Taxonomy & naming
Otopharynx is a genus of Lake Malawi haplochromine cichlids raised by Charles Tate Regan in 1920 and substantially revised by Rosemary Eccles and Ethelwynn Trewavas in their 1989 monograph of the lake's non-mbuna haplochromines. The genus gathers laterally spotted, sand- and intermediate-habitat cichlids distinguished from relatives such as Placidochromis and Copadichromis chiefly by details of the pharyngeal apparatus and melanin pattern. Genus diversity has continued to grow through the 2000s and 2010s as researchers, notably Michael K. Oliver, have formally named field-recognised colour and pattern forms that circulated informally for years before receiving a scientific name. Otopharynx peridodeka is documented on malawi.si from the South East Arm and is treated here as a distinct, currently recognised species within that genus; its describing author, year of publication, and the precise diagnostic feature referenced by the epithet peridodeka (from Greek peri-, 'around, about,' and dodeka, 'twelve' — plausibly a count of bars, spots, or fin elements) are not confirmed from sources available to this entry and should be checked against Eschmeyer's Catalog of Fishes before being stated as settled fact.
Morphology
Otopharynx peridodeka follows the general genus plan: a moderately deep, laterally compressed body with a terminal, moderately protrusible mouth adapted for picking prey from sand rather than for grazing. Otopharynx as a genus are typically medium-sized haps, most species falling in the 4–7 in range, with males coloring up in yellow, gold, or blue tones against a paler female pattern — the same broad dichromatism seen across the lake's sand-hap radiation. The genus's diagnostic laterally spotted melanin pattern (a suprapectoral shoulder spot, and supra-anal and precaudal spots that in some species fuse into a stripe) is the usual basis for telling similar Otopharynx apart, but the exact pattern documented for peridodeka specifically is not confirmed here and should be read from the original description or a verified photograph rather than assumed from the genus average.
Habitat
The species is documented from the South East Arm of Lake Malawi, a large, structurally varied basin off the Nankumba Peninsula and Mangochi district that supports a dense and well-studied community of sand-dwelling and intermediate-habitat haplochromines. Otopharynx as a genus typically occupy open sandy shoals and the sand-rock transition zone in roughly 16–98 ft of water, foraging over clean sand away from the dense rock cover favoured by mbuna. Lake Malawi's water in this zone is warm, alkaline, and well-buffered year-round. Whether peridodeka is confined to the South East Arm or occurs more broadly across the lake's southern sandy shoals is not established from the sources available here.
Feeding
No species-specific feeding study for Otopharynx peridodeka is confirmed here. As a genus, Otopharynx are benthic micropredators and generalist invertivores that work open sand for small invertebrates, typically picking prey items individually from the substrate rather than engulfing mouthfuls of sand in the manner of the sand-sifting Aulonocara peacocks. Diet is expected to consist of aquatic insect larvae, small crustaceans, and other soft-bodied invertebrates living on or just under the sand surface, consistent with the feeding ecology documented for better-studied congeners such as Otopharynx lithobates and Otopharynx tetraspilus.
Mating
Courtship has not been documented specifically for Otopharynx peridodeka. Lake Malawi's sand-dwelling haplochromines, Otopharynx included, are polygynous maternal mouthbrooders in which males typically establish a display site or shallow bower on open sand and court passing females from it, rather than forming any lasting pair bond. Coloured, egg-spot-bearing anal fins in breeding males function as a releaser during spawning across the genus. The specific display behaviour, territory type, and any bower-building habit of this species have not been documented and are inferred from the wider Otopharynx and sand-hap flock rather than observed directly.
Breeding
Otopharynx peridodeka is presumed to be a maternal mouthbrooder, as are all Lake Malawi Otopharynx and the haplochromine flock generally. A female is expected to take her fertilised eggs into her mouth immediately after spawning and to incubate them there for roughly three weeks before releasing free-swimming fry, with no male or biparental care beyond the initial spawning event. Clutch size, egg size, and fry development have not been documented for this species and should be assumed to fall within the modest range typical of medium-sized Otopharynx — likely several dozen eggs — rather than stated as a measured fact.
In the aquarium
Otopharynx peridodeka is not established in the aquarium hobby, and no husbandry history or trade name for it is confirmed here. General care for the genus, where better-known species such as Otopharynx lithobates ('Eureka Red') are kept, follows the standard sand-hap template: a spacious tank with a deep sand substrate and open swimming room rather than dense mbuna-style rockwork, alkaline, well-buffered water in the mid-20s Celsius with a pH around 7.7-8.6, and a varied carnivore-leaning diet of quality pellets supplemented with small frozen invertebrates. Aggression in Otopharynx is generally lower than in the rock-dwelling mbuna, and a single male with several females is the usual stable arrangement. These notes are extrapolated from the genus rather than observed for this species, which should be treated as essentially undocumented in captivity.
Conservation
No confirmed IUCN Red List status for Otopharynx peridodeka is available from sources used in this entry, and none should be assumed. Lake Malawi's sand-dwelling haplochromine community as a whole faces sustained pressure from artisanal and commercial fishing, shoreline sedimentation linked to catchment deforestation, and the broader stresses documented basin-wide in recent limnological reviews. A species known chiefly from a single arm of the lake, as this one is documented here, would be exposed to any localised decline in that area's habitat quality or fishing pressure; a confident assessment, however, requires consulting the IUCN Red List and Catalog of Fishes directly rather than inferring one from genus-level trends.