Grant: Discovery Grants Program - Individual

This research program investigates the mechanisms that underly fundamental physiological processes that freshwater (FW) aquatic insect larvae possess to regulate their internal ion and water levels, and that allow them to efficiently excrete the metabolic waste, ammonia. In this respect the long-term goal of my research is to significantly advance mechanistic knowledge of water and ion regulation as well as ammonia excretion in FW aquatic insect larvae. These mechanisms are studied in the context of the environmental contaminants, salt and ammonia, utilizing larvae of mosquitoes and mayflies. The mosquito Aedes aegypti spreads arboviral diseases like dengue, chikungunya and zika in tropical and sub-tropical regions of the world. In FW the larvae face dilution of body fluids because they maintain relatively high levels of ions (salt) in their hemolymph (blood) causing a gradient that favours ion loss and water gain to and from their habitat, respectively. However, recently these mosquitoes have been found in habitats contaminated with seawater and in septic tanks which are high in ammonia. These habitats are implicated in the prevalence of disease during dry seasons when traditional FW habitats are scarce. The research involves raising A. aegypti larvae in salt and ammonia contaminated water and examining and comparing the presence and function of specific proteins that are involved in transporting water, ions and ammonia through cells of epithelial tissues that are involved in regulating body fluid composition. We also examine proteins that regulate the permeability of the space between the cells in epithelial tissues. The nymph (larvae) stage of the mayfly Hexagenia rigida lives in sediment at the bottom of shallow FW lakes (e.g. Lake Erie) where it is an important part of the food web and an important indicator of ecosystem health. A recent study tracked salt levels of over 300 FW lakes in North America and noted sustained increases in salt levels in these lakes and predicted that levels would reach a concentration of 7 mmol l-1 within the next 50 years in many of these lakes. FW deemed suitable for drinking and for sustaining the ecosystem typically contains around 0.7 mmol l-1 of salt. This poses a threat to aquatic life and H. rigida nymphs are an excellent model organism to study these effects. This research involves exposing nymphs of H. rigida to FW contaminated with salt and performing assessments similar to that described above for the mosquito larvae. This research addresses important real-life societal problems. The research provides essential information about the underlying physiology that allow the disease vector A. aegypti to exploit new habitats (salt and ammonia contaminated water), and how salination of FW will affect aquatic FW animals. This has the potential to inform mosquito control programs and will inform policy makers contributing to the protection of inland sources of FW.