Taxonomy & naming
Hippopotamyrus psittacus was described by the Belgian-British ichthyologist George Albert Boulenger in 1897, with a type locality at Stanley Falls (the Wagenia Falls rapids on the upper Congo River, near present-day Kisangani, Democratic Republic of the Congo). It belongs to the family Mormyridae — the elephantfishes, a large and entirely African radiation — within the order Osteoglossiformes, the bonytongues: a scattered, deep-time radiation of fishes found today on four continents (South America, Africa, Southeast Asia and Australasia), united not by any shared modern habitat but by that toothed lingual bone, and counted among the most ancient lineages of living teleosts. Every mormyrid is weakly electric, a trait that evolved entirely independently of, and is unrelated to, the electric sense of the New World knifefishes (order Gymnotiformes) on the far side of the Atlantic — the two groups resemble one another in general body plan and habit only by convergence.
The genus name Hippopotamyrus combines Greek hippopotamos ("river horse", i.e. hippopotamus, from hippos, "horse", and potamos, "river") with the -myrus suffix borrowed from Greek myros, "eel", a root shared with several other mormyrid genera such as Mormyrus and Brienomyrus and generally read as alluding to the elongated, eel-like body many of these fish share; it likely also nods to the genus's large-river habitat. The species epithet psittacus is Latin for "parrot" (from Greek psittakos), most plausibly describing the fish's short, blunt, down-turned mouth. Some recent taxonomic treatments have moved this species into the genus Cyphomyrus; this article follows the widely used, historically catalogued name Hippopotamyrus psittacus, and a reader encountering the fish under either generic name should treat them as referring to the same species.
Morphology
Hippopotamyrus psittacus has the laterally compressed, elongate body typical of the Mormyridae, a small, close-set mouth without the pronounced trunk-like snout seen in genera such as Gnathonemus, and — as in every member of the family — an electric organ housed in the narrow caudal peduncle ahead of the tail. Reported maximum size is around 11.8 in total length (FishBase/GBIF), and a Congo River feeding study collected specimens ranging from about 2.2–12.6 in, putting it among the larger-bodied members of its genus rather than one of the smallest, throwaway mormyrids.
As in other mormyrids, an outsized cerebellum drives one of the highest brain-to-body mass ratios recorded in any vertebrate, the physiological overhead of running a fine-grained electrolocation and communication system built around that tail organ. Many mormyrids, this species included, look enough alike that confident field identification often relies on the fish's electric organ discharge (EOD) — its electrical "signature" — rather than on fin shape, colour or body proportion alone.
Habitat
The type locality for Hippopotamyrus psittacus is the Wagenia Falls stretch of the Congo River at Stanley Falls, near Kisangani in the Democratic Republic of the Congo — a turbulent rapids zone long worked by the Wagenia people's traditional fish traps. But the species is unusually wide-ranging for a mormyrid: beyond the upper Congo it has been recorded across a string of West African rivers, including the Niger, Benue, Volta, Ouémé and Ogun, with a native range spanning Angola, Benin, Burkina Faso, Cameroon, the Central African Republic, Côte d'Ivoire, the Democratic Republic of the Congo, Ghana, Guinea, Mali, Nigeria and Togo.
Collections near the type locality came from both the fast, rocky rapids water at Wagenia Falls and quieter sandbank habitat nearby (Beach Kikongo), suggesting the species tolerates a range of current and substrate rather than being confined to one microhabitat. Across its broader West African range, mormyrids typically occupy dim, sediment-laden river and floodplain water where electrolocation outperforms eyesight — the low-visibility conditions this family's electric sense evolved to read.
Feeding
A dedicated feeding study on the Congo River population (specimens 2.17–12.6 in, collected at Wagenia Falls and Beach Kikongo near Kisangani) found Hippopotamyrus psittacus to be a carnivorous, insectivorous bottom feeder, with invertebrate fauna — aquatic insects and other bottom-dwelling invertebrates — making up the bulk of its diet. As in other mormyrids, foraging in the turbid, low-visibility water of its rapids and floodplain habitats is presumed to lean heavily on electrolocation rather than sight.
The species is essentially unrecorded in the aquarium trade, so there is no species-specific account of its diet in captivity; the safe assumption, following the general mormyrid pattern, is that it would take live and frozen invertebrate foods — bloodworm, blackworm, brine shrimp — and sinking prepared foods, offered after dark when the fish is naturally most active.
Mating
Across the Mormyridae, courtship and mate recognition are thought to run substantially through the electric organ discharge rather than visual display — the pulse pattern itself may signal species identity, sex and spawning readiness — but this has not been specifically documented for Hippopotamyrus psittacus. Wild spawning in the family is generally understood to be seasonal, cued by rising water and the African rains, though no direct observations of this species' courtship have been reported in the available sources.
The electrical and acoustic noise of a home aquarium — filters, heaters, pumps, reflective glass — readily interferes with the weak EOD signalling mormyrids depend on for this kind of communication, which is one reason natural courtship in this family essentially never plays out in captivity.
Breeding
Breeding of Hippopotamyrus psittacus has not been achieved in the aquarium hobby, and — as with most mormyrids — its reproductive biology in the wild is poorly known. Spawning is presumed to be seasonal and flood-triggered, following the general pattern for the family, and some mormyrids are thought to guard their eggs among aquatic vegetation, but no such detail has been confirmed for this species specifically.
Sex determination in the genus is reportedly difficult by external appearance, and all aquarium-held Hippopotamyrus are wild-caught rather than captive-bred. Aquarists should not expect, or attempt to force, a breeding outcome with this fish.
In the aquarium
Hippopotamyrus psittacus is rarely if ever offered in the aquarium trade, and no species-specific husbandry account exists in the available sources; care recommendations here follow the general requirements documented for mormyrids as a group. That means soft, mildly acidic to neutral water (roughly pH 6–7.5) at 73–84 °F (optimal around 79–82 °F), a dimly lit tank with dense planting or cover, a soft sandy substrate that protects the electrosensitive skin used for foraging, and a reasonably spacious setup — 53 US gal upward is the usual hobby benchmark for mormyrids of this size.
Being a scaleless, electrosensitive fish, it should be expected to share the family's sensitivity to poor water quality and to many aquarium medications, particularly copper-based treatments, which call for conservative dosing. Mormyrids can also be intolerant of their own kind in confined quarters, and this species' social behaviour has not been specifically studied. Given how seldom it appears in the trade and how little is documented about it, anyone who does encounter this fish should treat it as a specialist proposition, not an impulse purchase.
Conservation
No IUCN Red List assessment has been published for Hippopotamyrus psittacus, and the sources behind this article located no formal listing; its status is recorded here as Not Evaluated (NE). Its comparatively wide distribution — spanning the upper Congo basin and a string of West African river systems across a dozen countries — offers no guarantee against localised pressure, but nothing in the available sources points to a specific documented threat.
As with many wide-ranging, data-poor African freshwater fish, the general pressures on West and Central African rivers — sedimentation, damming, habitat degradation and overfishing — remain the relevant long-term backdrop even without a formal assessment to quantify them.