Fuel use and corticosterone dynamics in hatchling green sea turtles (Chelonia mydas) during natal dispersal

During their natal dispersal hatchling sea turtles depart their nest, beach and inshore areas quickly to move into offshore developmental habitat using their finite energy stores. Patterns of fuel use and endocrine responses that could facilitate hatchling sea turtle dispersal activity are poorly understood. This study, examined aspects of intermediary metabolism by measuring plasma fuel use and an endocrine response of hatchling green turtles (Chelonia mydas) during terrestrial and aquatic activity coinciding with natal dispersal. Specifically, we measured plasma concentrations of glucose, non-esterised free fatty acids and protein to gauge the contributions of carbohydrate, lipid and protein metabolism for fuelling natal dispersal. In addition, we measured plasma levels of the steroid hormone corticosterone (CORT) a hormone implicated in regulating a number of metabolic events associated with migration and energy use in vertebrates. During terrestrial activity, hatchlings ascended through the sand from their nests and exhibited significant increases in plasma CORT and lactate indicating intense periods of anaerobic activity. During swimming, all plasma metabolites, with the exception of plasma protein, peaked between 1 and 4 h post-beginning swimming activity. Plasma CORT peaked at between 3 and 5 h of swimming activity. These plasma concentrations are consistent with intensive activity inducing catabolism of carbohydrate, lipid and protein stores to support prolonged activity. These results are similar to other vertebrates and suggest a relatively uniform cascade of physiological processes during such arduous migratory events.