Taxonomy & naming
Pollimyrus petricolus was described by the French ichthyologist Jacques Daget in 1954, as part of his survey of the fishes of the Fouta Djallon highlands and the Basse-Guinée (Lower Guinea) coastal rivers, published in the Mémoires de l'Institut Français d'Afrique Noire. The parenthetical form of the authority — (Daget, 1954) — signals that Daget did not originally place the species in the genus it carries today: as was standard practice for small West African mormyrids at the time, it was almost certainly first assigned to a broader genus such as Marcusenius, before later revisions of the family Mormyridae split off a distinct genus, Pollimyrus, for a group of small-bodied species now known collectively as the dwarf stonebashers.
The family Mormyridae sits within Osteoglossiformes, the bonytongue fishes — one of the oldest surviving lineages of teleosts, named for a toothed bony structure on the tongue that bites against a paired plate on the roof of the mouth. Within that family, Pollimyrus is a genus of several dozen small, weakly electric species scattered across West and Central African river systems. The precise type locality of P. petricolus is not confirmed here, but it falls within the region covered by Daget's 1954 survey — the highland streams and coastal drainages of the Republic of Guinea.
Morphology
Pollimyrus petricolus is a small mormyrid, consistent with the modest body size typical of its genus; most Pollimyrus species run well under 4 in in standard length, and no species-specific maximum for P. petricolus could be confirmed here, so any figure given for it should be read as an approximation rather than a measured record. The body follows the general dwarf-stonebasher plan: laterally compressed, with a short, blunt head, a small mouth set at or near the front of the snout rather than drawn out into an elongate chin barbel, and a single dorsal fin positioned opposite or just ahead of the anal fin base.
As in every mormyrid, an electric organ near the base of the tail generates a weak, species-specific pulse discharge, read through electroreceptors spread across the skin. This electric sense lets the fish navigate and locate prey in the turbid or nighttime water where mormyrids do most of their foraging, and it also does the work of telling apart species that often look nearly identical to the eye — visual identification within Pollimyrus is unreliable, and the discharge waveform, not body shape or color, is the more dependable marker between congeners. No electric organ discharge waveform has been published specifically for P. petricolus.
Habitat
Pollimyrus petricolus is known from Guinea, from the region spanning the Fouta Djallon highlands and the coastal river systems of Basse-Guinée (Lower Guinea) — the area surveyed in the paper that first described it. The species epithet petricolus, "rock-dweller," points toward habitat among rock and rapids, consistent with the fast-flowing, well-oxygenated highland streams that drain the Fouta Djallon massif toward both the Atlantic coast and the headwaters of the Niger system.
Detailed habitat data — substrate composition, flow regime, water chemistry — has not been documented for this species specifically. Fouta Djallon headwater streams are generally cooler and better oxygenated than the lowland floodplain rivers further downstream, running over rock and coarse sediment rather than the soft mud and standing vegetation typical of many other small mormyrids' habitat.
Feeding
Like other mormyrids, Pollimyrus petricolus is presumed to be a bottom-foraging invertebrate feeder, using its electric sense to locate small aquatic invertebrates such as insect larvae and worms hidden in sediment and among rocks, then taking them with a quick strike of the small mouth. No feeding study specific to this species has been published, and its diet is inferred from the pattern documented across the family rather than confirmed by direct observation.
No aquarium feeding record exists for P. petricolus, since the species has no established history in the trade. Small mormyrids in the wider genus are generally kept on live and frozen invertebrate foods such as bloodworm and brine shrimp, offered after dark to match their natural foraging rhythm.
Mating
Mormyrid electric organ discharges are thought to carry information beyond simple navigation, including signals used in courtship and in sex or species recognition. In the best-studied congener, Pollimyrus isidori, males have been documented producing acoustic sounds — pulsed grunts and moans — alongside their electric discharge during courtship, in research associated with Bruce Crawford and colleagues. That acoustic-plus-electric courtship system has not been documented in P. petricolus, and it would be a mistake to assume it applies here without direct study; the mating behavior of this species is simply unrecorded.
Breeding
No spawning account, captive or wild, has been published for Pollimyrus petricolus. Breeding across the genus and the wider family is poorly understood, and almost no Pollimyrus species has a confirmed captive-breeding record; the rare specimens that do reach the trade are wild-caught. Egg number, incubation period, and parental care cannot be stated for this species without inventing detail the literature does not support.
In the aquarium
Pollimyrus petricolus has no established presence in the aquarium hobby — it has no documented trade or captive-care history, and this account should not be read as implying otherwise. What can be said comes from general practice for keeping small mormyrids: a soft, sand-based substrate suited to a fish that forages by probing the bottom, dim lighting and ample cover such as driftwood or root tangles, and stable water quality, since mormyrids as a group tolerate poor water conditions and many common medications poorly.
If a specimen were ever available, its small size — in line with the dwarf-stonebasher group generally — would make it manageable for a modestly sized tank, but mormyrids can be territorial toward their own kind, and a single fish or an unbalanced pair often fares worse than either a lone specimen or an established group large enough to spread out aggression. Live or frozen invertebrate foods offered after the lights go down would suit its presumed foraging habits better than daytime flake feeding.
Conservation
Pollimyrus petricolus has not been assessed on the IUCN Red List; its conservation status is Not Evaluated. No population trend, range-wide survey, or species-specific threat assessment is available for this fish.
More broadly, the river systems of Guinea's Fouta Djallon highlands and Basse-Guinée coastal lowlands — the region where this species occurs — face pressure from mining, including bauxite extraction, along with deforestation and agricultural runoff, any of which can degrade water quality and streambed habitat in the kind of rocky highland reaches P. petricolus is presumed to occupy. Those are regional concerns rather than documented impacts on this species in particular, and should be read as context rather than as an assessed threat.