Meeting Abstract
To ensure survival and reproductive success, animals must optimally allocate energy among a wide range of costly physiological and behavioral processes while inhabiting environments that change predictably across and unpredictably within seasons. We examined the mechanisms by which seasonally-breeding rodents allocate energy between reproductive and immune systems and modulates the intensity of sickness responses to a simulated infection across seasons. Siberian hamsters inhibit reproduction and display lower body masses, lower levels of the adipose hormone leptin, and less intense sickness when housed in short, winter-like days compared to long, summer-like days. Using a range of techniques, we determined the role of energy in reproductive-immune trade-offs and seasonal regulation of sickness intensity. We examined energetic mechanisms involved in regulating reproductive-immune trade-offs in reproductively active female hamsters and show that glucose deprivation results in reproductive suppression, however suppression can be alleviated when animals ware provided with a hormonal signal of increased fat stores. Alternatively, reproduction is not inhibited when animals experience more severe glucose deprivation. We also examined the contributions of seasonal changes in energetic fuels and signals to seasonal variation in sickness intensity and show that seasonal variation in sickness-induced hypothermia is regulated by seasonal changes in glucose availability and leptin levels. Lastly, changes in insulin have both suppressive and enhancing effects on sickness intensity, depending on energetic context. Collectively, the results of these findings illustrate that physiological trade-offs and sickness intensity are sensitive to a variety of energetic modulators and that the effects of these modulators are dependent on their interactions with each other and the environment.
