Title: Divergent evolution of sleep homeostasis opens new perspectives on the function of sleep
Abstract: Sleep is a highly conserved behaviour among the animal kingdom, appearing in species as distant as jellyfishes and elephants. Understanding what drives this evolution and which traits are universal implies understanding what sleep really is and what it does. This is the ultimate question in the field.
It is generally believed that sleep serves a crucially important yet mysterious “core function” that is shared among all animals and that drives its evolution, but the evidence behind this hypothesis is lacking. In my talk, I will challenge this idea by telling the surprising story of how sleep evolved in seven different species of the Drosophila subgenus. We show that those aspects of sleep that are believed to be universal – such as its homeostatic regulation – are in fact only present in D. melanogaster and not in the other six Drosophila species we tested. We show that the difference in sleep homeostasis between melanogaster and the other species can be explained by a different underpinning cell-biology regulating synaptic strength upon prolonged wakefulness, at the same time providing a possible evolutionary mechanism and reinforcing the connection between sleep homeostasis and synaptic strength.