P1.210 Wednesday, Jan. 4 Rapid cold-hardening in the frozen state increases cold tolerance in the Antarctic midge, Belgica antarctica KAWARASAKI, Y.*; TEETS, N.M.; KOBELKOVA, A.; DENLINGER, D.L.; LEE, R.E.; Miami University, Oxford OH; Ohio State University, Columbus OH; Ohio State University, Columbus OH; Ohio State University, Columbus OH; Miami University, Oxford OH email@example.com
Endemic to the Antarctic Peninsula, the Antarctic midge, Belgica antarctica (Diptera: Chironomidae), is the southernmost insect. During its two-year life cycle, larvae must endure extended periods of sub-zero temperature. These larvae are unique in their capacity to undergo rapid cold-hardening (RCH) while frozen. In this study, we further characterized this acclimatory response. The temperature of crystallization was -7.3 ± 0.6 °C. RCH occurred at temperatures as low as -12 °C, significantly increasing survival rates from 22.0 ± 5.7% (control) to 98.2 ± 1.8% after exposure to -18 °C for 24 h. At the cellular level, RCH at -5 °C for 2 h significantly increased survival rates of midgut cells from 32.1 ± 5.9% to 76.0 ± 1.6%. To compare the capacity for RCH in supercooled and frozen larvae, two groups of larvae were acclimated at -5 °C for 2 h. Frozen larvae were significantly more cold tolerant than supercooled larvae, 84.8 ± 2.7% and 49.3 ± 5.8% respectively. As little as 1 h at -5 °C significantly increased survival of larvae at -18 °C. Similarly, protection by RCH was rapidly lost upon warming— After 2 h at 2 °C, the cold tolerance was indistinguishable from control values. These results suggest that larvae can quickly change their cold tolerance in response to diurnal and capricious changes in microclimatic temperature on the Antarctic Peninsula. Supported by NSF grants ANT-0837559 and ANT-0837613.