Integrating ionic regulation, acid-base balance and cardiorespiratory function in fish

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My research seeks to understand how physiological systems promote optimal function in diverse environments. The overarching approach is to harness the power of modern biomedical techniques to address questions about the fundamental physiology of fish that, increasingly, are experiencing environmental perturbation. I see a need to address profoundly important but simple questions how do animals sense their surroundings and how is this sensory information transformed into adaptive physiological responses? The short-term objectives build on current research and are centred on two areas; 1) mechanisms of chemoreception and ensuing cardiorespiratory responses and 2) mechanisms of ionic and acid-base regulation. The innovative new theme linking these areas is the metabolic cost of homeostasis. 1. Mechanisms of chemoreception and ensuing cardiorespiratory responses Chemoreception, the capacity of an organism to perceive changes in the chemical composition of its external or internal environment, is particularly important in fish that may experience large spatial and temporal fluctuations in environmental conditions. My laboratory has focused largely on the mechanisms allowing fish to sense changes in ambient oxygen and carbon dioxide levels and the downstream breathing and cardiac reflexes that are triggered. Ultimately, it is the physiological benefit of these reflex cardiorespiratory responses (e.g. increased breathing rates when oxygen levels fall) that enable fish to survive their labile environments. The current research proposal will address issues related to the functioning of the zebrafish chemoreceptor, the neuroepithelial cell (NEC). Experiments are designed to i) provide the first unequivocal evidence that NECs contribute to cardiorespiratory reflexes in vivo, ii) establish which neurotransmitters are involved, iii) investigate the development of chemoreception as chemoreceptors transition from the skin to the gill, and iv) assess the metabolic costs of chemoreception. 2. Mechanisms of ionic (salt) and acid-base (pH) regulation Freshwater fish must continually utilize energy to absorb salts from the dilute water to replenish those lost by diffusion. The proposed research will address the mechanisms whereby zebrafish absorb salts across specialized cells (ionocytes) on the skin of larvae and the gill of adults. Specific projects will include comparing ionocyte structure and function between larvae and adults, elucidating the relationships between salt uptake and cellular pH regulation, and determining the energetic costs of salt transport. It is anticipated that the proposed research will address four of the most important questions in fish chemosensory and ionoregulatory physiology while providing a fertile training ground for the research leaders of tomorrow.