Molecular basis of egg-laying across mosquitoes

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Half the world's population is at risk of contracting mosquito-borne viral disease and it is estimated that this number will grow by 1 billion over the next 50 years. Selecting an appropriate oviposition (egg-laying) site is critical to fitness in animals like mosquitoes that perform no subsequent parental care. The broad objective of my proposed Discovery Grant is to understand, at the molecular genetic and neural circuit level, how different species of mosquito decide where to oviposit. This work will help determine why some mosquitoes have spread, and continue to spread, across the globe while others remain restricted to specific ecological niches with important implications for understanding basic mosquito biology as well as developing targeted control strategies. Aedes aegypti originated in sub-Saharan Africa but are now found across a broad and rapidly expanding swath of the globe where they exploit human beings in two primary ways: i) specializing on humans for blood, which they use to develop eggs and ii) laying eggs in small bodies of fresh water associated with human settlement, such as drinking water containers, tires, or abandoned structures. Ae. aegypti larvae die in brackish water above ~10% seawater and adult females avoid ovipositing in these salinities. By contrast, Aedes togoi are not found in urban environments and breed in saline and brackish rockpools along the coast of western North America and Asia, with larvae able to tolerate salinities ranging from freshwater to 300% seawater. Little is known about how Ae. togoi select oviposition sites and, despite variation in life history traits and spread from the tropics to the subarctic, their range remains restricted to the coast. We propose to explore the basis of contrasting oviposition strategies, larval physiology, and habitat utilization flexibility across Ae. aegypti and Ae. togoi mosquitoes, with the following specific objectives: Objective 1: Determine the behavioural strategies guiding oviposition preference in Ae. aegypti and Ae. togoi using quantitative behavioural analysis and artificial selection Objective 2: Develop a comparative genomics approach for salt- and fresh-water breeding mosquitoes using de novo genome assembly and transcriptomics Objective 3: Identify causal molecular mechanisms and neural circuits underlying shifting oviposition preference using CRISPR/Cas9 to introduce novel alleles and elucidate circuit anatomy and function This research program will shed light on genetic and behavioural adaptations underlying habitat exploitation in mosquitoes by coupling a comparative approach with targeted genetic manipulation. Understanding how insects' nervous systems adapt and allow for exploitation of novel ecological niches is critical to predicting and pre-empting range increase of agricultural pest species and vectors of human and animal pathogens in a rapidly changing world.