Circannual Changes in the Liver and Retina of the Long Distance Migrant, Sylvia atricapilla

Open Access
Herestofa, Alexandra Shay
Area of Honors:
Animal Sciences
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Paul Allen Bartell, Thesis Supervisor
  • William Staniar, Honors Advisor
  • circadian
  • circannual
  • metabolism
  • migration
The Blackcap, Sylvia atricapilla, is a nocturnally migrating songbird which travels extreme distances and experiences significant changes in latitude to seek better wintering and breeding conditions. Migration places stress on the bird to maintain energy, overcome increased predation, limited resources, and meet the extreme metabolic demands of long-range flight. An endogenous circannual rhythm controls the timing of seasonal migration, and it has been shown that extreme metabolic changes are necessary for the bird to cope with these extreme stressors. The liver plays a major role in fat metabolism and energy balance in birds, suggesting that seasonal changes within the liver could be necessary to initiate the changes required for successful migration. The retina is an important component of the Neuroendocrine Loop controlling biological clocks in birds, and may be necessary for navigation by modulating visual sensitivity or for magnetoreception during nocturnal migration. I therefore hypothesized that the clock in the retina and liver would be altered during migration. Liver and retina were collected from migrating and non-migrating birds and analyzed for expression of clock and clock-controlled genes related to fat catabolism, glucose metabolism, and energy homeostasis. My investigations found that the clock in the liver changes dramatically across the migratory cycle, although the clock in the retina is only slightly modified. My data suggests that these clocks helps control the seasonal changes in metabolism necessary for completing long distance nocturnal migratory flight and may therefore be considered part of the “migratory syndrome”.