Taxonomy & naming
Neoplecostomus watersi was described by Silva, Reia, Zawadzki and Roxo in 2019 in Zootaxa (volume 4544, number 1, pages 93–102), in a paper presenting a new species of Neoplecostomus that lacks an adipose fin, from the upper Rio Paraná basin. The Catalog of Fishes (Eschmeyer, CAS) recognises the species as valid.
The genus Neoplecostomus is the type genus of the subfamily Neoplecostominae (tribe Neoplecostomini), a lineage of small, often torrent-dwelling loricariids of south-eastern and central Brazil. Note that FishBase's record lists the subfamily as Hypoptopomatinae, but Neoplecostomus is correctly placed in Neoplecostominae, the assignment followed here.
The specific epithet watersi honours George Roger Waters (born 1943), the English musician and co-founder of Pink Floyd — one of a number of loricariid epithets dedicated to rock musicians.
Morphology
Neoplecostomus watersi reaches about 3 in in standard length. It is diagnosed most readily by the absence of an adipose fin and of any azygous plates at the position where an adipose fin would normally sit — an unusual condition within the genus. The caudal fin is dark and carries a distinctive V-shaped hyaline (transparent) vertical area, a useful field mark. The lower lip reaches, or very nearly reaches, the transverse line of the branchial apertures, and the body has an angular cross-section. Fin counts include seven dorsal-fin soft rays and five anal-fin soft rays.
Habitat
The species occurs in the upper Rio Paraná basin of central Brazil. It is a freshwater, demersal, tropical fish recorded from clear water at the bottom of rivers, living among and beneath rocks. This rheophilic, rock-dwelling habit is typical of the genus.
Specific measured water parameters — temperature, pH, and hardness — were not detailed in the sources available, so no precise field chemistry is published here beyond the description of clear, rocky-bottomed flowing water.
Feeding
No diet study specific to Neoplecostomus watersi has been published. Neoplecostomus species are generally grazers of the biofilm and aufwuchs (algae, diatoms, and associated invertebrates) coating the rocks of their stream habitats, rasped up with the ventral suckermouth. A similar feeding ecology is plausible for N. watersi given its rock-bottom habitat, but it is noted here as a genus-level expectation rather than a documented observation.
Mating
Courtship and mating behaviour of Neoplecostomus watersi have not been documented in the sources consulted. No data on pairing, display, or spawning site selection is available.
Breeding
No reproductive biology has been published for Neoplecostomus watersi — clutch size, spawning mode, and parental care are all undescribed. Sexual dimorphism specific to this species was not detailed in the available sources, so no statement on male/female differences can be made here.
In the aquarium
Neoplecostomus watersi is not an aquarium fish. It is known only from scientific collection in the wild, and there is no husbandry, trade, or captive-care information for it. As a small, rheophilic, rock-dwelling species it would in principle demand cool, fast-flowing, highly oxygenated water — but no specific aquarium guidance is published, and its Critically Endangered status makes it an inappropriate target for collection in any case.
Conservation
The IUCN Red List assessed Neoplecostomus watersi as Critically Endangered in 2020, under criteria B1ab(iii)+2ab(iii) — reflecting a very small extent of occurrence and area of occupancy combined with a continuing decline in the quality of its habitat. This is among the most severe conservation categories applied to any loricariid: it signals an extremely high risk of extinction in the wild.
The upper Rio Paraná basin is heavily affected by hydroelectric impoundment, deforestation, agricultural runoff, and urban expansion, all of which degrade the clear, rocky, flowing stream habitat on which this species depends. For a fish with such a restricted known range, even localised disturbance — siltation of rocky beds, flow alteration, or pollution of a single drainage — could threaten a substantial fraction of the entire population. No targeted recovery measures specific to the species are documented, and protection of its remaining stream habitat is the overriding conservation priority.