Taxonomy & naming
Pareiorhaphis nasuta was described by Pereira, Vieira and Reis in 2007, in Neotropical Ichthyology (volume 5, issue 4, pages 443–448). It is known from the Rio Doce basin in Minas Gerais, south-eastern Brazil.
The genus Pareiorhaphis is placed in the subfamily Neoplecostominae in the Catalog of Fishes and this atlas's taxonomy (FishBase lists it under Hypoptopomatinae). The specific name nasuta — Latin for 'long-nosed' — points directly to the species' defining trait: it has the longest snout in the genus, with a snout length of about 71.1–75.6% of head length, against 52.8–69.9% in its congeners. Other diagnostic features include a small orbital diameter, bifid teeth bearing a small lateral cusp, a present adipose fin, and 1–3 preadipose azygous plates.
Morphology
Pareiorhaphis nasuta is a small loricariid reaching about 3.5 in standard length in the known (male or unsexed) material, with an elongate, plated body. Its most conspicuous feature is the elongated snout — the longest in the genus at roughly 71.1–75.6% of head length — paired with a comparatively small orbital diameter. The teeth are bifid, each with a small lateral cusp; an adipose fin is present, preceded by 1–3 azygous (unpaired) plates.
The species is reported as sexually dimorphic. The available sources note that nuptial males and larger individuals are found in stronger current among larger stones, but the specific external dimorphic characters are not detailed in the cache material, so no further claim is made here.
Habitat
Pareiorhaphis nasuta inhabits the Rio Doce basin in Minas Gerais, Brazil. The type locality is described as a small, shallow river with very clear, transparent water and slow-to-moderate current, over a bottom of rocks, loose stones and gravel. The fish were collected among loose stones and pebbles in rapids; nuptial males and larger individuals were taken in stronger current among larger stones — pointing to a preference for well-oxygenated, fast-flowing, stony microhabitats.
The sources do not report quantitative water chemistry (temperature, pH, hardness), so no figures are given. This is a freshwater, demersal, tropical, bottom-dwelling stream fish.
Feeding
No species-specific feeding study is published for Pareiorhaphis nasuta in the available sources. Small benthic loricariids of clear stony streams typically graze biofilm and periphyton from rock surfaces, but the diet of this species has not been documented and is left unstated.
Mating
Detailed courtship behaviour has not been described for this species. The collection records note that nuptial (breeding-condition) males occupy stronger current among larger stones, suggesting that fast-flowing, rocky microhabitats are important in the reproductive season, but no direct account of mating behaviour is published.
Breeding
No reproductive data — spawning mode, clutch size, or parental care — are published for Pareiorhaphis nasuta. Beyond the field observation that nuptial males are associated with stronger current among larger stones, its breeding biology remains undocumented, and no further detail is asserted here.
In the aquarium
Pareiorhaphis nasuta is not a hobby species. It carries no L-number, is not in the ornamental trade, and has no published husbandry record. As a rheophilic stream specialist requiring clear, fast, well-oxygenated water, it is best regarded as a subject of scientific interest rather than an aquarium fish.
Conservation
The IUCN Red List assessed Pareiorhaphis nasuta as Near Threatened (NT) on 18 May 2022, under criterion B1b(iii). Near Threatened indicates that the species does not currently qualify for a threatened category but is close to doing so, or may qualify in the near future — here on the basis of a restricted extent of occurrence combined with a continuing decline in habitat quality.
The Rio Doce basin has been subject to significant environmental pressures, and clear-water, stony-bottomed streams are sensitive to sedimentation, pollution, and altered flow. As a fish that depends on clean, fast, rocky stream habitat, P. nasuta is vulnerable to degradation of those conditions, which is the concern reflected in its Near Threatened listing.