Taxonomy & naming
Eigenmannia correntes was described by Campos-da-Paz & Queiroz in 2017 and placed in the family Sternopygidae — the glass and rattail knifefishes — within the order Gymnotiformes, the New-World electric knifefishes. Gymnotiformes are bony fish, but unusual ones: nearly every species produces a weak electric organ discharge (EOD) around its body, used for electrolocation in place of vision and for communication with other knifefish, and the order is built around a single long anal fin rather than the fin arrangement of ordinary fish. The Asian featherback and clown knifefishes (Chitala, Notopterus) share the name "knifefish" but are unrelated bonytongues; the resemblance is convergent, not a sign of kinship.
The species sits in the Eigenmannia trilineata species-group, a cluster of superficially near-identical glass knifefish that taxonomists only resolved into separate species through a combination of morphology and electric-signal analysis, work that produced several new species descriptions in the mid-2010s. Within that group E. correntes is distinguished by a conspicuous superior midlateral stripe and a subterminal mouth. The Catalog of Fishes (Eschmeyer, CAS) is the authority for the valid name.
Morphology
Eigenmannia correntes has the classic glass-knifefish build: a laterally compressed, semi-transparent body tapering to a fine point, no dorsal fin, and a single very long anal fin running most of the length of the underside that provides essentially all of its propulsion, undulating to drive the fish forward or backward with equal facility. Examined specimens have ranged from about 2.5–4 in in standard length, with the holotype at 4.5 in; species in the genus Eigenmannia can reach up to about 14 in total length, though there is no size data specific to large adult E. correntes.
Running the length of the body is the electric organ, paired with sensory pores across the skin that read the field it creates. Like other gymnotiforms it is scaleless, which matters for how it must be handled and medicated. In the wild the trilineata group's discharge is monophasic, wave-type and quasi-sinusoidal — a continuous electrical hum rather than the discrete pulses of some other knifefish families — and this is presumed to hold for E. correntes as a member of that group, though its EOD has not been directly measured and published.
Habitat
This species is known only from the upper rio Paraguai basin in Mato Grosso and Mato Grosso do Sul, Brazil — specifically tributaries of the rio Correntes within the rio Piquiri system. Records come from just three small streams: córrego de Baixo and córrego de Cima near Sonora (MS), and an unnamed stream at the rio Correntes near Itiquira (MT). That is an unusually narrow range even by the standards of a genus full of single-basin specialists, and no records exist outside this small cluster of headwater streams.
The trilineata species-group as a whole favours clearwater tributaries with swift current, over sand, pebbles and dead leaves, with intact riparian vegetation along the banks — the kind of well-oxygenated, structurally rich small stream typical of upland tropical drainages. E. correntes almost certainly shares this habitat as a close relative occupying the same general part of the Paraguai basin, though site-specific water chemistry has not been published for the type streams.
Feeding
No diet study specific to Eigenmannia correntes has been published. Across the genus, glass knifefish are omnivorous with a strong insectivorous lean, foraging mainly after dark and locating prey largely by electrolocation rather than sight — probing sediment, leaf litter and root tangles for aquatic insect larvae and small crustaceans, with plant material and detritus taken opportunistically. As a nocturnal micro-predator it is not a threat to fish of its own size or larger, but anything small enough to be mistaken for prey is at risk after lights-out.
In practice this is a fish with essentially no aquarium feeding record, so any husbandry advice has to be extrapolated from the wider genus: small meaty foods such as bloodworm, brine shrimp and chopped invertebrate matter offered in the evening, when Eigenmannia species become active, are the reasonable starting point rather than a documented protocol for this particular species.
Mating
Courtship in the Eigenmannia trilineata species-group, to which E. correntes belongs, is closely tied to its wave-type electric discharge. Each fish's EOD frequency is sex-specific, and pairs use these frequencies — and the jamming-avoidance response that lets two nearby wave-type fish shift their frequencies apart to avoid interference — as a channel of communication and, likely, mutual assessment during approach and spawning. Females in the group also differ from males in having a shorter snout, a subtle sexually dimorphic cue alongside the electrical signalling.
None of this has been observed directly in E. correntes; the picture above is drawn from study of the trilineata group generally, most thoroughly in laboratory work on close congeners. Specific courtship behaviour for this recently described, narrow-range species has not been documented in the field or in captivity.
Breeding
Members of the Eigenmannia trilineata species-group are egg-layers, spawning adhesive eggs among plant roots, typically triggered by conditions that simulate the rainy season — rising water level, changed conductivity, and altered photoperiod and rainfall. Females in the group first mature around 3 in and males around 2.5 in total length, with modest relative fecundity (roughly 0.27 oocytes per milligram of body weight in studied congeners), and parental care is minimal: eggs are left among vegetation with no guarding afterward. Breeding under simulated seasonal cues has been achieved in some Eigenmannia in captivity, making the genus one of the more approachable knifefish groups for spawning.
No breeding record exists for E. correntes specifically — it is a 2017 description from a handful of tiny streams, with essentially no aquarium history. Any breeding attempt would have to proceed from the trilineata group's general pattern rather than species-specific experience; data here is genuinely sparse.
In the aquarium
Eigenmannia correntes has no meaningful presence in the aquarium trade — it is not established as an ornamental fish, and any specimens in captivity would be scientific collections rather than hobby stock. What follows is therefore drawn from the wider genus rather than from keeping this species itself. Glass knifefish in general are considered one of the easier gymnotiforms to keep, doing well in a small shoal of its own kind, in a dim, quiet tank with soft, gently flowing, well-oxygenated water and plenty of fine cover such as roots or dense planting to retreat into by day.
As with all gymnotiforms, the absence of scales makes the genus sensitive to ammonia and nitrate, and to copper-based or harsh medications, which should be used at reduced doses if at all. Genus-wide water parameters reported for the closely related E. virescens are roughly 73–82 °F, pH 6.0–7.0, with soft to moderately hard water. Given how little is known of E. correntes and its very restricted natural range, keeping it — or any Eigenmannia — as a nocturnal, electrosensitive fish that is not community-safe with bite-size tankmates is the general rule to follow, rather than any protocol specific to this species.
Conservation
Eigenmannia correntes has not been formally assessed by the IUCN and is treated as Data Deficient. That status reflects how recently the species was described (2017) and how little survey work exists for it, rather than any evidence that it is currently thriving or declining.
Its known range — three small streams feeding the rio Correntes in the upper rio Paraguai basin — is narrow enough that habitat change in that specific drainage (agricultural runoff, deforestation of riparian vegetation, or damming) could plausibly affect the entire known population, in the way that single-stream endemics generally are more exposed than widespread species. No specific threats have been documented in the literature reviewed here, and a firm conservation judgement would need a targeted assessment of the rio Correntes tributaries themselves.