Taxonomy & naming
Sternarchogiton zuanoni was formally described by Carlos David de Santana and Richard P. Vari in 2010, in a paper on new rheophilic (rapids-and-waterfall-dwelling) electric knifefishes from the lower Rio Xingu. It belongs to the family Apteronotidae, the ghost knifefishes, within the order Gymnotiformes — the New-World electric knifefishes, a group of bony fish defined by their electric organs and by a single long anal fin that does the work most fish split between a tail and a set of paired fins. The genus Sternarchogiton is a small one within Apteronotidae, and the species epithet honours the Brazilian ichthyologist Jansen Alfredo Sampaio Zuanon.
As in the rest of the order, the common name "knifefish" is shared with, but has nothing taxonomically to do with, the Asian featherback and clown knifefishes (Chitala, Notopterus); those are bonytongues in an unrelated order, and the resemblance between the groups is convergent body shape rather than kinship. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the authority for the valid scientific name.
Morphology
Sternarchogiton zuanoni has the classic ghost-knifefish silhouette: a laterally compressed, blade-like body tapering to a slender tail, no dorsal fin, and propulsion supplied almost entirely by a long ribbon-like anal fin running along the underside, which it undulates to move forward or backward with equal ease. As in other Apteronotidae the skin is scaleless and carries the sensory pores of the electrosensory system, and the fish is nocturnal with correspondingly reduced reliance on vision.
The defining trait of the family, and of this species, is its electric organ discharge (EOD): a weak, continuous, high-frequency wave-type signal generated by an organ derived from modified nerve cells rather than muscle tissue — the arrangement that gives apteronotids the fastest, most refined electric sense in the order. That field is used for electrolocation, sensing rocks, prey and other fish in the dark, turbulent water it inhabits, and very likely for communication between individuals, as in its better-studied relatives. Detailed measurements of maximum size are not well documented outside the original description; within Apteronotidae as a whole, species range roughly 6–23.5 in in total length, and Sternarchogiton zuanoni sits toward the smaller-to-moderate end of that range.
Habitat
This species is known only from Cachoeira de Kaituká, a set of rapids and a waterfall on the lower Rio Xingu near Altamira, Pará, Brazil, and appears to be restricted to a very small area — on the order of a few square kilometres — around that single locality. Unusually for Apteronotidae, which typically inhabit deep, slow river channels with little light, Sternarchogiton zuanoni is rheophilic: it lives in swiftly flowing water directly at the base of the falls, over rocky substrate, and is reportedly the only species in its genus found in that kind of habitat rather than in calmer, deeper water.
That single-locality distribution makes the species a narrow-range Xingu endemic in the fullest sense, and it ties its fate directly to the condition of that one stretch of river rather than to the wider Amazon basin.
Feeding
Detailed dietary study of Sternarchogiton zuanoni itself is sparse, but the genus Sternarchogiton is distinctive within Apteronotidae for feeding on freshwater sponges growing on submerged wood, alongside the more typical gymnotiform diet of small aquatic invertebrates. Foraging in the rocky, turbulent rapids it inhabits is presumably guided, as in its relatives, largely by electrolocation rather than sight, given its nocturnal habits and the low-visibility water it lives in.
Because the species has no meaningful presence in the aquarium trade, there is no body of hobbyist observation on feeding behaviour or diet in captivity to draw on; what is known comes from field study of the genus rather than tank-side notes.
Mating
No courtship or spawning behaviour has been documented specifically for Sternarchogiton zuanoni. Across Apteronotidae generally, the wave-type electric organ discharge carries information about identity, sex and readiness to spawn, and courtship in well-studied relatives involves shifts in discharge frequency between males and females — an electrical exchange layered on top of physical approach in dark, turbid water. It is reasonable to expect a broadly similar role for electricity in this species' social and reproductive behaviour, but this has not been directly studied or reported.
Given the species was described only in 2010 from a single remote locality, and has no aquarium history, essentially nothing beyond this inference is documented — an honest position to hold rather than one to fill in with detail borrowed from other genera.
Breeding
Breeding biology for Sternarchogiton zuanoni is not documented. Like other Apteronotidae it is presumed to be an egg-layer, but there is no record of captive breeding, no known aquarium population to breed from, and no field data on spawning sites, fecundity or parental care at this specific locality. Data sparse is the honest summary.
Across the family, where breeding has been observed at all it tends to be occasional egg-scattering among cover with no substantial parental care afterwards, and most Apteronotidae seen in trade are wild-caught or, in a few species, farm-produced under hormone induction rather than bred naturally in aquaria. There is no reason to expect Sternarchogiton zuanoni to depart from that pattern, but nothing has actually been reported for it.
In the aquarium
Sternarchogiton zuanoni has no established presence in the aquarium hobby. It is a rheophilic, rapids-dwelling fish restricted to a single, remote waterfall locality on the Xingu, which makes wild collection difficult and any hobbyist availability essentially nonexistent; this account should not be read as encouragement to seek the species out. Were it ever kept, the general husbandry principles that apply to Apteronotidae would be a starting point — a scaleless, electrosensitive, nocturnal predator needing warm, clean, well-oxygenated water, secure cover, extreme care with medications (no copper-based treatments, and reduced doses generally), and tankmates too large to be preyed on after dark — but nothing in that list has actually been tested against this species.
The more useful message for aquarists is conservation-minded: this is a fish whose entire known population sits in one small stretch of river now altered by hydroelectric development, and it is not a species to pursue for the trade.
Conservation
Sternarchogiton zuanoni is assessed by the IUCN as Vulnerable, a rating driven almost entirely by its extremely restricted range: the species is known from a single locality on the lower Rio Xingu covering only a few square kilometres of rapids and waterfall habitat. That kind of single-site endemism leaves a species with essentially no buffer against local habitat change.
The specific and well-founded concern is the Belo Monte hydroelectric complex on the Xingu, which has altered flow regimes and inundated or dewatered stretches of the river in the vicinity of the species' only known home. Depending on how directly the Kaituká rapids habitat has been affected, conservation assessments have flagged the possibility that the species' status could deteriorate further, toward Critically Endangered or worse, without additional survey work to confirm its persistence. As with many narrow-range Xingu rheophiles, its story is a direct illustration of how dam development on Amazonian tributaries can threaten a species most aquarists will never have heard of.