Insect circadian plasticity as a proposed target for the expression of parasite extended phenotypes

Both parasite manipulation of host behavior and the roles of circadian clocks in infectious disease are not well understood. However, studies into parasite-manipulated insects suggest that host rhythms are altered at different levels of biological organization. Here, we discuss this hypothesis in the context of circadian plasticity. We argue that striking overlap between manipulation mechanisms and plastic functioning of the insect clock exists across independently evolved parasite-host systems. As such, investigating parasitic behavioral manipulation provides an opportunity to better understand circadian plasticity and how infection and clocks intersect across taxa.