Taxonomy & naming
The species was described by the Belgian ichthyologist Max Poll in 1952 from specimens taken off the coast of Moba, on the Congolese (then Belgian Congo) side of Lake Tanganyika, between about 15 and 197 ft depth; the holotype rests in the Royal Museum for Central Africa at Tervuren. The genus name blends the Greek plekein, "to fold," with odous, "tooth" — a nod to the unusual, blade-like recurved teeth the Perissodini use to scrape and grip; the epithet multidentatus simply means "many-toothed."
Nomenclature here is genuinely unsettled, and it is worth being precise. Eschmeyer's Catalog of Fishes lists the current valid combination as Perissodus multidentatus (Poll, 1952), following Konings' 2015 and 2019 treatments, while FishBase and much of the older literature retain Perissodus multidentatus. Several molecular studies have found Plecodus and Perissodus to be intertwined rather than cleanly separate, which is why the genus assignment keeps shifting; readers will encounter both names for the same fish. Whichever label is used, it sits within the Perissodini, the scale-eating tribe of the Tanganyikan cichlid flock, and phylogenetic work places it among the earlier-branching, less specialized members of that group rather than the extreme scale-eaters like Perissodus microlepis.
Morphology
This is a slender, laterally compressed cichlid built along the same general lines as the better-known Plecodus paradoxus, but smaller and more ornate. Reported maximum size is one of the clear conflicts in the literature: FishBase gives 4.5 in total length, while the specialist Tanganyikan reference tanganyika.si cites adults to roughly 9 in excluding the tail filament. The discrepancy probably reflects how few specimens have ever been measured — take the larger figure as the upper end seen by aquarists and the smaller as a conservative museum value.
The standout feature is the finnage. The species is described as the only known cichlid to develop a trailing filament exclusively from the lower lobe of the caudal fin, paired with more elaborate fin extensions and more complex body patterning than its plainer congeners. That ornamentation is not merely decorative: its overall coloration is thought to echo the deep-bodied, peaceful Benthochromis cichlids it shares deep water with — a case of aggressive mimicry, where a predator dresses like something harmless to get close to prey. The mouth carries the lineage's hallmark dentition — many small, recurved, multi-cusped teeth set in jaws that show the mild left-right asymmetry characteristic of the scale-eating tribe.
Habitat
Perissodus multidentatus is a Tanganyikan endemic, found nowhere outside the lake. Its documented distribution is thin: the type series came from Moba in the Democratic Republic of the Congo, and the handful of specimens that have reached the aquarium trade were reported from just south of Moba toward the Zambian shore. Whether it is genuinely localized or simply under-sampled lake-wide remains an open question.
It is an open-water fish rather than a rock-dweller, associated with zones where the bottom drops steeply away from shore. Depth reports vary — Poll's original description spans about 49–197 ft, while later sources extend the range to roughly 131–328 ft — placing it deeper than the brightly colored cichlids of the shallow rocky littoral and within the cooler, dimmer water where the sardine shoals and Benthochromis cruise. Like the rest of the lake's fauna it lives in hard, alkaline water, typically around pH 8.6–9.2 and high in dissolved minerals, with surface temperatures near 75–81 °F.
Feeding
The Perissodini are famous for lepidophagy — eating the scales of other living fish — and Perissodus multidentatus belongs to that guild, but with a twist. A stomach-content study of Tanganyikan scale-eaters found that fish skin (about 47.7%) and scales (about 46.8%) made up the bulk of its diet, with the scales drawn mainly from the lake's two endemic clupeid sardines (Stolothrissa and Limnothrissa). Tellingly, the scales were never found alone — always together with skin — suggesting this species bites off chunks of skin-and-scale from its prey rather than neatly flicking individual scales the way the hyper-specialized Perissodus microlepis does. FishBase places it at a high trophic level of about 4.4, consistent with a predator feeding on other fish.
That reliance on the open-water sardines, rather than on shallow-reef cichlids, sets it apart from most of its tribe and ties its fortunes to Tanganyika's vast pelagic food web. Larger individuals have also been suggested to take scales from deep-living Benthochromis tricoti and Benthochromis horii — which dovetails with the proposed mimicry of those species' coloration, letting the predator approach under cover of resemblance.
Mating
Courtship and spawning behavior in the wild are essentially undocumented, a direct consequence of how few people have ever observed the fish at depth. What can be said with confidence comes from the biology of the tribe: like other Perissodini, Perissodus multidentatus is a mouthbrooder, and the milder jaw asymmetry it shares with its relatives means individuals tend to approach prey — and likely rivals and mates — with a consistent left- or right-handed bias.
The broader Perissodini story is one of the most celebrated in evolutionary biology. In the closely related Perissodus microlepis, Michio Hori's long-term fieldwork showed the population is split into "left-mouthed" and "right-mouthed" individuals that attack prey from opposite flanks, with the rarer form enjoying a feeding advantage — a textbook case of frequency-dependent selection that keeps the two morphs in roughly equal balance. Perissodus multidentatus carries the same asymmetry in gentler form, a reminder that this small, obscure fish belongs to a lineage that has taught biologists a great deal about how variation persists in nature.
Breeding
Perissodus multidentatus is understood to be a maternal-style mouthbrooder, in keeping with the rest of the Perissodini, but the specifics are an honest gap: whether the female alone incubates the brood or both parents share the duty has not been established for this species, and no clutch counts, fry sizes, or brooding intervals have been published. The figures used in the data panel are therefore drawn from genus-typical mouthbrooding cichlids rather than from direct observation of Perissodus multidentatus.
What little is inferred follows the pattern of small Tanganyikan mouthbrooders — modest clutches of eggs taken into the female's buccal cavity, where they are incubated and the fry sheltered for a period after hatching before being released to fend for themselves. Anyone breeding it in captivity would be charting largely undocumented territory.
In the aquarium
For practical purposes, this is not a fish most hobbyists will ever keep. It is exported only sporadically and in tiny numbers, so there is no body of accumulated keeping experience the way there is for popular Tanganyikans — a search of the usual cichlid forums turns up essentially nothing species-specific, which is itself the honest takeaway. What guidance exists comes from a few specialist exporters and the deep-water, predatory nature of the fish.
The recommendations that do circulate point to an aquarium of at least roughly 100 US gal with plenty of open swimming space and only a few large, smooth stones, mirroring its open-water habitat rather than a rock pile. Hard, alkaline water and stable, well-oxygenated conditions are essential. The real challenge is its diet and disposition: a fish evolved to bite skin and scales off other fish is a poor neighbor, and keepers who have tried it report nipping and outright attacks, with a tank divider sometimes suggested to manage aggression, especially if breeding is attempted. Treat it as a specialist's curiosity, not a community fish.
Conservation
Perissodus multidentatus has not been evaluated for the IUCN Red List — FishBase records its status as "Not Evaluated," and a direct search of iucnredlist.org returns no assessment for the species under either Plecodus or Perissodus. It carries no CITES listing and faces no meaningful targeted fishery or collection pressure — it is too rare in the trade and too small to be a food fish. As an apparently lake-wide, open-water species rather than a narrow shoreline endemic, its extinction risk is plausibly lower than that of many micro-range rock-dwellers, but in the absence of a formal assessment that remains an informed inference rather than a documented conclusion.
The lake around it is the right frame for its long-term outlook. O'Reilly et al. (2003, Nature, doi:10.1038/nature01833) showed that climate warming has strengthened stratification and reduced the deep mixing that brings nutrients to the surface, cutting primary productivity with knock-on declines in fish yields. Cohen et al. (2016, PNAS, doi:10.1073/pnas.1603237113) found from paleoecological records that warming has shrunk the oxygenated benthic habitat in their study areas by about 38% and tracked declines in commercially important fishes. Because Perissodus multidentatus feeds largely on the pelagic clupeid sardines — the same Stolothrissa and Limnothrissa that anchor the commercial fishery feeding four nations — a warming-driven contraction of that open-water productivity, layered onto heavy fishing pressure, bears directly on this species through its prey base. Governance of those shared pressures falls to the four-country Lake Tanganyika Authority. The fair summary: an unassessed fish living in a strained lake, its fate tied less to direct exploitation than to whether Tanganyika's pelagic engine keeps running.