Cold-shock injury and rapid cold-hardening in the flesh fly, Sarcophaga crassipalpis.

Abstract

Direct exposure to -10 C, in the absence of tissue freezing, causes high mortality in Sarcophaga crassipalpis: this result suggests that injury is due to cold shock. However, brief acclimation at 0 C enables larvae, pupae, and pharate adults of Sarchophaga crassipalpis to survive -10 C. Chilling for as short a period as 10 minutes enabled 50% of the flies to survive a 2-hr exposure to -10 C. Enhancement of cold tolerance was linear over the first hour of chilling at 0 C. The optimal temperature range eliciting the rapid accumulation response was 6-0 C, but the effect could also be stimulated by high temperature (36 C). The rapid increase in cold tolerance correlates with concomitant increases in hemolymph osmolality and glycerol levels. This response suggests a novel role for glycerol in protecting insects against injury resulting from cold shock, although other unidentified mechanisms may be involved in this response. That both nondiapause- and diapause-programmed flies respond to short-term chilling indicates that this rapid response is not part of the diapause syndrome but probably functions in either type of fly as an adaptation to survive brief periods of low temperature.