Taxonomy & naming
Aphyosemion rectogoense was described by Albert Radda and Jean-Henri Huber in 1977, with the type locality centred on the Bateke plateau region of southeastern Gabon. The species epithet rectogoense references the former colony of French Congo (now Republic of Congo and Gabon), combined with the Latin rectus — in this context a directional reference to the eastern portion of the territory. The valid combination as recognised in the Catalog of Fishes (Eschmeyer, Fricke & van der Laan) is Aphyosemion rectogoense Radda & Huber, 1977.
Aphyosemion is one of the largest genera in the family Nothobranchiidae, encompassing several dozen described species of small West and Central African killies. The genus has historically been divided into a number of species groups based on colour pattern, distribution, and reproductive biology, though molecular phylogenetics has repeatedly reshuffled those groupings. Aphyosemion rectogoense is a non-annual species, occupying permanent or near-permanent watercourses — a mode shared with many forest-stream Aphyosemion but in contrast to the annual Nothobranchius and Fundulopanchax that rely on diapause to survive dry-season pool desiccation.
The taxonomy of the broader Aphyosemion complex remains an active area of revision. No subspecies of A. rectogoense are currently recognised in the Catalog of Fishes, though killifish collectors have historically documented locality variants from different collection points on the Bateke plateau that differ subtly in male colouration.
Morphology
Aphyosemion rectogoense is a slender, laterally compressed killifish reaching approximately 2 in total length in males; females are noticeably smaller, typically around 1.5 in. FishBase records a maximum of 2 in TL. The body form is typical of the genus: elongate and fairly cylindrical in the anterior half, tapering toward a slightly rounded caudal fin.
Males display the vivid colour patterning characteristic of Aphyosemion: a ground colour of blue-green to turquoise on the flanks, overlaid with rows of red to orange-red dots or dashes arranged roughly parallel to the lateral axis. The unpaired fins — dorsal, anal, and caudal — carry bold red and blue markings, often with yellow or white marginal bands. The caudal fin may show extension of the upper or lower rays. Females are considerably plainer, with a pale brownish to olive ground colour and little of the male's iridescent patterning; they are also distinguished by their smaller size and rounder belly profile when gravid.
The sexual dimorphism is pronounced, as is the rule across Aphyosemion: males are the ornamental sex, females the cryptic one. The bright male colouration is understood to function in both mate choice and male-male competition within this genus.
Habitat
Aphyosemion rectogoense is endemic to southeastern Gabon, specifically the Bateke plateau — a highland savanna landscape characterised by sandstone soils, open grassland, and gallery forest along watercourses. Its known range is centred on the upper drainages of the Lékoni-Djouya system and the upper M'passa, with collection records from near Leconi village and the Ossami and Djouele stream systems in the same region.
The streams it occupies are small, clear, and typically shallow — the clean sandy or gravelly brook habitats typical of African savanna plateau drainages. Water chemistry at collection sites is very soft and mildly acidic: the British Killifish Association records pH around 6.5 and hardness of approximately 2 dH from habitat surveys, reflecting the low-mineral sandstone runoff of the plateau. Temperatures are moderated by altitude and forest shade; reported ranges centre around 68–75 °F rather than the warmer temperatures of lowland West African streams.
Because the Bateke plateau streams are permanent rather than seasonally drying pools, A. rectogoense does not require diapause and its eggs do not enter dormancy — a direct consequence of the stable hydrological regime of its native habitat. The fish inhabits areas with submerged and marginal vegetation, roots, and leaf litter that serve both as cover and as egg-deposition substrate.
Feeding
Like most Aphyosemion, A. rectogoense is a micropredator feeding on small invertebrates in the wild. In the permanent forest-edge and savanna streams it inhabits, the diet is expected to consist of small aquatic insects, insect larvae, microcrustaceans, and other invertebrates of appropriate size — the typical prey base of a small surface-oriented killifish hunting in shallow, vegetated water.
In the aquarium, the species accepts a range of small live and frozen foods without difficulty. White worms, baby brine shrimp (Artemia nauplii), and similar small live foods are enthusiastically taken and are important for bringing fish into breeding condition. Killi.co.uk notes that pellets are accepted once fish are accustomed to captivity, but live and frozen foods should form the bulk of the diet. Good, varied feeding is noted as important for reliable spawning behaviour in this species.
Mating
Aphyosemion rectogoense is a non-annual, plant-spawning killifish. Pairs court in the lower and mid-water levels of the aquarium, with the male displaying his full colour to the female in a lateral broadside posture. Spawning occurs near the substrate or in the lower water column rather than at the surface, with the pair seeking out fine-leaved plants, spawning mops, or peat fibre into which they deposit individual adhesive eggs over a period of days to weeks.
The mating system is typical of non-annual Aphyosemion: pairs are not strictly monogamous and a male will court multiple females if they are present, though in a small aquarium a single pair or a trio (one male, two females) is the practical approach. Male colouration intensifies during active courtship, and the fish shows clear preferences for micro-habitat features — sheltered spots with plant cover — over open spawning in the water column. There is no bubble-nest building and no mouthbrooding; spawning is entirely substrate-directed and adhesive-egg-based.
Breeding
Breeding Aphyosemion rectogoense follows the standard non-annual Aphyosemion protocol. A small, well-planted aquarium — even a 3-gallon breeding tank is workable, as noted by Killi.co.uk — set up with dark substrate, low light, and a spawning mop or clump of fine-leaved plants near the bottom provides the essentials. Water should be very soft and slightly acidic (pH around 6.5, hardness 2 dH or lower), matching the habitat chemistry. Temperature is best kept in the cooler range for the genus: 68–73 °F, with the British Killifish Association reporting 75 °F as an upper end of their maintained range.
The pair should be conditioned on live or frozen small foods before being placed together. Eggs are deposited singly and adhere to plant leaves, mop fibres, or peat fibre over multiple sessions. Eggs can be collected periodically by hand-picking or by removing the mop to a shallow hatching container. Because the eggs are non-diapausing, they incubate in water at the same temperature — hatching typically occurs within two to three weeks depending on temperature. Fry are small and require appropriately sized first foods: infusoria or commercial fry powder initially, advancing quickly to microworm and newly hatched brine shrimp nauplii as the British Killifish Association recommends. The sex ratio at hatching is approximately equal, and the species is noted as average difficulty for non-annual Aphyosemion — accessible to a reasonably experienced killifish keeper.
In the aquarium
Aphyosemion rectogoense is maintained successfully in very soft, slightly acidic, cool water that mirrors the chemistry of its Bateke plateau streams. Killi.co.uk recommends keeping the temperature in the 68–73 °F range and emphasises low hardness; the species does not thrive in the warmer or harder water conditions that suit many other aquarium fish. A well-planted, low-light tank with dark substrate and a tight-fitting lid is the preferred setup. The fish is a capable jumper, as are most killies, and an uncovered aquarium will result in losses.
Aphyosemion rectogoense is not aggressive and is compatible with other calm, small fish of similar size that share its water-chemistry requirements. A species-only setup or a small community of similarly sized non-annual Aphyosemion is the most practical approach, since the soft, cool, acidic water needed by this fish excludes most community aquarium staples. The species is available through killifish specialist societies and dedicated breeders rather than the general trade; source fish from reputable keepers who can document the collection locality to ensure genetic integrity and avoid mixing populations.
Difficulty in the aquarium is rated as moderate — manageable for a keeper with some killifish experience but not ideal as a first killifish due to its specific water-chemistry and temperature requirements and its absence from mainstream retail channels.
Conservation
The IUCN Red List assessed Aphyosemion rectogoense as Vulnerable (VU) in 2009 (published 2010, assessed by Moelants). The Vulnerable designation reflects the species' narrow endemic range on the Bateke plateau of southeastern Gabon and the inferred threat from habitat degradation in that region. The Bateke plateau is subject to agricultural encroachment, burning, and — in parts — artisanal mining activity, all of which can affect the integrity of the small, clear-water streams on which the species depends.
As a single-locality endemic whose entire known range is confined to the upper Lékoni-Djouya and upper M'passa catchments in a few square kilometres of plateau savanna, A. rectogoense has inherently limited distributional resilience. Any significant degradation of its natal streams — through erosion, siltation, introduction of invasive species, or loss of riparian vegetation — could affect a substantial fraction of the global population. The species does not benefit from the buffer afforded by wide-ranging fish.
The killifish hobby maintains some captive stock of this species through specialist societies, which represents an informal ex situ reserve. However, captive populations are small and their long-term genetic health depends on periodic replenishment from the wild and disciplined record-keeping of collection-locality provenance. Formal conservation efforts in southeastern Gabon specifically targeting the highland savanna stream fauna remain limited; the species is likely to remain dependent on the stability of its plateau habitat for the foreseeable future.