Taxonomy & naming
Orthochromis katumbii was described in 2018 by Frederic D. B. Schedel, Emmanuel Vreven, Bauchet Katemo Manda, Pacifique Kiwele Abwe, Auguste Chocha Manda and Ulrich K. Schliewen, in Zootaxa, in the paper that named five new rheophilic Orthochromis from the upper Congo drainage of Zambia and the Democratic Republic of the Congo. The genus Orthochromis was erected by Greenwood in 1954 for small, current-loving haplochromine cichlids of African river rapids; the name combines Greek 'orthos' (straight) and 'chromis' (a cichlid), for the straight body profile of these stream fishes. As now applied the genus is a loose grouping of rheophilic haplochromine lineages spread across the Malagarasi, the Lufubu, other Lake Tanganyika–region rivers and the upper Congo (Lualaba, Luapula and Lufira) systems rather than a single natural clade. The describers placed katumbii among the upper-Congo rheophiles of the Bangweulu–Mweru region and diagnosed it in part by its reduced cheek squamation and its flank-bar pattern, distinguishing it from the similar Orthochromis mporokoso by having fewer vertical flank bars (about seven to nine, versus thirteen to fifteen) and by lacking cheek stripes; unlike Orthochromis gecki and Orthochromis indermauri it does not carry orange anal-fin eggspots. The specific epithet honours Moïse Katumbi Chapwe, a Congolese figure recognised for support relevant to the work.
Morphology
Orthochromis katumbii is a small-to-moderate rheophilic cichlid; the holotype measures 3.5 in standard length and FishBase gives a maximum of about 3.5 in SL, placing it among the larger members of the genus. It has the typical rheophilic-Orthochromis form — an elongate, low and only moderately compressed body with the straight dorsal profile that names the genus, built to hold position in current. Diagnostic features include reduced cheek squamation and a relatively small number of vertical flank bars, on the order of seven to nine, which separates it from the closely compared Orthochromis mporokoso with its thirteen to fifteen bars; it also lacks the cheek stripes seen in some relatives, and lacks the orange anal-fin eggspots present in Orthochromis gecki and Orthochromis indermauri. Live colour is the muted brown-grey of stream haplochromines, broken by the dark flank bars. Detailed sexual-dimorphism notes are limited, though breeding males are expected to be more strongly coloured than females.
Habitat
The type series of Orthochromis katumbii comes from the Kiswishi River near its confluence with the Matete stream, in the Luapula drainage of the upper Congo basin near Lubumbashi in Haut-Katanga, Democratic Republic of the Congo (around 9°23′S, 30°06′E), with further material reported from the Mambilima Falls on the Luapula River in Zambia. This is rheophilic habitat — rocky, fast-flowing river water with the broken, well-oxygenated flow that the genus favours — and the species is a benthic rheophile holding among the stones in the current rather than in still pools or any lake. The pairing of a Lubumbashi-area type locality with a record from a major falls on the Luapula underlines that this is a fish of the flowing upper-Congo network rather than of standing water, though, as with most rheophilic Orthochromis, its full range remains imperfectly mapped.
Feeding
No dedicated dietary study has been published for Orthochromis katumbii. By the ecology of the genus it is best understood as a benthic grazer-invertivore of fast water, taking aufwuchs — the algal-and-microinvertebrate film coating the stones of sunlit riffles — together with aquatic insect larvae and other small bottom invertebrates dislodged in the current. The low body and ventrally-oriented mouth typical of rheophilic Orthochromis suit a fish that rasps and picks at rock surfaces while bracing against flow. Any finer account of its diet remains to be documented and is here inferred from the genus rather than directly observed.
Mating
Courtship has not been described in detail for katumbii, but rheophilic Orthochromis are maternal mouthbrooders and the species is expected to follow the standard haplochromine pattern. A male holds and defends a small territory among the rocks, displays to passing females, and leads a receptive female over a chosen spawning site; the female takes the eggs into her mouth, where fertilisation is completed. Because katumbii lacks the conspicuous anal-fin eggspots of some congeners, any analogous fertilisation signalling would rest on body coloration and display rather than fin ocelli. The specifics for this species in its rapids habitat are inferred from the genus rather than documented.
Breeding
There is no published account of clutch size or fry development specific to Orthochromis katumbii. By the consistent biology of the rheophilic Orthochromis it is a maternal mouthbrooder: the female incubates the fertilised eggs and then the larvae in her buccal cavity for some weeks before releasing free-swimming fry, which may shelter back in her mouth when threatened, with the male giving no parental care. In a river haplochromine of this size, broods are likely modest — on the order of tens of relatively large eggs — the small clutch offset by the protection oral incubation provides in fast, predator-rich water. As with much of this fish's biology, the figures here are extrapolated from the genus rather than recorded for the species.
In the aquarium
Orthochromis katumbii is not established in the aquarium hobby. It is a recently described upper-Congo endemic and is essentially absent from the ornamental trade, so there is no body of keeping or breeding experience for it; the rheophilic Orthochromis as a group are kept only by a handful of specialists.
Any husbandry notes are extrapolated from its close relatives and its habitat. Rheophilic river cichlids of this kind need clean, hard, alkaline, very well-oxygenated water kept in strong motion, a rocky and rubble substrate with crevices and current-breaks, and stable warm temperatures. Powerheads or a river-tank flow manifold, vigorous filtration and frequent water changes are the essentials; soft, still, organically loaded water is the opposite of what they tolerate. At up to roughly 3.5 in SL, katumbii is among the larger Orthochromis and would want a correspondingly roomy, well-structured tank, kept as a group in a species setup or with other robust rheophiles rather than in a soft-water community. The realistic summary is that this is a fish for the committed river-cichlid keeper and one most readers will encounter on the page rather than in a tank.
Conservation
Orthochromis katumbii has not been assessed by the IUCN Red List and carries no formal conservation status, consistent with its 2018 description. Its conservation profile is that of a range-restricted upper-Congo rheophile, known from the Kiswishi near Lubumbashi and the Luapula at Mambilima Falls — a fish dependent on flowing, rocky river habitat in a region under real pressure. The Katanga / upper-Congo area faces extensive artisanal and industrial mining, with associated sedimentation and water-quality impacts, alongside deforestation, urban growth around Lubumbashi, and dam and weir development, all of which can degrade the fast, oxygenated, rocky water that rheophilic cichlids require. There is also a recognised regional concern from hybridisation and competition where non-native cichlids are introduced into upper-Congo waters. No CITES listing or fishery interest applies, but the combination of a limited range and a demanding fast-water niche makes the species a reasonable candidate for future conservation attention.