In the central African dry season, it does not rain. To survive when the ephemeral ponds it calls home dry up, the turquoise killifish of Zimbabwe and Mozambique has evolved an extreme solution. It dies.
But the embryos in its eggs, laid premortem on the pond bed, can enter a state of suspended animation until the rains resume and the pond fills with life-giving water again. The embryos may wait in this state – called diapause – for an average of eight months. That is a long time to effectively play dead with critical physiological processes on hold.
Buried in the soil of the lakebed, the embryo does not develop or grow until the rains return for at least three days. Spores of plants and microbes are famed for achieving suspended animation, some even surviving for tens of thousands and millions of years , but inanimate embryonic fish? Indeed. Yet even though diapause in turquoise African killifish has been known since the 1970s, we didn't know how it achieves it – especially as other killifish don't do this.
Now we do know. Diapause emerged in this fish very recently, just 18 million years ago, by "co-opting" primordial genes almost half a billion years old that existed in the common ancestor of all vertebrates, Param Priya Singh of the University of California and Anne Brunet of Stanford University reported Tuesday in Cell . Moreover, their analysis of diapause in wider Animalia, specifically referring to an embryonic state of suspended animation, not somnolent adults,.