Taxonomy & naming
Makunaima guaporensis was originally described by Carl H. Eigenmann in 1911 under the name Astyanax guaporensis, with the type locality given as the Río Guaporé basin within the Madeira drainage of Brazil. A 2013 redescription by Marinho and Ohara, published in Zootaxa 3652, clarified the species' distinguishing characters and traced its confused synonymy. The most significant taxonomic change came in 2020 when Terán, Benítez, and Mirande erected the genus Makunaima for a clade within the subfamily Megalamphodinae (family Acestrorhamphidae), naming this species as the type; the valid name therefore became Makunaima guaporensis (Eigenmann, 1911), with the authority in parentheses reflecting the original genus assignment.
Eschmeyer's Catalog of Fishes (CAS) is the governing authority for valid names in this atlas. The slug moenkhausia-guaporensis reflects an older assignment; the current valid genus is Makunaima. The species is not referable to Moenkhausia, from which it differs in a combination of dentition and pigmentation characters detailed by Marinho and Ohara. GBIF records the taxon under ID 11332082.
Morphology
Makunaima guaporensis is a small, slender-bodied characid. Diagnostic characters identified in the 2013 redescription include 5 to 9 teeth on the maxilla, a series of V-shaped marks aligned along the midlateral line, and the consistent absence of a dark blotch on the caudal peduncle — a feature that readily separates it from many co-occurring small characids that bear such a mark.
Beyond these key characters, the overall appearance is typical of small Amazonian characids: a laterally compressed, fusiform body with a silver base coloration, a complete lateral line, an adipose fin, and a forked caudal fin. Precise counts for dorsal-fin rays, scale rows, and standard-length range are documented in the Zootaxa redescription; FishBase data for this species were not retrievable during the research phase of this article.
Habitat
This species ranges across the Río Madeira basin of the Amazon drainage in Brazil, with documented records from several tributaries in and around the Guaporé system, including the small igarapés (forest streams) known as Belmont, Karipunas, and Caracol, as well as the main channel of the Guaporé itself. The habitat profile thus spans both large, lowland river margins and small, shaded forest streams.
Substrate is characteristically sandy at the collection sites. The waters are described as clear, consistent with the relatively low sediment loads typical of Guaporé headwater tributaries. No specific temperature or pH measurements were recorded in the available literature for this species, though the broader Madeira basin in southwestern Brazil experiences warm tropical conditions year-round, with water temperatures generally in the range typical of lowland Amazonian streams.
Feeding
Stomach-content analysis reported from the Zootaxa redescription literature shows that Makunaima guaporensis is an invertivore in the wild. Identified prey items include larvae and adults of Trichoptera (caddisflies), Diptera including Ceratopogonidae (biting midges), Ephemeroptera (mayflies), Hydracarina (water mites), and Hemiptera (true bugs). This assemblage of small, soft-bodied aquatic invertebrates is typical of insectivorous small characids that forage along the bottom and in the water column of sandy-substrate streams.
In an aquarium setting, similarly sized small characids with this feeding profile accept quality micro-pellets and crushed flake supplemented with frozen or live Daphnia, Artemia nauplii, and bloodworm, which support both condition and colouration.
Mating
No specific observations of courtship or mating behaviour in Makunaima guaporensis have been published in the available literature. Based on its placement in the subfamily Megalamphodinae and its general biology as a small, schooling characid of open-water and forest-stream habitats, it is expected to follow the egg-scattering reproductive strategy characteristic of most small characids: brief, non-pair-bonded spawning events with adhesive or semi-adhesive eggs deposited among fine-leaved aquatic plants or over sandy substrate.
Males of many small characids develop small hooks on fin rays during the breeding season, which may function in contact during spawning; whether this trait occurs in Makunaima guaporensis has not been documented in the available sources.
Breeding
Detailed breeding accounts for Makunaima guaporensis in captivity are absent from the available literature, and the species has not established a presence in the mainstream aquarium trade. By analogy with related small characids, spawning would be expected to involve scattering of adhesive eggs among fine-leaved vegetation or over a soft substrate, with no parental care and a tendency for adults to consume eggs if not separated.
Incubation periods and fry-rearing requirements are undocumented for this species. Aquarists working with wild-caught specimens would likely follow protocols developed for similar small Amazonian characids: soft, slightly acidic to neutral water, subdued lighting, and fine live or prepared first foods for the fry.
In the aquarium
Makunaima guaporensis is not established in the ornamental fish trade and is unlikely to be encountered outside specialist collections or research holdings. Its natural habitat — clear, sandy-bottomed igarapés and river margins of the Guaporé system — suggests it would appreciate a furnished aquarium with a fine sandy substrate, low to moderate flow, and denser planting at the margins providing cover.
As a small schooling characid, it would do best kept in a group of six or more individuals, with similarly sized and temperamentally compatible tankmates. The invertivore diet documented from wild specimens indicates live and frozen small invertebrates should form part of any captive diet. Water temperature in the range typical of southwestern Amazonian lowlands (roughly 75–82 °F) and neutral to mildly acidic pH would be appropriate, though specific husbandry data for this species remain unpublished.
Conservation
Makunaima guaporensis is assessed as Least Concern (LC) on the IUCN Red List (assessment 2022.2, taxon ID 167672). The LC assessment reflects a distribution across the Madeira basin that, while not expansive, encompasses multiple river systems and habitat types — from small forest igarapés to the main Guaporé channel — without documented evidence of population decline or significant range-wide threats.
The Guaporé valley and its tributaries in southwestern Brazil face ongoing pressures from agricultural expansion, deforestation, and hydrological alteration, though the species has not been specifically flagged as threatened. Continued monitoring of water quality and habitat integrity in the Madeira basin remains relevant to the long-term status of this and many other small characids endemic to the region.