Taxonomy & naming
Sternarchella duccis was described by Lundberg, Cox Fernandes & Albert in 1996 and belongs to the family Apteronotidae, the ghost knifefishes, within the order Gymnotiformes — the New-World electric knifefishes. Like all Gymnotiformes it is a bony fish set apart from ordinary aquarium fish by an electric organ and a ribbon-like anal fin used for propulsion; the Apteronotidae in particular carry an electric organ built from modified nerve tissue rather than muscle, giving them the fastest, most refined wave-type discharges in the order.
The species was originally described in the genus Magosternarchus, a small group of ghost knifefishes distinguished by a specialised tail-biting habit, and has since been treated as part of Sternarchella following taxonomic revision (as reflected in the SciELO Brazil taxonomic revision cited below). The Catalog of Fishes (Eschmeyer, CAS) is the authority for the currently valid name and combination. These New-World knifefishes are not related to the Asian featherback or clown knifefishes (Chitala, Notopterus); the similar blade-shaped body is convergence, not kinship.
Morphology
Sternarchella duccis reaches a recorded total length of about 10.5 in, placing it among the modestly sized members of the ghost knifefish family. As in other Apteronotidae, the body is a laterally compressed, tapering blade with no dorsal fin and no distinct tail fin; forward and backward movement is driven by undulations of a single long anal fin running along the underside. The skin is scaleless, and an electric organ runs along the body beneath a field of sensory pores that read the fish's own electric field as it is distorted by nearby objects, prey and other fish.
Within the family, Sternarchella and its close relatives (including the tail-biting group formerly separated as Magosternarchus) are noted for an unusually high-frequency wave-type electric organ discharge, reported up to roughly 2000 Hz — among the fastest electric signals recorded in any fish. Detailed external sexual differences are not documented for this species.
Habitat
Sternarchella duccis is endemic to the Amazon basin, with its type locality on the rio Branco in Roraima, Brazil. It is a deep-channel fish, recorded from depths of roughly 6 to 50 metres in the main river channels — well below the shallow, vegetated margins where many aquarium fish are collected, and a habitat that is inherently difficult to survey.
Specific water-chemistry data for this species have not been published, but the Amazon basin's whitewater and blackwater river channels it inhabits are characteristically warm, soft and acidic to near-neutral. As in other ghost knifefishes, life in deep, dark water places a premium on the electric sense over vision, and the species is presumed to be active largely out of the reach of daylight.
Feeding
The most distinctive fact known about this species' biology is dietary: Sternarchella duccis and its close relatives (the group formerly separated as Magosternarchus) are specialised predators of other electric fish, targeting and biting off the tails of other gymnotiforms rather than taking typical invertebrate prey. This is a striking departure from the generalised benthic-invertebrate diet of most ghost knifefishes and appears to rely on the same electrolocation sense used for general navigation — homing in on the electric signature of another electric fish specifically to attack its tail.
Beyond this tail-biting specialisation, detailed dietary data — proportions of other prey, feeding frequency, seasonal variation — are not available for the species; data are sparse.
Mating
No species-specific courtship behaviour has been documented for Sternarchella duccis. As in other Apteronotidae, the wave-type electric organ discharge is known from the family generally to double as a social signal — carrying information on identity, sex and reproductive state, and shifting in frequency during social and courtship encounters in well-studied relatives such as Apteronotus leptorhynchus. Whether S. duccis shows the same electrical courtship duet has not been established; this is inferred from family-level biology rather than direct observation of the species.
Breeding
Reproduction in Sternarchella duccis is essentially undocumented. Ghost knifefishes as a group are egg-layers, typically spawning among cover such as roots and crevices with no substantial parental care, but this species is known from deep-channel survey collections rather than from life-history study, and no spawning behaviour, breeding season or parental care has been recorded for it specifically. It is not known to be bred in captivity in any context — data are sparse, and none should be assumed beyond what is documented for the wider family.
In the aquarium
Sternarchella duccis is not an aquarium fish. It is a deep-channel Amazonian species known from ichthyological collections rather than the ornamental trade, and there is no established husbandry record to draw on. Like all Apteronotidae it would be expected to be scaleless and correspondingly sensitive to ammonia, nitrate and copper-based medications, and — given its tail-biting predatory habit toward other electric fish — a poor prospect for mixed gymnotiform collections even if it were available. Aquarists interested in ghost knifefishes are better served by well-documented species such as the black ghost (Apteronotus albifrons), which has an established care record; S. duccis should be treated as a study species, not a stocking option.
Conservation
Sternarchella duccis is assessed on the IUCN Red List as Least Concern. It is an Amazon basin species known largely from deep river channels around its type locality on the rio Branco, and its true distribution and abundance remain poorly surveyed by the nature of that deep-channel habitat. As with other little-known Amazonian gymnotiforms, the main plausible pressures are basin-scale habitat change — damming, deforestation and pollution affecting the rivers it depends on — rather than any documented direct threat to this species.