Mannitol ingestion causes concentration-dependent, sex-specific mortality in adults of the fruit fly (Drosophila melanogaster)

Mannitol, a sugar alcohol used in commercial food products, induced sex-specific mortality in the fruit fly Drosophila melanogaster when ingested at a single concentration (1M), and female mortality was greater than male mortality. We hypothesized that sex differences in energy needs, related to reproductive costs, contribute to increased mortality in females compared to males. To test for the effects of reproductive costs, we compared longevity to 21 days of actively mating and non-mating flies fed various concentrations of mannitol. We also asked whether mannitol-induced mortality was concentration-dependent for both males and females, and if mannitol’s sex-specific effects were consistent across concentrations. Females and males both showed concentration-dependent increases in mortality, but female mortality was consistently higher at all concentrations above 0.75M. Fly longevity to 21 days decreased further for both sexes when housed in mixed sex vials (as compared to single sex vials), suggesting the increased energetic demands of reproduction for both sexes may increase ingestion of mannitol. Mannitol fed to larvae did not alter emerging adult sex ratios, suggesting that sex-specific mortality due to mannitol occurs only in adults.