Meeting Abstract
Recent studies indicate that freeze tolerant insects subjected to multiple bouts of low temperature have reduced survival compared to animals exposed to a single freeze of the same cumulative duration. However, it is unclear if the reduced survival is due to repeated cellular osmotic stress and/or oxidative stress during oxygen reperfusion upon thawing. To determine if multiple anoxic events reduce survival and influence factors associated with oxidative stress we measured levels of oxidative damage to lipids, aqueous and lipophilic antioxidant activity levels, pupation rates, and cold tolerance of Eurosta solidaginis larvae subjected to either 0, 10, 20, or 30 cycles of diurnal anoxia/reperfusion or a single bout of anoxia for 15 days. Repeated exposure to anoxia reduced both aqueous and lipophilic antioxidant activity levels in all groups by approximately half compared to controls, which averaged 47 ± 10 and 9 ± 2 mm trolox•ng protein-1 respectively. Oxidative damage to lipids was greatest in those subjected to 30 bouts of anoxia (18 ± 6 µm MDA•ng protein-1), while levels in all other groups were similar (7 ± 2 µm MDA•ng protein-1). Even though repeated anoxia subjected animals to oxidative stress, it had little effect on animal survival, as pupation percentages averaged 75.2% for all groups. Interestingly, repeated oxygen reperfusion did limit cold tolerance as animals subjected to repeated anoxia followed by an exposure to -80°C for five days had reduced fat body cell survival (61.3 ± 2.5%) compared to controls (69.3 ± 2.9%). In conclusion, repeated anoxia and oxygen reperfusion did not reduce survival, but did result in oxidative stress and may limit cold tolerance.
