Taxonomy & naming
Makunaima multidens was described by the American ichthyologist Carl H. Eigenmann in 1908. Eigenmann's extensive surveys of Guiana Shield fishes produced dozens of new characid taxa, and M. multidens was among the species characterised from that material. The valid name as recorded in Eschmeyer's Catalog of Fishes is Makunaima multidens Eigenmann, 1908; no subsequent revision has moved the species to another genus, and because it was described in Moenkhausia, where it remains, no parenthetical authority is needed.
The genus Moenkhausia Eigenmann, 1903, named in honour of the German ichthyologist William John Moenkhaus, is one of the most species-rich genera in the family Characidae, currently containing well over 80 described species scattered across the major river systems of tropical South America. Many Moenkhausia are superficially similar silvery or translucent tetras distinguished chiefly by meristics — scale counts, fin-ray counts, and, as the name of this species signals, dentition. The generic boundaries of Moenkhausia have been repeatedly questioned, and molecular studies have shown the genus to be polyphyletic, meaning future revisions may realign some species. M. multidens has not been the subject of a dedicated revisionary study, and its precise phylogenetic placement within the genus remains data-sparse.
This fish was long listed as Moenkhausia multidens; Eschmeyer's Catalog of Fishes places the species in Makunaima, and the current combination Makunaima multidens is followed here.
Morphology
Like most members of the genus, Makunaima multidens is a laterally compressed, moderately deep-bodied characid with a silvery ground colour and the characteristic adipose fin of the family Characidae. It reaches a reported standard length in the range of 2.8–3.5 in, though documentation in the primary literature is limited and published size data should be treated as approximate.
The species' defining character, encoded in its name, is its dentition: multidens possess a notably high tooth count relative to congeners, a feature used by Eigenmann to separate it at description. The scales are cycloid and relatively large for the body size, a typical Moenkhausia trait. Coloration in life is silvery with variable iridescence under certain lighting; a dark or dusky caudal peduncle or basal caudal spot may be present, though published colour descriptions are sparse and preserved-specimen descriptions do not capture live appearance reliably. Females are likely deeper-bodied and more robust when gravid, as is typical in the genus, but formal dimorphism data for this species are not available in the published record.
Habitat
Makunaima multidens originates from the Guiana Shield drainage systems of northern South America, the area from which Eigenmann described it in 1908. The broader Guiana Shield encompasses portions of Guyana, Suriname, Venezuela, and northern Brazil, drained by rivers including the Essequibo, Corentyne, and numerous tributaries of the Amazon and Orinoco systems.
Habitat details specific to M. multidens are not extensively documented in the accessible literature. By analogy with well-studied Moenkhausia congeners occupying similar drainages, the species likely inhabits clear to blackwater streams, river margins, flooded forest edges, and slow-moving or still backwaters with abundant submerged or overhanging vegetation. Many Guiana Shield characids favour acidic, soft, tannin-stained waters, though Moenkhausia as a genus spans a considerable range of water chemistry. Precise temperature, pH, and conductivity records for this species' collection localities have not been traced in the available sources.
Feeding
No specific dietary study of Makunaima multidens has been located in the available literature. Moenkhausia species are generally opportunistic omnivores that exploit the upper and middle water column, taking small aquatic invertebrates, insect larvae, microcrustaceans, fallen terrestrial insects, and plant material or algae depending on what is seasonally available. The high tooth count of M. multidens may reflect an adaptation for processing tougher or more varied food items than congeners, though this remains speculative in the absence of gut-content studies.
In the aquarium, members of the genus typically accept a broad range of prepared and live foods: quality flake and micro-pellet diets supplemented with frozen or live Daphnia, brine shrimp, and bloodworm are suitable. A varied diet supports condition and natural coloration. Like other active characids, they benefit from feeding small amounts multiple times per day rather than a single large meal.
Mating
Specific observations of reproductive behaviour in Makunaima multidens in the wild are not documented in the accessible scientific record. The species can be expected to follow the general pattern established for the genus and for small Neotropical characids broadly: open-water egg scattering with no parental care, with spawning likely triggered or intensified by seasonal cues such as rising water levels, temperature shifts, or increased rainfall associated with the Amazonian and Guiana Shield flood pulse.
As in other Moenkhausia, males likely display to females in the water column, chasing and coursing alongside prospective partners before the pair releases eggs and milt in quick bursts over substrate, vegetation, or open water. Eggs are adhesive or semi-adhesive and may settle among fine-leaved plants or substrate debris. Males in good condition tend to be more slender-bodied than gravid females, which is the most consistent external cue for sexing the genus.
Breeding
Makunaima multidens has not been bred in captivity under documented aquarium conditions in the accessible hobbyist or scientific literature, or at least no accounts have been widely circulated. However, the general breeding approach for the genus provides a workable starting point. Moenkhausia are egg-scatterers that spawn freely over fine-leaved plants, Java moss, or synthetic mops; the adults show no parental care and will consume their own eggs if not separated from the spawning medium promptly.
A conditioning period on live and frozen foods typically brings adults into spawning condition. A slightly raised temperature — to the upper end of the species' tolerance — and a water change with slightly cooler, softer water often stimulates spawning activity, mimicking the onset of the rainy season. Eggs hatch in 24–48 hours at typical tropical temperatures, and the fry become free-swimming after a further 2–3 days. First foods for Moenkhausia fry are typically infusoria or very fine commercial fry preparations, followed by newly hatched brine shrimp nauplii as the fish grow. Growth rate and time to sexual maturity are not specifically recorded for this species.
In the aquarium
Makunaima multidens is not among the commonly traded tetras, and aquarium accounts are sparse. It is not regularly encountered in the hobbyist trade under its own name, and much that would apply to its care must be extrapolated from what is known of the genus and of similarly sized Guiana Shield characids. A group of six or more individuals is appropriate; like virtually all small characids, solitary or paired specimens are likely stressed and drab compared to a proper school.
Water conditions soft to moderately hard, slightly acidic to neutral, and warm (approximately 75–82 °F) are a reasonable starting point based on the Guiana Shield origin. A planted aquarium with dark substrate, some tannin staining, and subdued or natural-spectrum lighting would approximate the species' inferred natural habitat and is likely to encourage natural behaviour and good coloration. Given the data-sparse status of this species in both the scientific and hobbyist literature, keepers who maintain and spawn it should consider documenting observations and sharing them through aquarium societies or ichthyological journals, where such records have genuine scientific value.
Conservation
Makunaima multidens has not received a formal assessment on the IUCN Red List and is considered Not Evaluated (NE) at the time of writing. This reflects the general pattern for the majority of described freshwater fishes: most of the world's approximately 18,000 recognised freshwater fish species have not been assessed for extinction risk, not because they are necessarily secure but because the resources for assessment have not yet been applied to them.
The Guiana Shield drainages from which M. multidens was described are among the better-preserved tropical freshwater systems remaining in South America, with large areas still under intact forest cover. However, portions of the region face growing pressure from illegal gold mining, deforestation, and mercury pollution, all of which degrade stream habitats. For a small, range-restricted characid with limited dispersal capacity, local habitat loss can translate quickly into population decline. The scarcity of occurrence records and published natural history data for this species makes it impossible to assess its current population status with confidence.