Taxonomy & naming
Metaloricaria paucidens was described by the Dutch ichthyologist Isaäc J. H. Isbrücker in 1975 and is the type species of the genus Metaloricaria. The Catalog of Fishes (Eschmeyer, CAS) recognises the valid combination Metaloricaria paucidens Isbrücker, 1975.
The genus and species were subsequently reviewed by Isbrücker and Nijssen (1982), and the species was redescribed by le Bail and colleagues in the Atlas des poissons d'eau douce de Guyane (Planquette et al., 2000). It belongs to the subfamily Loricariinae, the whiptail catfishes — a group of elongate, dorsoventrally flattened loricariids distinguished by their depressed bodies and long, thin caudal peduncles.
Morphology
Metaloricaria paucidens reaches a maximum recorded standard length of about 10.5 in, making it a comparatively large whiptail. Like other Loricariinae, the body is strongly depressed and elongate, clad in the bony dermal plates typical of the family, and tapering to a long, slender caudal peduncle.
Detailed morphological diagnoses are given in the original description (Isbrücker, 1975) and the later revision (Isbrücker & Nijssen, 1982); the specific epithet paucidens ("few teeth") points to a reduced dentition. Sexual dimorphism has not been described in the literature available here.
Habitat
The species inhabits freshwater rivers of the Guiana shield in northeastern South America, recorded from the Oyapock, Sinnamary, and Marowijne (Maroni) River basins of French Guiana and Suriname.
Field accounts describe it as not abundant, occurring in zones of rapids with strong illumination (Planquette et al., 2000). It is a demersal, tropical species, consistent with a benthic life pressed to the substrate among fast-flowing, well-oxygenated water over rock.
Feeding
No direct dietary study for Metaloricaria paucidens is available in the sources consulted. As a benthic loricariine of illuminated rapids, it is most plausibly a grazer on the aufwuchs — the biofilm of algae, diatoms, and associated microfauna — that coats rocks in fast water, in line with the general feeding ecology of the subfamily. This should be treated as inference rather than a documented observation; no captive feeding data has been published.
Mating
No data on courtship or mating behaviour has been published for this species.
Breeding
No breeding report exists for Metaloricaria paucidens. Many Loricariinae are substrate spawners in which the male guards a clutch, sometimes carrying eggs against the body or beneath the head, but whether this applies to M. paucidens is unrecorded. There is no documented captive reproduction.
In the aquarium
Metaloricaria paucidens is essentially absent from the ornamental trade, and no husbandry data has been published. Any keeper attempting it would be working without precedent.
The ecological notes that do exist — a rapids habitat with strong current and high oxygenation, and a relatively large adult size near 10.5 in — imply that a successful setup would need a spacious tank with vigorous flow, well-oxygenated tropical water, and a rocky substrate. These are inferences from habitat, not tested recommendations.
Conservation
The IUCN Red List assessed Metaloricaria paucidens as Least Concern (assessed 14 January 2021). The species occurs across several Guiana shield basins, and there is no published evidence of a significant range decline. As with other rapids-associated fishes of the region, localised threats could arise from hydrological alteration, but the species is not currently considered threatened.