GIBBS, A. G.*; LARSEN, K. M. F.; University of Nevada, Las Vegas; University of Arizona: EFFECTS OF DAILY HEAT SHOCK ON DEVELOPMENT AND WATER BALANCE IN DROSOPHILA MELANOGASTER

Drosophila melanogaster is a widely used model for heat stress. Most studies, however, have subjected flies to a single bout of high temperature. In nature, developing larvae and pupae of D. melanogaster are likely to encounter high temperatures on a daily basis. We examined the effects of daily heat stress (35 minutes at 39 ^oC) on larval development and adult body size and water balance. Heat-stressed larvae suffered >90% mortality and took 4 days longer to reach adulthood than unstressed controls. Surviving adults were 30% less resistant to desiccation stress than controls, due to significantly higher water-loss rates. The effects of heat stress were reversed by a daily one-hour pre-treatment at 36 ^oC, followed by 35 minutes at 39 ^oC. Pre-treated larvae developed nearly as rapidly as unstressed controls, achieved the same body size, and were equally resistant to desiccation. We propose that daily heat stress disrupts cuticular development, and that this damage is prevented by synthesis of heat-shock proteins at 36 ^oC. Supported by NSF award 0110626 to AGG.