour has been documented for Neoplecostomus granosus. The species has not been maintained in captivity, and no field observations of courtship are on record. Reproductive biology is essentially unknown.
Breeding
Reproductive data for Neoplecostomus granosus are not available in the published literature. No captive breeding has been reported. The species is absent from the aquarium hobby, and its 1840 description predates any tradition of documenting loricariid reproductive behaviour in the field.
In the aquarium
Neoplecostomus granosus has no record of captive maintenance and does not appear in the aquarium hobby. No husbandry guidance, water chemistry parameters, feeding observations, or tank requirements have been established. Given its rheophilic ecology and absence from commercial collection, it is not a species hobbyists will encounter.
Conservation
Neoplecostomus granosus is assessed as Least Concern on the IUCN Red List, evaluated on 7 November 2018 by the Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio) as part of the Brazilian freshwater fish review process (IUCN 2018: e.T186469A1813527). The Least Concern status indicates that no major population-level threats were identified sufficient to qualify the species for a threatened or near-threatened category at the time of assessment.
Because the IUCN assessment page was not rendered in sufficient detail during research, and because the species' specific drainage-level distribution within Brazil is not confirmed in secondary sources, it is not possible to characterise the threat landscape in the same detail as for N. espiritosantensis. Atlantic coastal streams of south-eastern Brazil broadly face pressures from deforestation, agricultural runoff, sedimentation, and hydroelectric development. The species' long taxonomic history and LC status suggest it either occupies a wider range than its sister species, or that population data at the time of assessment did not indicate decline.