title: Exogenous corticosterone mimics a late fasting stage in captive Adelie penguins (Pygoscelis adeliae).
abstract: Fasting is part of penguin's breeding constraints. During prolonged fasting, three metabolic phases occur successively. Below a threshold in body reserves, birds enter phase III (PIII), which is characterized by hormonal and metabolic shifts. These changes are concomitant with egg abandonment in the wild and increased locomotor activity in captivity. Because corticosterone (CORT) enhances foraging activity, we investigated the variations of endogenous CORT, and the effects of exogenous CORT on the behavioral, hormonal, and metabolic responses of failed breeder Adélie penguins. Untreated and treated captive male birds were regularly weighed and sampled for blood while fasting, and locomotor activity was recorded daily. Treated birds were implanted with various doses of CORT during phase II. Untreated penguins entering PIII had increased CORT (3.5-fold) and uric acid (4-fold; reflecting protein catabolism) levels, concomitantly with a rise in locomotor activity (2-fold), while prolactin (involved in parental care in birds) levels declined by 33%. In CORT-treated birds, an inverted-U relationship was obtained between CORT levels and locomotor activity. The greatest increase in locomotor activity was observed in birds implanted with a high dose of CORT (C100), locomotor activity showing a 2.5-fold increase, 4 days after implantation to a level similar to that of birds in PIII. Moreover, uric acid levels increased three-fold in C100-birds, while prolactin levels declined by 30%. The experimentally induced rise in CORT levels mimicked metabolic, hormonal, and behavioral changes, characterizing late fasting, thus supporting a role for this hormone in the enhanced drive for refeeding occurring in long-term fasting birds.
authors.affiliation: Université de Strasbourg, Institut Pluridisciplinaire Hubert Curien–Départment Ecologie, Physiologie et Ethologie, 23 rue Becquerel, Strasbourg Cedex 2, France. marion.spee@c-strasbourg.fr
authors.forename: Marion
authors.initials: M
authors.lastname: Spée
authors.forename: Lorène
authors.initials: L
authors.lastname: Marchal
authors.forename: Anne-Mathilde
authors.initials: AM
authors.lastname: Thierry
authors.forename: Olivier
authors.initials: O
authors.lastname: Chastel
authors.forename: Manfred
authors.initials: M
authors.lastname: Enstipp
authors.forename: Yvon
authors.initials: Y
authors.lastname: Le Maho
authors.forename: Michaël
authors.initials: M
authors.lastname: Beaulieu
authors.forename: Thierry
authors.initials: T
authors.lastname: Raclot
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight / Q000187:drug effects; D016009:Chi-Square Distribution; D003345:Corticosterone / Q000008:administration & dosage* / Q000097:blood; D004343:Drug Implants; D004734:Energy Metabolism / Q000187:drug effects; D005215:Fasting / Q000097:blood; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005247:Feeding Behavior / Q000187:drug effects*; D005260:Female; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D011388:Prolactin / Q000097:blood; D046429:Spheniscidae; D013997:Time Factors; D014527:Uric Acid / Q000097:blood
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D004343:Drug Implants; D005230:Fatty Acids, Nonesterified; D014527:Uric Acid; D011388:Prolactin; D003345:Corticosterone