Taxonomy & naming
Serrapinnus lucindai was described by Fernando C. Jerep and Luiz R. Malabarba in 2014 in a paper reviewing the species of the genus Serrapinnus Malabarba, 1998 from the rio Tocantins-Araguaia basin, published in Zootaxa. That work, which covered three new species, was part of a broader effort to resolve species boundaries within Cheirodontinae in major South American drainages.
The genus Serrapinnus belongs to the subfamily Cheirodontinae within the family Characidae — a diverse assemblage of small South American characids with hooked anal-fin rays in males of most species. Eschmeyer's Catalog of Fishes is the authority for the valid name Serrapinnus lucindai Jerep & Malabarba, 2014. As the species was described in its current genus, the authority is not parenthetical.
Morphology
Serrapinnus lucindai is a miniature characid, with a maximum recorded standard length of 1 in. Like other members of the genus it has the slender, laterally compressed body typical of small cheirodontine tetras, with a relatively large eye and a small upturned mouth suited to feeding near the surface or in the water column.
The key diagnostic character separating S. lucindai from other Serrapinnus in the Tocantins-Araguaia basin is a higher number of ventral procurrent caudal-fin rays, ranging from 17 to 19. Males additionally bear hooks on the anal-fin rays, a feature common across Cheirodontinae and thought to function in spawning contact. Coloration in life is not fully detailed in available sources, but the species presumably shows the silvery, lightly pigmented appearance typical of small cheirodontine characids.
Habitat
The species is endemic to the rio Tocantins-Araguaia basin in Brazil, one of the major river systems draining the central Brazilian plateau into the Amazon estuary region. Documented localities include gravel and sand banks of the rio Tocantins near Tocantinópolis in the state of Tocantins — a habitat characterized by clear to moderately turbid water over coarse substrates in a tropical lowland environment.
As a benthopelagic species it occupies the lower to mid water column in its stream habitat. The Tocantins-Araguaia system spans a range of cerrado and transitional forest landscapes; the species' association with coarser gravel-and-sand-bank habitats suggests a preference for well-oxygenated reaches with moderate current rather than slow backwaters.
Feeding
FishBase records a trophic level of 2.7 (±0.5) for Serrapinnus lucindai, placing it squarely in the omnivore range typical of small cheirodontine characids. At this trophic level the diet is likely composed of small invertebrates — microcrustaceans, insect larvae, and zooplankton — together with algae, organic detritus, and fallen terrestrial matter.
In an aquarium setting, small cheirodontines of similar size and build are generally undemanding and accept fine-grade prepared foods, small live or frozen invertebrates such as Artemia nauplii and micro-worms, and quality micro-pellets. A varied diet supports good condition and natural coloration.
Mating
No detailed field or laboratory observations of mating behaviour in Serrapinnus lucindai are available in published sources. Based on the biology of the genus and subfamily Cheirodontinae more broadly, the species is expected to be an egg-scattering open spawner with no parental care — the standard reproductive mode for small characids.
The presence of anal-fin hooks in males is a consistent feature of cheirodontine breeding biology. These hooks are thought to facilitate brief contact between male and female during the spawning rush over fine-leaved vegetation or other substrates, allowing the male to clasp alongside the female momentarily at egg release.
Breeding
Serrapinnus lucindai has not been documented in captive breeding accounts in the available literature. By analogy with other small Serrapinnus and related cheirodontines, breeding would involve egg-scattering over fine-leaved plants or similar spawning substrate, with adhesive or semi-adhesive eggs scattered among vegetation and no subsequent parental attention. Adults would be expected to consume unguarded eggs if left in the spawning tank.
For any hobbyist attempting to breed the species, standard small-characid practice — a separate, well-planted breeding tank, removal of adults after spawning, and very fine first foods such as infusoria or commercial liquid fry food for the newly hatched fry — would be the appropriate starting point. Breeding temperature within the tropical range (75–82 °F) and soft to moderately hard water are consistent with the Tocantins basin habitat.
In the aquarium
Serrapinnus lucindai is not an established aquarium subject and is rarely if ever available in the hobby outside of specialist collectors with access to Brazilian export stock. Its tiny size (1 in SL), benthopelagic habits, and origins in clear, oxygenated stream reaches suggest it would do best in a small to medium biotope aquarium replicating the gravel-and-sand-bank habitat of the Tocantins, with gentle to moderate flow, fine substrate, and open swimming space.
As a social small characid it should be kept in a group of six or more. Given its size it is best housed with similarly small, peaceful tankmates — other miniature tetras, small corydoras, or pygmy catfishes that would not outcompete it at feeding. Water temperature in the tropical range of 75–82 °F and near-neutral pH suit the conditions of the Tocantins basin. Data on the species in captivity are sparse; it remains primarily of interest to biotope enthusiasts and researchers rather than the general hobby.
Conservation
Serrapinnus lucindai is assessed as Least Concern (LC) on the IUCN Red List, with the assessment completed in November 2018. This status reflects the species' occurrence across a broad and relatively intact river basin — the Tocantins-Araguaia system — which, despite ongoing deforestation and hydroelectric development pressures, still supports diverse small-fish fauna across much of its length.
The Tocantins basin has been substantially modified by a cascade of large dams, including the Tucuruí reservoir, and deforestation of riparian vegetation in the cerrado transition zone is an ongoing concern for small stream-specialist fishes throughout the region. While the current IUCN assessment does not flag the species as threatened, long-term monitoring of small cheirodontine populations in regulated river reaches remains important for detecting any future decline.