Taxonomy & naming
Sternarchogiton labiatus was described by de Santana & Crampton in 2007 as part of a revision of the deep-channel electric fish genus Sternarchogiton, within the family Apteronotidae — the ghost knifefishes — in the order Gymnotiformes, the New-World electric knifefishes. Like all gymnotiforms it is a bony fish but an unusual one, defined by an electric organ and a long ribbon-like anal fin rather than by the fin arrangement of typical teleosts. The Apteronotidae are set apart within the order by an electric organ built from modified nerve cells rather than muscle, giving them fast, high-frequency wave-type discharges.
The species epithet labiatus is Latin, from labium ("lip"), referring to the distinctive three-lobed lower-lip structure that defines the species. The original description separates S. labiatus from its congeners by this lip structure together with a set of internal skeletal characters: two rows of dentary teeth, a medial bridge on the second hypobranchial, an ossified first basibranchial, and cartilaginous posterior basibranchials. The Catalog of Fishes is the authority for the valid name; GBIF's species record confirms the authorship and placement. As with many deep-channel Apteronotidae, S. labiatus is not related to the Asian featherback or clown knifefishes (Chitala, Notopterus), which merely share the common name "knifefish" through convergent body shape.
Morphology
Sternarchogiton labiatus has the laterally compressed, blade-shaped body typical of ghost knifefishes, with a nearly straight dorsal profile and no dorsal or tail fin; the long anal fin, with 156–168 rays, runs beneath most of the body length and is the fish's main means of propulsion, while the caudal fin is reduced to 15–16 rays. Coloration is dark brown, darker across the back than on the flanks. FishBase records a maximum length of 8.5 in total length, modest compared to the largest apteronotids.
The species' defining feature is its mouth: a hard, prominent, three-lobed lower lip. In mature males this is accompanied by a hypermorphic (enlarged) snout and oral jaws, with enlarged external teeth on the dentary and premaxilla — a pattern of sexual dimorphism documented in a dedicated peer-reviewed study of the species. Females and immature males lack this exaggerated jaw and tooth development. As in other Apteronotidae, the skin is scaleless and carries the sensory pores used to read the fish's own electric field, which in S. labiatus is a wave-type discharge with a fundamental frequency reported between 1160 and 1587 Hz.
Habitat
Sternarchogiton labiatus is known from the Rio Tefé and the lower Rio Negro in the Brazilian Amazon, part of the wider Amazon basin. It occupies deep channel habitat, recorded at depths of roughly 20–46 ft, and has been found in both whitewater and blackwater river conditions — a broader habitat tolerance than some of its more specialized relatives.
As a deep-channel electric fish it lives in permanently dark or dim water where vision is of limited use, which is exactly the environment its electrosensory system is built for: a private electric field lets it detect prey, obstacles and other fish by the way they distort that field, without relying on light. This habitat, well below the surface layers usually sampled by aquarium collectors, is a major reason the species remains so poorly known outside taxonomic and physiological literature.
Feeding
Specific dietary data for Sternarchogiton labiatus is not documented in the available literature. Like other Apteronotidae it is presumed to be a nocturnal carnivore, using electrolocation to detect small invertebrate prey — insect larvae, worms and similar benthic animals — in the dark, sediment-rich channels it inhabits, in keeping with the general feeding pattern of the family.
The species' unusually developed lower lip and, in males, its enlarged jaws and teeth are the subject of ongoing interest regarding possible specialized feeding or male-competition roles, but no confirmed account of its natural diet or feeding behavior has been published; this remains data sparse.
Mating
As in other Apteronotidae, the wave-type electric organ discharge of Sternarchogiton labiatus likely carries information about a fish's identity, sex and reproductive state, and courtship in the group generally involves shifts in discharge frequency between individuals — an electric signalling system well studied in related genera. The pronounced sexual dimorphism documented in this species, with mature males developing an enlarged snout, jaws and external teeth beyond what is seen in females, points to some form of male-male competition or courtship display, but the specific behavior involved has not been directly observed or described.
FishBase notes that spawning has been observed during the high-water season in the Río Nanay, Peru, indicating a seasonal reproductive cycle tied to the flood pulse, consistent with the pattern seen across many Amazonian gymnotiforms. Beyond the timing of spawning, courtship and pairing behavior in this species is not documented.
Breeding
Sternarchogiton labiatus is an egg-layer, with spawning recorded during the high-water season in the Río Nanay, Peru. Beyond that seasonal association, its breeding biology is essentially undescribed: there is no published account of nest site, egg number, incubation, or parental care, and no record of the species being bred in captivity.
As with most deep-channel Apteronotidae, this is a species known almost entirely from museum specimens and field surveys rather than from aquarium observation, so the honest position is that its breeding mode beyond "egg-laying, high-water spawner" is poorly documented. No parental care has been recorded.
In the aquarium
Sternarchogiton labiatus is not an aquarium fish in any meaningful sense — it is a deep-channel species collected mainly for scientific study, not for the ornamental trade, and there is no established husbandry record to draw on. Anyone who did encounter it would need to apply the same baseline precautions that govern all gymnotiforms: it is scaleless, so ammonia, nitrite and nitrate must be kept low, and copper-based or harsh medications should be avoided or used at reduced dose; as a nocturnal electric fish it would need dim lighting, secure cover, and tankmates too large to be treated as prey after dark.
Given its natural depth range and channel habitat, this is a specialist's fish at best, and the responsible position for the hobby is to leave it to scientific collection rather than to seek it out for a tank it has no real husbandry track record in.
Conservation
Sternarchogiton labiatus is assessed by the IUCN as Least Concern, an assessment last updated in 2020. It is known from more than one Amazonian drainage — the Rio Tefé, the lower Rio Negro, and spawning has been recorded as far as the Río Nanay in Peru — suggesting a range broader than a single isolated river system, which supports the non-threatened assessment.
As with many Amazonian gymnotiforms, the main long-term pressures on this and related species are habitat change from deforestation, damming and pollution across the basin, even where a species is not currently considered threatened. There is no evidence of trade-driven collection pressure on S. labiatus, since it is not a commercial aquarium species.