P1.199 Wednesday, Jan. 4 Multiple freeze cycles induce oxidative stress and reduce survival in the freeze-tolerant goldenrod gall fly, Eurosta solidaginis DOELLING, A.R. *; WILLIAMS, J.B. ; Southern Illinois University Edwardsville; Southern Illinois University Edwardsville firstname.lastname@example.org
Most studies assess insect freeze tolerance by examining survival and/or parameters directly associated with extracellular ice formation immediately after a single, low temperature exposure. However, overwintering animals likely experience multiple freezing events and are potentially subject to a variety of stresses, such as the formation of reactive oxygen species as reperfusion of oxygen occurs post thaw. To determine if multiple freezing events reduce survival and influence factors associated with oxidative stress, we measured eclosion rates, levels of oxidative damage to macromolecules, and antioxidant capacity of larvae subjected to either 0 (control), 5, 10, 20, or 30 artificial diurnal freezes. Eclosion rates were similar for controls and animals experiencing only 5 freeze cycles (averaging 15%), but survival was reduced in groups subjected to 10, 20 or 30 freezing episodes (8%, 4%, and 2%, respectively). In contrast, oxidative damage to lipids (malondialdehyde levels) and protein (advanced oxidation protein product levels) were only higher in animals subjected to 30 freeze cycles (213.82±36.23 μmol TMOP●ng protein-1 and 25.06±2.39 mmol chloramine-T●μg protein-1, respectively) compared to others which averaged 67.47±11.24 μmol TMOP●ng protein-1 and 11.60±1.21 mmol chloramine-T●μg protein-1. Interestingly, no difference in antioxidant capacity (an animal’s ability to mitigate reactive oxygen species), was observed between groups, with values ranging from 9.8-25.1 mmol trolox●ng protein-1. In summary, the number of freezing events may dramatically increase oxidative stress and reduce survival in overwintering insects.