Taxonomy & naming
Petrocephalus mbossou was described in 2010 by Sébastien Lavoué, John Sullivan and Matthew Arnegard, in a Zootaxa revision (volume 2600) covering the electric fishes of the genus Petrocephalus from Odzala National Park in the Republic of the Congo. It belongs to the family Mormyridae, the elephantfishes and mormyrids, within the order Osteoglossiformes — the bonytongues, one of the oldest surviving lineages of teleost fishes, named for a toothed bony structure on the floor of the mouth that bites against a toothed pad on the roof. The Catalog of Fishes lists Petrocephalus mbossou as a valid name with no synonyms.
The genus name Petrocephalus comes from the Greek petros, "rock" or "stone", and kephale, "head", for the hard, bony head typical of these fish. The species epithet mbossou is not a Latinized eponym but a Lingala vernacular name applied to fish of this genus by people of the Congo River basin, adopted by the authors to recognize the group as a locally understood natural category rather than to honour a person or place.
The species is known from a single specimen, the holotype (CUMV 92389), taken by fish trap in the main channel of the Lékoli River. The type locality proper is a small tributary of the Lékoli within Odzala National Park, at approximately 0.62°N, 14.91°E. It was described in the same paper as four other new species from the park — P. zakoni, P. valentini, P. odzalaensis and P. pulsivertens — part of a broader revision that leaned on electric organ discharge waveform alongside morphology to separate closely similar Petrocephalus.
Morphology
Petrocephalus mbossou reaches about 5 in standard length according to FishBase, a modest size within the genus, though with only one known specimen the true range of size and proportion in the species is unknown. Like other members of its genus it has the compact, deep body and blunt, rounded snout typical of Petrocephalus, quite unlike the long, trunk-like schnauzenorgan of the more familiar aquarium elephantnose, Gnathonemus petersii.
As in all mormyrids, an electric organ in the caudal peduncle produces a weak, pulse-type discharge that the fish uses to sense its surroundings and, in many species, to signal to others of its kind. For Petrocephalus mbossou this discharge is unusually distinctive: a very brief pulse lasting only about 0.144 milliseconds, with a peak spectral frequency of roughly 22.11 kHz — high for the genus — and a waveform marked by a prominent head-negative fourth phase (P4) reaching about 5.7 percent of the total peak-to-peak amplitude. Because several Petrocephalus species from the same river system look almost identical externally, this discharge signature was one of the characters used to tell the new species apart.
Habitat
The species is documented from the middle Congo River basin: the Lékoli River, a tributary of the Likouala River, in the Republic of the Congo, and the Ubangui River in the Central African Republic. Its type locality is a small forest tributary stream of the Lékoli inside Odzala National Park, and FishBase classifies it as a benthopelagic, tropical freshwater fish of flowing tributary habitat rather than a lake or floodplain species.
The only known specimen was collected by fish trap in the main channel of the Lékoli itself, so direct habitat observation is limited to that single record. Specific temperature and pH data have not been published for this species; Congo Basin tributary streams of this kind are generally soft, tannin-stained and close to neutral to slightly acidic, but that should be read as a general expectation for the region rather than a measurement taken for Petrocephalus mbossou.
Feeding
No dedicated dietary study of Petrocephalus mbossou has been published. FishBase estimates a trophic level of about 3.3, consistent with a benthic invertebrate feeder rather than a species preying on other fish, in keeping with the family generally — mormyrids typically use their electric sense to locate insect larvae, worms and small crustaceans hidden in mud, sand and leaf litter, then take them with a quick strike of the small, downturned mouth.
Because the species has no aquarium-trade history, there is no documented account of its feeding response in captivity, and none is offered here beyond that general expectation for the genus.
Mating
Courtship and mate selection have not been described for Petrocephalus mbossou; the species is known from a single museum specimen, which rules out any direct field or captive observation of social or reproductive behaviour. Across the Mormyridae, the electric organ discharge is known to carry species- and often sex-specific information and is thought to play a role in courtship and mate recognition, but how any individual species uses its discharge to pair up has been studied closely in only a handful of well-known mormyrids, and this is not one of them.
Breeding
Breeding biology is entirely unrecorded for this species, in the wild and in captivity alike. With only one specimen ever collected, nothing is known about spawning season, site choice, egg deposition or parental care. Mormyrids as a family are rarely if ever bred in aquaria, and Petrocephalus mbossou, lacking any aquarium-trade history at all, has no captive-breeding record to draw on.
In the aquarium
Petrocephalus mbossou is not known to be present in the aquarium trade. It was described from a single wild-caught specimen taken from a national park drainage in the Republic of the Congo, and no husbandry account specific to the species exists; anything said here is extrapolated from general mormyrid care rather than direct experience with this fish.
Mormyrids as a group do best in dimly lit, well-cover tanks with soft sand substrate for probing, stable warm water and minimal turbidity. They are shy, largely nocturnal fish, sensitive to poor water quality and to a number of common medications — copper-based treatments in particular need conservative dosing — and are best kept either singly with calm tankmates or in an established group large enough to spread out territorial behaviour. None of this has been tested on Petrocephalus mbossou itself; it is offered as general practice for the genus, not a claim about this species.
Conservation
Petrocephalus mbossou has not been formally assessed by the IUCN Red List and is listed as Not Evaluated. The species is known only from the Lékoli River drainage in Odzala National Park, Republic of the Congo, and from the Ubangui River in the Central African Republic — a distribution built from very few records, since only one specimen has ever been collected.
The type locality lies within a protected national park, which offers some incidental habitat security, but the extremely limited sampling behind the species' known range makes any statement about population size or trend impossible. Data are simply too sparse to say more than that Petrocephalus mbossou is a poorly known Congo Basin endemic awaiting formal conservation review.