Taxonomy & naming
Rhabdolichops electrogrammus was described by Lundberg & Mago-Leccia in 1986 and belongs to the family Sternopygidae — the glass and rattail knifefishes — within the order Gymnotiformes, the New-World electric knifefishes. Gymnotiformes are bony fish but an unusual lineage: they are defined by an electric organ running the length of the body and by a single long anal fin that provides essentially all of their propulsion, since they lack a dorsal fin and any functional tail fin of the ordinary kind.
The genus Rhabdolichops sits alongside Distocyclus and Eigenmannia as one of the deep-channel, open-water glass knifefish genera in Sternopygidae, distinguished from the shallower-water Eigenmannia by details of body proportions and electric organ anatomy worked out in revisionary studies of the group. These New-World knifefishes are not related to the Asian featherback and clown knifefishes (Chitala, Notopterus) despite the shared common name; the resemblance is convergent, not a sign of kinship. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the authority for the valid name.
Morphology
Rhabdolichops electrogrammus is built like the rest of its genus: an extremely elongated, laterally compressed, near-transparent body that tapers to a fine point at the tail, with no dorsal fin and no distinct caudal fin. Locomotion comes from a very long anal fin running most of the length of the underside, thrown into travelling waves that move the fish forward or backward with equal ease — the same swimming plan used across the Gymnotiformes. Reported maximum size is around 11.5–12 in total length.
Running along the body is the electric organ that gives the family its "glass knifefish" nickname, paired with transparent electrocyte tissue visible toward the tail in life. The species is scaleless, like all gymnotiforms, and its skin is thin and largely see-through — an adaptation that, along with its weak wave-type electric organ discharge, suits a life spent reading the surroundings electrically rather than visually in the dim water of deep river channels. Sexes are not documented as externally distinguishable in the available literature.
Habitat
The species is recorded from the Orinoco, Rio Negro and Rio Branco basins of South America — a range centred on the Guiana Shield and Orinoco drainage rather than the wider Amazon. It is benthopelagic, living in tropical river channels, floodplains, lagoons and other deeper-water habitats rather than shallow marginal vegetation, which sets Rhabdolichops apart from the shallow-water glass knifefish Eigenmannia more familiar to aquarists.
As with other Sternopygidae, these are warm, freshwater habitats where visibility is limited by depth, current or tannin staining, and where a continuous electric field is a more reliable sense than eyesight. Little further habitat detail beyond basin-level distribution and general depth preference is documented for this species; the record is built mainly from museum and survey collections rather than close ecological study.
Feeding
Rhabdolichops electrogrammus is a nocturnal micro-predator, feeding on aquatic invertebrates — copepods, insect larvae and other zooplankton and benthic prey — consistent with its terminal mouth and with the diet recorded across the deep-channel Sternopygidae. Like other glass and rattail knifefishes it most likely locates this prey chiefly through electrolocation, sensing the small electrical and mechanical disturbances of animals hidden in sediment or drifting in open water, rather than by sight.
Beyond this general diet profile, detailed feeding behaviour has not been documented for the species; what is known follows from its family's well-studied electrosensory foraging strategy rather than from direct observation of this particular fish.
Mating
Courtship in Sternopygidae is closely tied to their electric organ discharge: because the wave-type signal is continuous and carries a signature frequency specific to species and sex, it functions as a channel for communication as much as for electrolocation, and related genera such as Eigenmannia are known to shift discharge frequency during social encounters — the jamming avoidance response — and during courtship interactions in the dark. It is reasonable to expect similar electric signalling plays a role in how Rhabdolichops electrogrammus locates and approaches mates, but this has not been specifically documented for the species.
No description of courtship behaviour, spawning site selection or pairing has been recorded for R. electrogrammus in the available literature; data are sparse for this deep-channel genus generally, and what would be a confident account for the family cannot be extended to the species without direct study.
Breeding
Reproduction in Rhabdolichops electrogrammus is undocumented. FishBase and the taxonomic literature record no details of spawning, egg deposition or parental care for this species. Sternopygidae as a family are egg-layers that scatter adhesive eggs among plant roots or submerged vegetation with little or no parental care, typically triggered by warm, soft, rising-water conditions in the wet season, and this is the most reasonable expectation for the genus's general breeding mode — but it has not been confirmed for this particular fish.
The species is not established in the aquarium hobby, and there is no record of it having been bred in captivity. Data sparse is the honest summary rather than any specific protocol.
In the aquarium
Rhabdolichops electrogrammus is not a hobby fish in any meaningful sense — it is essentially unknown in the aquarium trade, and what follows is drawn from the general husbandry needs of Sternopygidae rather than direct experience with this species. Like other glass and rattail knifefishes it would need warm, soft, near-neutral to slightly acidic water with gentle flow, dim lighting, and secure cover, since these are nocturnal fish that rely on electrolocation rather than eyesight and are stressed by bright, exposed tanks.
Being scaleless, gymnotiforms as a group are sensitive to ammonia and nitrate buildup and require reduced doses of copper-based and other harsh medications. As a deep-channel, open-water species reaching around 12 in, it would need considerably more swimming space than the shallow-water Eigenmannia typically sold as "glass knifefish," and — as with all nocturnal gymnotiform predators — should not be trusted with small or bite-size tankmates. In practice, anyone encountering this species is far more likely to be a researcher or museum collector than a retail buyer.
Conservation
Rhabdolichops electrogrammus is assessed as Least Concern on the IUCN Red List, an assessment made in December 2020 that reflects its distribution across the Orinoco, Negro and Branco river basins rather than any detailed population data. It is not a species of documented conservation concern.
As with many narrow-range, poorly studied gymnotiforms, the practical threats it would face are the general pressures on Neotropical river basins — habitat change, damming and pollution — rather than any species-specific driver identified in the literature. Its Least Concern status should be read as a reflection of a wide basin-level range and limited targeted study, not as a sign that the species has been closely monitored.