Peeps and PUFAs: Thermoregulatory and energetic physiology of a biofilm feeding sandpiper

Kevin G. Young, Western University

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 (T_b) through incorporation into membranes to affect membrane function and fluidity. In this thesis, I investigated how n-3 LCPUFA and temperature affect the T_b 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 T_b response to cold exposure and, (3) Energy use and T_b 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 T_b might promote the use of fat for fuel by mitochondria. Dietary n-3 LCPUFA changed sandpiper T_b regulation during cold exposure and influenced the regulation of metabolic rate and T_b at low temperatures. However, diet did not influence overall metabolic rate or T_b in mild cold. During endurance flight, neither T_b 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 T_b flew longer and further. Together, my results show that n-3 LCPUFA change how shorebirds respond to cold temperatures and regulate T_b. These effects of dietary n-3 LCPUFA do not consistently affect minimum or maximum energy consumption, but changes in T_b 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.