SHREVE, S.M.*; YI, S.-X.; LEE, R.E.; Miami University: Effects of Dietary Cholesterol on Cold Tolerance and Reproductive Output in Drosophila melanogaster

Other investigators have shown that cholesterol, an important component of cell membranes, in some ectotherms increases with cold-hardening. As an initial study, we decided to test the hypothesis that dietary cholesterol will improve cold tolerance and rapid cold-hardening capacity in the fruit fly Drosophila melanogaster. In order to test the effects of cholesterol, which insects are unable to synthesize, we manipulated the flies’ diet in two treatment groups by adding 0.4 mg or 1.0 mg of cholesterol per 1 mL of cornmeal-yeast medium. The 0.4 mg/mL modified diet did not have significant effect on the cold tolerance or the rapid cold-hardening ability of the flies. However, flies reared on the 1.0 mg/mL modified diet survived a 2-h exposure to -5�C at a significantly higher rate than flies on the control diet (71.0 � 6.6% vs. 36.0 � 8.1%). Furthermore, flies in this group were also statistically more successful than the control flies in their capacity to rapidly cold-harden to -7�C (36.7 � 4.4% survival vs. 20.0 � 2.9%). After a 10-day oviposition period, flies raised on the cholesterol augmented diet produced more adult offspring than those raised on the normal diet. However, the time required for development from egg to adult was not significantly different between the control and cholesterol treated flies. These results suggest that cold tolerance and rapid cold-hardening involve some form of membrane adaptation in the organism. We are currently working to determine whether increased dietary cholesterol also increased membrane cholesterol levels. Supported by NSF (IBN-0090204) grant.