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

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. 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. 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, when we let mosquitoes feed on experimental sugar solutions consisting of glucose, sucrose, fructose, or trehalose at concentrations of 1.97 or 19.97 kcal per 100 ml, 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. 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.