Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Biology

Supervisor(s)

Dr. Christopher Guglielmo

Abstract

Migration requires birds to sustain high intensity endurance exercise for periods lasting from hours to days. Similar to athletes, preparation and nutrition is key to success. Birds seasonally prepare for migration, which includes increasing the capacity to oxidize fat in the flight muscles. Beyond fuelling migration, n-3 long-chain polyunsaturated fatty acids (PUFA) are hypothesized to be natural doping agents and increase endurance and fatty acid oxidative capacity. I examined how birds prepare for and sustain migratory flight and directly tested the role of n-3 PUFA. Using yellow-rumped warblers (Setophaga coronata) as a model species, I first examined the effects of migratory season and endurance flight on the flight muscle transcriptome. I compared the transcriptomes of fall migratory and wintering birds and fall migrants at rest and after a four-hour flight in a wind tunnel. During the migratory season there was a coordinated upregulation of lipid metabolic pathways. Flight altered the transcriptome more than season did, and was characterized by the upregulation cytoplasmic fatty acid transporter gene expression and downregulation of genes related to glucose metabolism. Additionally, during flight there was an upregulation of pathways related to muscle damage and inflammation, and for protein synthesis and growth. Next, I tested the role of n-3 PUFA by feeding warblers diets enriched in n-3 or n-6 PUFA and assessed endurance flight performance and muscle metabolism. Neither PUFA diet altered endurance capacity or energy costs. However, contrary to the hypothesis, n-3 PUFA decreased muscle oxidative enzyme activites. Finally, as PUFA are prone to oxidative damage I investigated if diet and flight influenced antioxidants or oxidative stress. Endurance flight resulted in oxidative stress indicated by decreased glutathione: glutathione disulphide ratio and increased protein carbonyls, but no effect of PUFA was found. Protein oxidative damage was tightly related to the energy costs of flight, suggesting that optimizing flight efficiency reduces muscle damage. Overall, I found no strong positive or negative impacts of dietary PUFA. This suggests that seasonal preparation and maintenance of flight is not influenced by PUFA. Together these studies provide insight into how birds are adapted to meet the metabolic challenges of migration.

Supplemental File 1 Differential gene expression.xlsx (302 kB)
Differential gene expression results

Supplemental File 2 Migration KEGG pathways.pdf (3285 kB)
Migration KEGG pathways

Supplemental File 3 Flight KEGG pathways.pdf (2265 kB)
Flight KEGG pathways