Taxonomy & naming
Orthochromis indermauri 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 same paper that named five new rheophilic Orthochromis from the upper Congo drainage and the Lake Tanganyika region. The genus Orthochromis was erected by Greenwood in 1954 for small, current-loving haplochromine cichlids of African river rapids; the name joins Greek 'orthos' (straight) and 'chromis' (a cichlid), for the straight body profile of these stream fishes. As presently used the genus is a loose assemblage of rheophilic haplochromine lineages spread across the Malagarasi, the Lufubu, other Lake Tanganyika–region rivers and the upper Congo systems rather than a single tight clade. Within that assemblage indermauri belongs to the Lake Tanganyika ecoregion via the Lufubu, and the describers noted that its meristic counts overlap with those of the geographically distant upper-Congo species Orthochromis gecki, the two being separated on body shape and squamation. The specific epithet honours Adrian Indermaur, a Swiss ichthyologist whose underwater photography, video and aquarium observations contributed to knowledge of the species' behaviour and ecology.
Morphology
Orthochromis indermauri is a small cichlid: the holotype measures 2 in standard length, a paratype reaches 2.5 in, and FishBase gives a maximum of about 2.5 in SL — making it one of the smaller rheophilic Orthochromis. It shows the genus's characteristic build for life in current: an elongate, low-profiled, only moderately compressed body and reduced fins. A key diagnostic feature is its strongly reduced cheek squamation — typically only zero to one row of scales on the cheek — which separates it from several congeners. Like Orthochromis gecki and Orthochromis torrenticola, and unlike most Orthochromis, it bears eggspots or eggspot-like maculae on the anal fin. Living fish show the muted grey-brown ground colour and darker vertical flank bars typical of stream haplochromines; underwater observations of the species in its home river informed the original description. Beyond the male anal-fin markings, detailed sexual dimorphism is not extensively reported.
Habitat
The species is known only from the lower reaches of the Lufubu River in Northern Province, Zambia — the third-largest tributary of Lake Tanganyika — with the type series taken below the last series of rapids near Chomba village, about 16 mi from the river's confluence with the lake and some 12 mi south of Sumbu, at roughly 8°41′S, 30°33′E. Although the Lufubu drains to Lake Tanganyika, indermauri is a river fish, not a lake fish: it lives in the rocky, fast-flowing rapids reaches, where the bed is broken rock with patches of sand and gravel, the channel on the order of twenty metres wide and on average about half a metre deep. This is well-oxygenated, briskly moving water, and the fish is a benthic rheophile holding station among the stones in the current. So far the species has not been found above the rapids or elsewhere, suggesting a genuinely restricted range in the lower Lufubu.
Feeding
No dedicated dietary study has been published for Orthochromis indermauri. By the ecology of the genus and its habitat it is best read as a benthic grazer-invertivore of fast water, working the rocky substrate for aufwuchs — the algal-and-microinvertebrate film on the stones of sunlit riffles — together with aquatic insect larvae and other small bottom invertebrates carried in the current. The low body and ventrally-set mouth typical of rheophilic Orthochromis suit a fish that rasps and picks at rock surfaces while bracing against flow. Precise diet for the species remains to be documented and is here inferred from its relatives rather than directly observed.
Mating
Courtship is not described in detail for indermauri, but rheophilic Orthochromis are maternal mouthbrooders and the male's anal-fin eggspots mark out the standard haplochromine spawning system. A male holds and defends a small territory among the rocks, displays to females, and leads a receptive female over the chosen site; she takes up the eggs into her mouth, and the eggspots on the male's anal fin act as decoys that prompt her to snap at them, drawing milt in to fertilise the clutch she already carries. Adrian Indermaur's underwater and aquarium observations, acknowledged in the species' naming, are among the few behavioural notes available, but the fine details of pairing and territory in the wild Lufubu population remain largely undescribed.
Breeding
No formal account of clutch size or fry development has been published for Orthochromis indermauri specifically. By the consistent biology of the rheophilic Orthochromis it is a maternal mouthbrooder: the female incubates eggs and then larvae in her buccal cavity for some weeks before releasing free-swimming fry, which may dart back into her mouth when threatened, with the male giving no parental care. In a small river haplochromine of this size, clutches are modest — on the order of tens of relatively large eggs — the small brood offset by the protection that oral incubation gives in turbulent, predator-rich rapids. The species has been kept and observed in aquaria by the naturalist it is named for, but published breeding data remain thin and the figures here are inferred from the genus.
In the aquarium
Orthochromis indermauri is, in practical terms, a specialist's fish rather than a hobby staple. It has been kept and observed in aquaria — notably by Adrian Indermaur, whose observations fed into its description — but it is not a fixture of the ornamental trade and there is no broad body of keeping experience for it.
What husbandry notes exist are extrapolated from the rheophilic Orthochromis as a group and from the species' home river. These are fish of clean, hard, alkaline, very well-oxygenated water in strong, steady motion; FishBase associates the species with conditions around pH 8.0–8.6 and roughly 73–82 °F, which fits the Tanganyika-region river setting. A suitable tank reproduces the rapids: a rocky, rubble-strewn bottom with crevices and current-breaks, powerheads or a river-tank flow manifold to keep the water moving briskly, strong filtration and frequent water changes. They are small, busy, bottom-oriented fish best kept as a group in a species tank or with other robust rheophiles, not in a soft-water community. The realistic summary is that indermauri is an interesting, attainable-in-principle but uncommon fish for the dedicated river-cichlid keeper.
Conservation
Orthochromis indermauri has not been assessed by the IUCN Red List and carries no formal status, consistent with its 2018 description. Its conservation profile is that of a narrow-range endemic: on present knowledge it is confined to the lower, rapids reaches of a single river, the Lufubu, which makes the whole known population dependent on a short stretch of flowing water. River rheophiles of this kind are sensitive to anything that ponds, silts or de-oxygenates their rapids — dam or weir construction, water abstraction, deforestation and catchment erosion among them — and the Lake Tanganyika basin faces growing pressures of exactly these sorts. There is also a recognised conservation concern across the region from hybridisation and competition where non-native cichlids are introduced. No CITES listing or fishery interest applies, but the species' tiny known range and demanding fast-water niche make it a reasonable candidate for future conservation attention.