Taxonomy & naming
Moenkhausia levidorsa was described by Ricardo C. Benine in 2002 and is listed in Eschmeyer's Catalog of Fishes under Characidae. The specific epithet levidorsa is Latin in origin, combining levis (smooth or slight) with dorsa (back or dorsal surface), likely referring to a diagnostic feature of the dorsal region observed by Benine in the type specimens.
The genus Moenkhausia is one of the most species-rich in the family Characidae, with dozens of small to medium-sized tetra-like fishes distributed across South America. Relationships within the genus are complex and the subject of ongoing revision; M. levidorsa has received limited attention since its description, and detailed phylogenetic placement within Moenkhausia remains unpublished.
Morphology
Moenkhausia levidorsa reaches a maximum recorded standard length of 2.5 in in males and unsexed individuals, placing it in the mid-range for the genus — comparable to familiar aquarium Moenkhausia but smaller than the larger species such as M. oligolepis. As a characid it has the typical body plan: a moderately laterally compressed, fusiform profile, an adipose fin, and the terminal mouth typical of a mid-water forager.
Detailed meristic and morphometric data from the original description are not widely republished, and published photographs of the species in the wild or aquarium are rare. The species is described as benthopelagic in freshwater — spending time both near the bottom and in open water — as is typical for small characids that feed across the water column.
Habitat
Moenkhausia levidorsa is recorded from the Rio Aripuanã, a significant right-bank tributary of the Rio Madeira in the southern Amazon basin, in the state of Mato Grosso (and extending into Amazonas), Brazil. The Rio Aripuanã drains a largely forested catchment of the western-central Brazilian Shield, with water conditions that vary seasonally with the Amazon flood pulse.
Like most Amazonian small characids, M. levidorsa likely inhabits shallow, forest-margined rivers and streams, taking shelter among submerged roots and overhanging vegetation. Specific water-chemistry records for the species at its collection localities are not available in the published literature surveyed, but the Rio Aripuanã system is characterised by warm, soft, and mildly acidic to near-neutral waters typical of southern Amazonian tributaries.
Feeding
No species-specific dietary studies have been published for Moenkhausia levidorsa. Based on its guild placement — a small, benthopelagic characid in a lowland Amazonian river — the species almost certainly takes a varied diet of small invertebrates including insect larvae, microcrustaceans, and fallen terrestrial insects, supplemented with plant material and detritus as available seasonally.
Congeneric species studied in the wild and in captivity are broadly omnivorous, and aquarium hobbyists keeping related Moenkhausia report that the genus accepts a wide range of prepared and live foods without difficulty.
Mating
No specific observations of courtship behaviour in Moenkhausia levidorsa have been published. Moenkhausia as a genus consists of egg-scattering open spawners: males pursue females through vegetation or in open water, and spawning involves brief parallel swimming and egg release with simultaneous fertilisation. Sexual dimorphism, where described in the genus, is subtle — ripe females may appear fuller-bodied.
Based on patterns in closely related Moenkhausia species, courtship is likely opportunistic and not tied to a narrow seasonal window under stable tropical conditions, though reproductive activity in the wild may peak during or following the wet season when food is abundant and temperatures are elevated.
Breeding
Moenkhausia levidorsa has not been reported in the aquarium hobby literature as a captive-bred species, and there are no published breeding accounts. By analogy with well-documented congeners, the species is expected to be a non-guarding egg-scatterer: adhesive or semi-adhesive eggs deposited among fine-leaved plants or over the substrate, with no parental care and a tendency for adults to consume eggs if not removed.
Any aquarist wishing to attempt breeding would likely follow standard Moenkhausia protocol: a small, well-planted spawning tank, soft and slightly acidic warm water in the 75–82 °F range, a conditioning period on live and frozen foods, and removal of adults immediately after spawning. Fry would be expected to be small and to require infusoria or similar fine first foods before accepting newly hatched brine shrimp.
In the aquarium
Moenkhausia levidorsa is rarely, if ever, available in the aquarium trade and is essentially unknown to hobbyists. There are no commercial collection records published for the species. Any specimens that appeared would be expected to be hardy and adaptable in the manner of most small Moenkhausia: a peaceful, active schooling fish suited to a community tank with other small to medium South American fishes.
Care parameters inferred from the genus and from Rio Aripuanã water chemistry suggest a preference for warm (73–82 °F), soft to moderately hard, neutral to mildly acidic water. A planted tank with open swimming space and a secure lid — small tetras are capable jumpers — would provide appropriate conditions. The species is an omnivore and would accept flake and small pellets alongside frozen Daphnia, brine shrimp, or bloodworm.
Conservation
Moenkhausia levidorsa is assessed as Data Deficient (DD) on the IUCN Red List. This reflects a genuine lack of population data rather than any documented abundance: the species is known from the Rio Aripuanã drainage and has not been the subject of population surveys or targeted conservation study.
The Rio Aripuanã basin faces pressures common across southern Amazonia, including deforestation, agricultural expansion, and mercury contamination from alluvial gold mining (garimpo) that has historically been significant in the Aripuanã watershed. Whether M. levidorsa is genuinely rare, locally common but uncollected, or affected by these pressures is unknown. Targeted ichthyological surveys of the Aripuanã system would be required before any more precise assessment could be made.