Biology of the malaria vector Anopheles gambiae: behavioral and reproductive components of sugar feeding

Feeding on sugar from floral and extra-floral nectaries is an important, if less well known, part of mosquito biology.Male mosquitoes, as well as females of a few species, feed only on nectar.Females of blood feeding species feed on sugar to provide energy for flight and survival as well as to improve fecundity.This is the case for every species so far examined.One possible exception to this rule is Anopheles gambiae, the world's most important malaria vector.This endophilic, anthropophilic species is thought to forego sugar-feeding, instead taking multiple blood meals when necessary.However, this belief is based largely on observations that nectar sources and fructose-positive females are too infrequent to suggest that nectar feeding is obligatory.My laboratory experiments show that extra-floral nectar-producing plants found commonly near homes in Africa, as well as homopteran honeydew, contributed significantly to the survival of male and female An.gambiae when kept in their presence and that males require early access to sugar sources in order to survive and have any reproductive success.Results of a sugar digestion study show that An. gambiae digest even large sugar meals at a more rapid rate than other species, and the rate is even higher if metabolic reserves are low or if sugarmeal concentration is low, indicating the need for exercising restraint when interpreting field fructose results.Experiments focusing on the first gonotrophic cycle suggest that sugar feeding increases fecundity more than blood feeding alone.In iii addition, multiple blood meals, which occurred mostly after females were gravid, increased fecundity but delayed oviposition.There was no evidence of overlapping gonotrophic cycles due to multiple blood meals.The final set of experiments showed that, while males feed daily on sugar, females do not feed on sugar while developing their eggs.Instead, they sugar-feed after ovipositing and before taking their next blood meal.If blood or oviposition is delayed, they continue to sugar-feed daily for survival.Females can survive equally well on either blood or sugar, but feed less frequently on blood when sugar is available, suggesting that plants might be used to impede malaria transmission.iv Dedicated to my son v ACKNOWLEDGEMENTS I would foremost like to thank my advisor, Dr. Woodbridge Foster, who has continuously encouraged and nurtured my pursuit of this research.He has remained steadfast and patient in his support and mentoring through my personal and professional trials.I am truly