Foraging Behavior and Reproductive Success of the Malaria Mosquito Anopheles gambiae s.s. (Diptera: Culicidae) Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Christopher M. Stone. M.S. Graduate Program in Entomology The Ohio State University 2011 Dissertation Committee: Woodbridge A. Foster, Advisor David Denlinger Ian M. Hamilton Copyright by Christopher M. Stone 2011 Abstract The malaria mosquito Anopheles gambiae Giles s.s. has a diet consisting of nectar meals taken from plants and blood from warm-blooded animals, particularly humans. Foraging theory predicts that diets include only those items that maximize energetic intake (a proxy for fitness), yet previous studies indicate that for mosquitoes specializing on human blood, such as the yellow fever mosquito, Aedes aegypti, and An. gambiae, sugar has a negative effect on their fitness. The objective of this dissertation was to find how the presence of sugar- and blood-hosts in the environment affect the foraging decisions made by An. gambiae mosquitoes, their reproductive success, and their potential to transmit malaria. The experiments reported on in this dissertation were conducted to study the mosquito in a more (―semi‖-)natural environment than more commonly used laboratory cage environments, to more aptly reflect the energetic expenditures that come with meal-, mate-, and oviposition-site seeking behaviour in nature. Chapter 1 gives a description of the mesocosm, and develops the rationale for using such set-ups. The importance of male mosquitoes to population processes has long been overlooked, but their mating capability is strongly dependent upon access to sugar sources. Chapter 2 investigates the insemination rates of females per the presence or absence of environmental sugar; a matrix population model suggested that An. gambiae iii populations will not be viable in environments devoid of sugar sources, due to the hampering of male mating ability. Rather than maximizing energy intake and thereby directly increasing fitness, female sugar-feeding may reflect a behavioural constraint, e.g., finding and locating a swarm of males and selecting a mate may require energy best provided by a sugar meal, or sugar may be required to enable (blood-)host seeking. Thus, in Chapter 3 the sugar- feeding behaviour of females is placed in a behavioural context. Results indicated that females may take either a blood or a sugar meal as their first meal before mating and subsequently seek a blood meal. In Chapter 4 the opportunistic nature of the first meal of this species is investigated further, by altering nectar-bearing plant abundance and blood host accessibility, and assessing the meal choices of large- and small-bodied 1-d-old mosquitoes. With unrestricted access to a human throughout the night, blood was the preferred meal type. When access to a human was limited by the use of a bed net, a proportion of mosquitoes switched to sugar, and smaller (i.e., containing less energetic reserves) females were more likely to do so. When cohorts of An. gambiae were presented with various ―sugar-poor‖ plants or ―sugar-rich‖ plants, they experienced different, age-dependent, levels of mortality, and the plant community affected their human-biting rates. This resulted in mosquitoes in environments where sugar was less readily available having a higher vectorial capacity – a measure of their ability to propagate malaria (Chapter 5). Measures of fitness slightly iv favoured mosquitoes in sugar-rich rooms, supporting the notion of opportunistic sugar- feeding by this highly efficient vector of Plasmodium. v Dedication To Keith, Paulette and Karel Stone, and Holly Tuten. vi Acknowledgements Many people have contributed immensely to this dissertation, intellectually, through their support, or just through hard work. I feel fortunate to have been able to progress through this Ph.D. program under the guidance of my primary advisor, Woodbridge Foster, to whom many of the ideas and sentences in this document are to be credited. I am grateful for his support and encouragement these past 5 years. I thank the other members of my dissertation committee, David Denlinger and Ian Hamilton, for their suggestions and help, and in the case of Ian in particular for his contributions to Chapter 4. I was fortunate to have worked with Robin Taylor at the start of this program. Chapters 2-4 would not have been possible without her hard work, particularly on developing and setting up the mesocosms. I am also grateful to have collaborated with Bernard Roitberg on Chapter 3, which would have been much less appealing without his model. The last two years I have been lucky to be able to work with Bryan Jackson, without whose help the larger mesocosms used in Chapters 5 and 6 would not have been designed and set up, and performing the final experiment would have been much more grueling than it was. Robert Aldridge, Jonathan Terbot and Ashley Jackson eased several experiments by helping provide adult mosquitoes, and Jonathan Corbett provided useful assistance with the experiment described in Chapter 6. It was a pleasure to have worked alongside Babak vii Ebrahimi and Philip Otienoburu, and I am grateful for their help and support in various ways throughout. I am thankful for the support and encouragement received from my parents, Keith and Paulette Stone, and brother, Karel Stone. Finally, I thank Holly Tuten for support, inspiration, and her comments on, and careful editing of, several chapters. The author gratefully acknowledges the financial support of NIH grants R21-AI062857 and R01-AI077722. viii Vita January 29, 1980…………………………………….Born-IJsselstein, The Netherlands 1998………………………………………………... Oosterlicht College 2004………………………………………………... Doctoraal, Wageningen University 2006-2011…………………………………………. Graduate Teaching / Research Associate, The Ohio State University Publications . 1. Christopher M. Stone, Robin M. Taylor, and Woodbridge A. Foster. 2009. An effective indoor mesocosm for studying populations of Anopheles gambiae in temperate climates. Journal of the American Mosquito Control Association 25(4): 514-516. 2. C. M. Stone, R. M. Taylor, B. D. Roitberg, and W. A. Foster. 2009. Sugar deprivation reduces insemination of Anopheles gambiae (Diptera: Culicidae), despite daily recruitment of adults, and predicts decline in model populations. Journal of Medical Entomology 46(6): 1327-1337. 3. C.M. Stone, I.M. Hamilton and W.A. Foster. 2011. A survival and reproduction trade-off is resolved in accordance with resource availability by virgin female mosquitoes. Animal Behaviour 81(4): 765-774. Field of Study Major field: Entomology ix Table of Contents Abstract…………………………………………………………………….. ……... ii Dedication………………………………………………………………….. ……... v Acknowledgements………………………………………………………………… vi Vita…………………………………………………………………………………. viii List of Tables………………………………………………………………………. xi List of Figures……………………………………………………………………… xii Chapters 1. Introduction: Plant feeding and vectorial capacity………………….……... 1 Abstract……………………………………………..……………… 1 Introduction………………………………………………………... 3 1.1 Taxa involved and evidence…………………………………… 5 1.2 General features of plant feeding behaviour….……………….. 11 1.3 Obligatory or facultative nature of sugar feeding.……………... 18 1.4 Vectorial capacity…………………………..………………….. 29 1.5 Fitness…………………………………………………..……… 64 1.6 Male insemination capacity and competitiveness………………70 1.7 Flight activity and range……………………………………...... 75 1.8 Learning………………………………………………………... 76 1.9 Plant-Based Techniques for Vector Control……………............ 76 Conclusion………………………………………………………..... 92 Illustrations………………………………………………………… 94 2. An effective indoor mesocosm for studying populations of Anopheles gambiae (Diptera: Culicidae) in temperate climates…..……………………..……....96 Abstract…………………………………………………………….. 96 Body of text…………………………………………………………97 Illustrations………………………………………………………….102 x 3. Sugar deprivation reduces insemination of Anopheles gambiae (Diptera: Culicidae), despite daily recruitment of adults, and predicts decline in model populations…………………………………………………………………. 104 Abstract…………………………………………………………….. 104 Introduction………………………………………………………… 105 Materials and Methods……………………………………………... 107 Results……………………………………………………………… 118 Discussion………………………………………………………….. 121 Illustrations………………………………………………………….127 4. A survival and reproduction trade-off is resolved in accordance with resource availability by virgin female mosquitoes …………………………………. 133 Abstract…………………………………………………………….. 133 Introduction………………………………………………………… 134 Materials and Methods……………………………………………... 138 Results……………………………………………………………… 145 Discussion………………………………………………………….. 151 Illustrations………………………………………………………….159 5. The first meal choice (blood vs. sugar) of the malaria mosquito Anopheles gambiae s.s. is affected by bed net use and female size, but not plant abundance ………………………………………………………………………164 Abstract…………………………………………………………….. 164 Introduction………………………………………………………… 165 Methods……………………………………………......................... 170 Results……………………………………………………………… 176 Discussion………………………………………………………….. 179 Illustrations………………………………………………………….187 6. Plant community composition affects the vectorial capacity and fitness of the malaria mosquito Anopheles gambiae s.s. ………………………………… 194 Abstract…………………………………………………………….. 194 Introduction………………………………………………………… 195 Materials and Methods……………………………………………... 198 Results……………………………………………………………… 204 Discussion………………………………………………………….