Starvation tolerance associated with prolonged sleep bouts upon starvation in a single natural population of Drosophila melanogaster

Large genetic variations in starvation tolerance in animals indicate that there are multiple strategies to cope with low-nutrient conditions. Fruit flies (Drosophila melanogaster) typically respond to starvation by suppressing sleep and enhancing locomotor activity presumably to search for food. However, we hypothesized that in a natural population, there are costs and benefits to sleep suppression under low-nutrient conditions and that conserving energy through sleep could be a better strategy depending on food availability. In this study, we quantified the variation in sleep-related traits in 21 wild-derived inbred lines from Katsunuma, Japan, under fed and starved conditions and analysed the relationship between those traits and starvation tolerance. Although most of the lines responded to starvation by suppressing the total time in sleep, there were indeed two lines that responded by significantly increasing the sleep-bout durations and thus not reducing the total time in sleep. These genotypes survived longer in acute starvation conditions compared to genotypes that responded by the immediate suppression of sleep, which could be due to the reduced metabolic rate during the long uninterrupted sleep bouts. The coexistence of the enhanced foraging and resting strategies upon starvation within a single population is consistent with the presence of a behavioural trade-off between food search and energy conservation due to unpredictable food availability in nature. These results provide insights into the evolutionary mechanisms that contribute to the maintenance of genetic variations underlying environmental stress resistance.