Taxonomy & naming
Neoplecostomus selenae was described by Zawadzki, Pavanelli and Langeani in 2008, in Zootaxa (volume 1757, pages 31–48), in a paper introducing three new Neoplecostomus from the upper Rio Paraná basin. The species honours Selena Canhoto Zawadzki, daughter of the senior author, C.H. Zawadzki.
The genus Neoplecostomus is the type genus of the subfamily Neoplecostominae, a group of small benthic loricariids endemic to south-eastern and southern Brazil. (FishBase places the genus under Hypoptopomatinae; the Catalog of Fishes and this atlas's taxonomy treat it as Neoplecostominae.) Among its congeners, N. selenae is diagnosed by a distinctive male feature — enlarged odontodes set on swollen skin along the lateral margins of the snout and on ridges in front of the eyes — together with 28–30 lateral-line plates, a well-developed adipose fin and dorsal-fin spinelet, an orbital diameter of about 12.1–12.7% of head length, and dentary and premaxillary tooth counts of roughly 15–24 and 17–24 respectively.
Morphology
Neoplecostomus selenae is a small loricariid reaching about 4 in standard length in the examined (male or unsexed) material, with an elongate, plated body. It carries a well-developed adipose fin and a dorsal-fin spinelet, and bears 28–30 plates along the lateral line. The orbital diameter is small, around 12.1–12.7% of head length. Tooth counts run to roughly 15–24 on the dentary and 17–24 on the premaxilla.
The species is sexually dimorphic in a way that is diagnostically useful: mature males develop enlarged odontodes on conspicuously swollen skin along the lateral margins of the snout and along ridges located before the eyes. This hypertrophied odontode development on the head is a hallmark of breeding-condition males in the genus.
Habitat
Neoplecostomus selenae occurs in the upper Rio Paraná basin of Brazil. It is a freshwater, benthopelagic, tropical fish, consistent with the small clear-stream habitats characteristic of the genus.
Detailed in-situ water-chemistry data (temperature, pH, conductivity) are not published for this species in the available sources, so no figures are given. Its limited distribution within the upper Paraná drainage underlies its conservation status.
Feeding
No species-specific dietary study is published for Neoplecostomus selenae in the available sources. Small benthic Neoplecostomus generally graze biofilm — algae, diatoms, and associated micro-organisms — from stream substrates, but the diet of this species has not been documented and is therefore left unstated.
Mating
Courtship and mating behaviour have not been described for this species. The pronounced snout odontodes of mature males are presumed, as in related loricariids, to function in breeding-season competition or display, but no direct behavioural observation is published and none is asserted here.
Breeding
No reproductive data — spawning mode, clutch size, or parental care — are published for Neoplecostomus selenae. The species is known essentially from preserved material, and its breeding biology in the wild remains undocumented.
In the aquarium
Neoplecostomus selenae is not a hobby species. It has no L-number, is not in the ornamental trade, and has no published husbandry record. It should be regarded as a fish of scientific and conservation interest rather than an aquarium subject.
Conservation
The IUCN Red List assessed Neoplecostomus selenae as Endangered (EN) on 7 November 2018, under criteria B1ab(iii) — a category indicating a very high risk of extinction in the wild. The B1ab(iii) criteria point to a small extent of occurrence combined with severe fragmentation or few locations and a continuing decline in the quality of habitat.
The upper Rio Paraná basin, where the species is restricted, is one of the most heavily modified river systems in South America, affected by damming, agriculture, and urban expansion. For a small-stream fish with a limited range, these pressures translate into habitat loss and degradation of the clear, flowing waters it depends on. Conserving the species requires safeguarding the specific stream habitats within its narrow distribution.