Lean mass dynamics during flight and refueling in migratory birds: causes, consequences, and mechanisms

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

Migratory birds complete long journeys between the breeding and wintering grounds. This journey is comprised of a series of long-distance non-stop flights that can be 6-8 hours in duration for most songbirds, but could last for days in some shorebirds. During flight, metabolic rate is very high and migratory birds primarily fuel these long flights with stored fat. However, protein breakdown also occurs during flight resulting in dramatic organ and muscle mass reductions. Such dramatic reductions in muscle and organ mass could result in significant functional losses of organ systems but this has not been thoroughly investigated. This project proposes to investigate the causes, consequences, and mechanisms of protein breakdown during flight in migratory birds. This research will further our insight into the unique metabolism of migratory birds in flight, deepen our understanding of how migratory birds maintain homeostasis despite dramatic reductions in critical organ systems, and will provide novel insight into the molecular and biochemical mechanisms involved in muscle and organ degeneration and regeneration. Additionally, this project will provide a platform to engage many undergraduate and graduate students from diverse backgrounds in integrative research, providing exposure and training in a broad range of cutting edge techniques that will be applicable to many STEM fields. These students will also develop and implement science communication and outreach programming for middle school students in a local low-income school district. During flight, metabolic rate is 10-fold higher than at rest and rates of water loss are very high, placing extreme demands on the ability of birds to manage water and energy budgets. Migratory birds fuel long-duration flight primarily by the oxidation of fat, but a large amount of protein is also catabolized, resulting in reductions in muscle and organ mass of 20% - 40% from pre-flight levels. However, the functional limits and underlying mechanisms of lean mass catabolism during flight remain unclear. Migratory birds will be flown in a climatically controlled wind tunnel for extended periods to evaluate hypotheses for the causes of protein catabolism, while the consequences and mechanisms of protein catabolism will be assessed by measuring whole animal and tissue level changes in key physiological processes, and by investigating transcriptional differences that occur during flight. This will provide insight into physiological mechanisms that allow the maintenance of homeostasis despite dramatic organ and muscle remodeling, and will further our understanding of the basic mechanisms controlling phenotypic flexibility in vertebrates. Graduate and undergraduate students will receive integrative training in many cutting-edge techniques as part of this project, which will be broadly applicable to many STEM careers. This research will provide genuine research experiences for many undergraduates with emphasis on providing mentorship and training to encourage women and students from underrepresented groups to further pursue careers in STEM disciplines.