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Skeletal muscle remodeling in amphibious fishes out of water

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Title: Skeletal muscle remodeling in amphibious fishes out of water
Author: Rossi, Giulia
Department: Department of Integrative Biology
Program: Integrative Biology
Advisor: Wright, Patricia
Abstract: One of the most extreme ecological transitions has been the colonization of land by fishes. Moving between aquatic and terrestrial environments poses critical challenges for a number of processes, including locomotion. The focus of my PhD was to investigate how the skeletal muscle of fishes remodels in response to various forms of air-exposure (e.g., constant, fluctuating) and determine the functional implications of this plasticity. I used an amphibious killifish (Kryptolebias marmoratus) to first test the hypothesis that skeletal muscle remodelling in response to constant (28 d) air-exposure is driven by the increased oxygen availability in air. Indeed, oxygen was a driver for muscle remodeling on land, as both air-exposure and hyperoxia increased (>25%) the size of red muscle fibers in K. marmoratus. Since K. marmoratus can survive for weeks on land without food, I then questioned how fish were able to maintain their muscle integrity during prolonged periods of air-exposure (21 d). I tested the hypothesis that amphibious fishes that remain on land for weeks at a time use metabolic depression as a strategy to preserve muscle integrity. My results demonstrated that metabolic depression is important for slowing the use of endogenous energy stores by fish on land, including muscle protein. I also found that K. marmoratus seek hypoxic microhabitats during prolonged air-exposure that accentuate metabolic depression. Given the highly plastic nature of K. marmoratus muscle, I then tested the hypothesis that the scope for muscle plasticity is modulated by environmental conditions during early development. I found that fluctuating water-air conditions during development attenuated the scope for muscle plasticity in later life. Finally, I was interested to understand the broader role of muscle and terrestrial locomotion in facilitating land invasions by fishes. I tested the hypothesis that terrestrial exercise would improve spatial cognition in amphibious fishes, and enhance neurogenesis in the brain region linked to spatial cognition. I found that terrestrial excursions enhanced cognition in K. marmoratus, as both terrestrial exercise and air-exposure improved spatial learning abilities. Overall, my thesis integrates behavioural, morphological, and physiological perspectives to provide new insights into how amphibious fishes successfully colonize and exploit terrestrial habitats.
Date: 2021-06
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Related Publications: Rossi GS, Turko AJ, Wright PA (2018) Oxygen drives skeletal muscle remodeling in an amphibious fish out of water. Journal of Experimental Biology. 221, jeb180257.
Embargoed Until: 2021-12-31

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