Taxonomy & naming
Potamorhina pristigaster was described by the Austrian ichthyologist Franz Steindachner in 1876 under the original combination Curimatus (Anodus) pristigaster. It was later transferred to Potamorhina Cope, 1878, a genus erected by Edward Drinker Cope and confirmed by the Catalog of Fishes (Eschmeyer, California Academy of Sciences) as valid, with its type species fixed by monotypy. The genus sits in family Curimatidae, one of several characin lineages — alongside Prochilodontidae and Hemiodontidae — that make up the toothless, detritus- and algae-grazing characiform fauna of Neotropical rivers.
The species epithet pristigaster derives from Greek roots meaning roughly "saw-belly," a reference to the serrated, keel-like row of scutes running along the ventral midline ahead of the anal fin — a feature shared across curimatid genera and used in their identification. As with many Curimatidae, field identification of Potamorhina pristigaster against congeners relies on scale counts, fin-ray counts and the exact form of that ventral keel rather than on colour, since most species in the genus are similarly plain silver.
Morphology
Potamorhina pristigaster reaches a maximum recorded size of about 10.5 in standard length, a moderate size for a curimatid. The body is laterally compressed and silvery to silvery-brown, without the bold pattern or striking colour of many aquarium characins, and it carries adipose eyelids — a partial, transparent membrane over the eye typical of open-water, schooling Characiformes that spend time in bright, turbid river channels. The caudal fin is forked, consistent with a fish built for sustained shoal swimming rather than short bursts among cover.
Diagnostic to the genus and species are elevated counts of pored lateral-line scales and a relatively high number of anal-fin rays, along with the serrated pre-anal ventral keel referenced in the species name. Most tellingly, Curimatidae as a family lack jaw teeth entirely — Potamorhina pristigaster feeds by sucking and sifting substrate and fine particulate matter rather than biting, a mouth structure that immediately separates it from predatory or plant-shredding characins in the same order.
Habitat
Potamorhina pristigaster is native to South America, recorded from the Amazon basin with type material associated with the Rio Negro, and its range is understood to extend into the Orinoco basin as well. Like other Potamorhina species, it is a river-channel and floodplain fish, moving with the seasonal flood pulse that defines Amazonian hydrology — using flooded forest and floodplain lakes during high water and concentrating back into the main channels as water recedes.
Specific water chemistry data (temperature, pH, hardness) for this species was not found in the available sources. As a general characin of Amazon and Orinoco lowland river systems, it can be expected to experience warm, generally soft, circumneutral-to-acidic water typical of those basins, but that inference should not be read as a documented tolerance range — data here is sparse, and no aquarium-specific water parameters have been published for this species.
Feeding
As a toothless curimatid, Potamorhina pristigaster is a detritivore-grazer rather than a predator, browser or omnivorous scavenger. Fish of this genus and family typically feed by sifting fine organic detritus, biofilm, sediment-associated algae and microorganisms from the substrate and water column, a feeding mode shared with the closely related Curimata, Steindachnerina and Cyphocharax. There is no evidence this species takes flesh, fruit or hard plant material in the way that pacus, silver dollars or the larger frugivorous characins do.
No aquarium feeding record exists for Potamorhina pristigaster in the sources available for this account. Given its wild diet, a hypothetical captive diet would need to emphasise fine sinking foods — algae wafers, spirulina-based foods and detritus-mimicking preparations — but this is inference from its family's known biology, not a documented husbandry practice, and should be read as such.
Mating
No courtship or pairing behaviour has been documented for Potamorhina pristigaster in the sources reviewed for this account. Curimatid characins in general are not known for elaborate courtship; most river-channel Characiformes of this kind are believed to spawn in open water as part of larger shoal or migratory aggregations rather than forming pairs, but this has not been specifically confirmed for this species.
Breeding
There is no confirmed breeding record for Potamorhina pristigaster in aquaria or in the wild-spawning literature available for this account. Unlike the large migratory food-fish curimatids and their prochilodontid relatives (Prochilodus, Semaprochilodus), which are well studied as long-distance upriver spawners and are farm- and hormone-bred at commercial scale, no equivalent spawning data has been located for this species specifically. Given the family's general pattern, an open-water egg-scattering mode during the flood-season migration is plausible, but this account will not assert a breeding mode that is not supported by a source — the honest answer for Potamorhina pristigaster is that its breeding biology is effectively undocumented.
In the aquarium
Potamorhina pristigaster has essentially no presence in the aquarium hobby. No sources reviewed for this account describe tank size, water parameters, tankmate compatibility or captive diet specific to this species, and it does not appear to be part of the ornamental trade. This is consistent with its biology: a plain-silver, toothless, detritus-grazing river fish reaching 10.5 in has little of the visual or behavioural appeal that drives demand for its relatives, and it is best understood as a wild, largely undocumented food-web component of Amazon and Orinoco river channels rather than a species with an established care record.
Anyone encountering this species — whether via the aquarium trade, a public aquarium or a scientific collection — should treat it as an adult-sized (10.5 in) shoaling river fish that has not been kept or bred in captivity in any documented way, and should not assume that generic curimatid or characin husbandry notes from other genera apply without verification.
Conservation
Potamorhina pristigaster has not been assessed by the IUCN Red List and currently carries no formal conservation status (Not Evaluated). This is common among the many mid-sized, wide-ranging Amazon and Orinoco basin fishes that lack the commercial or high public profile that typically triggers a full Red List assessment.
No species-specific threats have been documented in the sources available for this account. In general terms, Amazon and Orinoco basin fishes of this kind face long-term watch items from damming, deforestation-linked sedimentation and water-quality change across their range, but without a formal assessment or targeted study, any specific conservation claim for Potamorhina pristigaster would be speculation rather than documented fact.