Sugar-sensitive neurone responses and sugar feeding preferences influence lifespan and biting behaviours of the Afrotropical malaria mosquito, Anopheles gambiae

Abstract

Floral nectar is the main source of carbohydrates for many insects including mosquitoes. Nonetheless, the physiological mechanisms underlying feeding on carbohydrates by the Afrotropical malaria mosquito Anopheles gambiae remain poorly understood. Here, we tested whether sugar sensitivity and sugar feeding preferences correlate with longevity in A. gambiae. We also tested whether feeding females on different sugar diets influences their biting behaviours. Electrophysiological recordings show that sugar neurones on the labella of females are most sensitive to sucrose, mixtures of glucose and fructose, and to melezitose; other sugars tested, including glucose and fructose presented alone, only weakly activate these taste neurones. Mosquitoes survive longest on sucrose, the most preferred sugar. Whereas feeding on a mixture of glucose and fructose is preferred over fructose or glucose alone, fructose supports higher longevity than either glucose or the mixture of the two hexoses. Females that had previously fed on glucose show a stronger biting response than those fed on sucrose, perhaps in an effort to compensate for their lower energetic state. These findings contribute to our understanding of the physiological basis of sugar feeding in A. gambiae and indicate how the sugar diet can affect laboratory-reared A. gambiae biting behaviours.

Lower Doses of Fructose Extend Lifespan inCaenorhabditis elegans

“…To our surprise, provided that we used equal molar amounts of each sugar, we observed heterogeneous effects of the sugars on lifespan and IFD in C. elegans . The biphasic dose-response curve seen with fructose, which increased lifespan at lower doses and reduced at higher doses, supported the results of some other studies using low or high doses (Smith et al, 2007, Kessler et al, 2015). The reduced lifespan by glucose & fructose or HFCS may be related to the dose that could be in the declining lifespan range of fructose treatment alone.…”

“…In yeast studies, either glucose or fructose at a concentration of 0.5% extends the lifespan of Saccharomyces cerevisiae mutants compared with a concentration of 2% due to the effect of caloric restriction (Smith et al, 2007). Interestingly, Anopheles gambiae consuming a diet supplemented with fructose (584 mM) or an equal amount of fructose plus glucose (292 mM) supported life compared with the water only control (Kessler, Vlimant, & Guerin, 2015). Feeding fructose to mice did not change body weight compared to a sugar-free, low-fat dietary control over a 3-month study period, and there was no change in triglycerides, free fatty acids, glucose sensitivity or leptin (Tillman et al, 2014).…”

Not Just from Blood: Mosquito Nutrient Acquisition from Nectar Sources

“…Although females are less susceptible to rapid mortality caused by sugar deprivation, their survival rate and fecundity can be compromised by reduced energy reserves [1,4]. The sensory cues that enable nectar-feeding include odors [1,2], tastants [5], and visual stimuli [6,7], but the molecular mechanisms of how these cues are perceived, as well as their relative contribution to the detection of a nectar source, are poorly understood (Figure 1). This review highlights the role of sugar feeding in the life cycle of mosquitoes, the plant sources they prefer, the volatiles that attract them, and the contribution of vision, olfaction, and gustation to this behavior.…”

microRNA tissue atlas of the malaria mosquitoAnopheles gambiae

“…Brain tissues, especially the central nervous system, play essential roles in the PV phase by regulating mosquito olfactory and circadian behaviors (53,54). Efficient response to blood feeding depends on timely accumulation of the ovary ecdysteroidogenic hormone in the granules of neurosecretory cells (55).…”