Taxonomy & naming
The African jewelfish was described by the French naturalist Henri-Émile Sauvage in 1880 as Rubricatochromis letourneuxi, in a short note on fishes collected by M. Letourneux in Épire, at Corfu, and in Lake Mareotis (Lake Mariout), the brackish coastal lagoon behind Alexandria in northern Egypt that serves as the type locality. The original series survives as syntypes split between the Natural History Museum in London (BMNH 1898.2.15.1, ex MNHN) and the Muséum national d'Histoire naturelle in Paris (MNHN A-5250). Two of Sauvage's own names fall into synonymy: Hemichromis saharae Sauvage, 1880 and Hemichromis rolandi Sauvage, 1881; the epithet is also frequently mis-spelled 'letourneauxi' in the older literature. The genus Hemichromis was erected by Wilhelm Peters in 1858 for the West African jewel cichlids, and letourneuxi belongs to the so-called 'five-spot' jewel-cichlid lineage that Paul Loiselle treated as the Hemichromis fasciatus species group in his 1979 revision of the genus (with an updated key in 1992); this is the assemblage of larger, more elongate, comparatively muted jewels, as distinct from the brilliant red 'two-spot' aquarium jewels of the bimaculatus/guttatus/lifalili groups. A molecular phylogeny and revision by Lamboj & Koblmüller (2022) split Hemichromis, moving the savannah jewels into a new genus, so that the species now appears in FishBase and the Catalog of Fishes as the valid combination Rubricatochromis letourneuxi; the long-familiar name Rubricatochromis letourneuxi remains in near-universal use in the conservation, invasion-biology, and hobby literature and is retained here.
Morphology
Rubricatochromis letourneuxi is a small cichlid with a fairly long, slender body and a rounded caudal fin. Loiselle (1979) gave a maximum of 4.5 in standard length and FishBase lists 4.5 in SL, but most wild fish are considerably smaller — around 3 in on average. The dorsal fin carries 13–15 spines and the anal fin three. Background colour is highly variable, shifting with sex, season, habitat and mood from greenish-yellow through red-brown to nearly black; a dark lateral blotch sits above the lateral line on each flank, with smaller spots on the gill-cover tab and the caudal peduncle (the 'five-spot' pattern of the group). Fine blue iridescent spangling is scattered over the head, body and fins and intensifies in breeding fish. Crucially for anyone who knows the brilliant aquarium jewels, wild-type letourneuxi is comparatively plain: it lacks both the whole-body crimson and the dense blue spangling that the trade prizes in red jewels such as Hemichromis lifalili. Sexual dimorphism is modest and is clearest at spawning, when both sexes deepen in colour and ripe males in particular develop red wash on the gill region and ventral surface; outside breeding the sexes are difficult to separate on colour alone.
Habitat
The native range spans the northern half of Africa in a broad band from the Nile drainage west to Senegal, and from the North African and Saharan fringe south to the Ivory Coast — roughly 4°N to 35°N. Across this range it is, in FishBase's phrasing, a 'savannah-associated species which prospers in a range of lentic habitats,' from brackish coastal lagoons (the type locality at Lake Mareotis is one) through large lakes and Saharan oases to seasonally flooded riverine plains. It haunts the vegetated margins and fringes of these still and slow waters rather than open channels. The species is notably tolerant of a wide chemical envelope: FishBase records a pH from about 6.0 upward and hardness from roughly 5 dH up, and field and laboratory work on the Florida population has shown it to be strongly euryhaline (surviving salinities up to about 50 parts per thousand, well into seawater strength) and remarkably resistant to hypoxia, an ability thought to let it exploit oxygen-poor, seasonally drying wetlands that exclude many competitors. As an introduced fish in Florida it occupies shallow vegetated or rocky margins of marshes, canals, culverts, tidal creeks and river banks over mud and sand — essentially the same shoreline-and-shallows niche it fills at home. Depth is not a meaningful axis for it: it is a shallow-water fish of the top metre or so of the water column.
Feeding
Rubricatochromis letourneuxi is an omnivore with a strong tilt toward carnivory — an opportunistic predator of small animals rather than a specialist. In its native waters it has been recorded feeding on the freshwater shrimp Caridina and on insects, and Nile and Sudd-swamp surveys place it among the small invertivore-piscivores of the floodplain. The Florida invasion has been studied in far more detail. The first dietary work there (Hogg, 1976) found filamentous algae, insect parts, juvenile cichlids (including its own young) and a good deal of plant matter, while later studies (Loftus et al. 2006; O'Connor & Rothermel 2013) concluded the diet is primarily small fishes and macroinvertebrates — shrimp, other crustaceans and insects — with the mix tracking whatever prey the season makes available. Feeding is heaviest as the marshes dry down and prey become concentrated in shrinking pools and limestone 'solution holes,' where the jewelfish preys heavily on native Eastern mosquitofish (Gambusia holbrooki) and other small fauna. Its trophic flexibility, fast growth and willingness to eat almost anything of the right size are a large part of why it establishes so readily.
Mating
Like all jewel cichlids, Rubricatochromis letourneuxi forms monogamous pairs, and the pair bond is durable — once formed, mates are reported to stay together for life. As a pair comes into spawning condition both fish intensify in colour and the brilliant blue spangling of the breeding dress becomes more pronounced, the male flushing red on the gills and belly. The pair then selects and cleans a spawning site, typically a flat rock or other firm surface, which the male defends vigorously while courtship proceeds; he pursues the female energetically to bring her into spawning. This is the same biparental, territorial, advanced-parental-care system that runs through the genus, and it is precisely this combination — site fidelity, strong pair bonds and aggressive defence of a nest — that makes the species both a tenacious colonist and, where introduced, a competitor able to crowd native fishes off their own spawning grounds.
Breeding
Rubricatochromis letourneuxi is a biparental open-substrate spawner. The female lays her eggs in rows across the cleaned flat surface and the male fertilises them in the manner typical of substrate-spawning cichlids; reported clutches run large for so small a fish, up to roughly 600 eggs. During incubation the labour divides in the usual jewel-cichlid way — the female tends and fans the eggs while the male holds the perimeter of the territory. The eggs hatch in about 72 hours, after which the wrigglers are shifted into one or more shallow pits dug in the substrate near the spawning site, then guarded and herded as free-swimming fry by both parents. In the wild, ripe and spent fish are most common early in the flood season, tying reproduction to the seasonal pulse of rising, prey-rich water. This advanced parental care, paired with high fecundity and fast growth, gives the species a high reproductive resilience (FishBase estimates a minimum population-doubling time under 15 months) and underpins both its success at home and its explosive spread where it has been introduced.
In the aquarium
The African jewelfish is a hardy, undemanding cichlid that has been kept in the hobby for decades, though wild-type Rubricatochromis letourneuxi is far less showy than the fire-red jewels (Hemichromis lifalili, Hemichromis bimaculatus, Hemichromis guttatus) usually sold under the 'jewel cichlid' name, and most aquarists who want a jewel cichlid will end up with one of those instead. It is nonetheless a perfectly keepable fish for someone who wants the genuine article. A single pair can be housed in a modest tank — on the order of 20–30 US gal — but because jewels become single-mindedly territorial and combative when breeding, a longer tank with broken sightlines, rockwork and planted cover greatly reduces bloodshed; this is not a community fish for small peaceful tankmates, which it will harry, out-compete and, if small enough, eat. The species is exceptionally tolerant of water chemistry: it does well across roughly pH 6.5–8.0 and accepts soft to fairly hard water, reflecting a wild range that runs from soft floodplain pools to brackish coastal lagoons, and it shrugs off warm temperatures, low oxygen and even substantial salinity. A temperature in the mid-to-high 20s °C (about 75–82 °F) suits it; the 72–77 °F figure often quoted for the species traces to aquarium-atlas recommendations rather than a hard limit. Feeding presents no difficulty — it takes flake, pellets and especially live or frozen meaty foods (bloodworm, brine shrimp, small crustaceans) with relish. The honest caveats are behavioural rather than technical: provide a flat stone or two as a spawning surface, expect intense aggression once a pair forms, and keep only robust, similarly sized tankmates (or a species tank). And the standing warning for any jewel cichlid applies with special force here — never release unwanted fish or tank water into local waterways, because this is precisely the species whose aquarium-trade escapes founded the Florida invasion.
Conservation
The IUCN Red List assesses Rubricatochromis letourneuxi as Least Concern (assessed 11 March 2020 by I. Diallo; published 2020), reflecting its very wide distribution across northern and central Africa and the absence of any identified range-wide threat; the assessment notes that no information is available on population trend. It carries no CITES listing and is harmless to humans. Within its native range it is a common, adaptable habitat generalist rather than a species of concern, and it is harvested only modestly for the ornamental trade. The species' real conservation story runs the other way. Introduced to canals near Miami and first reported in 1965 — for decades misidentified as Hemichromis bimaculatus — it is now firmly established across southern Florida, recorded from at least eighteen watersheds from the Everglades and Florida Keys to Tampa Bay and the Caloosahatchee, and still expanding northward and westward; a single Puerto Rico record remains taxonomically uncertain. The U.S. Fish and Wildlife Service screens it as a High overall invasion risk. Mesocosm and field studies in the Everglades show it can depress populations of native snails, grass shrimp and small fishes through predation, prey heavily on native mosquitofish in dry-season refuges, and suppress the spawning of native sunfish through aggression. It is, in short, a fish of no conservation concern at home that has become a documented problem abroad — a cautionary case in the ecology of the aquarium trade.