Meeting Abstract
Increasing membrane cholesterol content through augmented diets can enhance insect cold tolerance and rapid cold hardening (RCH). However, cholesterol is not readily available to phytophagous insects in nature. By contrast, other membrane ordering molecules, such as γ-tocopherol is readily available and is seasonally accumulated in some cold-adapted insects. To determine if γ-tocopherol also functions to enhance cold tolerance, survival to low temperature, ability to RCH, and recovery from chill coma was measured on Drosophila melanogaster fed either normal or supplemented food (cholesterol and/or γ-tocopherol). Flies fed food augmented with cholesterol or γ-tocopherol survived exposure to -6°C at a higher rate (71.2 ± 2.9 and 37.1 ± 1.6 %) than those fed a normal diet (2.3 ± 2.2%). In addition, animals fed augmented food were better able to pass a vertical walking test immediately after, and 12h after an exposure to 0°C for 5h (averaging 18.3 ± 2.4% and 83.2 ± 2.1%) than those fed a normal diet (2.3 ± 0.8%, 71.5 ± 2.3%). Furthermore, supplementation with cholesterol and γ-tocopherol enhanced a fly’s ability to RCH as 94.7 ± 1.0% and 82.9 ± 6.2% of those subjected to 10°C for 2h prior survived a 1h exposure to -6°C compared to only 60 ± 3.6% for those fed non-supplemented food. Lastly, augmenting food with cholesterol and/or γ-tocopherol also reduced chill coma recovery time from 19.2 ± 0.3 to 15.5 ± 0.4 min in animals exposed to 0°C for 5h after RCH. In summary, both cholesterol and tocopherol augmentation increased survival to low temperature, post-cold performance, and enhanced RCH.
