Taxonomy & naming
Pollimyrus plagiostoma was described by George Albert Boulenger in 1898. The parenthetical form of the authority — (Boulenger, 1898) — signals that Boulenger placed the species in a different genus originally; it was later moved into Pollimyrus as part of the broader twentieth-century revision of mormyrid systematics carried out by the Belgian ichthyologist Léon Taverne, beginning in the 1970s, which split apart what had once been a much larger, catch-all concept of Mormyrus. The species is currently recognized as valid in Eschmeyer's Catalog of Fishes, the standard reference for fish nomenclature.
Pollimyrus sits within the family Mormyridae — the elephantnoses and mormyrids — inside the order Osteoglossiformes, the bonytongue fishes, one of the most ancient surviving lineages of teleosts. The genus itself holds a large number of small, often plainly patterned mormyrids distributed across tropical Africa's river systems, sometimes called "dwarf stonebashers" in the hobby and literature. The specific type locality and original combination for Pollimyrus plagiostoma are not confirmed in the sources available for this account.
Morphology
As in other members of its genus, Pollimyrus plagiostoma is a small, laterally compressed mormyrid with a blunt, rounded head and a short snout. Pollimyrus species generally reach anywhere from a few centimeters to a little over ten centimeters in length, well short of the trunk-nosed giants of the family such as Gnathonemus, but a confirmed maximum size specific to this species is not available in the sources used for this account.
The species epithet plagiostoma is built from the Greek plagios, meaning oblique or slanting, and stoma, mouth — a name that almost certainly describes an obliquely set or slanted mouth, a detail plausibly used to separate it from close relatives. As in every mormyrid, an electric organ near the base of the tail generates a weak, species-specific pulse discharge, read by electroreceptors spread across the skin. Mormyrids also carry a disproportionately large, folded cerebellum devoted to processing this electrosensory stream, among the highest brain-to-body-mass ratios of any vertebrate group. No electric organ discharge waveform specific to Pollimyrus plagiostoma has been documented in the sources available here.
Habitat
Specific locality records, river systems and habitat descriptions for Pollimyrus plagiostoma were not confirmed in the sources available for this account. As a genus, Pollimyrus is distributed widely across tropical Africa, with its greatest diversity in the Congo basin and other Central and West African drainages, and its members typically favor slow-flowing, vegetated stretches of river, floodplain pools and backwaters with soft sediment — the same low-visibility habitat associated with mormyrids generally, where an electric sense outperforms eyesight.
That description is genus-level context rather than a confirmed account of where this particular species lives, and should be read accordingly.
Feeding
Feeding habits specific to Pollimyrus plagiostoma have not been documented in the sources available for this account. Mormyrids as a group, including other Pollimyrus species, are bottom-foraging invertebrate feeders that use their electric sense to locate small prey — insect larvae, worms and tiny crustaceans — hidden in mud, silt and leaf litter, taking it with a quick strike of the small, downturned mouth. Whether this species follows the same pattern has not been confirmed.
Mating
No published account of courtship or mating behavior specific to Pollimyrus plagiostoma is available in the sources used for this account. Within the genus, the best-studied species, Pollimyrus isidori, is a laboratory model for acoustic and electric courtship communication — males produce grunts and moans alongside patterned electric organ discharges during courtship, work associated with the researcher Crawford — but that detail belongs to P. isidori specifically and should not be assumed to hold for Pollimyrus plagiostoma without direct evidence.
Breeding
Breeding has not been recorded for Pollimyrus plagiostoma, in captivity or in the wild, in the sources available for this account. Almost all Pollimyrus species that reach aquarists, when they reach the trade at all, arrive as wild-caught fish rather than captive-bred stock, and spawning behavior across the genus is poorly documented outside a small number of well-studied laboratory species. Nothing about the eggs, spawning site or parental care of this species should be assumed from its relatives without direct evidence.
In the aquarium
Pollimyrus plagiostoma has essentially no track record in the aquarium hobby, and no husbandry account specific to this species is available in the sources used here. What can be said comes from general practice with small Pollimyrus and other dwarf mormyrids: a soft, sand-like substrate for probing, dim lighting, ample cover from roots, wood and plants, and clean, stable water — mormyrids as a group are known to be unusually sensitive to poor water quality and to some common medications, including many copper-based and formalin-based treatments. Live and frozen invertebrate foods such as bloodworm and brine shrimp are the standard offering for small mormyrids, taken more readily after dark, when this style of fish forages most actively; dry foods are typically ignored.
Because this species is not an established aquarium fish, anyone encountering it in the trade should treat the above as general genus-level precaution rather than a confirmed care sheet, and should expect scarce information on compatible tankmates, adult size and long-term husbandry.
Conservation
Pollimyrus plagiostoma does not appear to have been assessed by the IUCN Red List, and no conservation status specific to this species is confirmed in the sources available for this account. It is treated here as Not Evaluated rather than assigned a status that has not actually been published.
Many small, single-basin mormyrids in the genus Pollimyrus have never been formally assessed, which reflects a data gap rather than any known conservation problem. General pressures on tropical African freshwater systems — habitat degradation, siltation, damming and water-quality decline — are the kind of long-term concerns that could affect any narrowly distributed species in this genus, but none of these can be confirmed as threats to Pollimyrus plagiostoma specifically without a published assessment.