Taxonomy & naming
Serrapinnus zanatae was formally described by Jerep, Camelier, and Malabarba in 2016 as a new species from the rio Jequitinhonha basin in the state of Minas Gerais, Brazil. The genus Serrapinnus belongs to the subfamily Cheirodontinae within the family Characidae, a group of small characids characterised by multicuspidate premaxillary teeth arranged in a distinctive pattern. Catalog of Fishes (Eschmeyer) records the authority as Jerep, Camelier & Malabarba, 2016.
The species can be distinguished from congeners by a combination of meristic characters: premaxillary teeth bearing 7 to 9 cusps, 10 to 11 dorsal fin rays, and 19 to 23 anal fin rays. Cheirodontine systematics underwent considerable revision during the early 2000s, and Serrapinnus has absorbed species formerly placed in allied genera; the current limits of the genus are based largely on premaxillary tooth morphology and skeletal characters. S. zanatae fits within that framework as a recognisably distinct Jequitinhonha endemic.
Morphology
Serrapinnus zanatae is a small, slender characid reaching a maximum recorded standard length of approximately 1.5 in. Like other members of the genus it is laterally compressed and fusiform, with a relatively deep body for its length and a subterminal to terminal mouth bearing the multicuspidate teeth that define the Cheirodontinae. The premaxillary teeth carry 7 to 9 cusps, a feature important in distinguishing this species from related Serrapinnus.
Fin counts provide the primary meristic diagnosis: 10 to 11 dorsal rays and 19 to 23 anal rays. The relatively high anal ray count — characteristic of many cheirodontines — gives the fish a distinctive silhouette. Live colouration has not been described in detail in available sources, but most Serrapinnus species are silver to yellowish with a midlateral stripe and hyaline to lightly pigmented fins, and S. zanatae is likely similar.
Habitat
Serrapinnus zanatae is endemic to the rio Jequitinhonha basin in Minas Gerais state, southeastern Brazil. The Jequitinhonha is a relatively large coastal river draining the eastern slopes of the Espinhaço Range and flowing northeast into the Atlantic. The basin supports a distinctive ichthyofauna with a high level of endemism, reflecting both the river's isolation from adjacent Atlantic Forest drainages and the environmental gradients between its headwaters and lowland sections.
Detailed habitat data for this species are sparse in available sources. Given the ecology of other small cheirodontine tetras in similar southeastern Brazilian basins, S. zanatae likely inhabits clear to moderately turbid streams with some marginal vegetation, where it would school in the water column. Soft, slightly acidic to near-neutral water is typical for such environments, reflecting the granitic and metamorphic geology of the Minas Gerais interior, though specific physicochemical data for S. zanatae's collection localities have not been captured here.
Feeding
No feeding data specific to Serrapinnus zanatae have been recorded in the sources available for this article. Members of the genus Serrapinnus and the subfamily Cheirodontinae more broadly are omnivores feeding primarily on small invertebrates, zooplankton, algae, and fine particulate organic matter in the water column and near the substrate. The multicuspidate dentition typical of the group is adapted for grasping and processing small, soft prey rather than cutting plant material.
In the aquarium, related Serrapinnus species accept good-quality micropellets, flake food, and small frozen or live foods such as Daphnia, Cyclops, and baby brine shrimp. Offering a varied diet supports condition and colour in these small tetras.
Mating
No courtship data specific to Serrapinnus zanatae have been published in sources available here. The genus Serrapinnus, along with the broader Cheirodontinae, follows the egg-scattering reproductive strategy typical of small characids: males pursue females through the water column, with spawning occurring among fine-leaved aquatic vegetation or other submerged structure where adhesive or semi-adhesive eggs are deposited.
Schooling behaviour in small cheirodontines likely facilitates mating opportunities, with males competing for access to ripe females within the school. There is no parental investment after spawning, and adults may consume their own eggs if they encounter them.
Breeding
Serrapinnus zanatae has not been reported in the ornamental trade and no captive breeding accounts are available. Based on its placement in Cheirodontinae and the general biology of the subfamily, breeding behaviour is expected to follow the open egg-scattering pattern: adhesive eggs deposited among fine-leaved plants or spawning mops, with no parental care and adults predating unguarded eggs.
Were this species maintained in an aquarium, the approach successful with other small Serrapinnus would apply: condition a small group on live and frozen foods, provide a well-planted spawning area with Java moss or synthetic mops, slightly raise temperature to the upper end of the comfort range, and remove adults or transfer eggs to a separate rearing vessel after spawning. Incubation times for related species at typical tropical temperatures are in the range of 24 to 48 hours, with fry requiring infusoria or commercial fry food initially before graduating to newly hatched brine shrimp.
In the aquarium
Serrapinnus zanatae is not established in the ornamental hobby and is unlikely to be available through the trade. It is a narrow endemic described from wild specimens in the rio Jequitinhonha basin and has no documented history in captivity.
For hobbyists who might encounter related Serrapinnus species, general care requirements reflect the group's biology: a small, peaceful schooling fish best kept in groups of six or more, suited to a community aquarium with other small, non-aggressive fish. Soft to moderately hard, slightly acidic to neutral water at 73–81 °F covers the range of most Brazilian cheirodontines, with good filtration and regular water changes being more important than strict parameter targets. As a micro-tetra under 1.5 in, tankmates should be chosen carefully to avoid competition or predation.
Conservation
Serrapinnus zanatae has not been assessed by the IUCN Red List. Its status is Not Evaluated (NE). The species is known from the rio Jequitinhonha basin, a drainage under increasing pressure from agriculture, mining, and water abstraction across Minas Gerais state. The Jequitinhonha valley has historically experienced significant deforestation and riparian degradation, factors that are among the primary drivers of small-stream fish declines in southeastern Brazil.
As a newly described microendemic from a single river basin, S. zanatae is inherently vulnerable: any deterioration of its restricted range has an outsized effect on the global population. A formal assessment under IUCN criteria — particularly data gathering on its distribution within the basin and the condition of its stream habitats — would help determine whether precautionary protection is warranted. In the interim, general measures protecting Atlantic Forest stream catchments and riparian buffers along Jequitinhonha tributaries directly benefit this and the many other endemic small fish of the region.