Taxonomy & naming
Nothobranchius luekei was described by Hans-Otto Berkenkamp and Volker Etzel in 1992, with a type locality on Zanzibar, Tanzania. The species belongs to the genus Nothobranchius (family Nothobranchiidae), the East African annual killifishes — a group of roughly 90 or more described species distributed from the Sahel south to southern Africa, united by their annual life history in temporary savanna pools. Eschmeyer's Catalog of Fishes (CAS) is the governing authority for the valid name Nothobranchius luekei Berkenkamp & Etzel, 1992.
The genus name Nothobranchius combines the Greek nothos (false, illegitimate) with branchion (gill), a somewhat opaque coinage from the early systematics of the group; the word in practice simply names the genus rather than describing a diagnostic feature. The specific epithet luekei is presumed patronymic — named in honour of a collector or researcher whose contribution to fieldwork or the description supported the species' discovery, though the precise etymology has not been formally published in sources accessible to this atlas.
Morphology
Nothobranchius luekei is a small, laterally compressed killifish reaching approximately 1.5 in standard length. The body form is typical of the genus: moderately deep through the flanks, tapering to a fairly broad caudal peduncle, with a subterminal, upward-angled mouth suited to surface feeding and a distinctly rounded caudal fin.
Sexual dichromatism is pronounced, as in most Nothobranchius. Males are the more ornate sex: the body carries a blue-green metallic iridescence overlaid with the brick-red to orange-red scale edging characteristic of the genus, and the caudal fin displays the coloured banding or marginal patterning that helps distinguish species in this complex group. Females are considerably smaller and duller — an olive to brownish ground colour with minimal patterning. This strong dimorphism is both an aid to species identification and a signal of the lek-like, competitive male display system common to annual killies.
Habitat
Nothobranchius luekei is restricted to the coastal zone of Tanzania, centred on Zanzibar and the immediately adjacent mainland coast. It inhabits the shallow, temporary pools of coastal savanna — sun-baked clay-bottomed depressions and seasonally flooded grassland pans that fill with the long rains and dry completely during the dry months. These pools are typically turbid, warm, and organically rich, staining lightly with tannins and humic acids from decomposing grass and leaf litter.
Water chemistry in such pools tends toward the soft and near-neutral to mildly acidic end of the scale. Data from killifish literature and aquarium care records indicate conditions of GH 2–4 (very soft), pH 5.5–6.5, and temperatures of approximately 68–75 °F. The coastal situation of Zanzibar moderates temperatures compared with more continental East African Nothobranchius localities, meaning this species favours a somewhat cooler range than many savanna Nothobranchius from inland Tanzania or Mozambique.
Feeding
In the wild Nothobranchius luekei feeds on the abundant small invertebrates that colonise temporary pools alongside it: aquatic insect larvae (especially chironomid midges and mosquito larvae), microcrustaceans, worms, and other zooplankton. The upturned mouth is adapted for capturing prey at or near the water surface, though the fish also forages through the water column and across the soft sediment.
In aquarium settings the species accepts most small live and frozen foods readily: Artemia nauplii, white worms, micro worms, Daphnia, bloodworm (chironomid larvae), and finely chopped invertebrate flesh. A varied diet that mimics the invertebrate richness of a productive seasonal pool maintains condition and brings out the male's best colour. Overfeeding should be avoided — a lean, active fish in clean water is more reliably fertile and longer-lived than one held in heavily fouled water.
Mating
Like all Nothobranchius, N. luekei is an annual species and a substrate spawner: the reproductive strategy is built around the reality that the pool will disappear entirely before the year is out, so eggs must be capable of surviving desiccation buried in the substrate for months at a time. Males compete vigorously for access to females, displaying their iridescent flanks and extending their fins in lateral threat postures. Rival males may spar, but serious injury is uncommon.
When a female is receptive she joins the male in a spawning embrace in which the pair press side by side and briefly dive together into the soft mud or peat of the pool bottom. A small number of eggs — typically one to a few per dive — are deposited and immediately buried by the combined wriggling motion of the pair. The process is repeated many times across a spawning session, distributing eggs through the substrate where they are invisible to predators and protected from desiccation by the surrounding soil moisture.
Breeding
The eggs of Nothobranchius luekei are adapted to survive the complete drying of the pool during the dry season. Once buried, they enter a state of developmental arrest (diapause), which may progress through two or three distinct diapause phases depending on conditions and developmental stage. The embryos resume development only when the rains return and the pool refills — a response to dropping osmotic pressure and rising temperature after rainfall, which the eggs detect through the substrate.
In the aquarium, breeding follows the same substrate-spawning pattern. Hobbyists provide a container of boiled or sterilised peat or fine peat-sand mix, 2–3 in deep, into which a conditioned pair will spawn over several weeks. Once spawning activity slows, the peat is removed, pressed to remove excess moisture, and stored in a sealed plastic bag at room temperature (roughly 72–75 °F) for a dry-storage period of two to four months — mimicking the dry season. Re-wetting the peat triggers hatching, often within 24–72 hours. Fry emerge at a few millimetres, are immediately free-swimming and feeding, and grow rapidly; young males begin developing colour within a few weeks and can reach sexual maturity in as little as six to eight weeks, reflecting the compressed life cycle of a fish adapted to a vanishing habitat.
In the aquarium
Nothobranchius luekei is kept by specialist killifish hobbyists who appreciate the challenge and reward of annual species management. A modest tank of 10–15 US gal is sufficient for a breeding trio (one male and two females); a tight-fitting lid is essential as killies are skilled jumpers. Soft, slightly acidic water at a temperature of 68–72 °F suits the species, with careful attention to water quality — the small pool conditions that annual killies exploit in nature cycle nutrients rapidly, and in the aquarium equivalent this means partial water changes every few days rather than relying on biological filtration alone.
Due to their short natural lifespan (wild fish often live fewer than twelve months), aquarium specimens are best regarded as seasonal animals. Males may become aggressive with one another in confined space; keeping a surplus of females reduces male-on-female harassment. The species pairs well with other small, peaceful, similar-sized fish if tank-mates are required, though a species tank is the norm among dedicated killifish keepers. The main ongoing husbandry task is the peat-storage breeding cycle: maintaining an annotated schedule of storage dates and re-wetting windows is essential for managing successive generations without gaps in the colony.
Conservation
Nothobranchius luekei has not been formally assessed by the IUCN Red List as of 2026. This absence of assessment is common in the genus — with roughly 90 or more described species, many named only in the past two to three decades, the conservation assessment pipeline has not kept pace with new descriptions. The species' restricted range, centred on Zanzibar and coastal Tanzania, is an immediate source of concern. Island endemics with a single-island or single-watershed distribution are intrinsically vulnerable: any event or trend that affects the pool systems of that one locality can drive a species to extinction without affecting anything else.
Coastal development, agricultural conversion of savanna grassland, and increased groundwater extraction all reduce and fragment the temporary pool habitats on which annual killies depend. Zanzibar's expanding human population and tourism infrastructure create additional pressures on the island's low-lying wetlands. Within the genus Nothobranchius, multiple species with similarly restricted ranges have declined sharply or lost populations in recent decades. Until a formal IUCN assessment is completed, hobbyist breeding colonies serve as an informal ex-situ buffer — a role that killifish keepers have long acknowledged and that gives the breeding cycle described above a significance beyond the purely recreational.