Taxonomy & naming
Otopharynx sp. "Red Flat-jaw" has no describing author, no publication date, and no entry under a validated name in Eschmeyer's Catalog of Fishes; it is an informal trade name, not a scientific one. "Flat-jaw" is used across several Otopharynx trade forms recorded around the lake for a flattened, protruding lower jaw, a genuine anatomical feature rather than a purely cosmetic label, distinguishing this small group from Otopharynx species with a more standard jaw profile; "Red" marks the breeding-male colour recorded at Kadango, separating this population from blue-toned flat-jaw forms recorded elsewhere. The genus Otopharynx, raised by Regan in 1920, has proven taxonomically difficult, with numerous local colour and jaw-shape variants still undescribed, and no published study has established which described species, if any, this flat-jaw group is most closely allied to.
Morphology
As implied by its trade name, this form carries a flattened, forward-protruding lower jaw, distinguishing it from the more conventionally shaped jaw of most other Otopharynx. Breeding males are described as showing a red colouration, in contrast to the blue tones of other flat-jaw forms recorded at other localities. Beyond those documented features, detailed morphometrics have not been published for this population. The body is expected to follow the moderately deep, laterally compressed shape typical of the genus. Genus-typical size for mid-sized Otopharynx runs to roughly 4.5–6 in total length; no validated maximum has been recorded specifically for this form.
Habitat
The form is recorded from a single point at Kadango, a locality on the south-eastern arm of Lake Malawi, close to the Mozambique border. This part of the lake includes a mix of sand and rocky shoreline typical of the southern arm. A flattened, protruding jaw of the kind that gives this group its trade name is often associated in cichlids with picking prey from crevices or from among rubble rather than open sand or rock-face grazing, suggesting a similarly structured microhabitat here, though this has not been documented directly for this population. Surrounding water is warm, hard, and alkaline, consistent with Lake Malawi's littoral zone throughout.
Feeding
The flattened, protruding jaw shared across the "flat-jaw" Otopharynx forms suggests a feeding style adapted to extracting prey from crevices, gaps between rocks, or rubble, rather than the open grazing or sand-sifting seen in other Otopharynx groups, though no dedicated feeding study has confirmed this for Otopharynx sp. "Red Flat-jaw" specifically. A benthic invertivorous diet — small crustaceans and insect larvae picked from tight spaces — is the more likely pattern given the jaw's apparent function.
Mating
Breeding behaviour has not been documented specifically for this form. By analogy with other Otopharynx and the wider Lake Malawi haplochromine assemblage, males are expected to hold a breeding territory and display their red breeding colour to attract passing females, following the general haplochromine courtship pattern built around egg-spot markings on the male's anal fin. No field account of courtship exists specifically for this form.
Breeding
As in all Lake Malawi haplochromines, reproduction is by maternal mouthbrooding: the female carries the fertilised eggs and subsequent fry in her mouth, without normal feeding, for several weeks until they are large enough to be released as independent, free-swimming young. The male takes no further role after spawning. Clutch size and brooding duration have not been documented for this specific form; genus-typical figures for mid-sized Otopharynx suggest a modest clutch and a brooding period of roughly three to four weeks.
In the aquarium
Otopharynx sp. "Red Flat-jaw" is an uncommon fish in the hobby, generally reaching keepers through specialist Malawi cichlid importers rather than general retail, and is sought after in part for its unusual jaw shape and red breeding colour. A tank for it should provide a mix of sand substrate and rockwork with crevices and rubble, reflecting the jaw's likely function extracting prey from tight spaces. Water chemistry should follow the Lake Malawi standard — hard and alkaline, pH roughly 7.7 to 8.6, temperature 75–82 °F. Otopharynx species are generally less aggressive than rock-dwelling mbuna and are usually kept successfully alongside other calm, similarly sized Malawi haplochromines. Diet should include a quality cichlid pellet supplemented with small live or frozen invertebrates such as bloodworm and brine shrimp.
Conservation
Otopharynx sp. "Red Flat-jaw" has not been evaluated by the IUCN and, as an undescribed form, has no Red List status of any kind. Its documented range is limited to a single point at Kadango, on the south-eastern arm of the lake, but no population assessment or targeted study has been published for this specific form. In the absence of that data, the honest position is that it is unassessed, and that a form known from only one locality warrants the same general caution applied to other narrow-range Malawi endemics.