Taxonomy & naming
Marcusenius furcidens was described by the French ichthyologist Jacques Pellegrin in 1920, with its type locality given as Lagune Comoé (the Comoé Lagoon) in Côte d'Ivoire. 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 any 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 opposite side of the Atlantic.
The genus Marcusenius was erected by the American ichthyologist Theodore Gill in 1862 and is thought to honour a naturalist named Marcusen, though the full biographical record behind that dedication is not clearly documented in accessible sources. The species epithet furcidens is built from the Latin furca, "fork", and dens, "tooth" — literally "forked tooth", presumably describing a dental or jaw feature noted in the original description. As in most of the genus, reliable species-level identification within Marcusenius is difficult from external anatomy alone; closely related river and lagoon populations often look alike, and confident field identification typically leans on the fish's electric organ discharge rather than visible characters.
Morphology
Marcusenius furcidens shows the general mormyrid build: a laterally compressed body, a small, close-set mouth, and a caudal peduncle housing the tail-mounted electric organ that defines the family. FishBase records a maximum size of about 12.6 in standard length in male and unsexed specimens, placing it among the larger small-to-mid-sized West African Marcusenius.
Detailed published description of colouration and fin proportion for this species is thin in the sources consulted here, and — as with other mormyrids — visual identification among related Marcusenius from the same coastal river systems is notoriously unreliable; confident species-level identification typically relies on the fish's electric organ discharge rather than on external appearance alone. As in other mormyrids, an outsized cerebellum drives one of the highest brain-to-body ratios recorded in any vertebrate, the physiological cost of running a sensitive electrolocation and communication system built around that tail organ.
Habitat
Marcusenius furcidens is native to a cluster of coastal West African river systems in Côte d'Ivoire and Ghana — the Como, Bandama, Sassandra and Tano rivers — with its type locality a coastal lagoon, the Lagune Comoé. This places the species within a roughly 8°N to 4°N tropical band along the humid Guinean forest coast, a run of short, forest-fed rivers and lagoons distinct from the great interior drainages (Niger, Congo, Nile, Zambezi) that hold most other African mormyrids.
Mormyrids of these coastal systems are fish of stable water with minimal turbidity, generally soft and slightly acidic to neutral, and often tannin-stained by leaf litter and forest run-off — exactly the dim, low-visibility setting in which an electric sense outperforms eyesight. Water temperature in these tropical West African rivers runs warm, roughly 75–82 °F; no precise pH range specific to this species is available in the sources consulted here, so this article does not invent one beyond the general soft, dark-water pattern typical of the family.
Feeding
Marcusenius furcidens is a largely nocturnal forager that leans on electrolocation, using its weak electric organ discharge to detect prey hidden in soft substrate in water too dim or turbid for vision to be reliable. In the aquarium it takes live and frozen mosquito larvae, bloodworms and other small aquatic invertebrates, and does best when these are offered rather than relying on the fish to compete for flake or pellet food.
The species is noted as stress-sensitive: in an actively lit, busy tank it can be out-competed at feeding time and quietly starve rather than assert itself, so feeding after dark and providing calm, low-traffic conditions matters more for this fish than for most community tankmates. A fine sand or soft gravel substrate is worth providing too, since these fish forage by probing the bottom and a coarse or sharp substrate risks injuring the sensitive tissue around the snout.
Mating
Courtship and mate recognition in mormyrids are believed to run substantially through the electric organ discharge rather than through visual display — the pulse pattern itself may encode species identity, sex and readiness to spawn — though this has not been specifically documented for Marcusenius furcidens. Across the family, wild spawning is thought to be seasonal, cued by the rains and rising floodwater typical of the West African 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 why breeding behaviour in this species remains poorly known.
Breeding
Marcusenius furcidens is, so far as the sources consulted here record, essentially not bred in the aquarium hobby, and its reproductive biology in the wild is poorly understood. Breeding is presumed to be seasonal and flood-triggered like other mormyrids, but no such detail has been confirmed for this species, and its mode of parental care — if any — is not documented.
Aquarists should not expect or attempt to breed this fish. Mormyrids in the trade, this species included, are typically wild-caught, and any claim of routine captive spawning in this genus should be treated with real scepticism absent solid documentation.
In the aquarium
Marcusenius furcidens wants a tank of at least 39.4 in in length, kept dimly lit or shaded, since the species is nocturnal and stress-sensitive — a brightly lit, high-traffic tank can leave it hiding and undernourished rather than settled. A fine sand or soft gravel substrate suits its foraging habit, and cover in the form of roots, wood or dense planting gives it somewhere to retreat during the day; it becomes noticeably more active after dark. Offer live or frozen mosquito larvae, bloodworm and other small aquatic invertebrates rather than expecting it to compete for flake at the surface.
Water quality matters more for this fish than for most tankmates: mormyrids are notably sensitive to poor water quality and to many aquarium medications, copper- and formalin-based treatments in particular, so any dosing in a tank housing this species should be approached with real caution. Mormyrids can also be intolerant of their own kind and of other electric fish in a confined space, so stocking should account for potential aggression toward conspecifics; a single specimen or a properly sized group in a large, calm tank is a safer starting point than a casual mixed community. Breeding in captivity is rarely if ever achieved.
Conservation
The IUCN Red List assesses Marcusenius furcidens as Least Concern, an assessment dated 30 November 2019. This is a notable revision: the species had previously carried a Near Threatened listing before being downlisted to Least Concern in 2020.
It is recorded from multiple river systems along the Côte d'Ivoire and Ghana coast — the Como, Bandama, Sassandra and Tano — a spread broad enough that no specific range-wide threat is flagged in the sources consulted here. As with other fish of West Africa's coastal forest rivers, general long-term pressures on the region's waterways — habitat degradation, deforestation, damming and water-quality decline — remain the relevant backdrop even for a species not currently considered threatened.