GEFEN, E.*; MARLON, A.J.; University of Nevada, Las Vegas: The effects of selection for desiccation resistance on larval development of Drosophila melanogaster

We studied evolved differences in larval development and metabolic fuels acquisition among selected D. melanogaster lines, and their contribution to the performance of the adults under stressful conditions. Flies selected for desiccation resistance (D) have longer egg to adult developmental time in comparison with their starved (S) and fed (C) controls. However, larvae from both selected and control lines molted from second to third instar 81-84h after egg laying (AEL), whereas D larvae pupated 5-6h later than larvae of the C and D lines. The longer third instar duration of the D larvae is characterized by lower body growth rate. Nevertheless, despite the lack of significant differences in mass at 96h AEL, D flies had significantly higher body mass and water content than their controls at the wandering stage and as newly eclosed flies. Newly eclosed selected and control flies did not differ significantly in carbohydrate or lipid contents. In order to estimate the contribution of delayed pupation of D larvae to desiccation resistance during adulthood, larvae from the three experimental lines were transferred from food to agar vials at 96h AEL. Body mass, water content and desiccation resistance of newly eclosed flies were compared to those of adults which had fed normally as larvae. No differences were found in adult body size and water content of the former, whereas normal larval feeding resulted in significantly higher body mass and water content of newly eclosed D flies. Transferring larvae to agar at 96h AEL reduced the desiccation resistance of control adults by 8-9h, compared to >13h for D flies. This larger contribution of larval feeding in D flies to desiccation resistance of the adults is correlated with longer third instar feeding. Supported by NSF award IOB-0110626.