Taxonomy & naming
Ptychochromis loisellei was described by Melanie L. J. Stiassny and John S. Sparks in 2006, in a wholesale revision of the endemic Malagasy genus Ptychochromis (American Museum Novitates 3535) that named five new species and split off a sixth lineage as the new genus Katria. The holotype (AMNH 232462) and a paratype series held at the American Museum of Natural History, the Geneva natural history museum, and the Paris museum were taken at the type locality: the Mahanara River at Antsirabe-Nord, north of Sambava in the former Antsiranana Province of far northeastern Madagascar, just upstream of the bridge on national route N-5. The fish had been known to aquarists and field workers for several years before it had a name, circulating under a string of provisional labels — Ptychochromis sp. "nord-est" (de Rham & Nourissat, 2002), P. n. sp. "green garaka" (Sparks, 2003), and Ptychochromis sp. "Garaka" — that trace its slow recognition as a distinct form. Stiassny and Sparks placed it among the species they characterised as having the "eastern-type" palatine morphology, and the genus sits in the subfamily Ptychochrominae, the basal Malagasy radiation that, together with the Indian Etroplinae, occupies a position near the root of the cichlid family tree. The genus had been erected by Steindachner in 1880; loisellei is among its newest northeastern members, and no synonyms attach to the name.
Morphology
This is a moderately deep-bodied, laterally compressed cichlid with the high-backed profile typical of the family. Reported sizes vary by source and sex: the type series gave a maximum of about 4.5 in standard length (FishBase), while keepers and Paul Loiselle's own unpublished observations record males growing to roughly 8 in total length under good aquarium conditions, so the species is appreciably larger than the dry type-specimen figure suggests. Meristics run to 13–14 dorsal spines and 12–13 dorsal soft rays, three anal spines with 8–9 soft rays, and 27–28 vertebrae. The base coloration is an overall dark grayish-green — drab by the standards of the gaudy African and American cichlids, as is the rule for the genus — but the single diagnostic mark is unmistakable: an expansive, generally vertically oriented black band or cluster of black blotches set low on the body, below the lateral midline and just anterior to (and often extending over) the origin of the anal fin. No other Ptychochromis carries this pattern. The original describers also noted an apomorphic feature of the lower pharyngeal jaw — its tooth plate is laterally expanded at the front, obscuring the underlying bone when viewed from above. Sexual dimorphism is modest in everyday dress, but it sharpens at spawning time: breeding fish, especially males, flush from the dull green ground colour into an intense golden yellow, the trait behind the local name "garaka" and the trade epithet "green garaka."
Habitat
Ptychochromis loisellei is endemic to a small slice of northeastern coastal Madagascar centred on the Mahanara River and its tributaries near Antsirabe-Nord, in the high-rainfall belt inland of Sambava and Antalaha. Beyond the type basin it has been recorded from the lower Bemarivo and Fanambana rivers and from coastal lakes including Lake Mahatsara and Lake Nosiarina (Lake Mahatsara), but the entire documented range covers only about 5,0 mi². Drainages here belong to the Madagascar Eastern Lowlands freshwater ecoregion, a wet eastern-versant landscape of short, fast rivers running off the central highlands to the Indian Ocean. The species is a habitat generalist within that setting: it has been taken in clear, fast-flowing rivers and in clear to slightly turbid lakes alike, a flexibility consistent with the genus's reputation for hardiness and broad tolerance. Detailed in-situ chemistry has not been widely published; captive populations descended from wild stock thrive at roughly neutral, moderately soft water (around pH 7.5, ~230 µS/cm conductivity, ~3° KH carbonate hardness in zoo care), and the warm tropical lowland setting points to typical water temperatures in the mid-20s Celsius. As a low-elevation coastal fish it occupies shallow riverine and lake-margin water rather than any deep zone.
Feeding
Dedicated gut-content studies of wild Ptychochromis loisellei have not been published, but the available evidence points to a generalised omnivore. FishBase places it at a trophic level near 3.4, in the middle of the food web, and in captivity the fish is described as entirely unfussy — it takes commercial flake, frozen white, black and red mosquito larvae and brown shrimp, and live brine shrimp and mosquito larvae with no difficulty. Congeners in the genus are opportunistic feeders that work hard surfaces and the substrate for invertebrates, small prey, algae and detritus, and loisellei's robust jaws and the apomorphic, broadened lower pharyngeal tooth plate noted in its description are consistent with a diet that includes hard or tough items requiring crushing. In its native rivers and lakes it is best read as a mid-level benthic forager rather than a specialist, taking whatever small animal and plant matter its varied habitats provide.
Mating
Ptychochromis loisellei is a social fish best held in groups, and its pre-spawning behaviour reorganises that group around defended sites. Keepers maintain adults in shoals of roughly ten or more, ideally female-biased, precisely because pairs form within the group and unpaired or surplus fish need room to escape the territorial aggression that breeding triggers. As spawning approaches, both sexes deepen into the golden breeding colour and a pair claims and defends a spawning surface — typically a large stone or a patch of open bottom. The species is otherwise only moderately shy, but a settled pair becomes pointedly defensive of its chosen site, and intraspecific squabbling is the chief husbandry challenge: aggression can run high within the species even though the fish is not especially dangerous to unrelated tankmates. This is the standard biparental-substrate-spawner template of the genus, in which courtship and joint site defence precede an open-water spawning rather than any cave-sealing or mouthbrooding strategy.
Breeding
The blotched Madagascar cichlid is an open, biparental substrate spawner. Eggs are laid preferentially on stones (and sometimes directly on the bottom), in clutches reported up to about 400 eggs from breeding at Cologne Zoo. Parental roles are flexible: in different clutches keepers have seen the male alone tend the eggs — even driving the female off — while in others both parents shared brood care, or the male guarded first and the female took over later. A striking behaviour recorded in captivity is that the parents do not simply pick off fungused eggs; instead they relocate the remaining healthy eggs and larvae to a fresh spot in the tank, where development continues successfully. Free-swimming fry are escorted as a school by the attending parent(s) and were left with the adults until the next clutch came due before being reared on separately. The species is sensitive to disturbance during early larval care — a brief power cut, moving a root, or even an observer lingering too long at the glass has caused parents to abandon a brood — so quiet conditions are important while the young are small. Propagation has been achieved at an aquaculture facility in Andapa, Madagascar, and at several zoos abroad (first at Toronto Zoo, then Cologne), and the species is now bred for ex-situ conservation.
In the aquarium
Ptychochromis loisellei has only recently entered private aquaria — distributed to keepers from 2021 through the Citizen Conservation programme as a deliberate conservation-breeding effort — and the published husbandry comes mainly from the Cologne Zoo aquarium team led by Thomas Ziegler. It is rated as relatively easy to keep but capable of strong intraspecific aggression, so accommodation matters. A group of adults wants a tank at least 5 ft long holding 130 US gal or more; semi-adult groups of ten to twenty get by in a 39.5–47 in tank of roughly 40–95 US gal, and large fry schools can be grown on in 27.5 in/~200-litre tanks. Stocking as a group of about ten, with more females than males, spreads aggression and lets pairs form naturally — keeping a single antagonistic pair in a small tank is the common way to lose fish.
Décor should provide structure and sightline breaks: large stones (which double as spawning surfaces and hiding places), bogwood roots, and hardy plants such as Vallisneria, over a sand or fine-gravel substrate. The fish makes no special demands on lighting, so medium-brightness standard LED is fine. Filtration should be generous — an external or matten filter turning the tank volume over at least four times an hour — because stable, well-matured water is the foundation of success; the tank should be fully cycled before fish go in.
The species has proven tolerant of a range of water values. Cologne Zoo keeps and breeds it at about 75–77 °F, pH ~7.5, ~3° KH, and ~230 µS/cm — moderately soft, near-neutral, comfortably warm tropical water — and there is no need to chase soft, acidic extremes. Feeding is trouble-free: a varied diet of flake, frozen mosquito larvae and shrimp, and live brine shrimp and mosquito larvae keeps the fish in condition. The one husbandry trap, beyond simple overcrowding, is disturbance during brood care, which readily causes parents to eat or abandon a clutch; breeding tanks should be sited and serviced with that sensitivity in mind. Because every fish in the hobby traces to a tiny conserved population, keepers are encouraged to report spawnings and population counts back into the conservation network rather than treat the fish as an ordinary ornamental.
Conservation
The IUCN Red List assesses Ptychochromis loisellei as Endangered under criterion B1ab(iii), first assessed on 27 June 2016 by T. Ravelomanana and J. S. Sparks (with an amended version published in 2020), and the population trend is judged to be decreasing. The listing reflects a very small range — on the order of 5,0 mi² across the Mahanara, Bemarivo and Fanambana basins and a handful of coastal lakes — exposed to several converging pressures. The foremost is habitat degradation: Madagascar has lost over ninety percent of its original forest, and the resulting soil erosion pours suspended sediment into the rivers and lakes the fish depends on, altering its habitat. The species is also caught locally for human food, and it faces introduced competitors and predators — among them the blotched snakehead (Channa maculata) and Nile tilapia (Oreochromis niloticus) — that press on native fishes across the island. Local fishermen reportedly still find loisellei relatively common within the core of its range, but a habitat-specialist endemic with so small a footprint has little margin. It carries no CITES listing. Recognising the risk early, conservation breeding has been established both in Madagascar (an aquaculture facility at Andapa) and abroad through a zoo and Citizen Conservation network, an explicit insurance-population strategy for one of the many narrowly endemic, threatened cichlids of Madagascar's rapidly degrading fresh waters.