Taxonomy & naming
Apteronotus aguaruna was described in 2026 by de Santana, Peixoto, Dutra & Dillman as one of two new sexually dimorphic ghost electric knifefishes from the Andes of northern Peru, in the paper "Two New Species of Sexually Dimorphic Ghost Electric Knifefishes (Apteronotus: Apteronotidae: Gymnotiformes) from the Andes of Northern Peru." It belongs to the family Apteronotidae — the ghost knifefishes — within the order Gymnotiformes, the New-World electric knifefishes. These are bony fish, but unusual ones: Gymnotiformes are defined by their electric organs and their long ribbon-like anal fin, and the Apteronotidae are set apart within the order by an electric organ derived from modified nerve tissue rather than muscle, giving them the fastest, most refined electric discharges of any knifefish group.
The species epithet honours the Aguaruna (also spelled Awajún), an indigenous people of the Peruvian Amazon whose territory overlaps the Andean foothill rivers where the species was collected. Despite the shared common name, the New World "knifefishes" of Gymnotiformes are not related to the Asian featherback or clown knifefishes (Chitala, Notopterus), which belong to an entirely different order of bonytongues — the resemblance is convergent body shape, not kinship. As with all recently described species, the Catalog of Fishes (Eschmeyer, CAS) is the standing authority for the valid name; data on A. aguaruna beyond the original 2026 description are still sparse.
Morphology
As a member of Apteronotus, A. aguaruna shares the genus's signature body plan: laterally compressed and blade-like, tapering to a slender tail, with no dorsal fin and no conventional tail fin. Movement comes almost entirely from a long anal fin running along most of the underside, undulated in travelling waves that drive the fish forwards or backwards with equal ease. The species was described as sexually dimorphic — males and females differ in some aspect of body or fin shape, a trait shared with a number of Andean Apteronotus species and used by the describing authors to help distinguish it from its closest relatives — but the specific measurements and diagnostic details have not yet been widely published outside the primary description.
Like other ghost knifefishes it is scaleless, and it carries the family's electric organ running along the body together with sensory pores across the skin that read the resulting field. Precise maximum size, colouration and fin-ray counts for A. aguaruna are not yet available in secondary sources; data are sparse pending wider circulation of the 2026 description.
Habitat
Apteronotus aguaruna is known from the Andes of northern Peru, part of a broader pattern in the genus in which many species are narrow-range endemics of particular Andean foothill drainages rather than the wide Amazon-basin generalists exemplified by the black ghost knifefish. Andean foothill and headwater rivers in this region tend to be faster-flowing and more oxygenated than lowland Amazon channels, though still warm by temperate standards, and the family as a whole favours dim, often tannin- or sediment-stained water where electrolocation matters more than vision.
Broader distribution details, water chemistry at the type locality, and habitat associations (channel vs. margin, substrate, cover) have not yet been published in sources available to this account. Data sparse.
Feeding
No species-specific feeding data for A. aguaruna have been published yet. Ghost knifefishes as a group are nocturnal carnivores that hunt small benthic invertebrates — aquatic insect larvae, worms and small crustaceans — locating them in the dark largely through electroreception rather than sight, and it is reasonable to expect A. aguaruna follows the same general pattern as its congeners. This is an inference from the family's well-documented biology, not a confirmed observation of this species; data sparse.
Mating
Courtship in Apteronotidae is bound up with the family's wave-type electric organ discharge (EOD): a continuous, quasi-sinusoidal signal in the roughly 300–2000 Hz range that carries information about a fish's identity, sex and social status. In the best-studied relative, the brown ghost knifefish (A. leptorhynchus), males and females shift their discharge frequency during courtship in a kind of electrical duet, and rival fish produce distinctive frequency "chirps" when they meet — a signalling system now well documented by electrophysiologists. Given that A. aguaruna was described as sexually dimorphic, electric signalling plausibly plays into how males and females recognise one another, but this has not been studied directly in the species.
No observations of actual courtship behaviour in A. aguaruna have been published. What is known about gymnotiform courtship generally comes from laboratory electrophysiology on a handful of well-studied relatives, not from field or aquarium observation of this species.
Breeding
Breeding biology for A. aguaruna has not been documented. Ghost knifefishes as a family are egg-layers that spawn among cover such as roots, plants or crevices, with no meaningful parental care after spawning, and they are rarely bred in captivity even for well-established aquarium species like the black ghost — most trade specimens of common Apteronotus species are either wild-caught or produced on commercial farms using hormone induction. As a species described only in 2026 and not established in the trade, A. aguaruna's breeding mode can only be assumed to follow this general Apteronotidae pattern; nothing specific to this species is documented. Data sparse — poorly documented, prefer no fabricated protocol.
In the aquarium
Apteronotus aguaruna is not currently established in the aquarium hobby; as a species described in 2026 from Andean Peru it has not been reported in trade, and this account makes no claim about how it fares in captivity. General guidance for Apteronotus and Apteronotidae as a family is relevant if it should ever appear in the trade: these are scaleless fish, sensitive to ammonia, nitrate, and to copper-based or harsh medications, which should be used at reduced doses; they are nocturnal electrolocators that need dim lighting and secure cover such as tubes, caves or root tangles to feel settled by day; and as active nighttime hunters most are not safe with small, bite-size tankmates or shrimp. Prospective keepers of any little-known Apteronotus species should favour captive-bred stock where it exists and expect to provide a large, mature, well-filtered tank rather than a beginner setup.
Conservation
Apteronotus aguaruna has not yet been evaluated by the IUCN, consistent with its very recent description in 2026; formal assessment of newly described species typically lags publication by years. Its status is therefore unknown rather than confirmed as any particular threat category.
As an apparent narrow-range endemic of Andean foothill rivers in northern Peru — a pattern shared by several of its congeners — it may be more exposed to localised pressures such as deforestation, water pollution and hydrological change from damming than the wide-ranging lowland Apteronotus species, but no population or threat data specific to A. aguaruna have been published. This account does not assert a conservation status beyond what is documented.