Naturally equipped to resist ‘stress’? : Physiological responses of adult king penguins to an experimental increase in glucocorticoid levels

• Main Author: Raymond, Emilie
• Other Authors: Ecole Nationale Vétérinaire de Toulouse (ENVT), Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université de Toulouse (UT), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT), Annabelle Meynadier
• Format: Master Thesis
• Language: French
• Published: HAL CCSD 2023
• Subjects: Allostatic overload; Corticosterone; Energetics; Free radical theory of ageing; King penguin (Aptenodytes patagonicus); Mitochondria; Oxidative stress; Telomere; Corticostérone; Manchot royal; Télomères (génétique); Stress oxydatif; Manchot royal (Aptenodytes patagonicus); Métabolisme énergétique; Mitochondrie; Stress chronique; Stress oxydant; Surcharge allostatique; Télomère; Théorie radicalaire du vieillissement; Chronic stress; [SDV.BA.MVSA]Life Sciences [q-bio]/Animal biology/Veterinary medicine and animal Health; Manchot; Manchots; King Penguins
• Online Access: https://dumas.ccsd.cnrs.fr/dumas-04414294; https://dumas.ccsd.cnrs.fr/dumas-04414294/document; https://dumas.ccsd.cnrs.fr/dumas-04414294/file/T-2023-149.pdf

Animals' exposure to repeated environmental stress in their natural habitat could impact their life-history stage and have long-term deleterious effects. Glucocorticoids, which are stress hormones, allow adaptive response and modulation of energetics of the animal enabling it to cope with acute stress. However, it is widely assumed that chronic exposure to high glucocorticoids levels can cause oxidative stress and have a lasting impact on organisms. Recently, some studies have tried to highlight that species living in challenging environments exhibit adaptations in order to alleviate chronic stress’ negative effects on oxidative stress. We tested this hypothesis on adult king penguins in inducing chronic exposure to corticosterone high levels with corticosterone implants. Thereafter, we measured corticosterone levels, energetics dynamics and multiple oxidative stress markers over several weeks. Despite an increase in corticosterone levels, only one oxidative stress marker which shows oxidative damage reparations to DNA was significant. Slight variations in glucose and protein metabolism may also reflect adaptations to chronic stress. This study highlights the ability of animals to perfectly fit their environment and opens the door on possible physiological mechanisms allowing them to avoid or alleviate the adverse effects of a glucocorticoid allostatic overload. L’exposition des animaux à des stress environnementaux répétés dans leur biotope naturel pourrait impacter leurs cycles biologiques et avoir des effets délétères à long terme. Les glucocorticoïdes, hormones du stress, favorisent une réponse adaptative et une modulation de la physiologie énergétique de l’animal lui permettant de gérer un état de stress aigu. Cependant, il est supposé qu’une exposition chronique à taux élevés de glucocorticoïdes peut engendrer du stress oxydant et impacter durablement l’organisme. Récemment, des études ont cherché à montrer que les espèces vivant dans des milieux contraignants présentent des adaptations pour limiter les ...