The effects of oxidative stress on the development and overwintering success of the alfalfa leafcutting bee, Megachile rotundata

Generally associated with aging and senescence, oxidative stress causes detrimental consequences at multiple scales—producing effects that range from small molecular changes to large scale developmental and fitness effects. Oxidative stress is a by-product of aerobic metabolism and occurs when free radical production outnumbers antioxidant capacity. Most animals have evolved methods to prevent or combat oxidative damage. One such example is dormancy, a state characterized by a metabolic suppression, thus limiting the number of free radicals produced. Megachile rotundata is an important agricultural pollinator, and its life cycle includes an extended overwintering period, wherein prepupae enter diapause in the fall and emerge as adults in the summer. Oxidative damage occurs during long term storage at cold temperatures in M. rotundata. Studies on other insects have shown that ROS promotes diapause induction, and the sequestering of ROS increases the chances of survival from diapause. We used paraquat (PQ)—a toxic herbicide that promotes free radical production—and N-acetylcysteine (NAC)—a supplemental form of an amino acid which acts as an antioxidant by scavenging free radicals—to assess the affects of ROS on development and overwintering success. Increased oxidative stress led to faster development time, while reduced oxidative stress delayed development. Additionally, groups treated with PQ exhibit higher levels of activity during the first 48 hours after eclosion. Together, these results suggest that the emergence from overwintering with higher levels of ROS may be beneficial for speedy development and higher productivity.