| The goal of this dissertation was to exploit the tractability of the honey bee (Apis mellifera) to understand how the physiological and cellular mechanisms that determine the onset and duration of senescence are shaped by behavioral development and behavioral intensity. These data reveal how behavior can damage cells and consequently limit lifespan. The honey bee represents the ideal model to address these factors because age, behavior, functional senescence, and lifespan are easily manipulated independently of each other while in its natural environment. I determined if there was a cause-effect relationship between honey bee flight and oxidative stress by comparing damage accrued from intense flight bouts to damage accrued from D-galactose treatment, which is a known proxy of oxidative stress in other insects. Previously, we determined a commonly used method to induce oxidative stress, paraquat, did not induce oxidative damage in honey bees as in other animals. I also experimentally manipulated the duration and intensity of honey bee flight across a range of ages to determine their effects on reactive oxygen species (ROS) accumulation, the associated enzymatic antioxidant protective mechanisms, and gene expression. In bees fed D-galactose, lipid peroxidation (measured by MDA) increased when compared to age-matched bees with high flight experience and negligible flight experience. We then found that a marker of oxidative DNA damage (8-OHdG) increased in flying bees with high amounts of flight experience. These data suggest flight-induced oxidative stress plays a significant role in functional senescence of foraging honey bees. We also observed an imbalance between pro-oxidants (superoxide and H2O 2) and anti-oxidants (SOD and catalase) in bees with high amounts of flight experience. Our microarray data indicate the transition from behaviors requiring little to no flight (nursing) to those requiring intense flight (foraging), rather than the amount of previous flight per se, has a major effect on gene expression. Following behavioral reversion, gene expression partially reverted, but some aspects of forager expression patterns, such as those for genes involved in immune function, remained. Jointly, these data suggest an epigenetic control and energy balance role in honey bee functional senescence along with an imbalance of pro- to antioxidants. |
