Taxonomy & naming
Protomelas dejunctus belongs to the genus Protomelas, a group of predominantly sand- and intermediate-zone haplochromine cichlids recognised during the systematic splitting of the old catch-all genus Haplochromis into narrower, better-diagnosed Lake Malawi genera in the later twentieth century. Eschmeyer's Catalog of Fishes is the reference for the currently accepted describing authority and date for this species, not restated here to avoid an inaccurate citation. The Latin epithet dejunctus derives from the verb dejungere, "to unyoke" or "to separate/disjoin"; in cichlid species names this pattern of word usually points to a broken or interrupted marking — such as a lateral stripe or bar that does not run continuously — though the precise feature it names in the original description is not confirmed here.
Morphology
Protomelas as a genus includes some of Lake Malawi's larger, more robustly built haplochromines, several of which are prized in the hobby for bold male breeding colour. Precise published measurements for P. dejunctus are not confidently known here; comparable mid-sized Protomelas species commonly reach roughly 4.5–7 in total length. The body follows the typical elongate, laterally compressed Protomelas plan. Sexual dichromatism is expected to be pronounced, in keeping with the genus: territorial breeding males develop strong colour, often including the possibly interrupted or broken flank marking implied by the species name, while females remain comparatively plain and silvery.
Habitat
Protomelas dejunctus is documented from Chinyamwezi Island and Chinyankwazi Island, two small, closely spaced islands in the southern part of Lake Malawi near the Nankumba Peninsula. Protomelas species generally favour open sand and the sand-rock intermediate zone rather than dense rocky reef, often foraging over sandy plains adjacent to rocky outcrops. Water conditions in this part of the lake follow the standard Malawi profile — warm, hard, and strongly alkaline, broadly in the mid-20s Celsius with a pH on the alkaline side of neutral.
Feeding
Protomelas species as a group show varied feeding strategies, including aufwuchs grazing, insect and invertebrate picking from sand and rock surfaces, and in some species a more opportunistic, generalist diet. No species-specific dietary study for P. dejunctus is documented here, so this account reflects the broader feeding ecology of the genus rather than a confirmed study of this particular species. A diet of small benthic invertebrates supplemented by algal material would be a reasonable general expectation.
Mating
Reproduction is expected to follow the standard polygynous pattern of Lake Malawi haplochromines: territorial males in breeding colour hold and defend a spawning site, commonly on open sand, and display to attract females, which are not themselves territorial and move between males. No courtship study specific to P. dejunctus is documented here; this account reflects the general breeding biology described for Protomelas and Malawi haplochromines more broadly.
Breeding
Protomelas dejunctus is presumed to be a maternal mouthbrooder, as are the great majority of Lake Malawi haplochromines. After spawning at a male's territory, the female takes the fertilised eggs into her mouth and broods them alone through hatching and early development, releasing free-swimming fry after several weeks with no further parental investment from either parent beyond the female's brooding period. Clutch size and brooding duration are not documented for this species specifically.
In the aquarium
Protomelas dejunctus does not have an established or well-documented presence in the aquarium trade; specific keeping data for this species is not available here. Several of its congeners, including the popular Red Empress (Protomelas taeniolatus), are mainstream aquarium fish, and husbandry for this species would be expected to follow the same broad template: a spacious tank with an open sand area, hard alkaline water buffered into the high 7s to high 8s pH range, and a varied diet built around a quality cichlid pellet with modest invertebrate supplementation, avoiding fatty or excessively high-protein foods.
Conservation
No confident IUCN Red List status is available for Protomelas dejunctus and none is asserted here. As a species documented from a small pair of neighbouring southern-lake islands, it would potentially be exposed to a fairly restricted range, subject to the general pressures affecting Lake Malawi's island reefs — ornamental and food-fish collection pressure and inshore habitat disturbance — but no formal population assessment or precise range delimitation is documented in the sources consulted for this article.