Taxonomy & naming
Hypostomus melanephelis was described by Zawadzki, C. de Oliveira, R.R. de Oliveira & L.H. Rapp Py-Daniel in 2015, based on specimens collected from the rio Tapajós near Itaituba, Pará state, Brazil. The Catalog of Fishes (Eschmeyer, CAS) recognises the name as a valid species of Hypostomus, subfamily Hypostominae, family Loricariidae.
Within the genus, H. melanephelis was assigned to the Hypostomus cochliodon group — a morphological assemblage within the broad, not strictly monophyletic genus Hypostomus — and described as the eighth member of that group known from the Amazon basin. The cochliodon group is characterised by enlarged, spoon-shaped (spatulate) teeth, a configuration more associated with wood-rasping behaviour than the smaller, multi-cusped teeth of other Hypostomus.
The species epithet melanephelis is formed from two Greek roots: melanos (dark, black) and ephelis (freckle or lentil-spot). The name directly describes the colour pattern — the distinctive tiny dark dots scattered across a lighter ground colour — and inverts the typical pattern of the cochliodon group, in which dark-bodied fish often bear pale spots rather than the reverse. This unusual colour reversal was one of the characters distinguishing H. melanephelis from its congeners in the original description.
Morphology
Adults reach a maximum recorded standard length of 7 in SL. The body conformation is standard for a medium to large Hypostomus: dorsoventrally flattened, plated with bony scutes, and equipped with a ventrally directed suckermouth. Meristic data from the original description give 2 dorsal spines with 7 soft rays, 0 anal spines with 5 soft rays, and 29 vertebrae.
The diagnostic external feature is the colour pattern: a lighter ground colour covered with conspicuous tiny, roundish dark spots distributed across both the head and body. This freckled appearance is unusual within the Hypostomus cochliodon group, most members of which are dark-bodied with pale markings. A further morphological feature is the partially naked abdomen — the belly plates are reduced or absent over part of the ventral surface, a character that varies among Hypostomus species and was noted as diagnostically relevant in the original description. Spatulate teeth consistent with the cochliodon group assignment are present, suggesting at minimum a capacity for wood-rasping that may not be present in all Hypostomus.
Habitat
Hypostomus melanephelis is known from the rio Tapajós basin near Itaituba, Pará state, Brazil, approximately 4°16'S, 55°59'W. The Tapajós is a large clearwater Amazon tributary — one of the major southern tributaries of the main Amazon channel — rising in the Planalto Central of Mato Grosso and Para. The Itaituba region marks a transition between the upper and middle Tapajós, where the river passes through a series of rapids before widening into calmer reaches.
Clearwater Amazonian rivers of this type are typically acidic (pH 5.5–7.0), soft (low dissolved mineral content), and warm (79–86 °F), although specific water chemistry data for the H. melanephelis type locality were not included in the published description. The species appears restricted to this area of the Tapajós basin; its range has not been documented beyond the vicinity of Itaituba.
Feeding
No feeding studies have been conducted specifically for H. melanephelis. The assignment to the Hypostomus cochliodon group — whose members typically bear spatulate, spoon-shaped teeth suited to gouging wood — suggests that at least some degree of wood-rasping is within the feeding repertoire of this species, in addition to the biofilm and periphyton scraping common across Hypostomus more broadly.
In an aquarium context, a combination of driftwood for rasping, algae-based foods (spirulina wafers, algae discs), and blanched vegetables would provide a well-rounded diet consistent with the presumed natural feeding mode. The extent to which H. melanephelis relies on wood as a dietary component, as opposed to merely using it for shelter, is not established from published data.
Mating
No mating observations have been published for H. melanephelis. The species is not established in ornamental aquaculture and has not been the subject of captive behavioural study.
General Hypostomus biology predicts that males hold and defend territories around suitable spawning cavities — rock crevices, hollow logs, or undercut banks in the river. In the seasonally pulsed Tapajós system, where water levels fluctuate substantially between wet and dry seasons, reproductive activity likely follows the onset of the wet season as water temperatures rise and discharge increases, following patterns documented in other Amazonian loricariids.
Breeding
No captive breeding records for H. melanephelis have been published. The species is not known to be held in significant numbers by aquarists, and its biology in captivity has not been documented.
A cave-spawning mode with paternal brood care, as seen in closely related and broadly comparable Hypostomus species, is the most reasonable expectation based on group biology. Confirmation would require either field observation at the type locality or a documented aquarium breeding event.
In the aquarium
Hypostomus melanephelis is not established in the ornamental fish hobby and is not available through regular trade channels as of writing. Its medium-large adult size (up to approximately 8–8.5 in total length) and Amazonian clearwater origin would define the broad parameters of any husbandry approach: a spacious tank with adequate filtration, rocky and woody furnishings for grazing and shelter, warm water in the range of 79–86 °F, and soft to moderately soft, slightly acidic to neutral water consistent with a major clearwater Amazon tributary.
In the absence of specific captive data, detailed husbandry recommendations cannot be responsibly given. Aquarists who encounter this species should approach it as they would any medium to large clearwater Amazonian Hypostomus, prioritising water quality, dietary variety, and sufficient physical space.
Conservation
Hypostomus melanephelis has not been evaluated by the IUCN Red List. The species was described in 2015 and as of mid-2026 remains unassessed; FishBase (version 2025-2) records its status as Not Evaluated.
The restricted known range — the rio Tapajós near Itaituba — is a point of concern. The Tapajós basin has experienced significant deforestation pressure from soybean agriculture and cattle ranching, primarily in the upper basin in Mato Grosso, and the Brazilian government approved the controversial São Luiz do Tapajós hydroelectric dam project for the middle Tapajós, a reach that includes the Itaituba area. Environmental impact assessments and Indigenous rights disputes have delayed the project, but the long-term threat to benthic fish communities in this stretch of river — particularly endemic or range-restricted species — remains real. A formal IUCN assessment of H. melanephelis would be valuable given these pressures and the species' apparently narrow distribution.