Taxonomy & naming
Otopharynx selenurus was described in 1922 by Charles Tate Regan, the British Museum ichthyologist who had erected the genus Otopharynx itself only two years earlier, in 1920, for a group of laterally spotted Lake Malawi haplochromines. The genus has since been revised by later workers, notably Eccles and Trewavas in their 1989 classification of the lake's non-mbuna cichlid genera. The genus name combines the Greek ous/ōt-, “ear,” with pharynx, “throat.” The species epithet selenurus combines the Greek selene, “moon,” with oura, “tail,” describing a crescent- or moon-shaped marking on the caudal fin that distinguished the species in Regan's original description.
Morphology
Otopharynx selenurus shares the generally deep-bodied build and laterally spotted pattern typical of its genus, with the moon-shaped caudal-fin marking named in its epithet serving as a key diagnostic feature. Detailed meristic counts and full colour description have not been confirmed in the sources used here, reflecting the relatively terse morphological descriptions typical of early 20th-century cichlid taxonomy.
Habitat
As a member of Otopharynx, this species is expected to occupy sand or sand-rock transition habitats in Lake Malawi, following the general pattern of the genus, though specific locality records and depth range for Otopharynx selenurus have not been confirmed in the sources used for this article.
Feeding
No specific dietary study for Otopharynx selenurus has been confirmed here. Genus-mates span a range of feeding strategies from benthic invertebrate feeding to more specialised modes, but assigning a specific diet to this species without direct evidence would be guesswork rather than documentation.
Mating
Courtship behaviour has not been documented for Otopharynx selenurus. By the general pattern of Lake Malawi haplochromines, males are expected to hold territory and court females through colour display in a lek-like, female-choice system, but this has not been confirmed by direct observation for this species.
Breeding
Otopharynx selenurus is presumed to be a maternal mouthbrooder, following the near-universal reproductive pattern of Lake Malawi's haplochromine cichlids. No species-specific account of clutch size, incubation period, or fry development has been documented here.
In the aquarium
Otopharynx selenurus has no significant documented presence in the aquarium trade. As an early-described, little-studied species, it is not established in the hobby, and any husbandry recommendations would be extrapolated from the genus rather than grounded in direct experience with this fish.
Conservation
The CARES Preservation Program lists Otopharynx selenurus as CARES Endangered (CEN) in its July 2026 Cichlidae priority list, one of its more urgent categories. No IUCN Red List assessment for this species could be confirmed here, though the genus received some Red List attention around Michael Oliver's 2018 taxonomic revision, when several better-known Otopharynx species were assessed as Least Concern. As one of the oldest-described species in the genus, Otopharynx selenurus has had a full century to be affected by the pressures now recognised as bearing down on Lake Malawi's cichlid fauna: intensive artisanal and commercial fishing, sedimentation from catchment deforestation, and localised aquarium collection. Its Endangered CARES rating suggests the hobby community considers it considerably more at risk than the genus's better-documented members.