Taxonomy & naming
Lebiasina narinensis was described by Carlos Ardila Rodríguez in 2002. The type locality is in the Nariño department of southwestern Colombia, and the specific epithet narinensis is a toponym derived from that department name, following the standard Latin adjectival ending that means 'from Nariño'. Eschmeyer's Catalog of Fishes (CAS) records the valid name as Lebiasina narinensis Ardila Rodríguez, 2002.
The genus Lebiasina belongs to the family Lebiasinidae, the pencilfish family, within the order Characiformes. Lebiasinidae is divided into several subfamilies and includes well-known aquarium genera such as Nannostomus (pencilfish) and Pyrrhulina, alongside Lebiasina itself. Within Lebiasina, species are generally small to medium-sized and distinguished from one another by coloration, meristic counts, and details of the lateral-line system. The taxonomy of the genus has been revised incrementally by South American ichthyologists, and Ardila Rodríguez contributed several Colombian species descriptions in the early 2000s.
Morphology
Lebiasina narinensis is a slender, fusiform fish with the elongate body plan characteristic of the genus. Body depth is moderate relative to length, and the head is somewhat pointed; the mouth is terminal and angled slightly upward, consistent with surface or mid-water feeding. The caudal fin is forked. Pigmentation follows the general Lebiasina pattern: a dark lateral stripe or series of markings runs along the midline, and the flanks carry a bronzy or coppery ground colour. Precise meristic details and maximum size were established in the original description but are not widely reproduced in secondary literature, and data from the type series should be consulted for exact counts.
As with most Lebiasina species, sexual dimorphism is subtle and not well characterised in the published literature for this species specifically. In the genus broadly, females may appear somewhat deeper-bodied when gravid, and adult males in some species carry a few small hooks on the anal-fin rays — a feature that has been used taxonomically within Characiformes but whose presence in L. narinensis has not been confirmed in accessible sources.
Habitat
The species is known from the Nariño department of southwestern Colombia, a region of complex Andean drainage geography where Pacific-slope rivers descend from the Andes toward the Colombian Pacific lowlands. Lebiasinids in this part of South America typically inhabit slow-moving or still sections of small streams and forest creeks, often in areas with dense bankside vegetation, leaf-litter accumulation, and reduced current. Water in such habitats tends to be soft and mildly acidic, warmed by the tropical climate but occasionally cooler at higher elevations.
Precise habitat data for L. narinensis from the type-series collection are not widely available in secondary sources, and no detailed field surveys of the species appear to have been published independently of the original description. Its distribution may be narrow: many Lebiasina species show limited ranges tied to specific river basins, and the Nariño toponym suggests the currently known range does not extend widely beyond the type region.
Feeding
Lebiasina species are generally micro-carnivores that take small invertebrates — insect larvae, small crustaceans, worms, and terrestrial insects that fall to the water surface. The slightly upturned mouth of most Lebiasina is consistent with surface feeding on insects, and the genus is considered opportunistic in its foraging. No specific gut-content study for L. narinensis has been located in accessible literature, and feeding ecology is inferred from the genus.
In captivity, related Lebiasina species accept a range of small live and frozen foods including Daphnia, Artemia nauplii, bloodworm, and small chironomid larvae. Small, high-quality prepared foods may be taken once the fish has settled. Variety is preferred over a single food type, and live foods help maintain condition in newly imported or wild-caught specimens.
Mating
Breeding biology of Lebiasina narinensis specifically has not been documented in accessible published or hobbyist literature. Lebiasinids as a group include both egg-scatterers and species that deposit adhesive eggs on surfaces, and some show limited parental behaviour. Lebiasina species for which spawning data exist tend to scatter small adhesive eggs among fine-leaved plants or over firm substrates, with no prolonged parental care.
Male courtship in the genus typically involves lateral displays and chasing, with the male pursuing the female through vegetation prior to spawning. Given the limited aquarium keeping of this species, behavioural accounts are sparse, and the mating system of L. narinensis specifically should be regarded as data-sparse pending dedicated study or captive-breeding reports.
Breeding
No detailed captive-breeding account for Lebiasina narinensis has been located in accessible sources. By analogy with better-known congeners, breeding would likely require soft, slightly acidic water, a well-planted or well-furnished spawning space, and conditioning on live or frozen foods. Eggs in Lebiasina tend to be small and adhesive, laid in small numbers over plants or substrate, and adults are not expected to provide parental care; separating eggs or fry from adults would be standard practice.
Because the species is rarely if ever held in specialist collections outside Colombia, captive-breeding data may exist only in the original description or in unpublished observations. Any prospective breeder should consult the primary literature and treat accounts based on related species as provisional guides rather than confirmed protocols.
In the aquarium
Lebiasina narinensis is essentially unknown in the international aquarium hobby, and it is very unlikely to be encountered in the trade under its own name. It has no established common name. Were it to become available, husbandry would be guided by what is known of the genus: a small, planted aquarium with soft, slightly acidic water, subdued lighting, a dark substrate, and a quiet flow would suit most Lebiasina. The fish are generally peaceful toward similarly sized tankmates but may consume very small fish or fry; they are best kept with species that share their water-parameter preferences and are large enough not to be regarded as prey.
Data on temperament, tank size, and specific care requirements for L. narinensis are not available in secondary sources, and any husbandry information offered here should be understood as genus-level inference rather than species-specific guidance. Hobbyists encountering this species should document their observations and share them with the broader community.
Conservation
Lebiasina narinensis has not been assessed by the IUCN Red List and carries no formal conservation status. This is not uncommon for recently described, narrowly distributed Neotropical characiforms: the pace of taxonomic work in South American freshwater fish systematics means that many species are described faster than they can be evaluated. The Nariño department of Colombia contains portions of several biodiversity-rich river systems, some of which face pressure from agriculture, deforestation, and infrastructure development in the Andean foothills.
Without a formal range assessment and population survey, the conservation outlook for L. narinensis cannot be judged with confidence. Species known only from a restricted type locality in a region with ongoing habitat change are inherently at some risk, and the apparent absence of the species from trade or ex-situ collections means there is no captive buffer population. Formal assessment by a freshwater specialist group would be a useful first step toward understanding whether protective measures are warranted.