Taxonomy & naming
Aphyosemion bitaeniatum was described by Ernst Ahl in 1924, an authority rendered in parentheses in the Catalog of Fishes combination because the species has been transferred between genera since its original description. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) retains the valid combination as Aphyosemion bitaeniatum (Ahl, 1924), placing it within the large and species-rich African killifish genus Aphyosemion, family Nothobranchiidae (African rivulines).
The species has attracted taxonomic attention at the genus level because recent molecular work places several West African Aphyosemion — including bitaeniatum — in a clade that some authors treat as the separate genus Chromaphyosemion (Class 10 of the AKA classification scheme). The American Killifish Association lists the species under Class: Chromaphyosemion on its species registry. The name Chromaphyosemion bitaeniatum therefore appears in some hobby and trade literature alongside the traditional Aphyosemion placement; the Catalog of Fishes continues to treat Chromaphyosemion as a subgenus or synonym, so Aphyosemion bitaeniatum remains the nomenclaturally valid name under current practice. The IUCN assessment by Lalèyè and Olaosebikan (2020) likewise uses Aphyosemion bitaeniatum.
The specific epithet bitaeniatum derives from the Latin bi- ('two') and taenia ('band' or 'stripe'), a direct reference to the paired lateral stripe pattern that is characteristic of the species and that gives it its common English name, the two-striped killifish or two-striped aphyosemion.
Morphology
Aphyosemion bitaeniatum is a slender, laterally compressed killifish reaching a maximum total length of approximately 2 in (FishBase). Males are considerably more ornate than females: the body ground colour ranges from olive-gold to warm brown, overlaid with rows of red or rust-coloured spots and blotches that may coalesce into a reticulate pattern, and the flanks typically carry the two lateral stripes that give the species its name. The caudal, dorsal, and anal fins are extended and richly pigmented in males, often displaying contrasting red, blue, or orange markings edged with white or yellow.
Females are plainly coloured — dull olive or brownish with little or no fin extension — a dimorphism that is pronounced and immediately visible, making sex identification straightforward even in juveniles approaching maturity. The two-banded pattern is most clearly expressed in females and subdominant males.
Like all Aphyosemion, the species has a terminal or slightly upturned mouth adapted for surface or near-surface feeding, large eyes, and a relatively soft-rayed dorsal fin positioned well back on the body above the anal fin — a silhouette common to the non-annual African rivulines.
Habitat
The natural range of Aphyosemion bitaeniatum covers the coastal lowlands of southern Togo, southern Benin, and southern Nigeria — a strip of West African terrain lying south of the savanna zone, where the drainage flows through patches of lowland rainforest and secondary forest on quaternary sediment soils before reaching the Gulf of Guinea. The species inhabits small brooks, shaded forest streams, and seepage zones rather than large rivers, and is benthopelagic in habit — occupying the lower and mid water column near plant growth, roots, and leaf litter.
Water conditions in these habitats are characteristically soft and slightly acidic, stained brown by tannins leaching from leaf litter and decaying vegetation on the sandy or loam substrate. FishBase records a pH range of 5.8–7.2 and a temperature range of 72–75 °F, consistent with the relatively stable, shaded microhabitat provided by the forest canopy. These are permanent or near-permanent watercourses, not seasonal pools — the ecology that defines the non-annual life history of the species.
The American Killifish Association has documented 96 collection localities for bitaeniatum across its range, with named population localities concentrated in southwestern Nigeria (including the Lagos area, Meko, and Ijebu Ode), southern Benin (Zagnanado), and Togo, reflecting the fine-scale geographical structure typical of West African forest killies.
Feeding
In the wild, Aphyosemion bitaeniatum feeds primarily on small invertebrates — aquatic and terrestrial insects, insect larvae, microcrustaceans, and worms — captured at or near the water surface and in the lower water column. The upturned mouth and alert, forward-facing eyes are adaptations for picking off items that fall onto or drift across the water's surface film, a foraging strategy shared across most of the non-annual Aphyosemion.
In the aquarium the species is straightforward to feed. It accepts live and frozen invertebrate foods readily — Daphnia, Cyclops, bloodworm, white mosquito larvae, and small earthworms are all taken with enthusiasm — and will usually adapt to high-quality dried micro-pellets and flake over time. A varied diet of live or frozen invertebrates produces the best colouration and conditioning for breeding. The fish are active and visually-guided hunters; feeding should be targeted to ensure individuals of different sizes all receive adequate food, as dominant males may monopolise feeding stations.
Mating
Aphyosemion bitaeniatum is a non-annual killifish with a plant-spawning reproductive strategy. Pairs or small trios (one male, two females) engage in spawning bouts that are distributed over days and weeks rather than concentrated in a single event. The male courts the female through lateral displays that show off his extended fins and vivid colouration; after a brief chase or circling, the pair move close to a clump of fine-leaved vegetation, floating roots, or a spawning mop and position themselves side by side.
The female deposits a small number of adhesive eggs — typically one to a few eggs per spawning embrace — which she and the male simultaneously fertilise as they press together momentarily. The eggs adhere to the plant or mop fibres rather than falling to the substrate. This sequence is repeated multiple times per day across many days, building up a clutch of individually scattered eggs rather than the large communal mass characteristic of broadcast spawners. No peat burying, diapause, or drying period is involved — the eggs develop continuously in water.
Males are persistent in courtship and can harass females to exhaustion if a single pair is kept without adequate cover or a second female to distribute attention. The ripe female's rounded belly and the male's intensified colour and fin display are reliable signals that a spawning bout is underway.
Breeding
Eggs of Aphyosemion bitaeniatum incubate in water at temperatures of 72–75 °F, typically hatching within 12–18 days depending on temperature. No diapause occurs: the developing embryos require constant, moist, well-oxygenated conditions throughout incubation, in contrast to annual species whose eggs tolerate months of dry storage in peat.
Hobbyists use either the pick-and-place method — inspecting the mop daily and transferring eggs individually to a separate shallow container of soft, slightly acidic water — or the mop-and-transfer method, in which the entire mop is moved to a rearing tank every one to two weeks and replaced with a fresh one. Both approaches prevent the parents from eating the eggs. Infertile eggs turn white and should be removed promptly to prevent fungal spread.
Fry hatch at approximately 0.5 in and become free-swimming within a day. First foods are micro-sized live organisms: infusoria, freshly hatched Artemia nauplii, or commercial powdered fry food. Growth is steady in soft, acidic, clean water with regular small water changes; fry reach sexable size at around 6–8 weeks and adult size by three to four months. The hobby literature in the Journal of the American Killifish Association (25 issues with bitaeniatum coverage) provides a thorough reference for strain-specific breeding notes and the management of the multiple named population lines.
In the aquarium
Aphyosemion bitaeniatum is well established in the specialist killifish hobby and is one of the more accessible West African non-annual killies for aquarists new to the genus. A small species tank of 10–15 US gal is adequate for a breeding trio; subdued lighting, a dark substrate, and a background of floating plants or broad-leaved vegetation recreate the shaded forest-stream aesthetic and bring out the male's colour to best advantage. Spawning mops of fine wool or nylon hung in the water column serve as both cover and egg-catching substrate.
Water chemistry should be soft and slightly acidic to neutral — pH in the range of 6.0–7.0, hardness low to moderate, temperature 72–75 °F — consistent with the wild range recorded by FishBase. Regular water changes of 10–20% weekly maintain the clean, tannin-influenced conditions the species prefers and are important for successful breeding. A tight-fitting lid is essential, as killies are capable jumpers.
The species is best kept as a species tank or with small, peaceful, similarly sized fish that occupy different water layers. Avoid housing with fin-nippers or active, competitive species that may stress the male or out-compete for food. Multiple population strains circulate in the hobby — Lagos Red, Meko, Ijebu Ode, Zagnanado, and others — and hobbyists typically maintain strains separately to preserve locality integrity, following the AKA's strain-labelling conventions.
Conservation
The IUCN Red List assessment of Aphyosemion bitaeniatum, carried out by Lalèyè and Olaosebikan and published in 2020 (version 2025-2), places the species in the Least Concern category. The assessment reflects its comparatively broad range across the coastal lowlands of southern Togo, Benin, and Nigeria, and the presence of 96 documented collection localities spanning multiple drainages and watershed systems — a distributional breadth that buffers the species against localised habitat loss.
Nevertheless, the coastal West African lowlands face substantial and ongoing pressure from deforestation, agricultural expansion, urban development, and drainage modification. The narrow shaded forest streams that bitaeniatum favours are vulnerable to degradation when riparian forest is cleared: increased siltation, elevated water temperature, and altered hydrology can rapidly make a brook unsuitable for a species adapted to cool, shaded, stable-chemistry conditions. The concentrated populations in the Lagos metropolitan region in particular occupy habitats under severe urban and industrial pressure.
The AKA's documentation of 96 collection localities is a valuable baseline for future monitoring, and the active captive population in the killifish hobby — including multiple named locality strains held by specialist breeders — provides an insurance population for the species. Maintaining strain integrity and supporting field surveys in less well-studied parts of the range (particularly southern Togo and central Benin) would strengthen the conservation picture considerably.