Taxonomy & naming
Aplocheilichthys spilauchen was described in 1861 by the French zoologist Auguste Duméril, with the authority presented in parentheses because the species has since been transferred from the genus under which Duméril originally placed it. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) recognises Aplocheilichthys spilauchen (Duméril, 1861) as the valid name. The species has accumulated at least one junior synonym: Aplocheilichthys bensonii, cited by the American Killifish Association as an invalid name that once circulated in the older aquarium and scientific literature before being subsumed under the senior name.
The genus Aplocheilichthys belongs to the family Procatopodidae (the African lampeyes), a lineage of small, schooling killifish distributed across sub-Saharan Africa that are united by the distinctive iridescent supraocular organ — the 'lampeye' — above each eye. A phylogenetic study of Atlantic mangrove killifish (Bragança et al. 2021) placed A. spilauchen within the clade that colonised Atlantic coastal habitats and inferred an Early Miocene diversification for the group, consistent with the expansion of mangrove forests along the West African coast.
The species epithet spilauchen is compounded from the Greek spilos (spot, speck, blemish) and auchen (neck or throat), referring to a marked area on the anterior body — the meaning has sometimes been loosely rendered as 'spotted neck'. The common name banded lampeye references both the iridescent eye-organ and faint banding visible on the flanks.
Morphology
The banded lampeye is a slender, cylindrical killifish with a subterminal, slightly upturned mouth adapted for surface-feeding. FishBase records a maximum total length of 3 in for males; females are measurably smaller, reaching approximately 2 in TL. Sexual size dimorphism is thus pronounced: males are considerably longer and, in breeding condition, more intensely coloured.
The defining feature of the species — and the source of its common name — is the supraocular light organ: a crescent-shaped patch of iridescent blue-green tissue positioned above each eye. This structure, present in all procatopodid lampeyes, reflects available light and is thought to function in intraspecific recognition and schooling coordination in the murky, tannin-stained or turbid coastal waters the fish inhabits. The body colouration is otherwise subdued: a silvery to pale olive-grey ground with hints of blue iridescence on the flanks, and faint, irregular darker banding or mottling that gives rise to the 'banded' part of the vernacular name. The fins are largely hyaline, with males sometimes showing faint yellow or orange tinting on the dorsal and caudal fins in good condition.
Habitat
Aplocheilichthys spilauchen is predominantly a coastal brackish-water species, occurring along the Atlantic seaboard of West and Central Africa from the mouth of the Senegal River in the north to the Cuanza River in Angola. Within this range it is the dominant killifish of Atlantic mangrove ecosystems, as documented by Bragança et al. (2021), who describe its distribution as directly tracking the coverage of mangrove forest along the coast. It inhabits river mouths, estuaries, lagoons, tidal creeks, and the brackish swamps and backwaters associated with mangrove systems, as well as the lower reaches of coastal rivers where freshwater and saline water mix.
FishBase records a typical water temperature of around 82 °F, pH 8, and a hardness of approximately 12 dGH — alkaline, moderately hard, brackish conditions reflecting the coastal estuarine environment. The species has a well-developed tolerance of low salinity and thrives with a freshwater input component, but Bragança et al. note it has low resilience to salinity increase, making it sensitive to changes that push the estuarine environment toward higher, more marine salinities. In brackish conditions, egg production is significantly higher than in pure freshwater (Okyere et al. 2021), indicating that brackish water is the preferred reproductive habitat rather than a mere tolerance zone.
Feeding
As a surface-oriented schooling fish with an upturned mouth, the banded lampeye feeds primarily on small invertebrates — aquatic insect larvae, small crustaceans, zooplankton, and invertebrate material at or near the water surface. FishBase lists small invertebrates as the principal wild diet. The surface-feeding posture and habitat in mangrove tidal flats and coastal lagoons means the fish regularly encounters terrestrial and semi-aquatic invertebrate prey that falls or drifts onto the water surface as well as small aquatic organisms.
In the aquarium the species is undemanding and accepts a range of small live, frozen, and prepared foods. Daphnia, cyclops, frozen bloodworm, mosquito larvae, and fine-grade floating dried foods are all taken readily. Given the species' documented use in mosquito-larvae biocontrol research, the appetite for small dipteran larvae is clearly significant — a single school of banded lampeyes in a coastal water body can suppress mosquito larval populations measurably, a trait that has drawn scientific interest beyond the aquarium hobby.
Mating
Aplocheilichthys spilauchen is a non-annual, continuous spawner that reproduces in permanent brackish water throughout the year — a fundamental distinction from the seasonal annual killifish that bury diapausing eggs in drying substrates. As a lampeye, it belongs to a group characterised by continuous low-level egg deposition rather than explosive mass spawning events, and there is no dormant phase in the embryonic development.
Males court females within the school using the iridescent supraocular light organs as signals, displaying laterally to advertise size and condition. The courtship in lampeyes is typically brief; pairs separate from the school momentarily to spawn, then return to schooling behaviour. Spawning occurs continuously over a prolonged period rather than in concentrated seasonal bursts, which is consistent with the permanent nature of the mangrove and estuarine habitats the species occupies. The significantly higher egg production observed in brackish water compared to pure freshwater (Okyere et al. 2021) suggests that salinity may function as an environmental cue that promotes reproductive activity.
Breeding
Okyere et al. (2021) conducted a systematic study of spawning and embryonic development in this species, providing the most detailed breeding data available. The fish lays eggs on fine substrates — in experimental conditions a black spawning mop was significantly preferred over green, blue, or white mops — and eggs are non-adhesive, deposited continuously among the fibres of the mop or equivalent fine vegetation rather than adhering tightly to plant leaves as some egg-hanging killies do. Eggs hatch in approximately 230 hours (around 9.6 days) at standard tropical temperatures. Embryonic development proceeds rapidly: cleavage begins within 30 minutes of fertilisation, and organogenesis is underway by approximately 25 hours post-fertilisation.
In the aquarium, breeding is induced by maintaining slightly brackish conditions (a teaspoon of marine salt per 2.5 US gal as a minimum is often recommended) alongside dense fine-leaved plants or spawning mops. Eggs can be collected daily from the mop and incubated separately in small containers of shallow brackish water. Because the incubation period is relatively long at around ten days, vigilance for fungal infection is important; light methylene blue treatment is a common preventative measure. Fry are small at hatching and require infusoria or commercial fry powder as first foods before graduating to nauplii of Artemia and other small live or frozen fare. Growth is steady in warm, slightly brackish conditions.
In the aquarium
The banded lampeye is a peaceful, active schooling fish best kept in groups of eight or more, where the iridescent supraocular flash of the school becomes a striking display. A species aquarium or a carefully arranged community with other small, non-aggressive brackish-tolerant fish suits it well. The tank should be moderately planted with fine-leaved plants near the surface — Java moss, floating vegetation, or spawning mops serve both as shelter and as egg-deposition sites — with open water in the centre for schooling.
Water chemistry should reflect the estuarine origin: slightly brackish water with a teaspoon of marine-mix salt per ten litres, a temperature of around 79–82 °F, and a pH around 7.5–8.0. Soft, acidic water is not appropriate for this species and will suppress both health and breeding. Gentle filtration with minimal surface turbulence suits the surface-feeding habit. The species is hardy once established but, like many coastal brackish fish, can be sensitive to the sudden introduction to pure freshwater or dramatic salinity swings.
As a subject for hobbyists, the banded lampeye offers the reward of a continuously spawning fish that, if given the right brackish conditions, will produce fry without elaborate manipulation. It is not as widely kept as the more colourful annual killies, and obtaining healthy stock can require sourcing from specialist killifish associations or breeders, since it is rarely encountered in the mainstream trade.
Conservation
The IUCN Red List assessed Aplocheilichthys spilauchen as Least Concern in 2019, reflecting the species' wide coastal distribution from Senegal to Angola and its abundance as the dominant killifish in Atlantic mangrove systems. Nonetheless, the habitat it depends upon — coastal mangrove forest and estuarine wetlands — is among the most threatened coastal ecosystem types in West and Central Africa. Mangrove clearance for agriculture, aquaculture, fuelwood, and urban coastal development has reduced mangrove coverage across the species' range, and the freshwater input that sustains the low-salinity conditions the fish requires is increasingly affected by upstream water extraction, dam construction, and altered seasonal hydrology.
Bragança et al. (2021) note that the species has low resilience to salinity increase — a concern in the context of sea-level rise and reduced freshwater throughput to coastal estuaries, both consequences of climate change. While no immediate population collapse is documented, the combination of mangrove loss and shifting estuarine salinity regimes represents a long-term threat to the habitat matrix that supports this fish from Senegal to Angola. The species' value as a natural mosquito biocontrol agent in coastal wetlands adds an applied dimension to its conservation: healthy banded lampeye populations in mangrove swamps and coastal lagoons suppress Anopheles and Aedes larvae, and their local extirpation could have public health as well as ecological consequences.