In response to prolonged periods of fasting, animals have evolved metabolic adaptations helping to mobilize body reserves and/or reduce metabolic rate to ensure a longer usage of reserves. However, those metabolic changes can be associated with higher exposure to oxidative stress, raising the question of how species that naturally fast during their life cycle avoid an accumulation of oxidative damage over time. King penguins repeatedly cope with fasting periods of up to several weeks. Here, we investigated how adult male penguins deal with oxidative stress after an experimentally induced moderate fasting period (PII) or an advanced fasting period (PIII). After fasting in captivity, birds were released to forage at sea. We measured plasmatic oxidative stress on the same individuals at the start and end of the fasting period and when they returned from foraging at sea. We found an increase in activity of the antioxidant enzyme superoxide dismutase along with fasting. However, PIII individuals showed higher oxidative damage at the end of the fast compared with PII individuals. When they returned from re-feeding at sea, all birds had recovered their initial body mass and exhibited low levels of oxidative damage. Notably, levels of oxidative damage after the foraging trip were correlated to the rate of mass gain at sea in PIII individuals but not in PII individuals. Altogether, our results suggest that fasting induces a transitory exposure to oxidative stress and that effort to recover in body mass after an advanced fasting period may be a neglected carryover cost of fasting.
The authors declare no competing or financial interests.
Q.S. contributed to study design, data collection and analyses, and writing the manuscript. V.A.V. contributed to data analyses and writing the manuscript. H.S. contributed to data collection and laboratory analyses. A.S. and E.L. contributed to data collection. F.C. contributed to data analyses and writing the manuscript. P.B. contributed to study design, data analyses and writing the manuscript. J.-P.R. contributed to study design, data collection and writing the manuscript.
This research was funded by the Institut Polaire Français Paul Emile Victor (IPEV; Research Program 119) and the Centre National de la Recherche Scientifique (CNRS-INEE). Q.S. was funded by a doctoral fellowship from the Ministère de l'Éducation Nationale, de l'Enseignement Supérieur et de la Recherche. Field logistic support was provided by Terres Australes et Antarctiques Françaises.
Supplementary information available online at http://jeb.biologists.org/lookup/doi/10.1242/jeb.145250.supplemental
- Received June 27, 2016.
- Accepted August 8, 2016.
- © 2016. Published by The Company of Biologists Ltd