Taxonomy & naming
Hypostomus nigropunctatus was formally described by Garavello, Britski, and Zawadzki in 2012 in Neotropical Ichthyology (volume 10, number 2, pages 263–283), in a monograph reviewing the cascudos of the genus Hypostomus from the Rio Iguaçu basin. The paper redefined the limits of several Iguaçu Hypostomus and introduced nigropunctatus as a new species with a distinct combination of diagnostic characters.
The Catalog of Fishes (Eschmeyer, CAS) recognises Hypostomus nigropunctatus Garavello, Britski & Zawadzki, 2012 as the valid name; no synonyms are recorded. The species belongs to the family Loricariidae, subfamily Hypostominae — the largest subfamily within the armoured suckermouth catfishes.
Within Hypostomus, the authors distinguished nigropunctatus from the H. cochliodon species group by the combination of bifid, non-spoon-shaped teeth whose lateral cups are not fused to the mesial cusp, the absence of keels on the pterotic-supracleithrum, pre-dorsal plates, and lateral plate series, and by the small, closely set dark spots on the dorsal surface. Its placement within broader Hypostomus phylogeny awaits detailed molecular or expanded morphological analysis.
The common name 'black-spotted cascudo' translates the epithet directly and is used informally; the fish has no standardised trade name or L-number.
Morphology
Adults reach a maximum recorded standard length of 9 in SL, placing nigropunctatus in the medium-large range for the genus. The body is covered in the characteristic loricariid bony plate armour across the head, flanks, and dorsum. Fin counts as recorded in the original description are two dorsal spines, seven dorsal soft rays, and six anal soft rays.
The ground colour is dark, overlaid with numerous small, close-set dark spots on the dorsal surface of the head, trunk, and fins. A diagnostic character is that these spots are equal to or smaller than the diameter of the eye pupil — finer spotting than is seen in several related Iguaçu Hypostomus. The abdomen is completely plated, and the body is described as deeper than related species, with parallel moderate keels on the pre-dorsal plates — a subtler relief than the pronounced keels present in some congeners.
The teeth are bifid (two-cusped) with a standard loricariid morphology; the lateral cups are distinctly separated from the mesial one rather than fused, distinguishing this species from the cochliodon group in which the spoon-shaped tooth is diagnostic. No pronounced pterotic-supracleithral keel is present.
Sexual dimorphism is not characterised in the published description; the Hypostomus genus broadly shows males with more extensive interopercular odontodes during the breeding season, and females are often broader-bodied when gravid.
Habitat
Hypostomus nigropunctatus was described from the Rio Iguaçu basin in Paraná State, southern Brazil. The Iguaçu is a major right-bank tributary of the Paraná River, draining the southern Brazilian highlands before dropping dramatically over the Iguaçu Falls — one of the world's largest waterfall systems by volume. The portion of the basin above and below the falls hosts distinct fish communities, and many Iguaçu endemics are restricted to one side of this barrier.
The Rio Iguaçu in Paraná State is a medium to large river characterised by fast to moderate currents, rocky and cobble substrate, and clear to slightly turbid water. Water temperatures in the southern Brazilian highlands reflect a subtropical to warm-temperate climate, with seasonal variation between approximately 61–64 °F in winter and 75–79 °F in summer. The river is generally oligotrophic to mesotrophic, with near-neutral pH and moderate hardness.
A 2024 study by Burchardt and colleagues confirmed Hypostomus nigropunctatus from the Arroyo Urugua-í basin in Misiones Province, Argentina, representing the first record of the species from that country and extending its known range into the upper Paraná tributaries of northeastern Argentina. The Arroyo Urugua-í is a smaller river draining forested terrain in Misiones, with similar subtropical conditions to the Iguaçu drainage.
Feeding
No feeding study specific to Hypostomus nigropunctatus has been published. Members of the genus Hypostomus are primarily algivores and detritivores, using the ventrally positioned oral disc to rasp periphyton — the assemblage of algae, cyanobacteria, biofilm, and fine organic matter that colonises submerged hard substrates. The morphology of the bifid teeth in this species is consistent with a scraping, algivorous diet rather than the xylophagy or molluscivory seen in other loricariid lineages.
In the Rio Iguaçu, rocky substrates with current-maintained periphyton growth would be the primary foraging surface. Hypostomus in fast-flowing rivers often feed across a range of surfaces: exposed rocks, submerged logs, and hard clay banks. Gut content studies on other Iguaçu Hypostomus species have confirmed algae and detritus as dominant dietary components, a pattern expected to apply here.
In aquaria, comparable Hypostomus are maintained on sinking algae wafers, spirulina-based foods, and blanched vegetables such as courgette, cucumber, and sweet potato. Supplementary protein from sinking pellets or occasional meaty foods can be offered but should not dominate feeding.
Mating
No mating observations specific to Hypostomus nigropunctatus have been documented in the literature or the hobby. The reproductive biology of the species is assumed to follow the pattern common to Hypostomus: territorial males compete for and defend cavity sites, including rock crevices, undercut banks, and hollows in submerged wood.
In the Rio Iguaçu system, suitable spawning sites would be found among the extensive rocky outcrops and cobble substrates of the river. Males likely display intensified odontode development during the breeding season and engage in territorial interactions with rival males. The seasonal cycle of the Iguaçu — with its winter temperature minimum and summer peak — probably provides natural conditioning cues that trigger reproductive readiness in spring and early summer.
Because the species was described only in 2012 and has a restricted distribution in a non-commercially fished river, captive specimens are scarce and no aquarium breeding records are known to have been published.
Breeding
Breeding in Hypostomus nigropunctatus is undocumented in either scientific or hobbyist literature. The species' late description and limited accessibility to aquarists mean that no captive reproduction has been reported.
By analogy with better-studied Hypostomus, the species is expected to be a cavity spawner with paternal brood care. Males would select and defend a hollow — a burrow in a clay or earth bank, or a natural rock or wood cavity — and guard the adhesive egg clutch through incubation, fanning the eggs to maintain oxygenation and removing any that fungus or fail to develop. Fry would be guarded for a period after hatching before dispersing to feed independently.
Aquarists hoping to breed specimens should replicate the Iguaçu's seasonal temperature cycle, provide multiple cavity structures, and condition fish on a varied plant-based diet with periodic high-quality supplementation.
In the aquarium
Hypostomus nigropunctatus is not an established aquarium fish, and captive specimens are unlikely to be encountered in the ornamental trade. The Rio Iguaçu basin is not a significant source of export fish, and the species has no L-number or trade name that would mark it as a collected species. It is included here for completeness of the Paraná drainage Hypostomus record.
Should specimens ever become available, their care requirements would align with other medium to large Hypostomus from subtropical South America. A spacious aquarium of at least 80 US gal would be necessary for an adult approaching 9 in. Filtration should be powerful — Hypostomus of this size produce substantial waste — and the substrate should include flat stones and driftwood to provide resting surfaces and cover. Water temperatures of 64–79 °F reflecting the Iguaçu's seasonal range, pH 6.8–7.4, and moderate hardness would be appropriate.
The fish should be fed primarily plant-based foods: algae wafers, vegetables, and sinking spirulina discs. Ample horizontal space is important, as this size class of Hypostomus can be intolerant of conspecifics in confined quarters.
Conservation
The IUCN Red List assessed Hypostomus nigropunctatus as Least Concern in November 2018, at which time the known distribution was restricted to the Rio Iguaçu basin in Paraná State, Brazil. No major threats were identified at the time of assessment. The IUCN notes a population doubling time of 1.4–4.4 years, indicating medium resilience under the Froese and Pauly criteria used in that assessment.
In 2024, Burchardt and colleagues published the first record of the species from Argentina — specimens collected from the Arroyo Urugua-í basin in Misiones Province, based on morphological comparison with the original description. This distributional extension modestly broadens the species' known range, though the Urugua-í basin is itself a small river system and the population there requires further survey to assess abundance.
The Rio Iguaçu faces ongoing pressures from upstream dams (including the Salto Caxias and Segredo hydroelectric projects), agriculture-driven sedimentation, and water quality degradation. The ichthyofauna of the Iguaçu is notable for its high endemism, and any narrowly endemic species in this system is sensitive to such pressures even when not immediately threatened. The next IUCN assessment should incorporate the 2024 Argentine record and any new abundance data.