Taxonomy & naming
Petrotilapia sp. "Likoma Variable" has no describing author, no publication date, and no entry under a validated name in Eschmeyer's Catalog of Fishes. Its name combines a locality, "Likoma," for Masimbwe Island in the Likoma Island group, with "Variable," flagging a wide range of individual colouration recorded within this single population — a trait well documented across the genus, most notably in A. C. Marsh's 1983 taxonomic revision, which split the polymorphic Petrotilapia tridentiger complex into separate species (including P. genalutea and P. nigra) precisely because a single reef could otherwise appear to hold several "species" that were really colour variants of one. The genus Petrotilapia — from Greek petros, "rock," combined with a Tswana-derived root shared with Tilapia — comprises the lake's dedicated rock-dwelling algae scrapers. Whether this Masimbwe Island population is itself a distinct species or a variable population within a wider Petrotilapia complex has not been resolved by any published study.
Morphology
As implied by its trade name, individual males of this population are described as showing noticeably variable colouration, rather than the single, consistent breeding-male pattern typical of many other Petrotilapia locality forms. Detailed morphometrics specific to this population have not been published. The body should follow the genus-typical robust build shared by all Petrotilapia — a thick-set head and strong, closely packed comb-like teeth adapted for scraping tough algal turf from wave-washed rock, larger and heavier than most other mbuna. Genus-typical size runs to roughly 4.5–6 in total length, with males somewhat larger than females. Females, as across the genus generally, are expected to be considerably plainer than males and to resemble females of other Petrotilapia populations more closely than the variable males resemble one another.
Habitat
The form is recorded from Masimbwe Island, a small island within the Likoma Island group, itself a Malawian territory lying out in the open lake closer to the Mozambican shore than to mainland Malawi. Petrotilapia are specialists of wave-exposed, high-energy rocky shoreline, where strong surf keeps algal turf short, and this form is expected to occupy the rocky margins of Masimbwe Island, generally within the shallow-to-moderate depths typical of the genus. Water in this part of the lake follows the general Malawi profile: warm, hard, and alkaline.
Feeding
Petrotilapia are the lake's rock-scraping algae specialists, using broad, closely packed teeth to tear and scrape tough, wave-hardened algal turf from exposed rock, a niche their robust jaws are particularly well suited to compared with the more delicately toothed grazing mbuna. Petrotilapia sp. "Likoma Variable" is presumed to feed in this genus-typical manner, defending a feeding territory on exposed rock, though no feeding study specific to this population has been published.
Mating
Mature males are expected to hold and defend a feeding-and-breeding territory on exposed rock around Masimbwe Island, displaying their individually variable breeding colour to attract passing females. Petrotilapia territorial defence is generally more intense than in many other mbuna genera, given the value of well-exposed, algae-rich rock. The wide individual colour variation implied by this form's trade name may reflect either genuine polymorphism within a single interbreeding population, or the coexistence of multiple distinct Petrotilapia forms sharing the same reefs — a distinction that has not been resolved by any published study for this locality.
Breeding
As in all Lake Malawi haplochromines, reproduction is by maternal mouthbrooding: the female collects the fertilised eggs into her mouth after spawning and carries them, without normal feeding, for several weeks until the fry are ready for independent release, with the male taking no further role. Clutch sizes in Petrotilapia tend toward the larger end for mbuna given the genus's larger adult body size, though exact figures for this Masimbwe Island population have not been documented.
In the aquarium
Petrotilapia sp. "Likoma Variable" would be kept as a robust rock-grazing mbuna: substantial rockwork offering exposed grazing surfaces and retreats, a sand substrate, and good water movement suit its natural high-energy habitat. Water chemistry should match Lake Malawi's rocky zone — hard and strongly alkaline, pH roughly 7.7 to 8.6, temperature 75–82 °F. As with other Petrotilapia, expect pronounced aggression, generally more intense than typical mbuna, so a generously sized tank, careful stocking, and one male to several females (or a very large, densely decorated mixed-mbuna system) help manage conflict. Diet should be strongly vegetable-based — spirulina flake or pellet, algae wafers welcome — with fatty, protein-heavy foods minimised given the group's susceptibility to digestive bloat.
Conservation
Petrotilapia sp. "Likoma Variable" has not been evaluated by the IUCN and, as an undescribed form, has no Red List status. Its documented range is limited to Masimbwe Island in the Likoma group, and no dedicated population assessment has been published for this specific form. The general caution applied to narrow-range Malawi mbuna forms — vulnerability to concentrated collection or localised habitat change — applies here in the absence of any formal assessment.