Taxonomy & naming
Haplochromis curvidens was described in 2022 by Nathan Vranken, Maarten Van Steenberge, Annelies Heylen, Eva Decru and Jos Snoeks in a monograph in the European Journal of Taxonomy (vol. 815) titled 'From a pair to a dozen: the piscivorous species of Haplochromis (Cichlidae) from the Lake Edward system.' That study examined every cichlid in Lakes Edward and George with a fish-eating body plan: where earlier workers had recognised just two formally named piscivores (Haplochromis squamipinnis and Haplochromis mentatus), the authors redescribed those two and added ten new species, of which curvidens is one. The holotype, a male, is catalogued at the Royal Museum for Central Africa in Tervuren, Belgium as RMCA 2016.035.P.0219, with paratypes held at the same museum and at the Royal Belgian Institute of Natural Sciences (IRSNB 919). The type locality is Lake Edward on the Ugandan side, at roughly 0°24' S, 29°46' E.
The name Haplochromis is a long-recognised problem in African cichlid taxonomy: it has historically been used as a 'catch-all' genus for hundreds of riverine and lacustrine haplochromines that almost certainly do not form a single natural group. The keywords of the describing paper explicitly flag the genera Harpagochromis and Prognathochromis — names Greenwood erected in his 1979–1980 attempt to break Haplochromis into smaller, more natural units — as the lineages to which the Lake Edward piscivores are most likely allied. The authors nonetheless retained the conservative Haplochromis heading rather than commit to a generic reassignment, and that is the name carried here. The species sits within the haplochromine assemblage of the Lake Edward system, part of the wider East African great-lakes radiation, and the paper places it among the 'microdontic' piscivores — those with many small teeth, as opposed to the 'macrodontic' group with few large ones.
Morphology
Haplochromis curvidens is a small cichlid, reaching about 4.5 in in standard length (the largest measured specimen was 4.5 in SL). The fin counts are typical of the genus: 15–16 dorsal spines with 8–10 soft rays, three anal spines with 8–9 soft rays, and 29–31 vertebrae. The body is comparatively slender and shallow for a piscivore — body depth runs 29.0–32.0% of standard length — with a relatively shallow cheek and lacrimal.
The diagnostic feature, and the source of the name, is the dentition. The outer row of the jaws carries many small, strongly recurved teeth — 45 to 60 of them in the upper jaw, a notably high count. This 'microdontic' arrangement separates curvidens from the lake's large-toothed piscivores such as Haplochromis latifrons, Haplochromis mentatus, Haplochromis rex and Haplochromis simba, which carry far fewer (22–47) but larger teeth. It is further distinguished from its closest microdontic relatives by a combination of fine proportional differences: a shallower cheek than Haplochromis kimondo, Haplochromis falcatus and Haplochromis quasimodo; narrower lower jaws than Haplochromis kimondo; a shorter pre-dorsal distance than Haplochromis falcatus; and a shallower body than Haplochromis quasimodo and Haplochromis squamipinnis. It lacks the well-defined mid-lateral band seen in some of its congeners.
Colour in life is muted. Non-dominant males are described as dusky green with a blue sheen and five to seven faint vertical bars; specimens range from faint yellow to dusky green and, unlike the speckled-to-black Haplochromis pardus, are never strongly marked. The breeding (dominant-male) colour pattern — usually the most diagnostic trait in haplochromines — was unknown to the describing authors, who could not confidently assign nuptial coloration to this species. As in essentially all haplochromines, the anal fin of males bears egg-spots (ocelli) that function in spawning.
Habitat
Haplochromis curvidens is known only from Lake Edward, one of the smaller and shallower of the East African great lakes, straddling the border between the Democratic Republic of the Congo and Uganda within the Albertine Rift. Within the lake it has been recorded from inshore areas over muddy (mud-bottomed) substrates; FishBase classes it as a pelagic freshwater fish of the inshore zone. No depth range has been published for the species specifically, but the type and other material were taken in shallow, near-shore mud-floored habitat rather than the open or deep water, so it is best read as a fish of the shallow inshore band (on the order of the upper few metres).
Lake Edward itself is a warm, productive and strongly alkaline lake. Limnological surveys (e.g. Lehman 2002) describe surface waters that are well-mixed, mineral-rich and alkaline, with pH around 9, conductivity on the order of several hundred to roughly nine hundred microsiemens per centimetre, and surface temperatures in the mid-20s Celsius — broadly 75–81 °F. Unlike Lakes Victoria, Tanganyika and Malawi, Lake Edward lacks large open-water predators such as Nile perch (Lates) and the big pelagic characins, an absence that has shaped which niches its cichlid flock has been able to fill — including the suite of small piscivores to which curvidens belongs.
Feeding
On the strength of its body shape and dentition, Haplochromis curvidens is interpreted as a piscivore — a fish-eater — and that inference, rather than direct stomach analysis, is the basis of the classification; the describing authors call it 'most probably a piscivorous species.' Its place among the 'microdontic' piscivores, with many small, sharply recurved teeth rather than a few large fangs, suggests a predator suited to seizing and holding comparatively small, slippery prey: most likely smaller fish, including juveniles and other small haplochromines of the inshore mud-bottom community. The recurved teeth that name the species are a classic grasping dentition, angling backward to keep struggling prey from escaping the mouth. FishBase estimates a trophic level of about 3.4, consistent with a mid-level predator rather than an apex one. In the Lake Edward food web it occupies the small-piscivore guild that, in the absence of Nile perch and other large open-water hunters, is filled entirely by cichlids.
Mating
No courtship or social behaviour has been described for Haplochromis curvidens specifically — it is known only from preserved museum material, and the authors could not even establish its dominant-male breeding coloration. What can be said comes from the wider biology of haplochromine cichlids, which is well documented and remarkably consistent across the East African flocks. These fish are polygynous: sexually active males develop bright nuptial colours, hold or roam a small territory, and court passing females with lateral displays and quivering, advertising the egg-spots on the anal fin. Pair bonds are fleeting, lasting only as long as the spawning act, and the male provides no parental care. For curvidens the specifics of where and how males display remain undocumented; the muted, faintly barred appearance of the non-dominant males recorded so far is presumably set aside for a brighter, as-yet-unrecorded pattern when a male becomes reproductively dominant.
Breeding
Breeding has not been observed in Haplochromis curvidens, and no clutch size, egg count or developmental data exist for the species. Its reproductive mode is inferred from the overwhelming pattern across the haplochromine cichlids of the East African lakes, which are without known exception maternal mouthbrooders. In this strategy the female takes the fertilised eggs into her mouth — drawn in immediately after laying, with fertilisation often completed inside the buccal cavity as she snaps at the male's anal-fin egg-spots — and broods them there through hatching and the early free-swimming stage, releasing the fry only when they can fend for themselves and taking them back into her mouth at any threat. The male contributes nothing beyond fertilisation. Clutch sizes in small haplochromines of this size class are modest, typically a few dozen comparatively large eggs (congeners in the Lake Edward and Lake Victoria flocks commonly lay on the order of 20–60), reflecting the heavy investment that mouthbrooding demands; the exact figure for curvidens is unknown. Until the species is studied alive, all of this remains a genus-typical expectation rather than a direct observation.
In the aquarium
Haplochromis curvidens is essentially unknown in the aquarium hobby. It was described from museum specimens in 2022, has no established presence in the ornamental trade, and is not a fish that aquarists are likely to encounter. There is no body of keeping experience to draw on, and nothing species-specific can honestly be said about its requirements, temperament or breeding in captivity.
Were it ever maintained, the general principles for small Lake Edward and Lake Victoria haplochromines would apply. It is a strongly alkaline-water fish: hard, well-buffered water around pH 8–9 and a temperature in the mid-20s Celsius would mirror its native lake. As a small piscivore it would require live or meaty foods and could not be trusted with tankmates small enough to swallow; like most haplochromines, the males would be expected to be territorial and aggressive toward one another, so generous space and a sex ratio favouring females would be needed. None of this is a recommendation to seek the fish out — it is a wild endemic of conservation interest, not an aquarium subject, and is described here only for completeness.
Conservation
Haplochromis curvidens has not been evaluated by the IUCN Red List — a direct check of the Red List returns no assessment, so its status is formally 'Not Evaluated.' This is unsurprising for a species described only in 2022 and known from a single lake. It carries no CITES or CMS listing.
Absence of an assessment is not the same as security. The species is a narrow-range endemic confined to Lake Edward, and single-lake endemics are inherently vulnerable to anything that degrades that one water body. Lake Edward and its catchment, shared between the Democratic Republic of the Congo and Uganda and bordering Virunga National Park, face pressures common to the region: intensive and sometimes illegal fishing, shoreline and catchment disturbance, and the prospect of oil exploration in the rift. The wider lesson of the East African lakes — most starkly the collapse of Lake Victoria's haplochromine flock following the spread of introduced Nile perch — is that these small, ecologically specialised cichlids can disappear quickly when a lake's ecology is disturbed. Lake Edward has so far escaped a Nile-perch introduction, which is part of why its flock, including its many small piscivores, remains comparatively intact; sustaining that intactness is the species' best protection in the absence of a formal assessment.