Taxonomy & naming
Diplotaxodon dentatus belongs to the genus Diplotaxodon, erected by Ethelwynn Trewavas in 1935 for Lake Malawi's silvery offshore haplochromines, with Diplotaxodon argenteus as the type species. The genus name is a compound of Greek roots meaning roughly "double tooth-row." Most of the roughly ten currently recognised Diplotaxodon species were formally described considerably later than the genus itself, chiefly through revisions by George Turner, Jay Stauffer, and colleagues from the late 1990s onward. The precise original description and year for Diplotaxodon dentatus specifically have not been confirmed against a primary source for this article, so no formal describing authority is asserted here. The epithet dentatus is straightforward Latin for "toothed," presumably describing dentition more prominent or more numerous than in some related species — a detail consistent with a diet that may lean more toward larger prey than the genus's classic zooplankton-picking members.
Morphology
Diplotaxodon dentatus is expected to share the genus's fusiform, torpedo-shaped build suited to cruising open water, with the silvery, countershaded colouration typical of pelagic fish. The diagnostic feature implied by its name is dentition — teeth more conspicuous or robust than in the genus's more purely plankton-picking species, a build that would suit taking somewhat larger prey items, including small fish, alongside plankton. As in other Diplotaxodon, the eyes are likely enlarged relative to shallow-water cichlids, an adaptation to gathering light in deeper or more open water, and ripe males in the genus typically develop subdued, largely monochromatic black-and-white breeding patterns rather than bright shallow-water colours.
Habitat
Diplotaxodon dentatus is documented here from Monkey Bay and Thumbi East Island, both well-studied sites in the southern basin of Lake Malawi near the Cape Maclear peninsula and Lake Malawi National Park. Like the rest of its genus it is expected to be a benthopelagic, open-water associated fish rather than one confined to rocky shoreline, though the specific depth preference for this species has not been confirmed. Diplotaxodon as a group range from moderate depths into the lake's deep, cool, dimly lit offshore zone, and the water throughout that column carries the lake's characteristic warm, hard, alkaline chemistry near the surface, cooling and darkening with depth.
Feeding
Diplotaxodon as a genus are principally zooplanktivores, taking small crustaceans, insect larvae — notably the lake's abundant Chaoborus phantom-midge larvae — and diatoms from the open water column, though the more heavily toothed members of the genus, a category dentatus's name suggests it may belong to, are understood to take a greater proportion of small fish alongside plankton. Collectively the offshore Diplotaxodon make up a large share of Lake Malawi's pelagic fish biomass and form a key link between the lake's plankton production and its larger open-water predators. Specific dietary data for Diplotaxodon dentatus has not been documented here, so this account follows the general feeding ecology established for the genus.
Mating
In the dim, blue-filtered light of open water, the bright colour signals that distinguish shallow-water cichlid species do not carry well, and related Diplotaxodon are documented relying instead on subtle, largely monochromatic black-white-and-silver breeding patterns to signal readiness and maintain species boundaries. Diplotaxodon dentatus is presumed to follow this same pattern, though courtship behaviour specific to the species has not been documented. As in other haplochromines, males are expected to display and compete for female attention with no lasting pair bond, all subsequent parental care falling to the female.
Breeding
As with other Lake Malawi haplochromines, Diplotaxodon dentatus is presumed to be a maternal mouthbrooder. The genus is notable for unusually low fecundity given how abundant it is in the lake — well-studied congeners are typically found carrying only one or two well-developed fry per brood rather than large clutches, a strategy trading egg number for heavy investment in a few large young. Specific fecundity data for dentatus has not been documented. There is no fixed nest site and no paternal role beyond fertilisation and display; the female alone shelters the developing brood in her mouth until the fry are released.
In the aquarium
This is not a fish suited to captivity, and no established aquarium-husbandry tradition exists for it. Diplotaxodon as a genus are taken almost exclusively by commercial trawl or research net rather than by shoreline aquarium collectors, and are essentially absent from the ornamental trade. A cool-water, open-schooling, dimly-lit-habitat fish shares little with the bright, territorial rock-dwellers that dominate typical Malawi tanks. As with its congeners, Diplotaxodon dentatus is best regarded as a species to know about through the lake's ecology rather than one to keep.
Conservation
No IUCN Red List assessment specific to Diplotaxodon dentatus is confirmed here, so no status is asserted. As an offshore, open-water endemic it would not face the aquarium-collection pressure that affects some shallow-water Malawi cichlids, but the broader Diplotaxodon community is a meaningful target of the lake's mid-water trawl fisheries, and the genus is exposed to basin-wide pressures — a warming, more strongly stratified lake that reduces the nutrient mixing feeding its productivity, and intensifying fishing pressure across the open-water fish community. Its specific population trend and full range have not been documented here.