Taxonomy & naming
Otopharynx antron was described in 2009 by Rachel M. Cleaver, Adrianus F. Konings and Jay R. Stauffer Jr. in the journal Ichthyological Exploration of Freshwaters, in a paper titled 'Two new cave-dwelling cichlids of Lake Malaŵi, Africa' — the companion species being Otopharynx spelaeotes. The genus Otopharynx (Regan, 1920; revised by Eccles and Trewavas, 1989) is a group of laterally spotted, non-mbuna haplochromines endemic to the lake. The holotype of Otopharynx antron (PSU 4461.1, a 3.5 in SL specimen) was collected at Nametumbwe on the eastern shore. The authors diagnosed it against the other cave-associated Otopharynx — distinguishing it from Otopharynx spelaeotes and Otopharynx lithobates chiefly by its predominantly unicuspid outer jaw teeth, its smaller horizontal eye diameter, and its deeper caudal peduncle. The epithet antron is from the Greek noun antron, 'cave' or 'cavity,' a direct reference to the species' habit of living in and defending small caves; its addition, together with Otopharynx spelaeotes, brought the recognised Otopharynx species count to fourteen at the time.
Morphology
Otopharynx antron is a small to medium cave-hap, the largest known specimen reaching 4 in standard length. It is relatively deep-bodied, with the greatest body depth at the base of the seventh or eighth dorsal spine. The dorsal fin carries 16–17 spines and 9–10 soft rays, the anal fin 3–4 spines and 8–9 soft rays, and there are 29–31 scales in the lateral line — fewer than in the related Otopharynx argyrosoma. Its eye is notably large, 31.4–34.7% of head length, larger than in most other Otopharynx, an unsurprising trait in a fish of dim cave interiors. The caudal peduncle is comparatively deep. Diagnostically important are the oral teeth: the outer rows of both jaws are made up primarily of single-pointed (unicuspid) teeth, in contrast to the bicuspid-fronted dentition of many congeners, with 15–19 teeth in the outer row of the left lower jaw. This unicuspid armament, the authors suggested, points to a diet of larger or harder prey than the small bicuspid teeth of typical sand-sifting haps would handle.
Habitat
Otopharynx antron is, as its name announces, a cave fish. It is known from the eastern shore of Lake Malaŵi, between Gome and Nametumbwe in Malaŵi, over a depth range of about 33–197 ft. Males have been observed defending small caves with sandy floors — natural recesses and overhangs in the rocky substrate — primarily against other males of their own species. This is an intermediate, rock-and-sand habitat at moderate depth, deeper and more shadowed than the sunlit upper rocky zone where surface-loving mbuna swarm. Living in and around caves rather than out over open sand or in the water column sets Otopharynx antron apart from the many shoaling, open-bottom members of its genus, and aligns it ecologically with the handful of other cave-associated Otopharynx such as Otopharynx lithobates and Otopharynx spelaeotes.
Feeding
No quantitative gut-content analysis has been published for Otopharynx antron, but the describers drew an explicit functional inference from its teeth. The predominantly unicuspid outer jaw teeth, they noted, suggest a diet of larger invertebrates or even small fish — single-pointed teeth being well suited to seizing and holding sizeable, mobile prey, whereas the bicuspid 'comb' teeth of many haps suit scraping aufwuchs or picking tiny items. FishBase places the species at an estimated trophic level of about 3.4, consistent with a carnivore. In its cave and rubble habitat it most plausibly hunts the larger invertebrates — insect larvae, crustaceans and the like — sheltering in crevices and on the sandy cave floors, possibly supplemented by small fishes. As with much of its biology, this remains an informed inference rather than a documented diet.
Mating
Direct observations of spawning behaviour in Otopharynx antron are limited, but its territorial habits give an unusually clear picture for a member of this genus. Males defend small caves with sandy bottoms, holding these recesses chiefly against rival males — behaviour consistent with a cave or shelter being the focus of a male's display and breeding territory. As a Lake Malaŵi haplochromine, Otopharynx antron is a polygynous maternal mouthbrooder in which males court visiting females at their territories rather than forming pairs. The combination of a defended cave and male-male aggression suggests a system in which females are attracted to and select among territory-holding males within the rocky, cave-studded habitat, after which spawning and the transfer of eggs to the female's mouth take place. Finer details of courtship and the spawning act itself are not described.
Breeding
No detailed breeding account — clutch size, egg size, incubation period or fry development — has been published for Otopharynx antron. Like virtually all Lake Malaŵi haplochromines, it is a maternal mouthbrooder: the female takes the fertilised eggs into her buccal cavity and incubates them there, typically for about three weeks, before releasing free-swimming fry that may continue to shelter in her mouth when threatened. The egg-dummy ocelli on the male's anal fin, characteristic of the flock, are presumed to play their usual role in fertilisation during spawning. Given the cave-centred territoriality of males, spawning is likely to occur in or near the defended caves. All specifics remain undocumented for this species and are inferred from the reproductive biology shared across the Malaŵi haplochromine radiation.
In the aquarium
Otopharynx antron is, at most, a rarity in the aquarium hobby rather than an established trade fish. It is occasionally referenced and photographed by specialist Malaŵi cichlid keepers — Ad Konings, one of its describers, has documented it in the field — but it is not a routine import, has no widely used trade name, and lacks any substantial body of captive-breeding experience. Its moderately deep, cave-bound habitat makes it less readily collected than shallow shoreline species.
For the experienced Rift-lake keeper, the species' biology suggests fairly clear requirements should it become available: hard, alkaline Malaŵi water; a tank built around rockwork that provides genuine caves and overhangs with patches of open sand, mirroring the male's natural territory; and a carnivore-leaning diet of meaty frozen and prepared foods to suit its unicuspid, prey-seizing dentition. Males would be expected to be cave-territorial and aggressive toward conspecific males, so generous space and structure would matter. These remain extrapolations from its natural history, however, not a documented aquarium track record.
Conservation
Otopharynx antron was assessed by the IUCN Red List as Least Concern in 2018. The assessment reflects that, although it is a Lake Malaŵi endemic with a restricted known range along the eastern shore, it is not currently considered to face range-wide threats severe enough to warrant a higher category. That status should be read in the context of the lake as a whole, where intensifying artisanal and commercial fishing, sedimentation from catchment deforestation, nutrient runoff and the effects of a warming, more strongly stratified water column are recognised pressures on the cichlid fauna. A cave-associated, depth-restricted species could be locally sensitive to habitat disturbance and to changes in deep-water oxygenation, but on present evidence its populations are regarded as stable enough to qualify as Least Concern. Continued monitoring of Lake Malaŵi's rock- and cave-dwelling communities is the sensible safeguard.