Taxonomy & naming
Lebiasina unitaeniata was described by the German-British ichthyologist Albert Günther in 1864, in the fourth volume of his Catalogue of the Fishes in the British Museum. Günther assigned it to the genus Lebiasina, where Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) continues to record the valid name. Because the species was originally described within Lebiasina, the authority is written without parentheses: Lebiasina unitaeniata Günther, 1864.
Lebiasina is the nominotypical genus of the family Lebiasinidae, a clade of small neotropical characins that includes the pencilfish (Nannostomus), the pencilfishes' larger relatives, and the splash tetras (Copella, Pyrrhulina). Within Lebiasina the species are typically distinguished by the arrangement and number of dark lateral stripes; L. unitaeniata is defined by a single such band (hence uni-, one, and taeniata, striped or banded), distinguishing it from congeners that carry two or three parallel stripes. The family Lebiasinidae has been subjected to several phylogenetic revisions, but the core Lebiasina assemblage has remained stable, and L. unitaeniata has not been reassigned.
Morphology
Like other members of the genus, Lebiasina unitaeniata is a slender, cylindrical to slightly compressed fish with a relatively small head, upturned mouth, and large eyes. The body form is adapted for life in shallow, often dense or cluttered microhabitats — the streamlined shape allows rapid movement through vegetation and leaf litter, and the anterior position of the mouth suits surface and near-surface foraging.
The diagnostic character is a single dark lateral stripe running from behind the head to the base of the caudal fin, often accompanied by a caudal spot. Ground coloration is pale tan to olive-bronze, with a silvery or yellowish sheen on the flanks. Finnage is small and unadorned; the adipose fin, characteristic of the broader characin lineage, is present. Published size data from FishBase are limited, but Lebiasina species generally reach 2–4 in in length, and the overall body form is consistent with the genus. Detailed meristic data for this species are sparse in the accessible literature.
Habitat
Lebiasina species are characteristic of tropical lowland and foothill streams in northern and north-western South America, occurring in the Orinoco and Amazon drainages and in Pacific-slope river systems of Colombia, Ecuador, and Peru. The genus is also notable for its tolerance of marginal habitats: several species have been collected in seasonally flooded forest, swampy margins, and even in moist terrestrial conditions where they move through mud or wet leaf litter between isolated water bodies — an ability linked to their accessory air-breathing capacity.
The specific natural distribution of Lebiasina unitaeniata is not precisely documented in widely available sources, though the species' known range falls within the broader Guiana Shield and northern South American lowlands consistent with other members of the genus. Habitat is presumed to include clear-water and blackwater forest streams with soft, acidic to near-neutral water, moderate temperatures, and low to moderate water flow. Data on depth ranges and specific water chemistry parameters remain sparse for this species.
Feeding
Lebiasina species are generalised predators and insectivores, feeding primarily on small invertebrates — insects, insect larvae, small crustaceans, and worms — taken at or near the water surface and from the substrate. The upturned mouth of Lebiasina unitaeniata is consistent with surface feeding habits typical of the genus, and the fish likely supplements invertebrate prey with small amounts of plant material and detritus.
In captivity the species would be expected to accept small live and frozen foods readily — mosquito larvae, Daphnia, bloodworm, and brine shrimp — as well as good-quality small flake or micro-pellets. Specific published feeding observations for L. unitaeniata are not available in the accessible literature, but husbandry experience with congeners suggests an undemanding feeder that responds well to a varied diet.
Mating
Reproductive behaviour has not been specifically described for Lebiasina unitaeniata in the accessible literature. Based on the biology of the genus and the family Lebiasinidae, the species is expected to be an egg-depositing, plant-associated spawner with no significant parental care — the default mode for small, non-mouthbrooding Lebiasina.
Some Lebiasina species are known to spawn in shallow, vegetated margins or even in moist terrestrial conditions, placing adhesive eggs on damp leaves or mud near the water's edge. Whether L. unitaeniata shares this semi-terrestrial spawning tendency or is a more conventional aquatic plant spawner is not documented. Males in breeding condition may show intensified lateral stripe colouration, as is common in the genus, and courtship likely involves brief parallel-swimming displays near the spawning site.
Breeding
No captive breeding accounts specific to Lebiasina unitaeniata appear in the available literature. By analogy with better-documented congeners, the species is assumed to deposit small, adhesive eggs among fine-leaved aquatic vegetation or on submerged plant surfaces, after which adults provide no parental care and will consume eggs given the opportunity.
Breeding in captivity would likely follow the model used for other small Lebiasinidae: a well-planted tank, soft to moderately soft acidic water, live or frozen conditioning foods, and removal of eggs or parents after spawning. Incubation periods and fry requirements are undocumented for this species specifically; fry would be presumed to require infusoria or very fine first foods before graduating to newly hatched brine shrimp, consistent with the family.
In the aquarium
Lebiasina unitaeniata is not an established aquarium fish and is rarely if ever available in the ornamental trade. The genus Lebiasina as a whole has a limited hobby presence compared with the pencilfish (Nannostomus) and related lebiasinids. Where species do appear, they are typically of interest to specialist keepers of smaller South American characins or biotope enthusiasts focusing on Guiana Shield or Orinoco-system communities.
Based on the biology of the genus, an aquarium for this species would be best furnished with soft, slightly acidic water, subdued lighting, a dark substrate, and dense planting or floating cover to replicate the shaded, leaf-littered forest streams the fish inhabits naturally. A tight-fitting lid is advisable given the semi-terrestrial mobility of Lebiasina. The species is likely peaceful toward fish of similar or larger size but may consume very small tankmates. Given data scarcity for this specific species, care guidance from closely related congeners should be treated as indicative rather than definitive.
Conservation
Lebiasina unitaeniata has not been assessed for the IUCN Red List and carries a status of Not Evaluated. No published conservation assessments, population surveys, or threat analyses specific to this species were identified in the sources consulted.
The broader genus Lebiasina occupies lowland and foothill stream habitats in northern South America — regions that have experienced significant deforestation, agricultural conversion, and water-quality degradation over recent decades, particularly in the Amazon and Orinoco lowlands. Without a formal assessment it is not possible to characterise the conservation status of L. unitaeniata, but the absence of evaluation should not be read as an indication of abundance or security. Further field surveys and a formal IUCN assessment would help establish whether habitat pressures affect this species and what, if any, conservation measures are warranted.