Taxonomy & naming
The lamena was first collected in 1991 by the French cichlid explorers Jean-Claude Nourissat and Patrick de Rham, in the Mangarahara River and its tributary the Amboaboa, near the town of Mandritsara in the Sofia drainage of northwestern Madagascar. Nourissat formally described it in 1998 in the French aquarist journal Revue française des Cichlidophiles, and — believing it different enough from the established Madagascan cichlids to deserve recognition apart from them — he placed it in a new monotypic genus, Lamena, as Lamena nourissati. The holotype (MNHN 1997-4172, a 4 in fish) and four paratypes are held at the Muséum national d'Histoire naturelle in Paris. The separate genus did not last. When John S. Sparks and Paul Reinthal reviewed the Malagasy cichlids in 1999, and decisively in Sparks's 2008 monograph on the subfamily Etroplinae and the genus Paretroplus, the lamena was shown to nest firmly inside Paretroplus — as the small-bodied sister, with the closely allied Paretroplus tsimoly, to the larger P. lamenabe. Lamena Allgayer was therefore synonymized, and the valid name is Paretroplus nourissati (Allgayer, 1998), the parentheses recording the move out of its original genus. The older binomial Lamena nourissati still surfaces in hobby literature from the 1990s and early 2000s, but it has no current standing. Within Paretroplus — a Madagascar-endemic radiation in the ancient subfamily Etroplinae, whose only other living members are the Etroplus and Pseudetroplus of India and Sri Lanka — nourissati, tsimoly and lamenabe form a distinctive clade of rheophilic, elongate species set apart from the deep-bodied lake and floodplain damba.
Morphology
Paretroplus nourissati is the odd one out in a genus of disc-shaped fish: it is shallow-bodied and elongate, fusiform rather than deep, its body depth only about 38–44% of standard length where most damba are far stockier. It is also one of the smaller members of the genus, reaching about 6.5 in (6.5 in) standard length; aquarium males may run to roughly 6–8 in total length, with females staying about a third smaller. The fins carry 14–16 dorsal spines and 12–15 soft rays, and 7–8 anal spines with 10–13 soft rays. Its signature is color. In breeding condition the flanks blaze bright orange to reddish-orange, crossed by broad black vertical bars; the two central bars, which converge below the lateral midline, are far more prominent than the rest — a pattern it shares only with its larger relative P. lamenabe. The blood-red fins of ripe fish are what earned the FishBase name 'blood-finned Madagascar cichlid,' and the orange-red ground color is the source of the Malagasy name lamena, 'red one.' Sparks separates it from the otherwise similar P. lamenabe and Paretroplus tsimoly by the absence of the bluish-gray to bluish-black lips, lower jaw, cheek and belly those two species show, and from Paretroplus tsimoly specifically by lacking enlarged, lobed lips. It is further told from P. lamenabe by its shallower body, by pelvic fins that fall short of the anal-fin origin when folded back, and by its smaller adult size. The sexes differ chiefly in size and intensity: males grow larger and color up most strongly, while ripe females are rounder in the abdomen.
Habitat
The lamena is a Madagascar endemic with one of the most restricted ranges of any described cichlid. Its core distribution is the Amboaboa and Mangarahara rivers near their confluence, in the vicinity of Mandritsara in the Sofia River drainage basin of northwestern Madagascar (Mahajanga Province), at around 689 ft elevation; it is also reported from small neighboring lakes a few kilometers from the confluence, and later surveys located additional populations on the upper Amboaboa near Marotandrano and on the Anjombony River near Marovato. This is not a fish of still, deep water. Near the type locality the Amboaboa and Mangarahara are shallow, clear and low in turbidity, with a swift current broken by small cascades and riffles; the rivers flow over broad sheets of exposed bedrock, with a rocky substrate of scattered boulders interspersed with patches of sand. Paretroplus nourissati is rheophilic — it haunts the shallow, rocky, fast-flowing stretches and is frequently collected in swift water only a few inches deep, where it wedges itself under rocks in the riffles and cascades. Its streamlined body is plainly an adaptation to this swift-water life, a sharp contrast to the slow, vegetated floodplain and lake habitats favored by most of its genus. Recorded aquarium-keeping water for the species runs near-neutral to mildly alkaline and warm, consistent with the warm, clear, oxygen-rich streams it inhabits.
Feeding
No formal gut-content study of wild Paretroplus nourissati appears in the literature, and FishBase carries no diet record beyond a model-estimated trophic level of about 2.8 — the level of a low-end omnivore rather than a predator. In its rocky-riffle habitat, where it lurks under stones in fast water, the most plausible natural diet is small benthic invertebrates and the encrusting algae and organic film (aufwuchs) of the rock surfaces, taken from the substrate of the cascades it shelters in. In captivity it is unfussy and accepts the standard range of prepared and frozen foods readily, in keeping with an opportunistic, generalist feeder. Where most damba in the genus are robust molluscivores or floodplain omnivores, the slender, swift-water lamena is best read as a generalized stream forager; its precise wild diet remains undocumented and should be treated as inferred rather than measured.
Mating
Like its congeners, the lamena is a biparental cichlid that forms a pair bond and defends a territory around a chosen spawning site. Aquarium observation by Sonia Guinane and Dave Tourle gives a clear picture of courtship: a ripe male moves alongside a swollen female, quivering with fins erect, and she answers with the same trembling display, the pair intensifying their red coloration markedly as they bond. Several females may court a single male at once, and he may display to more than one before settling on a partner. Once paired, the two patrol the tank together and prospect for a spawning cavity, the male often glancing off and clearing a patch of sand outside the chosen site — a substrate-touching, nest-clearing behavior the same keepers noted in true Paretroplus before spawning. Pairs are territorial toward tankmates during this phase. The species is described as relatively aggressive toward its own kind compared with its close relative Paretroplus tsimoly, so in confined quarters the courtship can carry real risk to subordinate fish, and plentiful cover is needed to let lower-ranked individuals stay out of the way.
Breeding
Paretroplus nourissati is a biparental substrate spawner that lays its eggs on the roof of a cave or sheltered surface, in the manner of its genus. In aquaria, females have selected small terracotta caves and laid their adhesive eggs on the cavity ceiling, with the male following to fertilize; clutches are modest — a related aquarium spawning of the sister form produced about 60 eggs — consistent with the small-to-moderate clutches typical of the genus rather than the large broods of open-water spawners. Care of the eggs follows an unusual, reversed division of labour shared with its close relative Paretroplus tsimoly: it is the male that tends the eggs directly on the cave roof, while the female instead guards the surrounding territory — a complete reversal of the more familiar cichlid arrangement in which the female does the close brood care. The notable difficulty is that, unlike the generally reliable P. tsimoly, captive P. nourissati pairs frequently eat their own eggs, especially inexperienced or poorly matched fish; keepers have repeatedly watched males consume a clutch as it was being laid. The workaround developed in Europe and the United States is to strip the eggs and hatch them artificially, treated against fungus, though fry pulled too early become visibly distressed and early survival has often been poor — a problem some breeders trace to protozoan infection and water-quality issues rather than to the fish themselves. Successful spawnings and rearing have nonetheless been achieved (Patrick de Rham and others in Europe; Bolton Museum Aquarium in the UK; hobbyists in the US), making captive propagation a genuine, if demanding, conservation asset for a critically threatened fish. Larvae in a related spawning hatched in about four days and were free-swimming roughly six days later, schooling tightly near the surface in their first days.
In the aquarium
The lamena is a specialist's fish, kept by a small circle of Madagascan-cichlid enthusiasts and conservation aquaria rather than the general hobby, and it is rarely offered for sale. It is a slow grower; F1 fish have taken years to reach adult size in keepers' tanks. The single most important husbandry point is intraspecific tension: the species is comparatively aggressive toward its own kind, so a group needs a large tank generously furnished with rocks, tubes, driftwood and other refuges so that subordinate fish can escape dominant ones — keepers describe abundant hiding places as 'absolutely necessary.' Konings goes further, judging a species-only tank unsuitable for raising a group at all, and instead recommending six or more juveniles be grown on together in a mixed Madagascan cichlid community — explicitly not alongside other Paretroplus, and especially not Paretroplus tsimoly, which the lamena does not tolerate well. Even that approach is not foolproof; other aquarists report mixed results keeping groups of P. nourissati together regardless of tank format. One documented setup nonetheless housed a group of five sub-adults successfully in a 90-US-gallon (about 340-litre) species tank over an inert sandy substrate with rockwork and tubes; for a colony or a breeding group kept this way, that is a sensible minimum footprint, and larger is better.
These are warm, clear-water stream fish, and they should be given clean, well-oxygenated water with some movement rather than a stagnant tank. Reported maintenance conditions were about 79 °F (79 °F) with regular weekly water changes; the keepers' tap water was distinctly hard and alkaline (pH about 7.7–7.8, KH ~8, GH ~15 dH) and the fish bred in it, so the species does not appear to demand soft, acidic water. A practical target is roughly 72–82 °F and pH near neutral to mildly alkaline (about 7.0–8.0), with strong filtration and good current to mimic the riffles it comes from. Feeding is straightforward — it takes prepared, frozen and live foods readily. The chief difficulties are not diet or chemistry but behavior: pairing the fish without bloodshed, and getting pairs to keep rather than eat their eggs. A breeding tank should offer several cave-type spawning sites (terracotta pots and pipes), and keepers intent on raising fry should be prepared either to manage a volatile pair carefully or to remove and artificially hatch eggs, with attention to fungus and protozoan control during rearing. Given the wild population's plight, every captive line maintained responsibly has real value.
Conservation
Paretroplus nourissati is one of the most threatened cichlids in the world. The IUCN Red List assesses it as Endangered (criterion B1ab(iii,v)), assessed on 26 June 2016 by Tsilavina Ravelomanana and John S. Sparks, with a decreasing population trend. The rationale is stark: the species is known only from the Sofia drainage — essentially the Amboaboa and Mangarahara rivers near their confluence plus a few nearby waters — with an estimated extent of occurrence under 5,0 mi², a single, fragmented location, and ongoing decline in habitat quality driven by deforestation, dams, drought and introduced exotic fishes. The defining blow came in the late 1990s, when a World Bank–financed dam was built on the Mangarahara above its confluence with the Amboaboa to allow year-round rice cultivation; this left the Mangarahara below the dam completely dry through the dry season, extirpating native fishes for kilometers downstream. The same river system gave rise to one of conservation's most famous fish stories — the 2013 ZSL London Zoo appeal for the 'world's loneliest fish,' the Mangarahara cichlid (Ptychochromis insolitus), a different species from the same desiccated drainage whose plight focused global attention on these waters. For the lamena itself, field surveys tell of steep decline: relatively common in the mid-1990s, it was hard to find even a single specimen at the Amboaboa–Mangarahara confluence by 2013, with only small numbers recovered at upstream sites. Against this, captive populations maintained by aquarists and institutions in Europe and North America represent a genuine insurance line, and disciplined ex-situ breeding is part of the species' best hope.