Meeting Abstract
The Antarctic midge, Belgica antarctica, is the world’s southernmost insect and the only insect endemic to Antarctica. Larvae of this species are highly tolerant of a variety of environmental stressors and can survive freezing down to -20°C in the laboratory. However, field microhabitat temperatures rarely approach -10°C, indicating that most freezing events are sublethal. To cope with sudden drops in temperature, the midge is capable of rapid cold hardening (RCH), a rapid acclimation response that enhances cold tolerance. Previous work has demonstrated that RCH protects against lethal freezing at extreme temperatures, but the extent to which RCH provides benefits during sublethal freezing is unknown. Here, we test the hypothesis that RCH promotes faster recovery, preserves energy balance, and protects against protein and tissue damage following sublethal freezing. Larvae were either directly frozen at -9°C for 24 h, or given 2 h of RCH at -5°C prior to 24 h at -9°C. Larvae exposed to RCH before freezing recovered more quickly and resumed normal movement well before those that were directly frozen. Furthermore, larvae that underwent RCH had higher metabolic rates 2 h after cold stress. Thus, RCH preserves metabolic function and allows larvae to resume normal activity more quickly following a bout of freezing. In ongoing analyses, we are testing the ability of RCH to maintain tissue integrity, conserve energy, and modulate stress-protein expression. Taken together, this work will indicate the extent to which RCH preserves function at the molecular, cellular, and organismal levels following ecologically relevant freezing events.
