Just Chilling: Development of drosophila melanogaster chilling in the pupal stage

Abstract

Temperature is a kind of environmental stress that significantly affects ectotherms. Thermal adaptation known as Rapid Cold Shock Hardening (RCH) allows them to tweak their physiological state in response to rapid temperature changes. De- spite progress in previous years, there is still considerable uncertainty regarding the physiological basis of RCH in insects. In holometabolous insects, pupa being the most energetically and physically vulnerable stage is susceptible to injury in cold temperatures. Response to cold can reveal vital information about fitness costs and the mechanisms involved to prevent and cope with cold damage. In this study, I investigated the survival and fitness parameters of adults of Drosophila melanogaster cold stressed in the pupal stage. Early pupae were examined for their tolerance to cold shock either directly or after a pre-treatment to estimate the induction of RCH response. Pre-treatment was given at 0°C for 2 hours and cold shock at various temperatures (-2°C, -5°C, -8°C) for 1 hour. I observed a significant increase in mortality and development time with a decrease in temperature. Pre-treatment further increased mortality and development time. Body size was not affected. Contrary to expectations, I found that pre-treatment did not induce RCH response in the pupal stage; instead, it had adverse effects. I think it is most likely due to the cost associated with the hardening treatment in this vulnerable stage. Exposure to chilling temperatures depletes the energy reserves, suggesting that systemic regulation in these reserves may be an essential part of the mechanisms to cope with the variations of temperatures in the environment.