Taxonomy & naming
Pterobrycon landoni was described by Carl H. Eigenmann in 1913 from material collected in the Atrato River drainage of Colombia. The type locality is Boca de Raspadura, at the junction of the Río San Pablo with the Raspadura canal — a historically significant waterway linking the Atrato and San Juan basins near the Pacific–Caribbean divide. The holotype is deposited at the Field Museum of Natural History (FMNH 56250), and Eschmeyer's Catalog of Fishes records the species as valid within family Characidae, subfamily Stevardiinae. Subsequent ichthyological checklists by Bussing (1998), Weitzman (2003), Thomaz et al. (2015), and DoNascimiento et al. (2017) all maintain the species as a valid taxon.
The genus Pterobrycon is a small, poorly studied member of subfamily Stevardiinae, the inseminating characids. Its placement within the subfamily has been clarified by molecular and morphological revisions over the past two decades, but the group remains one of the less-worked corners of the enormous family Characidae. The specific epithet landoni honours Alonzo Landon, who assisted Eigenmann's Colombian fieldwork.
Morphology
Pterobrycon landoni is a miniature fish, with FishBase recording a maximum standard length of 1 in. Beyond its diminutive size, published morphological descriptions are sparse, as almost all records trace back to the single holotype. The genus name — from the Greek pteron (wing or fin) and brycon (a biting or jaw reference common in characid generic names) — suggests a fin feature that distinguishes the genus, but detailed published accounts of the species' external appearance in live colouration are essentially absent from the accessible literature.
Like other stevardiine characids, the species would be expected to show the family's typical fusiform body plan, a single dorsal fin, an adipose fin, and a forked caudal fin. Data on live colouration, fin formulae, and squamation for this specific species are data sparse.
Habitat
The known range of Pterobrycon landoni is the middle and upper Atrato River basin in north-western Colombia, a lowland to foothill system draining the western slope of the Colombian Andes into the Gulf of Urabá on the Caribbean coast. The type locality, Boca de Raspadura, sits in a lowland region where the Atrato and Pacific-draining San Juan basins approach each other — a biogeographically interesting contact zone. FishBase classifies the species as benthopelagic freshwater.
Specific habitat details — substrate preference, depth, aquatic vegetation associations, current regime — are not documented in the accessible literature, a direct consequence of the species being known from effectively one collection event. The Atrato basin is characterised by warm, highly productive lowland rivers and associated flooded forests, generally soft and slightly acidic to near-neutral in water chemistry, though the precise conditions at the type locality are unrecorded for this species.
Feeding
FishBase records a trophic level of approximately 3.0 for Pterobrycon landoni, placing it in the lower carnivore or omnivore tier typical of small insectivorous characids. At this trophic level the natural diet likely consists of small invertebrates — insect larvae, microcrustaceans, and similar items — though no direct gut-content studies have been published for this species.
In the absence of specimen data, dietary inference rests on the ecology of similarly sized, related stevardiine characids from comparable Neotropical lowland habitats, where small arthropods and zooplankton form the dietary core. Data on feeding behaviour, prey selectivity, and seasonal dietary shifts are sparse for this species.
Mating
No published accounts of spawning behaviour in the wild are available for Pterobrycon landoni. Within subfamily Stevardiinae, many species practice internal insemination — the male transfers sperm directly to the female, who stores it and fertilises eggs internally before depositing them. Whether Pterobrycon landoni exhibits this derived stevardiine reproductive strategy or retains more ancestral egg-scattering with external fertilisation is not documented in the accessible literature.
In the aquarium hobby, the species has not been established as a captive-bred fish, and anecdotal spawning accounts are absent from the published record. Courtship and spawning behaviour remain undescribed.
Breeding
Pterobrycon landoni has not been bred in captivity under documented conditions, and no reliable breeding accounts appear in the literature. Given its membership in Stevardiinae and its tiny adult size, any captive spawning effort would likely require very soft, warm, slightly acidic water mimicking the Atrato lowlands, fine-leaved vegetation or spawning mops, and conditioning on live or frozen invertebrate foods.
Whether the species produces adhesive eggs among plants, practices insemination, or has any form of parental care is unknown. The almost complete absence of live specimens in the hobby means that breeding biology data will depend on future fieldwork or the rare acquisition of live material.
In the aquarium
Pterobrycon landoni has never been established as a hobby fish in any meaningful sense. The one notable exception is the report of specimens entering Germany as bycatch alongside Nematobrycon palmeri (emperor tetra) shipments, suggesting that the two species share habitat in the Atrato drainage and are collected together in the field — though no sustained import trade in Pterobrycon landoni followed. At 1 in maximum it would be a nano-scale fish suitable only for very small, calm aquaria with equally diminutive tankmates.
Any aquarist fortunate enough to obtain specimens would be working without a husbandry literature and should treat soft, slightly acidic, warm water (reflecting its Colombian lowland origin) as the starting assumption. Its rarity means virtually no captive-care data exist — keeping it would be a genuine contribution to knowledge of the species.
Conservation
Pterobrycon landoni is assessed as Data Deficient (DD) on the IUCN Red List, with the assessment dated 2014. Data Deficient does not mean the species is secure; it means that information is insufficient to make a reliable assessment of extinction risk. With the taxon known from a single holotype collected over a century ago and with no systematic survey effort recorded in the literature, the data-deficiency classification is appropriate but also a measure of how little attention this species has received.
The Atrato basin faces ongoing pressure from gold and platinum mining (the river system is historically one of the most intensively mined in South America), agricultural conversion, deforestation, and associated sedimentation and water-quality changes. Whether Pterobrycon landoni persists in the middle and upper Atrato, and in what numbers, is unknown. Re-collection at or near the type locality and a systematic survey of Stevardiinae diversity in the basin would be prerequisites for any meaningful reassessment.