Taxonomy & naming
Otopharynx sp. "Heterodon Boadzulu" has no describing author, no publication date, and no entry under a validated name in Eschmeyer's Catalog of Fishes. The trade name follows the standard convention for an undescribed form allied to a known species: the genus, a reference to the described relative Otopharynx heterodon (Trewavas, 1935) — Greek for "different teeth" — and "Boadzulu," the island locality where this form has been collected. Otopharynx heterodon is a genuinely wide-ranging Lake Malawi species, with populations already documented from Chilumba, Nkhata Bay, Likoma Island, Monkey Bay and Mozambique's Chiloelo among others, so a form at Boadzulu Island — close to Monkey Bay in the South East Arm — falls well within its known range. The IUCN assessment for O. heterodon itself notes that the species "may be a complex of species" in need of taxonomic revision, and Konings distinguishes true heterodon from at least one close relative, Otopharynx sp. "heterodon likoma," that builds spawning bowers, a behaviour the true species lacks. Whether Boadzulu Island represents ordinary O. heterodon or a locally distinct population has not been settled by any published study.
Morphology
This form is presumed to follow the build of Otopharynx heterodon, which reaches roughly 5–6.5 in total length depending on the source (FishBase gives 5 in TL; field data compiled by Konings record males to about 6.5 in and females to about 5.5 in), with dominant, colour-holding males a metallic royal blue marked by darker vertical bars, a yellow chest and a dark eye-stripe, while females and juveniles are cryptic sandy-silver with three black flank blotches. That description is drawn from the described species generally and used here as a genus/species-typical reference; no colour or measurement data specific to the Boadzulu Island population have been published.
Habitat
Otopharynx sp. "Heterodon Boadzulu" is recorded from Boadzulu Island, a well-known collecting locality in the South East Arm of Lake Malawi, near Monkey Bay. Otopharynx heterodon, the described relative this form is named after, favours the intermediate zone where rocky shoreline gives way to open sand, and is also found over sediment-rich substrate in deeper water, a habitat choice tied to its attraction to stirred-up sediment while foraging. The IUCN gives the species a broad estimated extent of occurrence of around 29,373 mi² lake-wide but a much smaller occupied area of roughly 1,137 mi², reflecting how patchily suitable bottom is distributed. Water at Boadzulu Island follows the general Lake Malawi profile — warm, hard and strongly alkaline.
Feeding
Otopharynx heterodon is an opportunistic benthic feeder, taking small invertebrates, organic particles and detritus from sediment drifting in the water column or stirred up off the substrate, rather than rasping algae from rock or hunting in open water. It is actively attracted to sediment disturbed by other foraging fish or by water movement. Otopharynx sp. "Heterodon Boadzulu" is presumed to feed similarly, though no dedicated feeding study has been published for this island population specifically.
Mating
Otopharynx heterodon follows the familiar lek-style courtship of Lake Malawi haplochromines: a colour-holding male quivers, flares his fins and leads a ripe female over a chosen patch of sand, where she lays a small clutch and immediately takes the eggs into her mouth for fertilisation. Notably, males of this species are reported to be only rarely territorial, defending space mainly while actively spawning, and at least one population is documented spawning on open sand between rocks without constructing the elaborate bowers built by some related forms — an unusually mild-mannered pattern among Malawi haps. Whether the Boadzulu Island population follows this same pattern has not been directly observed.
Breeding
Otopharynx heterodon is a maternal mouthbrooder: after fertilisation the female broods the eggs buccally for roughly three weeks — about 21 days, per field data compiled by Konings — before releasing free-swimming fry, often sheltering among rocks until the young are ready. Reported clutch sizes run modest, on the order of 20 to 60 eggs. Parental care is female-only, with the male contributing nothing beyond fertilisation. No breeding data specific to the Boadzulu Island population have been published; the account here reflects the described species generally.
In the aquarium
Where available, Otopharynx sp. "Heterodon Boadzulu" would be kept as Otopharynx heterodon generally is — the "royal blue hap" has a long-standing, if cyclical, place in the Malawi cichlid hobby and is genuinely one of the easier-tempered haps to live with. A harem arrangement (one male to several females) in a long tank of at least roughly 51 in and 90 US gal suits its social structure, with a sand bottom that lets the fish forage naturally and rockwork to break sightlines. Water should be hard and alkaline in the standard Malawi range. Because it is a mild, non-aggressive species, boisterous mbuna or hyper-dominant haps make poor tankmates; calm Aulonocara and other gentle sand-dwelling haps are better company. It is not a fussy eater, taking quality pellet or flake rounded out with frozen brine shrimp and mysis. Keepers who value the Boadzulu Island provenance should avoid mixing it with heterodon from other collection points.
Conservation
Otopharynx sp. "Heterodon Boadzulu" has not been evaluated by the IUCN and, as an undescribed form, has no Red List status of any kind. Its described relative, Otopharynx heterodon, is assessed as Least Concern lake-wide (2018, errata 2019), reflecting a wide distribution and no known major range-wide threat, though the species is noted to face some collection pressure for the ornamental trade at other localities and the IUCN itself flags the possibility that "heterodon" as currently understood may comprise more than one species. Boadzulu Island lies within the South East Arm, an area with a long history of both artisanal fishing and ornamental collection. No population-specific data exist to assess the status of this particular island form; the honest statement is that it is unassessed.