Taxonomy & naming
Coptodon gutturosa was described in 1992 by Melanie L. J. Stiassny, Ulrich K. Schliewen and Wallace J. Dominey in their landmark paper on the cichlid species flock of Lake Bermin, which erected eight new species of Tilapia at once (a ninth, Tilapia bemini, had been named by Thys van den Audenaerde in 1972). The species was originally placed in the catch-all genus Tilapia as Tilapia gutturosa, with the holotype (AMNH 98269) and an extensive paratype series (AMNH, MRAC and ZSM material) collected from Lake Bermin in the Nguti subdivision of Cameroon's South West Province, at roughly 5°09′30″N, 9°38′E. The specific name was treated by the describers as an adjective. For two decades the Bermin flock was carried under Tilapia, but Dunz and Schliewen's 2013 molecular phylogeny dismantled that polyphyletic assemblage and resurrected several older genus names; the Bermin radiation was transferred to Coptodon, so the fish is now validly Coptodon gutturosa (the masculine spelling Coptodon gutturosus also appears in FishBase and the Catalog of Fishes, a gender-agreement variant of the same name). All nine Bermin Coptodon trace to a single colonising ancestor closely allied to the widespread West African Coptodon guineensis, making them a textbook example of an extremely young, narrowly endemic adaptive radiation.
Morphology
This is a small cichlid: FishBase records a maximum of 2.5 in standard length, and even the largest Bermin Coptodon top out near 5.5 in, so gutturosa sits toward the lower-middle of the flock's size range. Meristically it carries 14–16 dorsal spines and 10–11 dorsal soft rays, three anal spines and 7–8 anal soft rays, with 13–16 gill rakers on the first arch. The diagnostic features the describers used are largely in the mouth and pharynx: a robust, massive lower pharyngeal jaw bearing a large heart-shaped tooth plate covered in numerous fine, regularly arranged teeth; oral-jaw teeth that are fixed and have non-spatulate crowns; a smooth lower-lip margin; and a lower jaw that is longer than it is wide. Distinguishing the nine Bermin species from one another is notoriously difficult — speciation here is so recent that the boundaries between forms are still blurry — and aquarium strains often blend traits. Body colour is a warm metallic brass, frequently with blue, swollen lips and, depending on mood, a dark belly keel. The most striking change comes with breeding: like its presumed ancestor Coptodon guineensis, gutturosa develops a deep red flush across the breast and throat in brood-care dress. Sexual dimorphism is modest and typical of substrate-spawning tilapiines, males tending to grow somewhat larger and more intensely coloured, but the sexes are not reliably told apart outside of spawning condition and venting.
Habitat
Coptodon gutturosa is endemic to Lake Bermin and occurs nowhere else. Bermin is a small volcanic crater lake on the Cameroon Line, the chain of extinct volcanoes running southwest-to-northeast through the country's highlands; it lies in the Western Equatorial Crater Lakes freshwater ecoregion (FEOW 519), alongside better-known Barombi Mbo, Ejagham and Dissoni. The lake is tiny — roughly 2297 ft across and little more than 0 mi² in surface area — and shallow, reaching only about 49 ft at its deepest. It has no inflowing streams and just one small outflow that ultimately drains toward the Cross River system, so the lake and its fish are effectively sealed off from surrounding rivers; that isolation is what allowed an endemic flock to evolve in place. Recorded water conditions are warm and gently buffered: surface temperature around 75 °F (about 75 °F), pH near 7.5, and low alkalinity. As warm equatorial water the species tolerates a broad envelope in captivity, roughly 75–86 °F and pH on the order of 6.5–8.0. Within the lake gutturosa is a benthopelagic fish of the shallows, where its eggs and fry are tied to the leaf litter, submerged wood and sediment of the littoral zone.
Feeding
Like most of the Bermin flock, Coptodon gutturosa is a generalist that grazes the lake's algal and detrital resources, but it shows a distinctive twist: FishBase reports that it prefers sponges, with smaller quantities of diatoms, plants (mostly algae) and detritus also turning up in stomach contents. Lake Bermin supports freshwater sponges, and the flock includes a dedicated sponge specialist (Coptodon spongotroktis) that has evolved to process the glassy spicules these sponges use for structure; gutturosa appears to exploit the same unusual food source to a lesser degree while remaining a broad feeder. This is consistent with the wider ecology of the flock, in which most species share a largely detritivorous, algivorous diet supplemented by aufwuchs, phytoplankton, plant matter and the occasional insect. The heavy, broad lower pharyngeal jaw and fine tooth plate fit a fish that crushes and processes tough, low-value material rather than one that hunts. In practical terms it is best regarded as a herbivore-leaning omnivore with a taste for things most cichlids cannot use.
Mating
Coptodon gutturosa is a pair-bonding, biparental species — behaviourally it resembles the more peaceful Central American substrate spawners (keepers compare the Bermin Coptodon to the smaller Amatitlania and other 'convict'-type cichlids). Outside of breeding it is sociable and not aggressive toward other species, but it can be scrappy with its own kind, and that edge sharpens dramatically once a pair commits to spawning. In the lake, spawning happens in the shallows and is colonial: FishBase, drawing on the original Bermin study, notes that the fish build loose breeding colonies of up to about six pairs, with adjacent nests separated by roughly 12 in. A pair forms, claims and defends a small patch of substrate, and the partners coordinate the cleaning of a spawning surface among the leaf litter and wood. Pairs are devoted but territorial; dominant females in particular will defend a brood fiercely and have even been seen to gather and adopt the fry of subordinate females, sometimes triggering serious squabbles when the rightful mother tries to reclaim them.
Breeding
This is an open, biparental substrate spawner — the ancestral tilapiine mode — with both parents guarding the brood. In the wild the eggs are laid and hidden among leaves and pieces of submerged wood in shallow water, within the colonial nesting arrangement described above. A clutch-size figure specific to gutturosa has not been published; as a small substrate-spawning Coptodon it lays a modest adhesive clutch on the order of a few hundred eggs (genus-typical for small Coptodon), which the pair fans and defends through hatching. The species matures and breeds at a strikingly small size: females of the Bermin Coptodon have been recorded spawning at under 2 in, and in the smallest relatives reproduction begins near 1 in. Parental care is biparental and thorough — these are tilapiines, and even young females raise fry competently — with the pair guarding free-swimming young that can take newly hatched brine shrimp, microworms and powdered fry foods from the outset. In aquaria the fish often deviate from their open-spawning habit and choose more sheltered sites, including the interiors of flowerpots or ceramic caves, but the biparental guarding behaviour is unchanged. Fry grow quickly, reaching breeding readiness themselves within roughly six months.
In the aquarium
The Lake Bermin Coptodon are well established among dedicated cichlid and conservation keepers, and gutturosa is a rewarding, manageable aquarium fish — small, hardy and a good parent — provided its one quirk is respected. Care is straightforward and generalises across the flock. A tank of at least 35.5 in is a sensible minimum even for these modest fish, because they can be a little quarrelsome with conspecifics; the standard advice is to start with a group of six to eight juveniles and let a pair form. Wild parameters are undemanding (around 75 °F, pH near 7.5, low alkalinity), and the species is adaptable enough that ordinary dechlorinated tap water within a temperature range of roughly 75–82 °F and pH 6.5–8.0 suits it without special treatment. Large regular water changes — on the order of 50 percent weekly to every ten days — plus robust biological filtration keep them in good condition. One caveat: members of this flock will nibble sponge filters (a legacy of the sponge-eating habit), so canister or hang-on-back filtration is preferable.
Furnish the tank to break up sight lines — driftwood, rock piles, ceramic caves and flowerpots laid on their sides — so subordinate fish can escape and so a spawning pair can be screened from the group. Plants are treated as food rather than décor: keepers report these fish eating even tough Anubias, Java fern and Java moss, so a planted aquascape will not last. Feeding is easy and should lean herbivorous: a quality vegetable-based cichlid or mbuna pellet, supplemented with greens such as blanched peas, spinach, broccoli and the like, with only occasional live or frozen treats — a high-protein, meaty diet is bad for them over time. Tankmates are not a problem in principle; the fish are peaceful toward other species and do well with mid-sized African tetras, larger barbs, rainbowfish or robust South American tetras. Avoid plecos and other algae-grazers, which compete for the same grazing space. The genuine difficulty is intraspecific and seasonal: when a pair spawns they turn aggressive, and it is best to move the other fish out (or have a tank divider ready) so the spawn does not trigger lethal fighting. Beyond that, the species is undemanding, breeds readily, and — because it is a Critically Endangered single-lake endemic and a CARES-priority fish — is genuinely worth keeping for the right hobbyist.
Conservation
Coptodon gutturosa is assessed by the IUCN Red List as Critically Endangered (criteria B1ab(iii)+2ab(iii)), assessed on 16 February 2009 by T. Moelants and published in 2010, with population trend listed as unknown. The listing reflects a single, overriding fact: the species' entire global range is one lake of barely half a square kilometre. Any localised disturbance — pollution, sedimentation, deforestation of the crater rim, introduction of a non-native fish, or over-collection — could imperil the whole population, and a single catastrophic event could extinguish the species outright. Cameroon's crater lakes are notorious for limnic eruptions, the sudden release of dissolved gas that killed more than 1,700 people around Lake Nyos in 1986 and can wipe out a lake's fauna; Bermin's shallowness makes such a turnover comparatively unlikely, but it remains a worst-case scenario for an endemic flock with nowhere to retreat. The whole nine-species Bermin radiation carries similar threatened listings for the same reasons of extreme range restriction. The species is not CITES-listed. Against this backdrop, ex-situ conservation matters unusually much: the Bermin Coptodon are maintained as CARES-priority species by hobbyist breeders, and that captive insurance population is a meaningful part of the species' long-term security.