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BEYOND THE FAT: PROTEIN METABOLISM AND MUSCLE FUNCTION AS PART OF THE MIGRATORY SYNDROME OF SONGBIRDS

Abstract
Migration allows animals to seasonally exploit favorable habitats that are geographically disparate, and migratory animals have a suite of adaptations to complete their extraordinary journeys. This “migratory syndrome” of traits is comprised of seasonally-responsive adaptations that together result in changes to metabolism, body composition, and reproductive status, all of which act to increase the probability of a successful migration. The focus of my dissertation is to investigate the suite of changes in metabolism and muscle function that enable birds to undertake long-duration flights. In chapter 1, I compare fuel use in flight between two related migratory warbler species that migrate vastly different distances, showing that both species catabolized fat and lean mass similarly in flight, with fat burned at a steady rate while protein loss starts off high early in flight and declines exponentially over time. In chapter 2, I investigated seasonal changes in protein metabolism between White-throated Sparrows in the non-migratory and migratory condition. I found that birds in the migratory condition increased activity of fat catabolism enzymes as expected, but also increased activity of protein catabolism enzymes and should greater water loss and lean mass catabolism in the migratory condition. In chapter 3, I performed RNA-seq analysis on muscle and liver tissues from a subset of birds in the migratory and non-migratory conditions in Chapter 2 to show metabolic changes to the two tissues in preparation for migration and potential changes to the capacity for rapid muscle remodeling in the migratory condition. Finally, in chapter 4 I explored the potential for altered Ca2+-pumping efficiency in the muscle of migratory birds, finding increased expression of the sarcolipin uncoupling gene and proposing that seasonal changes to gene expression in the flight muscle may precede the fattening that is associated with migratory body composition. These studies move beyond our current understanding of fuel use during migration to suggest that dynamic protein metabolism and unique alterations to muscle physiology are important, and underexplored, aspects of the migratory syndrome in songbirds.
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openaccess
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dissertation
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http://creativecommons.org/licenses/by-nc-nd/4.0/