Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Biology

Supervisor

Guglielmo, Christopher G.

Abstract

In preparation for migratory endurance flights, many shorebirds deposit fuel by feeding on mudflats where algal biofilms produce n-3 long-chain polyunsaturated fatty acids (omega-3/n-3 LCPUFA). Western sandpipers (Calidris mauri) eat biofilm directly and the abundant n-3 LCPUFA they consume are hypothesized to improve migration performance by priming muscles for endurance flight. Dietary n-3 LCPUFA could affect metabolism or body temperature (Tb) through incorporation into membranes to affect membrane function and fluidity. In this thesis, I investigated how n-3 LCPUFA and temperature affect the Tb and energy metabolism of western sandpipers. I controlled the amount of n-3 LCPUFA in the diets of western sandpipers to understand their impact on (1) energy consumption and production of reactive oxygen species (ROS) by muscle mitochondria, (2) the metabolic rate and Tb response to cold exposure and, (3) Energy use and Tb patterns when flying with cold exposure. I found that n-3 LCPUFA do not directly change muscle mitochondrial energy metabolism, but they reduce ROS emission which could reduce cellular damage. Regardless of diet, low Tb might promote the use of fat for fuel by mitochondria. Dietary n-3 LCPUFA changed sandpiper Tb regulation during cold exposure and influenced the regulation of metabolic rate and Tb at low temperatures. However, diet did not influence overall metabolic rate or Tb in mild cold. During endurance flight, neither Tb nor energy use were consistently affected by diet, although n-3 LCPUFA may allow birds to switch to fat burning earlier in flight. Regardless of diet, birds with lower Tb flew longer and further. Together, my results show that n-3 LCPUFA change how shorebirds respond to cold temperatures and regulate Tb. These effects of dietary n-3 LCPUFA do not consistently affect minimum or maximum energy consumption, but changes in Tb may influence energy use over longer time periods. This thesis improves our understanding of how the migratory performance of shorebirds may be affected by the availability of natural diets rich in n-3 LCPUFA. This research is important for understanding the functional role of n-3 LCPUFA as a potentially declining resource with sea surface warming.

Summary for Lay Audience

Shorebirds fly long distances all over the world and stop at coastal mudflats to eat and recover during migration. Human development and climate change are affecting the number and value of mudflats and shorelines for birds. These habitats are rich in omega-3 long-chain polyunsaturated fatty acids (omega-3 LCPUFA) produced by algal biofilm. Western sandpipers (Calidris mauri) and other shorebirds eat biofilm and invertebrates that are rich in biofilm-produced omega-3 LCPUFA to fuel their migrations. This omega-3 LCPUFA-rich diet may prime bird muscles for flight by changing metabolism or body temperature control, especially in the cold, to improve performance. In my thesis, I studied how omega-3 LCPUFA and temperature affect the body temperature and energy metabolism of western sandpipers. For these studies, I controlled the amount of omega-3 LCPUFA western sandpipers were eating, and measured the responses of the birds to cold temperatures. Across three studies I explored how diet and temperature affect (1) muscle metabolism, (2) body temperature and energy use at rest, and (3) and body temperature and energy use when flying. I found that omega-3 LCPUFA reduce the amount of damaging molecules produced by muscles. This change could reduce the amount of damage to cells and organs during activities such as flight. Birds eating omega-3 LCPUFA also had different patterns of body temperature over time, which means that they may spend less energy heating their bodies. Omega-3 LCPUFA did not affect the amount of energy sandpipers used for flight over four hours. However, sandpipers used less energy when flying in the cold. These changes in physiology with omega-3 LCPUFA might lead to energy savings over longer time periods in wild birds. For wild animals that are always active, using less energy is important for survival and allows for flexibility to cope with difficult challenges during migration. This research shows the value of omega-3 LCPUFA for sandpiper physiology. Rising sea surface temperatures and shoreline developments may reduce the amount of omega-3 LCPUFA in nature, which will likely impact wildlife. This research provides evidence for the value of natural mudflats to these declining birds.

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