Taxonomy & naming
Haplochromis bicolor was described by the Belgian-British ichthyologist George Albert Boulenger in 1906, in the Annals and Magazine of Natural History, from material collected at Bunjako on the Ugandan shore of Lake Victoria. The lectotype (BMNH 1906.5.30.414), held in the Natural History Museum, London, was later fixed by C. Tate Regan in his 1922 revision of the lake's cichlids, with a paralectotype (BMNH 1906.5.30.378) from the same series. The species sits within the vast endemic radiation of haplochromine cichlids that makes Lake Victoria one of the textbook examples of explosive speciation. Its taxonomic home, however, is genuinely unsettled. Regan, and later Greenwood (1983), regarded the fish as distinctive enough to anchor its own genus, Macropleurodus Regan 1922, of which bicolor is the type and only species; Eschmeyer's Catalog of Fishes accordingly lists it as valid in the combination Macropleurodus bicolor. Most modern workers on the Victoria flock, following van Oijen et al. (1996), instead provisionally retain all the lake-basin haplochromines in the single large genus Haplochromis Hilgendorf 1888 pending a complete revision, and FishBase follows that convention — the usage adopted here, with the species heading kept as Haplochromis. Whichever name is used, the fish belongs to the oral-shelling, mollusc-eating segment of the flock, a trophic group that Greenwood's monographic work made one of the best-studied guilds in the lake.
Morphology
Haplochromis bicolor is a moderately deep-bodied haplochromine reaching about 6 in in standard length, large for a member of the Victoria flock. Boulenger's original description fixes the name: he reported the fish as 'bright yellow, irregularly blotched or marbled with black, the black sometimes forming irregular crossbands on the body,' and it is this conspicuous two-tone livery that the epithet bicolor ('two-coloured') records. The diagnostic feature, and the basis of the generic name Macropleurodus, lies in the mouth: the outer oral teeth are stout, the dentition is heavy and obliquely arranged, and the jaws are modified for prising and crushing hard-shelled prey rather than for the rasping or sucking seen in many congeners. Like other haplochromines the species is sexually dimorphic in colour — breeding males develop the brighter, more saturated nuptial pattern and bear the egg-spots (ocelli) on the anal fin used in spawning, while females and non-breeding fish are plainer — though the detailed nuptial coloration of this particular species is not well documented in the accessible literature, and reported figures should be treated cautiously given how readily Victoria haplochromines are confused.
Habitat
The species is endemic to Lake Victoria, the great shallow equatorial lake shared by Uganda, Kenya and Tanzania, and is not known from any other water body. Within the lake it is a fish of the littoral and sublittoral zones, occurring most often where the bottom is hard — rock, gravel and shell — and only rarely over soft mud, a distribution that tracks the snails it feeds on. FishBase gives a depth range extending to about 39 ft, placing it in the well-lit inshore shelf rather than the deeper, more oxygen-poor offshore waters. Lake Victoria itself is warm and only weakly mineralised: surface temperatures across the year sit broadly in the mid-20s Celsius, the water is circumneutral to alkaline (pH roughly 7.2 to 9), and conductivity is low. No published in-situ chemistry specific to this species' microhabitat was located, so the parameters given here are the general lake values within which it lives.
Feeding
Haplochromis bicolor is a molluscivore — a snail specialist — and FishBase places its trophic level near 3.6, typical of a predator on hard-shelled invertebrates. Within the Victoria flock, mollusc-eaters split into two engineering solutions: pharyngeal crushers, which mill snails between heavily ossified throat (pharyngeal) jaws, and oral shellers, which use modified outer mouth teeth to wrench the snail's body from its shell or to crack the shell directly. As the type of Macropleurodus, bicolor belongs to the oral-shelling group; its stout, obliquely set oral dentition is the tool for this work. Field and gut-content studies record it feeding mainly on snails and insect (especially chironomid midge) larvae, supplemented by detritus and phytoplankton, so while molluscs are the specialism the diet is not exclusively so. Its preference for hard substrates reflects this trophic role, since snails are most abundant over rock and shell bottoms. As a mollusc predator it forms part of the inshore benthic food web that the introduced Nile perch and the lake's wider ecological upheaval later disrupted.
Mating
No species-specific account of courtship or pair formation in Haplochromis bicolor was found in the accessible literature, so its mating behaviour is described here from the well-established pattern of the Lake Victoria haplochromine flock to which it belongs. These cichlids are polygynous maternal mouthbrooders with no lasting pair bond. Males establish and defend small temporary territories during the breeding period and display their nuptial colours to passing females; the anal-fin egg-spots (ocelli) function as a spawning signal. A receptive female deposits a small clutch of eggs and takes them into her mouth, where fertilisation is completed when she mouths at the male's egg-spots — a behaviour central to the group's reproductive biology. The male contributes nothing beyond fertilisation, and the female alone carries and tends the developing brood.
Breeding
Direct observations of spawning and brood care in Haplochromis bicolor have not been published, but its reproductive mode is not in doubt: FishBase records it simply as a mouthbrooder, and as a member of the East African haplochromine flock it is a maternal (female-only) mouthbrooder. By the pattern universal to the group, the female incubates the fertilised eggs in her buccal cavity for several weeks, the developing young drawing on their yolk while sheltered in her mouth; once free-swimming, fry continue to dart back into the mother's mouth when threatened before becoming fully independent. Clutch sizes are small in these lacustrine haplochromines — congeners of comparable size typically carry on the order of a few dozen eggs (very roughly 20 to 80), a fecundity trade-off that buys the high survival of mouthbrooded young. No fecundity figure specific to this species was located, so that genus-typical band should be read as indicative rather than measured.
In the aquarium
Haplochromis bicolor is essentially never seen in the aquarium hobby and there is no established body of husbandry experience for it. Unlike the colourful 'Victorian haps' that circulate among specialist keepers, this snail-shelling species has not entered the trade in any meaningful way, and its scarcity in the wild since the Nile-perch era makes wild collection both unlikely and inadvisable. Any keeping notes therefore have to be inferred from close relatives in the flock. A specialist maintaining it would treat it as a hard-water Victorian haplochromine: a spacious tank with open swimming room and a hard substrate of sand, gravel and rock to suit a bottom-foraging molluscivore; warm water in the mid-20s Celsius; and the alkaline, moderately mineralised conditions of its native lake (pH around 7.5 to 8.5). The maternal-mouthbrooder social system means a harem of one male to several females reduces the male's relentless pressure on any single female. Live or frozen snails and invertebrate foods would best match its natural diet. None of this is documented practice for this species specifically — it is extrapolation, and the honest summary is that Haplochromis bicolor is a fish of the lake and the museum drawer, not of the aquarium.
Conservation
The IUCN Red List assesses Haplochromis bicolor as Vulnerable (criterion D2), assessed on 1 April 2010 by Witte, Brooks and de Zeeuw, with the range given as Lake Victoria across Kenya, Tanzania and Uganda. The D2 listing reflects a very restricted effective range and a plausible threat capable of driving the species to a more threatened category in a short time — the hallmark vulnerability of a Lake Victoria endemic. The wider context is the catastrophe that overtook the lake's endemic cichlids in the late twentieth century: the introduction of the predatory Nile perch (Lates niloticus), compounded by eutrophication and intensified fishing, is held responsible for the collapse and in many cases extinction of a large fraction of the Victoria haplochromine flock, including the near-disappearance of this species over roughly two decades. A partial recovery of some haplochromine groups followed in the 1990s as Nile-perch stocks were themselves heavily fished, but the lake remains ecologically transformed, and mollusc-eating specialists like this one — tied to particular substrates and prey — are among the more exposed. No CITES listing applies.