Taxonomy & naming
Pyrrhulina spilota was formally described by Stanley H. Weitzman in 1960 in volume 7, number 4 of the Stanford Ichthyological Bulletin. The type material is held at the California Academy of Sciences: holotype CAS-SU 52352, with a single paratype CAS-SU 52353. Eschmeyer's Catalog of Fishes (CAS) treats the name as valid through at least 2026, placing the species in subfamily Pyrrhulininae of the family Lebiasinidae. No synonyms are recorded, and the authority has never been moved to parentheses because the species was described directly in Pyrrhulina.
The genus Pyrrhulina comprises roughly two dozen small, surface-oriented characoids distributed across tropical South America. They are closely related to the pencilfish genera Nannostomus and Nannobrycon, and share with them the characteristic oblique resting posture near the water surface. Weitzman's 1960 revision of the group clarified the boundaries between several species whose black-blotch patterns had previously caused confusion in the literature.
Morphology
Pyrrhulina spilota reaches a maximum recorded standard length of 3 in, making it one of the larger members of its genus, though most specimens in both wild collections and the aquarium are somewhat smaller. The body is elongate and moderately compressed, with a strongly upturned mouth adapted for surface feeding and the typical oblique swimming posture of the group.
The most diagnostic feature is a series of four distinct dark blotches arranged along the lateral midline of the body, often appearing as squarish spots against a pale tan to silvery-gold background. The fins are well developed and notable for their black borders, and the anal fin carries additional black markings. These fin markings, combined with the blotch row, reliably separate P. spilota from other Pyrrhulina species in its range. The caudal fin is rounded to slightly forked. Like most Pyrrhulina, it shows modest sexual dimorphism: males tend to develop more elongated fins with stronger pigment, and the body becomes somewhat deeper in mature individuals.
Habitat
Pyrrhulina spilota is known from the upper Amazon River basin, centred on the Iquitos region of Loreto, Peru; GBIF occurrence records extend the recorded range into adjacent parts of Bolivia. It inhabits slow-moving to standing waters — flooded forest margins, oxbow lakes, small streams, and forest pools — that typify the vast Amazonian lowland mosaic around Iquitos.
FishBase records the following water parameters associated with the species: temperature 73–79 °F, pH 5.8–7.0, and hardness up to 15 dH (soft to moderately soft). The fish is benthopelagic in habit, spending much of its time just below the water surface among overhanging vegetation, leaf litter, and floating plants that provide shade and invertebrate prey. Like most Pyrrhulininae, it is a still-water specialist that finds both food and refuge in the surface film of sheltered, often darkly stained habitats.
Feeding
Pyrrhulina spilota is a microcarnivore of the water surface and immediate subsurface zone. FishBase assigns a trophic level of 3.3, consistent with a diet centred on small invertebrates — primarily terrestrial and aquatic insects, small crustaceans, and zooplankton intercepted at or near the surface. The upturned mouth is well suited to snatching prey from the film.
In the aquarium, the species takes small live and frozen foods readily: fruit flies (Drosophila), small crickets, Daphnia, brine shrimp, and bloodworm. Floating or slowly sinking prepared foods are accepted once the fish is settled, but live surface prey is generally preferred and helps maintain condition for spawning. Feeding in the upper third of the water column where the fish naturally forages will reduce competition and stress.
Mating
Pyrrhulina spilota reproduces by depositing adhesive eggs on a substrate — typically a broad leaf or a smooth flat surface — in a manner typical of the genus. Males establish and defend a small spawning territory, courting females with fin displays that emphasize the bold black markings on the fins. Spawning pairs come together briefly at the chosen site, release and fertilize a small batch of eggs, and the male then guards the site.
Unlike the egg-scattering habit of many tetras, Pyrrhulina species are substrate spawners with short-term paternal care: the male fans the egg mass and defends it from intruders until hatching. This makes the genus unusual among New World characoids of comparable size and helps explain the relatively large, yolky eggs.
Breeding
In captivity, Pyrrhulina spilota can be bred in a species-only aquarium with very soft, slightly acidic water matching its natural parameters (temperature around 77–79 °F, pH 6.0–6.8). A low water level of 6–8 in is useful because the species spawns on surfaces and the male fans the eggs: keeping the water shallow reduces the effort needed and concentrates the breeding pair near the substrate.
Broad-leaved plants or tilted smooth stones serve as spawning sites. The male guards the clutch until the eggs hatch after approximately 24–36 hours at breeding temperature; fry become free-swimming after another day or two once the yolk sac is absorbed. The male should be removed once the fry are free-swimming to prevent predation. First foods are infusoria and commercially available fry food of equivalent particle size, followed by newly hatched brine shrimp nauplii as the fry grow. Growth to juvenile size is relatively rapid under good conditions.
In the aquarium
Pyrrhulina spilota is a specialist's fish rather than a community-tank staple. Its surface orientation, preference for soft acidic water, and relatively modest size make it best suited to a quiet, well-planted biotope aquarium that replicates the shaded, still-water habitats of the Loreto flooded forest. A dark substrate, tannin-stained water (from Indian almond leaves or peat filtration), and a canopy of floating plants will bring out the best behaviour and colour.
The species should be kept in groups of six or more to distribute aggression among males and encourage natural social behaviour. Tankmates, if any, should be small, peaceful, and undemanding of the same upper-water zone — small pencilfish (Nannostomus), dwarf cichlids, or Apistogramma species that occupy the bottom layer are sensible companions. Avoid fast, surface-active species that will outcompete P. spilota at feeding. Water temperature should be held at 75–79 °F; because the fish cruises at the surface, a tightly fitting cover is essential to prevent jumping.
Conservation
Pyrrhulina spilota is assessed as Least Concern (LC) on the IUCN Red List, with the assessment dating to April 2014. The species is broadly distributed across the upper Amazon basin of Peru and Bolivia, a region that — while experiencing ongoing deforestation and land-use change in its outer portions — still retains large areas of intact flooded-forest habitat in and around Iquitos. Its low fishing vulnerability score (10 out of 100) recorded by FishBase indicates it is rarely targeted by commercial fisheries.
Trade collection at the hobbyist scale from the Iquitos region is a long-established, relatively sustainable activity overseen by local exporters, and the species is not known to be collected at volumes that threaten wild populations. No CITES or CMS listing applies. The principal long-term risk, as for most Amazonian lowland species, is large-scale habitat alteration rather than direct exploitation.