Taxonomy & naming
Tylochromis pulcher was described by the American ichthyologist Melanie L. J. Stiassny in 1989, in her monographic taxonomic revision of the African genus Tylochromis published by the Koninklijk Museum voor Midden-Afrika (Royal Museum for Central Africa) in Tervuren, Belgium. That revision — a 161-page treatment with notes on the anatomy and relationships of the group — remains the foundational work on these fishes and is the source of the name. The holotype (MRAC 100813) and a series of paratypes (MRAC 78585, 78586, 96775 and 101467) are deposited in the Tervuren museum, and the type locality is given as Lac Tumba in the Democratic Republic of the Congo. The species was described as new and has no junior synonyms. Within the family Cichlidae it belongs to the subfamily Pseudocrenilabrinae and to the small, distinctive tribe Tylochromini, of which Tylochromis is the only genus. Stiassny placed Tylochromis at or near the base of the African cichlid radiation, and her companion analyses treated the genus as a phylogenetically pivotal group for understanding how the African Cichlidae are assembled — a position that subsequent molecular phylogenies have continued to test, generally recovering Tylochromis as an early-diverging African lineage. The genus name pairs the Greek tylos, a knot, knob or lump — a reference to the strong bony apophysis on the underside of the skull (the posterior parasphenoid) that Regan noted when he erected the genus in 1920 — with chromis, an ancient fish name dating to Aristotle that became a standard suffix for cichlids.
Morphology
Tylochromis pulcher is a medium-large, fairly deep-bodied cichlid that reaches about 9 in in standard length, making it one of the larger members of a genus whose species commonly run from roughly 6–10 in. The build is solid and a little heavy-headed, in keeping with the genus's mode of life: the skull is reinforced to anchor powerful jaw and pharyngeal musculature, and the lower face carries enlarged sensory pores of the laterosensory system, an adaptation shared with other sand-probing cichlids for detecting the small movements of buried invertebrates. The mouth is sub-terminal and the lips are not greatly thickened. Like its congeners the species has small, deeply embedded scales over the head and predorsal region and a relatively long-based dorsal fin. Coloration in life is a silvery to brassy ground, often with a dark mid-lateral marking and faint vertical barring, and it is the heightened colour of breeding males — the trait that earned the fish its name pulcher, 'beautiful' — that distinguishes it among the more soberly marked Tylochromis. Sexual dimorphism is present but modest outside the breeding season: males grow somewhat larger and intensify in colour as they ripen, while females, which alone brood the young, are recognised in season by the swollen buccal cavity of a mouthbrooding fish. Precise meristic and colour diagnostics separating pulcher from neighbouring Congo-basin Tylochromis are laid out in Stiassny's original key.
Habitat
The species is endemic to the middle Congo River basin in the Democratic Republic of the Congo. It is recorded from the mainstream of the middle Congo and, most characteristically, from the great shallow blackwater lakes of the Cuvette Centrale — Lac Tumba (the type locality) and Lac Mai-Ndombe — together with the lowland rivers that drain into and out of them, including the Kasai, the Lukenie and the Ruki. These are warm, lowland, slow-moving waters. Lake Mai-Ndombe is an irregularly shaped blackwater lake of roughly 2,300 km2 with an average depth of only about three metres; its waters are stained dark with humic acids, strongly acidic, and seasonally swollen by the flood pulse of fourteen major tributaries. Field measurements from shallow Mai-Ndombe blackwater habitats record pH as low as about 4.2 to 5.5 and temperatures in the range of roughly 22 to 29 degrees Celsius. As a demersal fish, Tylochromis pulcher works the bottom of these soft-substrate floodplain systems, and its range tracks the connected Tumba-Mai-Ndombe-Kasai drainage rather than the clearer Congo mainstem. The genus as a whole favours exactly this kind of habitat: sandy and silty bottoms in lakes and the lower, sluggish reaches of rivers, where sediment can be sifted for food.
Feeding
Tylochromis pulcher is a benthic sand-sifter and hard-prey specialist. FishBase summarises its diet as larger particles, plant material and insects, and the genus is built around the processing of hard-shelled benthic food: Tylochromis carry a robust, molariform pharyngeal mill — the second set of jaws in the throat formed from the modified gill arches — that lets them crush snails and other thick-shelled invertebrates that softer-toothed cichlids cannot exploit. The feeding routine is the one common to sand-sifting cichlids the world over: mouthfuls of substrate are taken up, sorted, and the inedible sand and silt expelled through the gill openings and mouth while edible items are retained and passed back to the crushing pharyngeal jaws. The enlarged cephalic sensory pores that mark the genus help locate prey moving beneath the surface of the sand. In the productive, organically rich blackwater floodplains it inhabits — where much of the available food is delivered from terrestrial sources and floating vegetation on the seasonal flood — a generalist that can handle molluscs, insect larvae and plant detritus is well placed to make a living on the lake and river bottom.
Mating
Tylochromis pulcher is a maternal mouthbrooder that does not form a pair bond, and its mating system reflects that. Rather than the cooperative, territorial pairing seen in substrate-spawning cichlids, brooding is the female's affair alone: the male's contribution effectively ends at fertilisation, and there is no lasting partnership between the sexes. This places the species among the more 'primitive' or basally branching of the African mouthbrooders, lacking the elaborate lek-display and bowering behaviour developed by the haplochromine and tilapiine radiations that followed. Detailed in-situ courtship observations for Tylochromis pulcher specifically are scarce — these are turbid, blackwater, hard-to-observe habitats — but the genus pattern is clear: ripe males colour up (the heightened colour that gives pulcher its name), court passing females over the bottom, and spawning is brief, after which the female takes the eggs into her mouth and departs to brood them on her own. Territoriality, where it exists, is transient and tied to the act of spawning rather than to the prolonged joint defence of a nest.
Breeding
Breeding follows the maternal-mouthbrooding mode confirmed for the species: the female takes the fertilised eggs into her buccal cavity and carries them there through incubation, with no participation by the male and no pair bond. Eggs and developing larvae are held in the mouth, protected from predators and from the low-oxygen conditions of the bottom, until the young are released as free-swimming fry; as in other mouthbrooding cichlids the female does not feed, or feeds little, while carrying. Exact clutch size, incubation period and fry-development timing for Tylochromis pulcher have not been published in the detail available for popular aquarium species; brood counts are not recorded in the standard references. Genus-typical fecundity for Tylochromis is modest by cichlid standards — the trade-off inherent in mouthbrooding, where a parent can shelter only as many eggs as will fit in the buccal cavity, favours relatively few, comparatively large eggs and well-developed fry over the large clutches of open substrate-spawners (congeners are reported to produce broods on the order of tens of eggs). The seasonal flood, which inundates the swamp forests around Tumba and Mai-Ndombe and triggers a feeding-and-breeding migration of fishes into the warm, food-rich shallows, is the most likely natural spawning cue.
In the aquarium
Tylochromis pulcher is essentially an ichthyological rather than an aquarium fish: it is rarely if ever exported from the remote interior lakes of the central Congo, and it has no established presence in the hobby, so there is no body of captive husbandry or breeding experience specific to it. What can be said is drawn from the genus and from the fish's documented biology, and any keeping would be an experiment. This is a large, active, bottom-oriented sand-sifter that would need a correspondingly large tank — well over 105 US gal for a single adult, more for a group — with a deep bed of fine sand it can actually sift, since the sifting behaviour is central to how the fish feeds and behaves; gravel is unsuitable. Water should mirror the warm, soft, acidic blackwater it comes from: temperatures around 24 to 29 degrees Celsius and a distinctly acidic to neutral pH (roughly 6.0 to 7.5 as a safe captive range, lower if blackwater conditions are recreated), with very soft water and strong, well-oxygenated but not torrential filtration to cope with the waste load of a large sediment-feeder. Tankmates would need to be robust, similarly sized, warm-soft-water species; small fishes risk being treated as food or simply outcompeted at the bottom. Because it is a non-pair-bonding maternal mouthbrooder rather than a substrate spawner, any breeding attempt would centre on conditioning a group heavily on live and meaty foods (including snails, which suit the crushing pharyngeal mill) and watching for a male to colour up and court. In short: a striking, manageable-in-principle but seldom-seen fish for the specialist with space, not a community-tank cichlid.
Conservation
Tylochromis pulcher is assessed on the IUCN Red List as Least Concern (assessed in 2009, published 2010; assessor T. Moelants). The listing reflects a species that, while endemic to one country, is distributed across a sizeable and relatively intact block of central-Congo habitat — the Tumba and Mai-Ndombe lake systems and their connected rivers — much of it remote, sparsely populated and, in places, within protected areas such as the Salonga complex to the north. The population trend was recorded as unknown at assessment. The broader Mai-Ndombe (Cuvette Centrale) ecoregion is considered poorly explored ichthyologically, so local abundance and any fine-scale declines are not well quantified. The most plausible long-term pressures on a fish of this kind are the generic ones facing central-Congo freshwater systems — artisanal and subsistence fishing of lake stocks, deforestation and land-use change in the surrounding flooded forest, and the disruption of the seasonal flood pulse on which the productivity of these blackwater lakes depends — rather than any threat specific to the species. None of these is documented as currently driving a decline in Tylochromis pulcher, but they form the backdrop against which its status should be read.