Taxonomy & naming
Mormyrops lineolatus was described by the Belgian-British ichthyologist George Albert Boulenger in 1898, in his survey "Matériaux pour la faune du Congo" (Materials for the Fauna of the Congo) — part of the same wave of turn-of-the-century Congo basin fish descriptions that produced many of the region's mormyrids. It belongs to the family Mormyridae within the order Osteoglossiformes — the bonytongues, one of the oldest surviving lineages of teleost fish, named for a toothed bone on the floor of the mouth that bites against a toothed plate on the roof. The order is a scattered, deep-time radiation across South America, Africa, southeast Asia and Australasia; the Old World featherback knifefishes (family Notopteridae) belong to this same order, while the visually similar electric knifefishes of South America (Gymnotiformes) do not — the resemblance between the two groups is convergent, not close kinship.
The genus name Mormyrops combines mormyrus, the old fish name that also underlies the family name Mormyridae, with the Greek suffix -ops, "appearance, face" — together, "Mormyrus-like". The species epithet lineolatus is Latin for "marked with fine lines", describing the dark longitudinal lines running along the sides of the body that help distinguish this species from its many close congeners. Mormyrops holds several similarly built species across Central and West Africa, and — as in much of the family — some are reliably separated only by their electric organ discharge (EOD) rather than external appearance alone.
Morphology
Mormyrops lineolatus has the elongated, laterally compressed body typical of its genus: a comparatively blunt, generalist snout rather than the trunk-like schnauzenorgan of Gnathonemus or the down-curved snout of Campylomormyrus, a single dorsal fin set well back on the body opposite a long-based anal fin, and a deeply forked caudal fin. The ground colour is silvery to brownish-grey, and — as the epithet promises — fine dark lines run along the flanks, the feature that most reliably separates it from other Mormyrops in the field.
FishBase records a maximum size of 15.7 in total length for this species, but aquarium reports commonly describe specimens closer to 5.9–7.9 in — a gap that most plausibly reflects fewer old, fully grown fish reaching the trade, or some degree of growth-limiting captive conditions, rather than a true difference in maximum size; the wild 15.7 in figure should be treated as the reliable ceiling. As in all mormyrids, a weakly electric organ in the caudal peduncle produces a continuous, species-specific pulse-type electric organ discharge (EOD), sensed by electroreceptors across the skin. Processing that constant electrosensory stream falls to a greatly enlarged cerebellum, and mormyrids as a group post some of the highest brain-to-body-mass ratios of any fish — the family's well-earned reputation as "thinking fish".
Habitat
Mormyrops lineolatus is a Congo River basin endemic, recorded from the Democratic Republic of the Congo, including Pool Malebo (Stanley Pool), Lake Mai-Ndombe and the Wagenia Falls on the upper Congo near Kisangani. FishBase lists it as demersal, living and foraging over the river and lake bottom in warm tropical freshwater, with a trophic level around 3.2 consistent with a diet of small invertebrates and other bottom-associated prey rather than larger fish.
Precise temperature and pH data specific to this species were not found in the sources reviewed here, but it fits the general pattern of Congo basin river and floodplain habitat: soft, mineral-poor, warm and often turbid or tannin-stained — the dim, low-visibility water in which an electric sense for navigation and prey detection is a genuine advantage over eyesight. A specific pH or temperature range beyond that general basin characterisation should not be assumed for this species.
Feeding
Detailed feeding data specific to Mormyrops lineolatus is limited in the sources reviewed here, but FishBase's trophic level estimate of 3.2 places it among the invertebrate- and small-organism feeders typical of mid-sized mormyrids, foraging over the bottom and using electrolocation to find prey in murky Congo basin water where vision is of limited use.
In the aquarium it takes live or frozen invertebrates readily — bloodworm and brine shrimp are both reported as accepted foods — and, like most mormyrids, feeds most actively after dark. Newly imported or recently settled fish can be reluctant feeders and benefit from a calm, uncrowded tank and some patience before they take food reliably.
Mating
Wild reproductive behaviour has not been documented for Mormyrops lineolatus in the sources reviewed here. As in mormyrids generally, courtship is thought to be mediated substantially through the electric organ discharge: species- and sex-specific variation in the EOD pattern is believed to help mormyrids recognise appropriate mates and advertise reproductive condition in water too dark or turbid for visual courtship to work reliably.
Beyond that electrical role, almost nothing concrete is documented about how, when or where this species pairs or spawns. Mormyrids as a family are generally understood to be seasonal spawners cued to the rainy-season flood pulse of their rivers, but no species-specific account of that cycle exists for M. lineolatus in the sources available, and any more detailed claim about courtship display or spawning site would be speculation rather than fact.
Breeding
Mormyrops lineolatus is essentially unknown to have been bred in the aquarium. Captive breeding across the mormyrid family as a whole is rare and poorly documented, and this Congo basin species — occasionally seen in the trade but far from a hobby staple — has no established aquarium breeding protocol in the sources reviewed here. Its reproduction is best summarised, like that of most of its relatives, as a seasonal, flood-triggered event in the wild about which the details remain largely unrecorded, rather than a process aquarists can currently replicate on purpose.
Parental care, if any exists in this species, is not described anywhere in the sources reviewed and should be treated as unknown rather than assumed. Prospective keepers should plan around wild-collected stock and not expect to breed this fish.
In the aquarium
Mormyrops lineolatus does appear in the aquarium trade occasionally, and general elephantnose care guidance places it in a dimly lit tank with soft substrate and minimal turbidity, plus caves or other hideaways for daytime cover — conditions that echo its dim Congo basin habitat rather than a bright, open aquascape. It is sensitive to poor water quality and needs stable, clean conditions; being an electric fish it is also best kept away from strong medications and treated conservatively with copper-based products.
Care guides note it can be aggressive if kept in pairs, so a single specimen or a properly spaced group in a large enough tank is the safer approach rather than a pair, which risks one fish harassing the other. At up to around 15.7 in total length in the wild it is not a small fish, even though aquarium specimens are often reported smaller; it should be sized for its full potential growth. Its large brain-to-body ratio and evident intelligence make it a genuinely engaging fish for a keeper prepared to meet these specific water and social requirements, though it is not a beginner community choice.
Conservation
The IUCN Red List assesses Mormyrops lineolatus as Least Concern, an assessment dated 16 February 2009 and carried into the 2022.2 Red List update. As a Congo basin species recorded across multiple sites — Pool Malebo, Lake Mai-Ndombe and the Wagenia Falls — it appears to have a reasonably wide distribution within the basin rather than being restricted to a single locality, consistent with its unthreatened status.
FishBase reports medium resilience with a population doubling time of roughly 1.4 to 4.4 years, suggesting the species can recover at a moderate pace from population pressure. As with other Congo basin fish, longer-term risks are generic to the basin as a whole — sedimentation, damming and water-quality pressure, and fishing intensity — but nothing in the sources reviewed here points to a specific documented threat to this species beyond its current Least Concern status.