Meeting Abstract
Migratory birds undergo a variety of physiological changes to support long distance flight. Numerous studies have focused on the shifting metabolic demands and fuel utilization of avian flight muscle during migration, however, relatively few focus on how birds may morphologically meet the dynamic mechanical challenges of migratory flight. Myosin is a protein integral to muscle function, and the contractile properties of muscle are strongly linked to the isoforms of myosin present within fibers. In this study, we examined the expression of myosin heavy chain (MHC) in the pectoralis of the migratory white-crowned sparrow (Zonotrichia leucophyrys gambelii), using SDS-PAGE electrophoresis and western blots. Flight muscle samples were collected over three life history stages: February – winter condition, April – spring departure on wintering grounds, and May – spring arrival on breeding grounds. MHC expression changed substantially throughout the 3 stages. Overwintering birds expressed a single novel MHC isoform that does not match isoforms previously identified in the muscles of the domestic chicken. At spring departure, MHC expression included two isoforms: the novel isoform and one similar to the chicken adult fast isoform. Finally, at spring arrival, the MHC isoforms found in April specimens remained present but the relative proportions of the two isoforms differ with a higher percentage of the adult fast isoform (34.6% to 57.1%). To the best of our knowledge, this study is the first time a change in pectoral MHC isoform expression has been observed in avian species and may represent a specific adaptation for long distance, migratory flight. Further, this change, if present in other species, may provide a useful diagnostic tool to monitor changes in avian migratory status.
