A temperature-dependent shift in dietary preference expands the viable temperature range of Drosophila

How cold-blooded animals adapt their behaviour and physiology to survive seasonal changes in temperature is not completely understood - even for well-studied model organisms like Drosophila melanogaster. Here, we show that Drosophila can extend their viable temperature range through temperature-dependent changes in feeding behaviour. Above 15˚C, Drosophila feed and lay eggs on yeast. In contrast, below 15˚C, Drosophila prefer to feed and lay eggs on plant material. The different lipids present in yeast and plants improve survival at high and low temperatures, respectively. Yeast lipids promote high tempera-ture survival by increasing systemic insulin signalling. This expands the range over which developmental rate increases with temperature, suggesting that faster nutrient utilization is required to fuel biochemical reactions driven faster by ki-netic energy. In addition to speeding development, yeast lipids increase fertility. Thus, yeast provide cues that could help Drosophila to exploit a transient summer food resource. Plant lipids, on the other hand, are required to maintain mem-brane lipid fluidity at low temperature, and increase cold-resistance of larvae and adults. The cold-resistance and lowered insulin signalling conferred by feeding on plants allows adults to survive for many months at temperatures consistent with overwintering in temperate climates. Thus, temperature-dependent changes in feeding behaviour produce physiological changes that could promote seasonal adaption.