Effects of nectar and sugar on the longevity of the mosquito Anopheles gambiae s.l

Background In addition to taking blood-meals, mosquitoes regularly feed on the nectar of plants. The nectar, in particular the sugar it contains, serves as a source of energy that underlies many life-history traits, including longevity. Methodology To understand better how different nectars and sugars influence the longevity of mosquitoes, we allowed adult Anopheles gambiae s.l. to feed on several plant species (the flowers of Thevetia nerifolia , Mandalium coromandelianum , Ixora coccinea , and Tabernanthe iboga , and the fruit of Carica papaya ), measured the concentrations of sucrose, fructose and glucose in the nectar and fruit juice, estimated the size of their sugar meal and measured their longevity. In another experiment, we provided mosquitoes with experimental sugar solutions (glucose, sucrose, fructose, or trehalose) at two concentrations (1.97 and 19.97 kcal per 100 ml) and monitored longevity. Results The plant that the mosquitoes fed on affected their longevity (which ranged from an average of 8.2 days when they fed on C. papaya to 21.1 days when they fed on M. coromandelianum ), and the mosquitoes took larger meals (in a separate experiment) from the plants that gave a longer life. However, longevity was only slightly affected by the concentrations of glucose, fructose, sucrose, or total sugar in the sugar meals. In contrast, in the other experiment with sugar solutions, both the type and the concentration of sugar affected longevity. The mosquitoes lived approximately one week longer when fed sugar at the higher concentration and they lived longest (14.1 days) when fed with sucrose and shortest (4.8 days) when fed with trehalose. Conclusion Overall, our results show the importance of nectar and sugar on the longevity of mosquitoes but suggest also that non-sugar components of nectar may have a large impact.