Taxonomy & naming
Hyphessobrycon metae was described by Carl H. Eigenmann and Arthur W. Henn in 1914, with the type locality recorded as Barrigona on the Río Meta, Orinoco drainage, Colombia. The holotype is held at the California Academy of Sciences (CAS 61751), with a large paratype series also at CAS. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) lists the valid name as Hyphessobrycon metae Eigenmann & Henn, 1914, placing it in the family Characidae.
The genus Hyphessobrycon is one of the most species-rich tetra genera, comprising dozens of small, often strikingly coloured South American characids. Historically some authors have placed parts of it in other genera or subfamilies; current Catalog of Fishes treatment retains the species in Hyphessobrycon within the family Characidae.
Morphology
H. metae is a slender, moderately compressed tetra reaching approximately 1.5 in standard length, with FishBase reporting a maximum of 1.5 in SL. Females tend to be deeper-bodied and slightly larger than males, a pattern typical of the genus.
The body colour lends the fish its popular name: a purplish to violet wash over the flanks, intensifying in well-conditioned individuals under appropriate lighting, with the finnage sometimes carrying reddish or hyaline tints. Like other small hyphessobrycons, it carries a dark lateral stripe element and a humeral spot. Colour intensity is influenced by water chemistry, lighting, and the overall health of the fish — specimens in soft, acidic conditions matching their natural habitat typically show their best coloration.
Habitat
This species is endemic to the middle Orinoco watershed, recorded from Colombia (departments of Meta, Casanare, Arauca, Vichada, and Guainía) and Venezuela (states of Amazonas, Apure, Guárico, and Bolívar). Its core range is the vast savanna lowlands of Los Llanos, one of the largest tropical grassland-wetland systems in South America.
Within this landscape H. metae favours morichals — stream and gallery habitats dominated by the moriche palm (Mauritia flexuosa) — as well as blackwater floodplain streams and shallow lakes. These environments are characterised by transparent to tea-coloured water, sandy substrates, dense marginal and submerged vegetation, and notably soft, acidic chemistry. Seriously Fish records the natural water parameters as pH 4.0–7.0, hardness 18–143 ppm, and temperatures 68–82 °F. The species occurs in areas that experience pronounced seasonal flooding cycles, and some populations use temporarily connected floodplain habitats during high-water periods.
Feeding
Hyphessobrycon metae is an omnivore in the wild, taking small invertebrates, crustaceans, and algae from the water column and substrate surfaces of its soft-water home. Small insect larvae and microcrustaceans likely form the bulk of the animal-protein component.
In the aquarium the species is undemanding and accepts a wide variety of foods. A diet built around high-quality micro-pellets or finely crushed flake, supplemented regularly with live or frozen small invertebrates such as bloodworm, Daphnia, and brine shrimp nauplii, keeps fish in good colour and condition. Small, frequent feedings suit the species better than single large meals.
Mating
Hyphessobrycon metae is an egg-scattering open spawner with no parental care, following the typical pattern of the genus. Males display to females among fine-leaved vegetation or spawning mops, and the pair releases adhesive eggs that catch on plant material or settle among substrate debris.
Sexual dimorphism in the species is modest in terms of coloration but pronounced in body shape: females in breeding condition become noticeably deeper-bodied and plumper than males. Spawning has not been extensively documented in the published literature, but the broad pattern — brief courtship chase, scatter of small adhesive eggs, immediate abandonment by both parents — is consistent with other Hyphessobrycon of similar size.
Breeding
Captive breeding reports for H. metae are sparse in the published literature, though hobbyists have bred it under soft-water conditions. The standard Hyphessobrycon approach applies: condition a small group in a species tank with fine-leaved plants or synthetic mops, very soft and acidic water (pH around 5.5–6.5, hardness as low as practicable), and a temperature in the mid-to-upper 20s Celsius. Provide dim lighting and a dark substrate to encourage normal behaviour.
Eggs are small, semi-adhesive, and non-guarded; the adults will consume both eggs and fry, so spawning medium should be removed to a separate hatching container once spawning is observed. Incubation and fry development follow the general Hyphessobrycon pattern: eggs hatch within two to three days at typical temperatures, with free-swimming fry appearing a day or two later. First foods are infusoria or commercial liquid fry food, graduating to newly hatched brine shrimp as the fry grow.
In the aquarium
The Purple Tetra is a peaceful, sociable fish best maintained in schools of eight or more individuals. In a group it becomes bolder, shows better colour, and behaves more naturally than isolated specimens. A planted aquarium of 15 US gal or more, with soft and slightly acidic water to match the morichal habitat, suits it well; dense planting around the perimeter and some open swimming space in the centre mirrors its natural environment.
Water chemistry is worth attending to: while the species tolerates a broad pH range in captivity (Seriously Fish lists 4.0–7.0), it displays best and is likely healthiest in soft, slightly acidic conditions. Temperature of 72–79 °F (FishBase) is appropriate for long-term maintenance. The species is entirely compatible with other small, peaceful soft-water fish — other small tetras, dwarf cichlids, and small corydoras catfish are natural companions. It presents no special feeding challenges. The IUCN assessed it as Least Concern in 2020, and the species is commercially bred for the aquarium trade, so hobbyists can readily source tank-raised stock.
Conservation
The IUCN Red List assessed Hyphessobrycon metae as Least Concern (LC) on 1 December 2020. The assessment, conducted by a team of Venezuelan and Colombian ichthyologists including Donald Taphorn, Edgar Esteban Herrera-Collazos, Douglas Rodríguez-Olarte, Carlos DoNascimiento, Saulo Usma, and Francisco Villa-Navarro, found no significant threats documented at that time, noting that the species occurs across a substantial portion of the Orinoco watershed and in protected tributaries.
FishBase rates the species' resilience as high, reflecting its relatively broad distribution and the ecological productivity of the Los Llanos system. Continued monitoring is prudent given that the Llanos wetlands face pressures from agriculture, water management, and land-use change, but the species' distribution across both Colombian and Venezuelan portions of the Orinoco basin provides some buffer against localised impacts.