Circadian rhythms enable organisms to mediate their molecular and physiological processes with changes in their environment. Although feeding behavior directly affects within-organism processes, there are few examples of a circadian rhythm in this key behavior. Here, we show that Daphnia have a nocturnal circadian rhythm in feeding behavior that corresponds with their diel vertical migration (DVM), an important life history strategy for predator and UV avoidance. In addition, this feeding rhythm appears to be temperature compensated, which suggests that feeding behavior is robust to seasonal changes in water temperature. A circadian rhythm in feeding behavior can impact energetically demanding processes like metabolism and immunity, which may have drastic effects on susceptibility to disease, starvation risk, and ultimately, fitness.
Keywords: Biodare2; Daphnia; behavior; circadian rhythm; diel vertical migration; feeding.