Taxonomy & naming
Hyphessobrycon mavro was described by Carlos A. García-Alzate, César Román-Valencia, and Saúl Prada-Pedreros in 2010, with the original description published in the Colombian botanical and zoological journal Caldasia (vol. 32, no. 2, pp. 443–461). The Catalog of Fishes records it as a valid species and confirms the authority and combination as originally published, with no subsequent synonymy.
The species belongs to Hyphessobrycon, an enormous and historically difficult genus of small tetras distributed across South and Central America. No commonly used English name has been established for this species in the hobby or in the scientific literature.
The specific epithet mavro is derived from Greek mavros, meaning 'black' or 'dark', likely referencing a dark pigmentation pattern visible in specimens. No subspecies or geographic variants have been described.
Morphology
Hyphessobrycon mavro is a small fish, reaching a maximum recorded standard length of 1.5 in. Meristic data recorded by FishBase and the original description include 11 dorsal soft rays, 20–21 anal soft rays, and 32 vertebrae — characters that help distinguish it within a genus where counts often overlap broadly across species.
Diagnostic features separating H. mavro from closely related congeners include the absence of bony hooks on the fins of males (a character present in some other Hyphessobrycon), a snout length of 9.9–15.2% of head length, 4–6 teeth in the maxilla, and 17 teeth in the dentary. Like all hyphessobrycons, the body plan is that of a small, laterally compressed tetra with a forked tail and the family's distinctive adipose fin.
Live coloration in the field is not well documented in sources available at this time; the specific name's derivation implies dark or black pigmentation, and formal data sparse on pattern details beyond what the original description provides.
Habitat
The species is distributed in the upper Orinoco River basin in Colombia. This is a highland catchment in the Andean foothills and adjacent lowland transition zones, a region notable for its high fish diversity and ongoing taxonomic discovery. Faunal surveys of the Colombian Amazonia and Orinoco regions have documented H. mavro among a rich characid fauna shaped by the basin's topographic and hydrological complexity.
FishBase classifies the species as benthopelagic and tropical, typical of small Neotropical tetras that occupy the mid-water to near-bottom zones of forest streams and creeks. Specific habitat parameters such as water temperature range, pH, and substrate preferences are not well recorded in the literature available for this species at this time.
Feeding
No detailed dietary study specific to Hyphessobrycon mavro has been published in sources available at this time. As a small tetra in the Orinoco basin, it almost certainly feeds as an opportunistic omnivore in the manner of most small hyphessobrycons: taking small invertebrates including aquatic insect larvae and microcrustaceans, as well as organic detritus and algae, in proportion to local availability.
In an aquarium context, small-mouthed tetras of this size accept finely crushed dry foods, micro-pellets, and small live or frozen foods such as Daphnia, Cyclops, and newly hatched brine shrimp. A varied diet benefits condition and coloration.
Mating
No published observations on the mating behaviour of Hyphessobrycon mavro are available in the literature or hobby accounts at this time. The species is expected to follow the general characid reproductive strategy of egg-scattering open spawning, with eggs deposited among fine-leaved aquatic plants or in the water column and no parental care extended by either sex after spawning.
In typical small hyphessobrycons, males court females with fin-spreading displays; spawning triggers include rising temperature, water changes mimicking seasonal rainfall, and the presence of suitable spawning vegetation. Whether sexual dimorphism is visible in this species beyond fin hooks (which are absent in males, per the original description) is not recorded.
Breeding
Hyphessobrycon mavro has not been documented in captive breeding accounts in the hobby literature available at this time. Based on the biology of the genus, breeding would be expected to follow the standard small-tetra pattern: the pair scatter small adhesive or semi-adhesive eggs among fine-leaved plants or spawning mops, the adults provide no parental care and will consume eggs if given the opportunity, and eggs hatch within 24–72 hours at tropical temperatures depending on water temperature.
Fry would be expected to be very small at hatching and would require infusoria or commercial liquid fry foods before progressing to newly hatched brine shrimp nauplii and finely powdered dry food. Data on clutch sizes, incubation times, and specific breeding requirements for this species are sparse.
In the aquarium
Hyphessobrycon mavro is not established in the aquarium hobby and is not known to be available in the trade at this time. Based on its size (1.5 in SL) and presumed biology as a small Orinoco basin tetra, it would be suited to a well-planted species or community nano aquarium with soft, slightly acidic to neutral water and subdued lighting that mimics the dappled forest-stream environment.
Small tetras from the Orinoco headwaters generally do well at temperatures in the mid-to-upper 20s Celsius with gentle filtration to replicate low-energy stream conditions. Should the species become available, keepers experienced with Amazonian micro-tetras and the Hyphessobrycon genus would be best placed to maintain and breed it. Its small size and presumed peaceful temperament make it compatible in principle with other small, non-aggressive species.
Conservation
The IUCN Red List assessed Hyphessobrycon mavro as Least Concern (LC) on 15 November 2020. The assessment reflects that no major range-wide threats have been identified that would place the species at risk of decline to a threatened category under the Red List criteria at this time.
The species is restricted to the upper Orinoco River basin in Colombia — a region that, while currently supporting substantial fish diversity, faces incremental pressures from deforestation, agricultural runoff, and the expansion of mining activity in the Orinoco headwaters. As a recently described species with a relatively restricted range, it may warrant monitoring as human pressures on Andean-foothill watersheds continue to intensify.