Taxonomy & naming
Marcusenius wamuinii was described in 2019 by Decru, Sullivan and Vreven, with the description published in the journal Ichthyological Exploration of Freshwaters and recorded as the authority reference in the Catalog of Fishes (Eschmeyer, California Academy of Sciences), which treats the name as valid. The type locality is inside Mangroves National Park (Parc National des Mangroves, MNP) on the Lower Congo River near the river's Atlantic mouth in far-western DR Congo — notably, the fauna of that park was so poorly surveyed that this mormyrid stands as the first new fish species ever formally described from it. It belongs to the family Mormyridae, within the order Osteoglossiformes, the bonytongues: a scattered, deep-time radiation of fishes found on four continents — South America, Africa, Southeast Asia and Australasia — united not by a shared modern habitat but by that toothed lingual bone, and numbered among the most ancient lineages of living teleosts. The Mormyridae are an exclusively African family, every member weakly electric, and entirely convergent with — not related to — the electric knifefishes of South America (order Gymnotiformes), which evolved an equivalent electric sense independently on the far side of the Atlantic.
The genus name Marcusenius was erected by the American ichthyologist Theodore Gill in 1862 and is thought to honour a naturalist named Marcusen, though the fuller biographical record behind that dedication is not clearly documented in accessible sources. The species epithet wamuinii most likely commemorates a person or place connected to the Mangroves National Park type locality, following the common pattern for recent Congo Basin fish descriptions, but the precise derivation was not accessible in the sources consulted here — the primary description paper sits behind a subscription paywall — so this account does not assert a specific dedication it cannot support.
Morphology
The original description flags Marcusenius wamuinii as large-scaled with a notably slender caudal peduncle, a combination used to separate it from superficially similar Marcusenius already known from the wider Congo system. Beyond those diagnostic points, it shows the general mormyrid build shared across the genus: a laterally compressed body, a small, close-set mouth adapted for probing rather than biting, and a caudal peduncle housing the tail-mounted electric organ that defines the family.
Maximum recorded size is about 5.7 in standard length (FishBase, sexes unsexed), making it a comparatively small member of a genus whose species range from a few centimetres to well over 11.8 in. As in other mormyrids, an outsized cerebellum gives the species one of the highest brain-to-body ratios recorded in any vertebrate — the physiological cost of running a sensitive electrolocation and communication system. Because Marcusenius wamuinii was described only recently and sits among several similar Congo Basin congeners, confident field identification likely rests on the scale-count and caudal-peduncle characters used in the original description, or on its electric organ discharge (EOD), rather than on casual external appearance.
Habitat
Marcusenius wamuinii is known from freshwater habitats within Mangroves National Park on the Lower Congo River, in the far west of the Democratic Republic of the Congo near the river's Atlantic-coast mouth — a range so far documented only from this one protected area, whose fish fauna remained essentially unrecorded before this description. Broader distribution within the wider Lower Congo system, if any, has not been documented in the sources consulted here.
Species-specific temperature and pH figures for Marcusenius wamuinii were not available in the sources consulted here — data sparse. Mormyrids of Lower Congo floodplain and estuarine-fringe freshwaters are typically fish of soft, slightly acidic to near-neutral, often tannin-stained water in the roughly 75–82 °F range, and this article presumes that general Congo Basin pattern for the species rather than asserting precise figures it cannot support.
Feeding
No species-specific feeding study for Marcusenius wamuinii was located in the sources consulted here, but its biology is presumed to follow the general mormyrid pattern: a largely nocturnal, electrolocation-guided forager with a small mouth and weak dentition, sweeping soft substrate for small aquatic invertebrates hidden in mud, sand or leaf litter, using its weak electric organ discharge to locate prey in water too dim or turbid for vision to be reliable.
Across Marcusenius generally, aquarium-kept fish take mosquito larvae, bloodworm, white worm, black worm, Daphnia, Tubifex and Cyclops, live or frozen, once settled — a diet built around soft-bodied invertebrate prey rather than flake or hard pellet. No aquarium-specific feeding record for this exact species was found, so that pattern is offered here as the reasonable expectation for the genus rather than a confirmed fact for Marcusenius wamuinii.
Mating
Courtship and mate recognition in mormyrids are believed to run substantially through the electric organ discharge rather than through visual display — the pulse itself may encode species identity, sex and readiness to spawn — but this has not been specifically documented for Marcusenius wamuinii. Across the family, wild spawning is thought to be seasonal, cued by rising floodwater in the wet season.
The electrical and acoustic noise of a home aquarium — filters, heaters, pumps, reflective glass — readily interferes with the weak EOD signal mormyrids rely on for this kind of communication, one reason natural courtship essentially never plays out under aquarium conditions for fish in this family, and this recently described species is no exception.
Breeding
Marcusenius wamuinii is, so far as the sources consulted here record, essentially not bred in the aquarium hobby, and — as with most mormyrids — its reproductive biology in the wild is poorly understood. Breeding is presumed to be seasonal and flood-triggered, and some mormyrids are thought to guard eggs among vegetation, but none of that detail has been confirmed for this species.
Given that the species was only described in 2019 from a single protected area and has essentially no documented aquarium history, keepers should not expect to breed it, and any claims of captive spawning in this species should be treated with real scepticism absent solid documentation.
In the aquarium
Marcusenius wamuinii has no documented aquarium history; care information specific to this species is essentially absent from the literature, and it is not known to be established in the trade. General Marcusenius/elephantnose guidance applies as a baseline: a tank of at least 39.4 in in length, soft substrate, dim lighting and ample hiding places (roots, wood, plant thickets) to offset a naturally shy, nocturnal temperament, and mormyrids should not be kept solitary — a group, or at minimum a compatible companion, suits their social biology far better than a single fish alone.
As with other mormyrids, keepers should be cautious about tankmates and water quality: mormyrids can be intolerant of their own kind and of other electric fish in a confined space, and — being scaleless-skinned, electrosensitive fish — they are notably sensitive to poor water quality and to many aquarium medications, copper-based treatments especially. Given the species' apparent restriction to a single small protected area and its complete absence from documented trade history, this article offers no guidance on sourcing beyond that fact; any specimen reaching a hobbyist tank would be a genuine rarity.
Conservation
The IUCN Red List has Not Evaluated Marcusenius wamuinii — unsurprising for a species described only in 2019 from a single, poorly surveyed protected area, with population size, trend and full range still undocumented.
Because the species is currently known only from freshwater habitats within Mangroves National Park at the Congo River's mouth, its status is tied to that park's ecological integrity; the general pressures on Lower Congo estuarine and coastal freshwaters — habitat modification, sedimentation and development along the river mouth — are the plausible long-term concerns, though the sources consulted here do not detail a species-specific threat assessment beyond the range-restricted, data-poor status itself.