Taxonomy & naming
Rhabdolichops lundbergi was described by Correa, Crampton and Albert in 2006, one of three new Rhabdolichops species erected in the same Copeia paper alongside R. nigrimans and R. navalha. It belongs to the family Sternopygidae — the glass and rattail knifefishes — within the order Gymnotiformes, the New-World electric knifefishes, a group of bony fish defined by their electric organs and their long, ribbon-like anal fin rather than by any resemblance to ordinary fish shapes.
Sternopygidae is one of several gymnotiform families built around a continuous, wave-type electric organ discharge, in contrast to the pulse-type signal of families such as Gymnotidae. Despite sharing the common name "knifefish", Rhabdolichops and its relatives are not related to the Asian featherback and clown knifefishes (Chitala, Notopterus), which belong to an entirely different order of bonytongues; the similarity is convergent body shape, not kinship. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the authority for the valid name.
Morphology
Rhabdolichops lundbergi has the classic Sternopygidae build: an extremely slender, laterally compressed body tapering to a fine point at the tail, with no dorsal fin and no true caudal fin. Propulsion comes almost entirely from a very long anal fin running most of the underside of the body, thrown into travelling waves that let the fish glide forward or backward with equal control. The original description notes relatively long pectoral fins that are all-dark or dark-tipped, a detail used to separate it from its close relatives R. nigrimans and R. navalha.
As in all gymnotiforms, an electric organ runs the length of the body beneath the skin, paired with electroreceptor pores scattered over the head and flanks that read the field it produces — a wave-type discharge, continuous rather than pulsed. The species is scaleless, like every member of its order, leaving the skin exposed and making it far more sensitive to water quality and medication than a scaled fish. The genus as a whole spans roughly 6.5–19.5 in; a precise maximum length specific to R. lundbergi is not established in the available literature.
Habitat
This species is known from the central Amazon Basin in Brazil, where the original description records it almost exclusively from the main channel of high-conductivity whitewater rivers and their adjacent floodplain channels — sediment-rich, nutrient-laden water draining from the Andes, in contrast to the low-conductivity blackwater rivers favoured by its relatives R. nigrimans and R. navalha. Its known range appears narrow and tied to this particular river-channel habitat type.
Whitewater main channels are turbid, fast-flowing and effectively dark to vision below the surface, which is exactly the setting in which an electric sense pays off: Rhabdolichops reads its surroundings — current, obstacles, other fish, and drifting plankton — through the field generated by its electric organ rather than by sight. Documented ecological detail beyond the original description is sparse, consistent with a fish that has attracted little attention outside taxonomic work.
Feeding
Rhabdolichops lundbergi is built as a plankton feeder: the original description notes well-developed gill rakers, the filtering structures typical of fish that strain small drifting prey from open water rather than pick at the substrate. This fits its main-channel habitat, where plankton carried in the current is a more available food source than the burrowed invertebrates favoured by bottom-oriented knifefishes.
As in other gymnotiforms, its electric sense likely plays a role in locating prey in the turbid, low-visibility water it inhabits, though feeding behaviour has not been directly studied for this species. Detailed dietary data — proportions of zooplankton versus other prey, foraging times, seasonal shifts — is not documented in the sources available and should be treated as data sparse rather than assumed from related species.
Mating
As in other wave-type Sternopygidae, the electric organ discharge in Rhabdolichops almost certainly carries a social as well as a sensory function — a continuous signal that can encode identity, sex and readiness to spawn, and that features in courtship and rival interactions in well-studied relatives such as Eigenmannia. Whether R. lundbergi shows the same electrical signalling behaviour has not been directly documented; it is inferred from the biology of its family rather than observed in this species specifically.
No courtship behaviour, spawning site preference, or mate-selection detail has been recorded for R. lundbergi in the available literature. This is a fish known almost entirely from museum specimens and a single taxonomic description, and reproductive behaviour in the wild remains unstudied.
Breeding
There is no documented account of Rhabdolichops lundbergi breeding in captivity, and it does not appear to be established in the aquarium trade. Based on the reproductive pattern typical of Sternopygidae, it is presumed to be an egg-layer that scatters adhesive eggs among plant roots or floodplain vegetation, with little or no parental care afterward — but this is inference from the family, not an observation of the species.
Given how narrowly this fish is known — a taxonomic description from whitewater river channels in the central Amazon, with no aquarium history — any specific breeding protocol would be invented rather than documented. The honest statement is that R. lundbergi is unbred and essentially unknown outside scientific collection.
In the aquarium
Rhabdolichops lundbergi is not an established aquarium fish; it is not known to appear in the ornamental trade, and no husbandry record exists for the species specifically. What follows draws on the general requirements of Sternopygidae rather than direct experience with this fish. Being scaleless, it would need the same caution given to all gymnotiforms: no copper-based medications, reduced dosing of standard treatments, and consistently clean water, since exposed skin makes these fish unusually sensitive to ammonia and nitrate.
As a main-channel, open-water plankton feeder, it would likely need generous swimming space, steady flow, and dim lighting reflecting its native turbid water, plus secure cover to retreat to given the nocturnal habits typical of the group. Because it is essentially unknown in captivity, none of this can be treated as a tested care sheet — a prospective keeper would be working from family-level inference, not a track record, and should expect very limited support in sourcing or troubleshooting the fish.
Conservation
Rhabdolichops lundbergi is assessed on the IUCN Red List as Least Concern. Its known range — the main channel of whitewater rivers in the central Amazon Basin of Brazil — places it within a region facing real pressures from deforestation, damming and mining-related sediment and mercury pollution, but no data links these pressures specifically to this species' population.
Given how little else is documented about the species beyond its taxonomic description, this Least Concern listing should be read as reflecting a lack of evidence for decline rather than a detailed population study.