Membrane composition has been related to maximum lifespan in mammals, birds, bivalve molluscs and the nematode C. elegans. In all cases, a long maximum lifespan is associated with low polyunsaturated fatty acids (PUFA) in membrane lipids. Female honeybees (Apis mellifera) show the same relationship. Female larvae can become either workers or queens. Adult workers typically live for only weeks while adult queens can live for up to 8 years! The membrane lipids of larvae and pupae of workers and queens are similar all having low PUFA levels. Queens are fed mouth-to-mouth by workers throughout adult life with “royal jelly” (has no PUFA) and therefore maintain low PUFA membranes. In contrast, after emergence workers commence eating pollen (with high PUFA content) such that by day 4 of adult life there is a 5-fold increase in proportion of PUFA in their membranes.
To test the hypothesis that this diet-related difference in membrane PUFA is responsible for the much shorter lifespans of workers compared to long-living queens, we fed four populations of newly-emerged adult workers with four different diets; two contained PUFA (honey+pollen; honey+casein+PUFA) while the other two had no PUFA (honey+yeast; honey+casein). The diets with PUFA resulted in membrane lipids with normal worker PUFA levels while worker bees on PUFA-deficient diets had no increase in membrane PUFA. Furthermore, the maximum lifespan (i.e. average longevity of longest-living 10% of population) of honeybees on the PUFA-deficient diets were ~35% greater than those on PUFA-containing diets (p<0.01). This extended maximum longevity of worker honeybees by experimental diet manipulation supports the proposed link between membrane composition and lifespan and will provide a new experimental tool to investigate the processes of aging.
Nicolas. Martin 1-2, A.J. Hulbert2, J.E.P.W. Bicudo2, T.W. Mitchell1 and P.L. Else1.
1 School of Medicine, University of Wollongong, Australia; 2 School of Biological Sciences, University of Wollongong, Australia