Taxonomy & naming
Argopleura diquensis was described by Carl H. Eigenmann in 1913, with the type locality recorded as Soplaviento, a settlement on the Dique Canal (Dique de Cartagena) in Departamento Atlántico, Colombia. The holotype is catalogued as FMNH 56272, a male measuring 2 in standard length, housed at the Field Museum of Natural History (ex Carnegie Museum specimen CM 5072); further type material is held under FMNH 56273. Eschmeyer's Catalog of Fishes at the California Academy of Sciences records the valid name as Argopleura diquensis (Eigenmann, 1913), with the parenthetical authority indicating the species was originally described in a different genus before transfer to Argopleura.
The Catalog places the genus in the family Stevardiidae (subfamily Argopleurinae) within the broader characiform radiation, though the family-level classification of South American characids remains an active area of phylogenetic debate and different authorities treat these groups at varying ranks. The species was confirmed in the Colombian ichthyofauna by Vari and collaborators in a Smithsonian checklist of the freshwater fishes of Colombia, and the holotype's precise measurements and locality were documented in a phylogenetic study of the xenurobryconin (glandulocaudine) characids by Weitzman and Menezes.
Morphology
Argopleura diquensis is a slender, laterally compressed small characid reaching a maximum recorded standard length of 2.5 in; FishBase records a maximum weight of 4.3 g. Like others in the genus, it displays the bright or shining lateral band that gives Argopleura its name — Greek argos (shining, white) combined with pleura (side) — and which distinguishes the genus visually from allied forms.
Detailed meristic and colour data for this species are sparse in the available literature. It is a benthopelagic freshwater fish, occupying the water column in tropical lowland rivers and canals rather than specialising in bottom-dwelling or surface-dwelling habits. Sexual dimorphism in Argopleura, as in many glandulocaudine or stevardiid characids, includes glandular tissue associated with the caudal region in males, which plays a role in pheromonal courtship signalling.
Habitat
The species is a freshwater endemic of Colombia's Atlantic-slope lowlands. Its known range centres on the Dique Canal and associated waters of the Departamento Atlántico — the canal is a 115-km artificial waterway first excavated in the seventeenth century to connect the lower Río Magdalena to the Bay of Cartagena and has since been widened and deepened multiple times. FishBase records the type locality as Soplaviento, Colombia, in a tropical, benthopelagic freshwater environment.
The lowland canal and its lateral floodplain lakes occupy flat, seasonally flooded terrain at near sea level. Conditions in these waters are typically warm year-round in keeping with the tropical climate of Colombia's Caribbean coast, and the canal receives inputs from the productive Magdalena floodplain system. Precise water-chemistry data for the Argopleura diquensis microhabitat are not available in the surveyed sources.
Feeding
No dedicated dietary study is available for Argopleura diquensis in the surveyed literature. Based on the ecology of similarly sized, lowland-dwelling Characidae, the species is presumed to be an opportunistic micro-predator or omnivore, taking small invertebrates, zooplankton, and organic particles from the water column and substrate.
In captivity, small characids of this size class typically accept live and frozen foods such as Daphnia, brine shrimp nauplii, and micro-worm, as well as fine-grade commercial prepared foods. However, specific aquarium-feeding observations for A. diquensis are absent from the available sources, and keepers of the species should treat generalised characid husbandry as a starting framework rather than a confirmed protocol.
Mating
Argopleura belongs to a group of characids — historically called glandulocaudines or stevardiids — known for a distinctive reproductive biology involving pheromonal courtship. Males in this group possess specialised glandular caudal tissue; during courtship the male positions his caudal fin near the female's head, releasing chemical signals that stimulate or synchronise spawning behaviour. The ETYFish Project notes that stevardiid breeding involves courtship displays mediated by pheromonal signalling via this glandular tissue.
Beyond this group-level trait, specific mating observations for Argopleura diquensis have not been published in the available sources. Like other egg-scattering characids it likely spawns among fine-leaved aquatic vegetation, with the male's pheromonal display preceding egg deposition. No parental care is expected.
Breeding
Detailed breeding accounts for Argopleura diquensis in captivity are absent from the surveyed literature. The species' membership in the stevardiid / glandulocaudine lineage suggests an egg-scattering reproductive mode: adhesive or semi-adhesive eggs scattered among fine-leaved plants or deposited in sheltered microhabitats, with no parental care following spawning. Incubation conditions and fry requirements are not documented for this species specifically.
The pheromonal courtship mechanism described for the broader stevardiid group — in which male caudal-fin glands release chemical cues — means that spawning induction may depend on the presence of displaying males rather than purely on water-chemistry triggers. Aquarists interested in breeding this species would be advised to consult published accounts for closely related Argopleura or stevardiid genera as the nearest available proxy.
In the aquarium
Argopleura diquensis is a rarely encountered species in the aquarium hobby, and specific keeping accounts are sparse. Its small size — under 3 in standard length — makes it suitable for a modestly sized planted aquarium, and its tropical lowland origins suggest warm water in the range of 75–82 °F is appropriate. A soft, slightly acidic to neutral water chemistry consistent with Magdalena-basin tributaries would be a reasonable starting point.
As a benthopelagic fish from densely vegetated lowland canal and floodplain habitats, a planted tank with subdued or dappled lighting and gentle filtration is likely to encourage natural behaviour and reduce stress. Given the rarity of this species in the trade and the paucity of husbandry data, keepers should document observations carefully and share them with the broader ichthyological and hobby community.
Conservation
Argopleura diquensis is assessed as Least Concern (LC) on the IUCN Red List, with the assessment referenced to IUCN version 2025-2 via FishBase. The assessment date recorded by FishBase is 08 October 2014. The species' distribution in the Dique Canal system and associated Atlantic-slope waters of Departamento Atlántico, Colombia, makes it a freshwater endemic tied to a modified but extensive lowland waterway.
The Dique Canal and Magdalena floodplain system face ongoing pressures including water extraction, agricultural runoff, channelisation, and flood-control infrastructure that alter natural hydrological cycles and connectivity. These pressures affect the broader ichthyofauna of the Colombian Atlantic slope, though A. diquensis's current Least Concern rating suggests it has not been identified as particularly threatened relative to other species in the region. Monitoring of endemic lower-Magdalena characids remains important given continuing habitat modification across the Caribbean-slope lowlands of Colombia.