Taxonomy & naming
Moenkhausia andrica was described by Reia, Oliveira & Benine in 2021, with the original description published in the Journal of Fish Biology (Wiley). The type locality is the upper rio Juruena, within the rio Tapajós basin of Mato Grosso state, Brazil. Eschmeyer's Catalog of Fishes (Catalog of Fishes) records the valid name as Moenkhausia andrica Reia, Oliveira & Benine, 2021.
The species belongs to the vast genus Moenkhausia (family Characidae), one of the largest and most taxonomically challenging tetra genera in South America. Molecular work accompanying the original description documented high genetic divergence in the COI mitochondrial marker, supporting the recognition of the species as distinct. The description also notes late development of the lateral-line system and population-level variation in meristic counts, both of which are relevant to identifying the species across its range.
Morphology
Moenkhausia andrica reaches a maximum recorded standard length of 3 in. Its most diagnostic feature is the presence of minute bony hooks on the fin rays of all fins in both mature females and mature males — an unusual condition because in most characids with fin hooks the character is restricted to males. The prepelvic region is distinctly flattened, another character that sets the species apart from congeners.
Meristic counts from the original description (accessible via the PubMed abstract and FishBase) are: lateral-line scales 28–32; scale series above lateral line 5; scale series below lateral line 5; circumpeduncular scales 13–14; anal-fin rays 16–19. A well-defined humeral blotch is present, extending approximately 2 scales horizontally and 2 scales vertically. In life, the dorsal portion of the eye shows a distinctive blue coloration, which is lost after preservation and therefore absent from museum specimens.
Habitat
The species is known from the upper rio Juruena and its tributaries, including the rio Arinos, rio do Sangue, and rio Papagaio — all draining into the rio Tapajós basin of central-western Brazil. This system spans a mosaic of cerrado (savanna) and Amazon transition-forest habitats, generating both clearwater and blackwater tributaries depending on substrate and catchment vegetation.
Regional survey data for Characidae in the Tapajós basin indicate that tetras typical of these systems inhabit slow-moving to gently flowing streams and flooded forest margins with sandy to silty substrates. Water chemistry in the clearwater tributaries tends toward warm, soft, and mildly acidic conditions — temperature roughly 73–82 °F and pH broadly in the range 5.5–8.0 — while blackwater headwaters run more acidic. M. andrica is a benthopelagic freshwater species, occupying the middle and lower water column of these tropical streams.
Feeding
No specific dietary data for Moenkhausia andrica have been published. Based on the trophic ecology of the genus and of small Characidae in the Tapajós basin generally, the species is expected to be an opportunistic omnivore feeding on small invertebrates (aquatic insect larvae, microcrustaceans), terrestrial arthropods falling to the water surface, and some plant material or algae.
In the aquarium, small Moenkhausia species typically accept a wide range of prepared, frozen, and live foods. A diet of quality micro-pellets or fine flake supplemented with frozen Daphnia, brine shrimp nauplii, or cyclops is likely to meet the species' nutritional needs and is consistent with what is known for the genus.
Mating
Specific mating behaviour for Moenkhausia andrica has not been described in the literature. Characids of this size and body form are typically open egg-scatterers without parental care. In closely related Moenkhausia species, spawning involves the broadcast release of small adhesive or semi-adhesive eggs among fine-leaved aquatic plants or submerged vegetation, where they settle without further tending by either parent.
The bony hooks present on all fins in both sexes of M. andrica are thought to play a role in spawning contact, possibly during the close-bodied contact between male and female at the moment of gamete release — a function hypothesised for fin hooks across Characidae more broadly, though the mechanics remain incompletely understood for most species.
Breeding
No captive breeding reports for Moenkhausia andrica appear in the accessible literature, and the species is not established in the ornamental trade as of its description in 2021. Breeding parameters must therefore be inferred from the genus. Moenkhausia species bred in captivity are generally egg-scattering open-water spawners: adults are conditioned with live and frozen foods, a temperature rise to the upper end of the natural range may trigger spawning, and eggs are deposited among fine-leaved plants or a synthetic spawning mop.
Because adults of most Moenkhausia species show no parental care and will consume their own eggs, separation of eggs or removal of adults after spawning is standard practice. Fry are small at hatching and require fine first foods. The late lateral-line development noted in the original description of M. andrica may affect the fry's ability to orient and feed in early life, though this has not been studied experimentally.
In the aquarium
Moenkhausia andrica is not an established aquarium fish as of 2021 and has not appeared in the ornamental trade. Its husbandry can be anticipated from that of comparably sized Moenkhausia tetras, which are generally adaptable, peaceful schooling fish suited to community aquaria with other small, non-aggressive species.
A group of six or more would be appropriate to allow natural shoaling behaviour. Water chemistry matching the soft, warm, mildly acidic conditions of the Tapajós tributaries — temperature 75–82 °F, pH around 6.0–7.5, low to moderate hardness — is a reasonable target. The species' distinctive blue eye coloration in life makes it potentially attractive to specialist collectors, but its availability remains very limited. Any specimens that do enter the trade would be expected to be wild-caught from the upper Juruena region.
Conservation
Moenkhausia andrica has not been assessed by the IUCN Red List as of 2021, reflecting its recent description rather than any conclusion about population size or trend. Its status is therefore Not Evaluated (NE). The cache notes from the original-description research indicate that the tributaries within its known range — the rio Arinos, rio do Sangue, and rio Papagaio — face documented pressures from agricultural expansion (particularly soy cultivation and cattle ranching in the cerrado) and from a series of hydroelectric projects planned or under construction in the upper Juruena system.
Small, range-restricted characids in heavily impacted Amazonian sub-basins are broadly considered at risk even before formal assessment. The combination of a geographically limited known distribution, habitat degradation, and hydro-infrastructure development in the region warrants monitoring as the species becomes better documented.