Meeting Abstract
For freeze-tolerant insects, internal ice formation presents additional challenges beyond cold per se, but few studies have directly compared freezing vs. supercooling at the molecular and physiological level. Here, we investigated molecular responses and physiological costs of freezing in the Antarctic midge, Belgica antarctica. In previous work, we demonstrated substantial costs to freezing in summer-acclimatized larvae, including mortality and tissue damage, reduced locomotion, and damage to proteins. In this talk, first we directly compare the physiological effects of freezing and supercooling in winter acclimatized larvae. Winter larvae survive freezing and supercooling equally well, and we observed no evidence of sublethal tissue damage in either condition. However, short-term freezing elicited higher expression of certain heat shock protein transcripts, suggesting a higher degree of cellular stress in frozen larvae. Biochemical responses were similar in both cold treatments, although frozen larvae tended to have lower levels of glycogen reserves, suggesting additional energetic costs to being frozen. In an ongoing transcriptomics study, we are directly comparing molecular responses to sublethal freezing and supercooling. Preliminary analyses indicate distinct molecular responses to each treatment, with supercooling eliciting a larger number of gene expression changes overall but freezing resulting in higher expression of stress-related proteins. Together, these studies will contribute towards identifying the precise molecular and physiological processes that are required to survive in the frozen state.
