Taxonomy & naming
Pareiorhaphis ruschii was described by Pereira, Lehmann A., and Reis in 2012, in Neotropical Ichthyology (volume 10, number 3, pages 539–546). The describing paper's title explicitly identifies it as a new species of the neoplecostomine catfish Pareiorhaphis. The Catalog of Fishes (Eschmeyer, CAS) recognises it as valid (genus id 34, species id 72445).
The genus Pareiorhaphis belongs to the subfamily Neoplecostominae, the lineage of small armoured catfishes of south-eastern and southern Brazilian streams. FishBase still lists the genus under Hypoptopomatinae, but both the describing authors and the modern literature treat it as a neoplecostomine, which is the placement adopted here.
The specific epithet ruschii honours the Brazilian naturalist Augusto 'Gutti' Ruschi (1915–1986).
Morphology
Pareiorhaphis ruschii reaches about 3.5 in in standard length (maximum recorded, male or unsexed). The species is diagnosed by several features: a lower-lip margin that is densely fringed; a series of 6 to 10 (usually 7 to 9) small median pre-adipose azygous plates forming a low post-dorsal ridge; and a hypural plate that is asymmetrical, with the lower lobe longer than the upper. The body is elongated.
The most striking sexual feature is the pectoral-fin spine of adult males, which is very long and straight, reaching the distal third of the pelvic fin when laid back against the body — a marked male trait within the genus.
Habitat
The species is known from the coastal river basins of Espírito Santo in eastern Brazil. The type material was collected from a shallow creek roughly 2 ft deep and 13–16 ft wide, situated just downstream of a reserve boundary where the river remained well preserved. The species is described as tropical and benthopelagic, living close to the bottom in flowing water, and the genus is noted for facultative air-breathing. Specific published figures for temperature and pH are not available from the sources at hand.
Feeding
No detailed dietary study of Pareiorhaphis ruschii is published in the sources at hand. Members of the genus typically graze the periphyton coating rocks in their streams, so a similar grazing habit is plausible, but this should be regarded as inference rather than documented fact for this species.
Mating
No data on courtship or mating behaviour have been published for this species. The pronounced male pectoral-spine elongation points to the kind of male ornamentation common in territorial loricariids, but specific reproductive behaviour is undocumented.
Breeding
No breeding data are available for Pareiorhaphis ruschii.
In the aquarium
Pareiorhaphis ruschii is not a species of the ornamental trade and there is no body of aquarium experience to draw on. As a rheophilic stream catfish it would require cool, fast, well-oxygenated water over rock, suiting only a dedicated biotope set-up. No specific captive-care parameters have been published.
Conservation
The IUCN Red List assessed Pareiorhaphis ruschii as Least Concern, with the assessment dated 7 November 2018. The species occupies coastal basins of Espírito Santo and is not presently considered threatened. The chief long-term concern for narrowly distributed coastal stream fishes of eastern Brazil is habitat degradation from land use outside protected reserves.