Abstract
Mosquitoes are major vectors of diseases such as malaria, dengue, yellow fever, and Zika, collectively infecting hundreds of millions and killing over 700,000 people annually. Their ability to locate hosts for blood-feeding and find suitable oviposition sites is crucial for their reproductive success and vector competence. Humidity detection (hygrosensation) plays a vital role in these behaviors, yet the underlying cellular and molecular mechanisms remain poorly understood. This thesis provides a comprehensive investigation of hygrosensation primarily in the dengue mosquito Aedes aegypti, elucidating key molecular players, their neuronal expression patterns, and their contributions to vector-relevant behaviors.Chapter 1 offers an extensive review of hygrosensation across insect species, highlighting the gaps in our knowledge of mosquito hygrosensation and setting the stage for subsequent chapters. Chapter 2 explores the roles of ionotropic receptors Ir40a and Ir68a in Ae. aegypti, revealing their contributions to the detection of dry and moist air respectively. Notably, while both receptors act redundantly to promote blood-feeding, only Ir68a is crucial for oviposition site seeking. Chapter 3 maps the brain projections of thermo- and hygro-sensory neurons in Ae. aegypti and An. gambiae, establishing a foundational reference for future studies on sensory integration and neural circuitry in mosquitoes. Chapter 4 discusses the implications of our findings, proposes models for humidity detection mechanisms, and explores how hygrosensation interacts with other sensory modalities in the broader context of mosquito biology.
The study significantly advances our understanding of mosquito hygrosensation at the molecular and neuronal levels. By elucidating key components of humidity detection pathways and their roles in guiding critical behaviors, this work lays a strong foundation for developing novel vector control strategies targeting mosquito sensory systems. The findings provide valuable insights for both basic research in mosquito biology and applied approaches to mitigate the global burden of mosquito-borne diseases.