Taxonomy & naming
Lebiasina uruyensis was described by the Venezuelan ichthyologist Alfredo Fernández-Yépez in 1967. The species belongs to the genus Lebiasina, the largest genus in the family Lebiasinidae, a family of small to medium-sized characiforms distributed across tropical South America and Panama. The Lebiasinidae are sometimes informally grouped with the pencil-fishes (Nannostomus and allies) and the pencilfishes of the subfamily Pyrrhulininae, though the family as currently circumscribed is supported by molecular and morphological evidence as a monophyletic assemblage within the broader characiform radiation.
The valid name is listed in Eschmeyer's Catalog of Fishes as Lebiasina uruyensis Fernández-Yépez, 1967, with the authority unparenthesised because the species was described within the genus Lebiasina and has not been transferred. Within Lebiasina, species are distinguished primarily by body proportions, scale counts, the configuration of lateral-line scales, and the pattern of horizontal stripes or spots along the flank. Data sparse for this species relative to its better-studied congeners.
Morphology
Members of the genus Lebiasina are elongate to moderately deep-bodied characiforms with a rounded snout, a terminal or slightly superior mouth suited to surface and mid-water feeding, and a complete lateral line. The body is laterally compressed. Like most lebiasines, L. uruyensis bears one or more prominent dark horizontal stripes or a series of blotches along the midlateral surface, which provide both camouflage in dappled forest-stream light and a basis for species identification.
Detailed morphometric data for L. uruyensis specifically are not widely available in accessible literature; formal size records are limited. Based on the general range of the genus, adults likely reach 2.5–4.5 in total length, though this range should be treated with caution in the absence of confirmed data for this species. The caudal fin is forked; the dorsal fin is set back toward mid-body, and the adipose fin is present, a retained character in this family.
Habitat
Lebiasina uruyensis is endemic to the Orinoco drainage of Venezuela, with its name referencing the Uraima or Uruyan region of that drainage basin. Lebiasina species typically inhabit small to medium-sized forest streams, tributary creeks, and seasonally flooded marginal habitats within lowland and piedmont zones of tropical South America. These are generally warm, soft, and acidic to slightly acidic waters, heavily shaded by riparian gallery forest, with substrate of sand, fine gravel, leaf litter, and submerged roots.
The Orinoco system encompasses a wide range of microhabitat types, from blackwater forest streams with very low conductivity and pH well below 6 to clear-water tributaries draining the Guiana Shield. Without detailed collection records, the precise microhabitat preferences of L. uruyensis are uncertain, but the pattern across its genus points to shallow, well-vegetated or debris-laden stream margins rather than open main-channel water.
Feeding
Lebiasina species are opportunistic carnivores and micropredators, feeding primarily on small aquatic and terrestrial invertebrates. The terminal to slightly upturned mouth position in lebiasines is associated with surface and near-surface foraging: insects falling onto the water, small crustaceans, insect larvae, and worms form the bulk of the natural diet. Some plant material and detritus may be ingested incidentally.
In the aquarium, closely related lebiasines accept a range of live and frozen small invertebrate foods — Daphnia, Artemia, bloodworm, Tubifex — as well as suitably sized dry foods. A diet with a substantial live or frozen component better matches their predatory nature and supports conditioning. As with many small insectivorous characiforms, feeding small portions frequently produces better results than single large meals.
Mating
Specific spawning observations for Lebiasina uruyensis are not documented in readily available literature. The genus Lebiasina, along with other lebiasines, is generally considered to practise open egg-scattering spawning, with adhesive or semi-adhesive eggs deposited among fine-leaved aquatic plants, root tangles, or leaf litter on the stream bottom. No specialised parental care has been described for the genus.
Sexual dimorphism in lebiasines is typically subtle outside the breeding season; females may appear deeper-bodied when gravid. Males of some Lebiasina species develop small hooks on the anal-fin rays — a character shared with various other characiforms — which may play a role in courtship or spawning behaviour, though the functional significance remains incompletely studied.
Breeding
No captive breeding reports for Lebiasina uruyensis are known from mainstream hobby literature. By analogy with related lebiasines, conditioning with live and frozen foods, a slight drop in water temperature or increase in rainfall simulation, and provision of fine-leaved plants or spawning mops would be reasonable starting points. Eggs in egg-scattering characiforms are typically small, non-adhesive to weakly adhesive, and are left by the parents after spawning; removing adults post-spawning protects the clutch from predation.
Fry would be expected to be small at hatching and to require fine first foods such as infusoria or commercial micro-fry diets before accepting newly hatched brine shrimp nauplii. Given the species' obscurity in the trade, captive breeding observations would represent a genuine contribution to knowledge of the genus.
In the aquarium
Lebiasina uruyensis is essentially absent from the international aquarium trade and is not established as a hobby fish. It would be suited to a biotope-style setup replicating an Orinoco forest stream: soft, warm, slightly acidic water; subdued lighting; a dark substrate of fine sand with scattered leaf litter and tangles of driftwood and roots; and a tight-fitting lid, as lebiasines are capable jumpers.
By comparison with better-known lebiasines and related pencil-fish relatives, a temperature range of roughly 75–82 °F and a pH of 5.5–7.0 in soft, low-conductivity water would be a reasonable starting baseline. The species should be kept away from significantly larger or aggressive tankmates. Peaceful community fish of similar size from soft-water South American habitats — small tetras, dwarf cichlids, and corydoras — would represent compatible companions if a mixed setup is preferred over a species tank.
Conservation
Lebiasina uruyensis has not been assessed by the IUCN Red List and carries a status of Not Evaluated (NE). The absence of an assessment reflects limited data availability and the relative obscurity of the species within a large, species-rich family rather than any confirmed finding of security or threat. Endemic range within the Orinoco drainage means any significant habitat degradation in its known collection area would affect the entire known population.
Broader threats to Orinoco-drainage fish fauna include deforestation and land conversion in the riparian and catchment zones, artisanal and small-scale mining (especially alluvial gold mining in Guiana Shield tributaries), and the associated increases in sedimentation and mercury contamination. Whether L. uruyensis is directly affected by these pressures at its specific localities is unknown. Its collection and formal assessment by IUCN evaluators would improve understanding of its status considerably.