Taxonomy & naming
Hypostomus topavae was described by Maurício Camargo Godoy in 1969, based on a single specimen — the holotype — from the Rio Grande in São Paulo state, Brazil. The Catalog of Fishes (Eschmeyer, CAS) recognises the valid combination Hypostomus topavae with Godoy as sole author.
The species belongs to subfamily Hypostominae within Loricariidae. Beyond its placement in Hypostomus, its phylogenetic affinities within that diverse genus have not been resolved in sources available. The name topavae refers not to a person but to a physical landscape feature: a topava is a zone of exposed basaltic rocks that emerge from a river bed when water levels are low — locally significant as a fishing location and the precise setting from which this catfish was collected. Its description from a single holotype means the species lacks any comparative series, and subsequent ichthyological surveys of the Rio Grande basin have not produced confirmed additional specimens.
No L-number or trade code has been assigned to this species.
Morphology
FishBase records a maximum size of 27.5 in standard length (SL) for Hypostomus topavae. This figure derives entirely from the single holotype and must be treated with considerable caution: it is a single-specimen measurement and is not a reliable guide to the species' typical or maximum adult size. A measurement of 27.5 in SL would make H. topavae one of the largest Hypostomus on record — a claim that cannot be substantiated without additional specimens.
The body conforms to the general Hypostomus plan: armoured flanks covered in keeled scutes, a ventral sucker-mouth with bicuspid teeth, a broad pectoral-fin spine, and the triangular dorsal fin characteristic of the genus. No information beyond what is implicit in the holotype's preservation is available on coloration, fin-ray formula, or any feature that would distinguish this species morphologically from congeners. Detailed morphological description beyond the size figure is not reproducible from available sources.
Data sparse.
Habitat
The holotype of Hypostomus topavae was collected from the Rio Grande in São Paulo state, Brazil. The Rio Grande is a major right-bank tributary of the Paraná River system, draining a broad plateau region of interior southern Brazil before joining the Rio Paranaíba to form the Paraná proper.
The specific type locality was a topava — an area of exposed basaltic rock that rises above the water surface during low-water periods. Such basalt outcrops in the Paraná basin are associated with clear, highly oxygenated water, strong current, and rock surfaces densely colonised by algae and diatoms. No water-chemistry data are available for the collection site or time of capture.
The Rio Grande basin has been substantially altered since 1969 by the construction of large hydroelectric reservoirs (including Furnas, Marimbondo, and Água Vermelha dams), which have inundated or disrupted much of the river's natural hydrological character. Whether the type locality itself survives in a recognisable form is not known from available sources.
Feeding
No dietary data exist for Hypostomus topavae. The species is known from a single holotype, and no feeding observations have been recorded. General loricariid biology suggests an aufwuchs-based diet — algae, diatoms, and microbial biofilm rasped from hard rocky substrate — consistent with the exposed basaltic habitat of the type locality.
Data sparse.
Mating
Mating behaviour in Hypostomus topavae is entirely undocumented. No captive specimens have been reported, and field observations are absent. Nothing beyond inference from congeners can be stated.
Data sparse.
Breeding
No breeding data exist for Hypostomus topavae. The species is known solely from its holotype, and no reproductive information of any kind is available.
Data sparse.
In the aquarium
Hypostomus topavae is entirely absent from the aquarium hobby and, given that it is known only from a single holotype, is not available in the trade. The 27.5 in SL figure recorded from the holotype, if it reflects a genuine adult size, would in any case place it among the largest loricariids — well beyond the practical limit for any domestic aquarium.
No husbandry information exists or can be ethically extrapolated from the available data.
Conservation
The IUCN Red List assessed Hypostomus topavae as Data Deficient in 2018. This designation is appropriate given that the species is known only from its 1969 holotype and has not been reported from subsequent ichthyological surveys of the Rio Grande basin.
The extensive hydroelectric development of the Rio Grande — which has converted much of the river into a chain of reservoirs since the 1960s — represents a plausible but unconfirmed threat to any population that may exist. Basaltic rock habitats of the kind represented by the type locality topava are precisely the microhabitats most likely to be inundated and transformed by impoundment. Whether H. topavae persists anywhere in the Rio Grande system is unknown; the absence of records over more than half a century is itself a cause for concern, though it may also reflect insufficient targeted survey effort in remaining lotic sections of the river.