SCIENTIFIC NAME Nothobranchius furzeri

TAXONOMY PHYLUM: Chordata CLASS: Actinopterygii ORDER: Cyprinodontiformes FAMILY: Nothobranchiidae

General description

Credit: Kim Caesar/Nature Publishing Group

African turquoise killifish is a short-lived, teleost fish found in temporary pools of Mozambique and Zimbabwe1. To survive the unusually harsh conditions of these pools, N. furzeri spawn daily once they reach sexual maturity 30–40 days post hatching, and they die within 4–6 months2. This is considered the shortest life cycle of any reported captive-bred vertebrate. Adults, reaching a total length of 6.5 cm, exhibit sexual dichromatism and dimorphism, with males displaying predominantly brilliant turquoise scales overlaying crimson skin and females that are smaller, dull and pale brown. Additionally, N. furzeri males have caudal fins with geographically distinctive red and yellow phenotypes1.

Husbandry

African turquoise killifish can be maintained in the laboratory as a brackish warm water species. Although water temperature in the wild can fluctuate as much as 15 °C (ref. 3) and conductivity may range 50–625 μS/cm (ref. 1), it is best to stabilize water parameters in the laboratory at pH 6–7.5, 23–26 °C and 3,500–4,500 μS/cm. These fish prefer to eat small crustaceans in the wild but will consume typical laboratory fish prey items such as Tubifex worms, Artemia nauplii and Daphnia zooplankton, and captive-reared fish readily accept commercial feed and pellets1. It should be noted, however, that Tubifex and other chironomid larvae have been linked to cases of hepatic steatosis4. Like other Nothobranchius species, N. furzeri is polyandrous and each female can lay 20–50 eggs daily1 with male fish displaying a dominance hiearchy3. Although wild females deposit eggs directly in pool sediments, captive females readily use sand, peat moss or even zebrafish spawning setups1. Like zebrafish, adults consume eggs so one should collect eggs soon after oviposition or allow fish to spawn over mesh. Embryos can be incubated on wet substrates or in liquid culture1.

Research résumé

Despite its short life span, the African turquoise killifish completes its life without skipping pathologies and phenotypes associated with old age, which occurs as soon as 2 months after hatching2. Multiple studies of its genome1,5 and RNA transcription6 demonstrate that the African turquoise killifish is a viable model to study human aging, and as N. furzeri age, they display many stereotypical ailments such as losing body mass, kyphosis, dulling, reduced activity, loss of cognitive functions and organ failures1. For oncologists, this species might be of additional interest since African turquoise killifish develop hepatic and renal neoplasia in an age-dependent fashion and at a much higher incidence than other finfish4.

Various lines of African killifish allow investigators to study integrative, cellular and even molecular traits of different aging phenoytypes. The grandfather of all inbred lines is the GRZ line, which is highly inbred and with a median lifespan of 3 months, is considered the shortest lived of all killifish1. Microinjection techniques allow the creation and germline transmission of stable transgenic lines. For example, the promoter drive for green fluorescent protein has been successfully introduced into N. furzeri7. Other techniques are now on the horizon including the CRISPR-Cas9 targeted knock-in approach1,2 and ENU random mutagenesis1. These powerful tools and this species' short generation time will advance biomedical research, especially in fields of developmental biology and aging.