Dietary polyunsaturated fatty acids affect volume and metabolism of Drosophila melanogaster sperm

Dietary fatty acids can accumulate in sperm and affect their function in
vertebrates. As Drosophila melanogaster shares several pathways of lipid
metabolism and shows similar lipid-dependent phenotypes but lacks some
hormones that in vertebrates regulate lipid metabolism, there is currently
no clear prediction as to how dietary fatty acids affect the sperm of D.
melanogaster. We manipulated the amount and identity of dietary
polyunsaturated fatty acids (PUFA) in the food of D. melanogaster males (a
treatment known to affect membrane fluidity) and measured changes in sperm
parameters. We found that i) males reared on food containing PUFA-rich,
plant-derived lipids showed a slower increase in sperm volume over male
age compared to males reared on yeast-derived lipid food which is richer
in saturated fatty acids. ii) The resistance of sperm membrane integrity
to osmotic stress was not altered by dietary lipid treatment but iii) food
containing yeast-derived lipids induced a 46% higher in-situ rate of
production of reactive oxygen species in sperm cells. These findings show
that dietary lipids have similar effects on sperm parameters in Drosophila
as in vertebrates, affect some, but not all, sperm parameters, and
modulate male reproductive ageing. In concert with recent findings of
sex-specific seasonal variation of diet choice in the wild, our results
suggest a substantial dietary impact on the dynamics of male reproduction
in the wild.