Taxonomy & naming
Stomatorhinus polli was described by the ichthyologist Hermann Matthes in 1964, part of the wave of Congo basin fish surveys carried out under the Belgian-run Musée royal de l'Afrique centrale in Tervuren during that period. The species is classified in the family Mormyridae, the elephantnoses and mormyrids, within the order Osteoglossiformes — the bonytongue fishes, one of the oldest surviving lineages of teleosts. No later revision has moved the species out of Stomatorhinus, and the original combination is the one carried in Eschmeyer's Catalog of Fishes, the standard reference for valid fish names.
The genus name Stomatorhinus combines the Greek stoma (mouth) and rhis/rhinos (nose, snout), describing a mouth set close to the tip of the snout — a diagnostic feature that separates Stomatorhinus from mormyrid genera with a larger, more terminal mouth. A precise type locality and any taxonomic history specific to S. polli beyond the original description are not documented in the sources available for this account; the species is treated here as a valid but rarely reported member of the genus.
Morphology
Detailed morphometric data for Stomatorhinus polli has not been published in a form accessible for this account. Members of the genus Stomatorhinus are uniformly small mormyrids, most well under 4 in in standard length, with a laterally compressed body and a small, oblique to inferior mouth that lacks the fleshy chin barbel seen in related genera such as Gnathonemus. On genus-level grounds S. polli can be expected to share this general body plan, though a species-specific description of its proportions and fin counts has not been located.
As in every mormyrid, an electric organ in the caudal peduncle generates a weak, low-voltage discharge that the fish reads through electroreceptors spread across its skin, using the resulting field to navigate and find prey in the low-visibility water typical of Congo forest streams. No electric organ discharge waveform has been published for S. polli specifically. In genera like Stomatorhinus, where several small species look nearly identical, the discharge pattern is usually the more dependable way to separate them — appearance alone is not considered reliable.
Habitat
Stomatorhinus is a Congo basin genus, and S. polli is known from within that basin, most likely the Democratic Republic of the Congo, where Matthes carried out the fieldwork behind the original description. Beyond that basin-level placement, no specific river system, coordinate, or catchment has been documented for this species in the sources consulted here.
The genus as a whole is associated with slow-flowing forest streams, swamps, and turbid or blackwater tributary habitat within the Congo drainage — structurally complex, low-visibility water where an electric sense outperforms eyesight. No measured temperature or pH range has been published for S. polli; Congo basin forest waters of this general kind tend to run warm and soft to slightly acidic, but that is a regional expectation rather than a figure recorded for this species.
Feeding
No dietary study specific to Stomatorhinus polli has been published. Mormyrids in general, and small Congo basin genera such as Stomatorhinus in particular, are bottom-foraging invertebrate feeders that use electrolocation to find insect larvae, small worms, and other invertebrates hidden in mud, sand, and leaf litter, then take them with a quick strike of the small downturned mouth. This diet is presumed for S. polli by family-wide analogy rather than direct observation of this species.
Mating
No courtship or spawning behaviour has been recorded for Stomatorhinus polli. Mormyrids are known to use their electric organ discharge for communication as well as navigation, and in some genera the pulse pattern is thought to carry information relevant to sex and species recognition and to courtship. That has not been studied in Stomatorhinus polli itself, and extending it to this species is an inference from family biology rather than a documented observation.
Breeding
Breeding has not been recorded for Stomatorhinus polli, in the wild or in captivity. Reproduction in mormyrids generally is difficult to study and is rarely observed even in well-known aquarium species; for a small, seldom-collected Congo genus such as Stomatorhinus, no spawning account of any kind is available, and none should be assumed.
In the aquarium
Stomatorhinus polli has no established presence in the aquarium hobby. It has no documented import or captive-care history and should be treated as unavailable rather than merely uncommon. General mormyrid husbandry would still apply if the species were ever kept: a soft substrate for probing, dim lighting, ample cover, and stable, clean water, with live or frozen invertebrate foods offered after dark, since mormyrids typically ignore dry foods and forage more readily once the lights are down.
Mormyrids as a family are also known for sensitivity to poor water quality and to some medications, which would warrant conservative dosing and slow acclimation for any wild-caught individual of this genus that reached a tank.
Conservation
Stomatorhinus polli has not been evaluated by the IUCN Red List; no status or assessment year is available for this species. No species-specific threats have been documented. Congo basin forest-stream and swamp habitats generally face pressure from deforestation, siltation, and localized water-quality decline, and small, poorly studied mormyrids such as this one are hard to monitor for exactly that reason — but this general context is not a substitute for a formal assessment, which does not yet exist for this species.