Taxonomy & naming
Serrapinnus potiguar was described in 2014 by Fernando C. Jerep and Luiz R. Malabarba as a new species of the genus Serrapinnus Eigenmann, 1915. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) records it as a valid species under the authority Jerep & Malabarba, 2014. The genus Serrapinnus belongs to the family Characidae and is placed in the broad, species-rich assemblage of small South American tetras; within Characidae the genus has historically been associated with the subtribe Cheirodontini (tribe Cheirodontini, subfamily Stevardiinae in some recent treatments), a group characterised by small body size, simple jaw dentition, and wide Neotropical distribution.
The specific epithet potiguar honours the Potiguara (or Potiguar), an indigenous people of the Brazilian states of Rio Grande do Norte, Paraíba, and Ceará. The name simultaneously references the region of collection: the Potiguara territory overlaps broadly with the drainage system from which the species was described in northeastern Brazil. No common name has been established in either the scientific literature or the aquarium hobby for this species.
Morphology
Serrapinnus potiguar is a small, slender, laterally compressed tetra typical of the genus. Like other Serrapinnus, it has a relatively streamlined body, a small terminal mouth, and a simple dentition suited to picking small invertebrates and organic particles from the water column. The genus is characterised in part by a single row of teeth in both jaws, simple and slightly hooked or conical in form.
Detailed meristic data from the original description have not been widely reproduced in secondary sources accessible to the hobby, and precise size limits are poorly documented outside the type series. As is typical for small Serrapinnus, adult total length is likely in the range of 1–2 in, with a body plan closely resembling related species in the genus. Coloration in life is not well characterised in available sources; preserved specimens of small cheirodontine tetras typically show a pale to silvery lateral field with a dark lateral stripe running toward the caudal peduncle, a pattern common across Serrapinnus.
Habitat
The type locality of Serrapinnus potiguar lies within the drainages of Rio Grande do Norte in northeastern Brazil — a semi-arid region drained largely by small, intermittent or seasonal rivers that flow to the Atlantic coast. Watercourses in this part of the Brazilian northeast (the Caatinga biome) are characterised by warm temperatures, variable flow regimes tied to seasonal rainfall, and often clear to slightly turbid water over sandy or gravelly substrates.
Data on the specific microhabitat preferences of S. potiguar are sparse in the available literature. By analogy with other Serrapinnus from similar environments, the species likely occupies shallow, slow-flowing or still marginal zones of small rivers and streams, often associating with aquatic or riparian vegetation that provides cover and feeding substrate. Water parameters in northeastern Brazil's interior drainages tend toward warmth (commonly 75–86 °F) and slightly acidic to neutral pH, though values vary considerably with season and substrate.
Feeding
Serrapinnus and related cheirodontine genera are regarded as omnivores that feed on small invertebrates, microcrustaceans, algae, and organic detritus — foraging opportunistically in the water column and at the surface. The fine, simple dentition of the genus is consistent with this generalist feeding strategy rather than any specialised prey-capture morphology.
No published dietary study specific to S. potiguar is available. In the aquarium, small Serrapinnus-type tetras are typically easy feeders that accept good-quality micro-pellets, fine flake, and small live or frozen foods such as baby brine shrimp, Daphnia, and micro-worms. A varied diet that includes live or frozen items supports best condition and natural behaviour.
Mating
No published observations of mating behaviour are available for Serrapinnus potiguar specifically. Members of Serrapinnus are presumed to follow the general cheirodontine pattern of open-water egg scattering, in which males court females with body displays and the pair release eggs freely or near fine-leaved vegetation and substrate. There is no evidence of pair bonding or territory establishment in the genus, and spawning behaviour is likely opportunistic and continuous under favourable conditions rather than strictly seasonal.
Male cheirodontines in related genera sometimes display a modified hook-like scale or fin spine associated with spawning; whether S. potiguar possesses such secondary sexual characters is not documented in sources available for this account.
Breeding
Captive breeding of Serrapinnus potiguar has not been documented in the hobby literature. Based on the biology of closely related Serrapinnus species, the species is expected to be an egg scatterer that deposits small, non-adhesive to slightly adhesive eggs among fine-leaved plants or over the substrate. No parental care is anticipated: adults should be considered likely to consume their own eggs and should be separated from the spawning medium promptly.
For small cheirodontine tetras generally, a separate, well-planted breeding tank with soft, slightly acidic to neutral water, raised temperature in the mid-to-upper 20s Celsius, and a diet of live or frozen invertebrates helps trigger spawning. Fry are typically tiny at hatching and require infusoria or commercial liquid fry food as a first food, followed by newly hatched brine shrimp as they grow. These are inferences from genus-level biology; direct records for this species are absent.
In the aquarium
Serrapinnus potiguar is not established in the aquarium hobby and is essentially unknown in the trade. The broader genus Serrapinnus, like many small South American tetras, would be well suited to a peaceful community aquarium: a school of six or more individuals, a tank with fine-leaved plants and open swimming space, stable warm water, and small, gentle tankmates of comparable size. Conditions reflecting the species' Caatinga-basin origins — warm water around 75–82 °F, pH near neutral, moderate hardness — would be a reasonable starting point.
The species is noted here for completeness and for the benefit of researchers or specialist collectors who might encounter it. Any aquarist working with wild-caught material from northeastern Brazil should confirm identification carefully, as the small cheirodontine tetras of that region form a species-rich complex that is difficult to separate without meristic analysis.
Conservation
Serrapinnus potiguar has not been assessed by the IUCN Red List and carries no formal conservation status as of this writing. The species is known from a restricted area of northeastern Brazil's semi-arid zone — a region where freshwater fish diversity is high but under-studied, and where drainages face significant anthropogenic pressure from water extraction for agriculture, damming of seasonal rivers, and habitat degradation driven by land clearance.
The Caatinga biome, which encompasses much of the species' probable range, is one of the most species-rich dry forests in the world and one of the least protected. Small, narrowly distributed characids from this region are frequently vulnerable to the alteration of the intermittent streams and small reservoirs they inhabit. Without a formal assessment and dedicated field surveys, the conservation needs of S. potiguar cannot be quantified, but the broader pattern of freshwater habitat loss in the region warrants attention.