Taxonomy & naming
Eigenmannia wazowskii was described in 2025 by Uliam, Ribeiro & Dutra in Neotropical Ichthyology (23(3):e250004), from material collected in the Rio Negro basin of Brazil. It belongs to the genus Eigenmannia in the family Sternopygidae, the glass and rattail knifefishes, within the order Gymnotiformes — the New-World electric knifefishes. Gymnotiformes are bony fish, but highly modified ones: nearly every species in the order generates a weak electric organ discharge (EOD) around its body, used both to sense the surrounding world in the dark and to communicate with other individuals of its kind, a trait unlike almost anything else in the freshwater aquarium hobby.
The species name honours Mike Wazowski, the one-eyed monster from Pixar's Monsters, Inc., a playful reference to the unusually large eyes that distinguish it within Eigenmannia. Despite the common name "knifefish", Sternopygidae are not related to the Asian featherback and clown knifefishes (Chitala, Notopterus) — those are bonytongues in an entirely different order, and the resemblance between the two groups is convergent body shape rather than kinship. The Catalog of Fishes (Eschmeyer, CAS) is the authority for the valid name; as a species described in 2025, it has not yet accumulated a body of secondary literature beyond its original description.
Morphology
As in other members of its genus, Eigenmannia wazowskii has the classic glass-knifefish build: a laterally compressed, elongate, tapering body with no dorsal fin and no proper tail fin, propulsion coming almost entirely from a long ribbon-like anal fin that runs beneath most of the body's length. The body is semi-transparent to translucent, a feature that gives the genus its common name of "glass knifefish." The original description records a size of 7 in LEA (length to end of anal-fin base, roughly 7 in total length).
The defining feature that separates this species from its close relatives is eye size: its eyes measure roughly 22.0–29.3% of head length, the fourth-largest proportion recorded in the genus Eigenmannia. Running along the body is the electric organ that produces the fish's wave-type discharge, along with the sensory pores that read the field it generates — the electrosensory system that effectively substitutes for vision in the dark, turbid water these fish inhabit. Like other Sternopygidae, it is scaleless, a detail that carries directly into how the species must be kept in captivity.
Habitat
Eigenmannia wazowskii is known from the Rio Negro basin in Brazil, part of the wider Amazon drainage and one of the largest blackwater rivers in the world. As a Neotropical gymnotiform, its range lies entirely within South American fresh water; the genus Eigenmannia as a whole is distributed across South American river systems, typically favouring deeper channels with current, submerged vegetation, and root tangles rather than open, still water.
The Rio Negro is emblematic of the tannin-stained, acidic blackwater habitats favoured by many glass knifefish — dim, soft and low in dissolved minerals, conditions under which eyesight is of limited use and an electric sense becomes the primary way of reading the environment. Data on this particular species' habitat preferences beyond the type locality are sparse, given how recently it was described; its ecology is inferred substantially from better-studied congeners such as Eigenmannia virescens.
Feeding
Specific dietary data for Eigenmannia wazowskii have not been published; feeding habits are inferred from the genus. Glass knifefish are nocturnal micro-predators that hunt small invertebrates — aquatic insect larvae, worms and tiny crustaceans — locating prey in the dark largely through electrolocation rather than sight, sensing the way small organisms distort the fish's own electric field.
In the aquarium, Eigenmannia species readily take meaty foods such as bloodworm, brine shrimp, and small frozen or live invertebrate foods, generally becoming most active and willing to feed after dark or in dim light. There is no published information suggesting E. wazowskii would differ from this pattern, but as an undescribed-until-2025 species with no aquarium history, any care or feeding notes here are extrapolated from the genus rather than observed in this species directly.
Mating
Eigenmannia is the textbook genus for wave-type electric signalling in courtship and social behaviour: its continuous, near-sinusoidal electric organ discharge runs at roughly 250–600 Hz, and the frequency differs by sex and by individual, serving as a signature used in mate recognition. When two Eigenmannia meet with similar discharge frequencies, their signals interfere, and the fish adjust their own frequencies apart from one another — the jamming-avoidance response, one of the most thoroughly studied phenomena in sensory neuroscience and a behaviour presumed to extend to courtship and rival interactions within the genus.
No species-specific courtship observations exist yet for E. wazowskii, described too recently for behavioural study. What can be said with confidence is that, as in its relatives, electric signalling — not visual display — is almost certainly central to how individuals of this species locate, recognise and approach one another in the dark, tannin-stained water it inhabits.
Breeding
Breeding data specific to Eigenmannia wazowskii do not exist; the species is too newly described. In the genus generally, and in Sternopygidae as a family, reproduction follows an egg-laying, parceled-spawning pattern: eggs are adhesive and are scattered among plant roots or floating vegetation rather than deposited in a nest, with little or no parental care afterward. Reproductive activity in studied congeners such as Eigenmannia trilineata correlates with photoperiod and water conductivity, and spawning is typically triggered by the rise in water level and softer, more dilute water of the wet season.
Eigenmannia as a genus is bred in captivity more readily than most gymnotiforms — the glass knifefish is one of the more approachable members of the order for a dedicated aquarist — but there is no record of E. wazowskii itself having been kept or spawned outside its type locality. Any breeding programme for this species would have to proceed from the general Sternopygidae pattern rather than from established protocol.
In the aquarium
Eigenmannia wazowskii is not established in the aquarium trade; it was described in 2025 from wild-collected Rio Negro material, and there is no evidence it is currently kept or bred by hobbyists. Any care guidance here is necessarily drawn from its better-known relative, the glass knifefish Eigenmannia virescens, and should be treated as a starting point rather than a tested protocol for this exact species.
Glass knifefish in general do well in a small shoal in a tank with current, cover such as caves, wood or dense planting, and dim lighting — conditions that suit their nocturnal, electrolocation-dependent lifestyle. Being scaleless, the genus is sensitive to copper-based medications and to poor water quality, needing mature filtration and stable, low ammonia and nitrate. They are peaceful toward tankmates too large to eat but remain nocturnal micro-predators of small invertebrates and fry. Should E. wazowskii ever enter the hobby, captive-bred stock should be favoured over wild collection from its apparently narrow-range Rio Negro population.
Conservation
Eigenmannia wazowskii has not yet been assessed by the IUCN Red List; its status is Not Evaluated, which is typical for a species described as recently as 2025. No population, threat or trend data are available.
It is known only from its Rio Negro type locality, which places it among the many narrow-range, single-basin gymnotiform endemics whose conservation status is unknown simply for lack of study. The Rio Negro basin faces pressures from deforestation, mining-related pollution and hydrological change elsewhere in the Amazon, but there is no evidence linking those pressures to this species specifically, and nothing here should be read as an assessment of its risk.