title: Seasonal variations of basal cortisol and high stress response to captivity in Octodon degus, a mammalian model species.
abstract: Across vertebrates, the hypothalamic-pituitary-adrenal axis is a conserved neuroendocrine network that responds to changing environments and involves the release of glucocorticoids into the blood. Few studies have been carried out concerning mammalian adrenal regulation in wild species either in the laboratory or field, and even fewer have been able to determine true glucocorticoid baselines. We studied the South-American caviomorph rodent Octodon degus, a diurnal and social mammal that has become an important species in the biological research. First, we determined the plasma cortisol baseline and the acute stress concentrations during the non-reproductive and mating seasons in free-living individuals. Second, using the same protocol we assessed the impact of long-term captivity on the adrenal function in wild-caught degus and degus born in laboratory. Third, we examined laboratory groups formed with degus taken from two distant natural populations; one of them originally occurs at the Andes Mountains in high altitude conditions. The data revealed seasonal modulation of basal cortisol in the wild associated with mating. In laboratory, degus presented higher cortisol stress responses, with greater magnitudes shown in degus born and reared in captivity. No differences between populations were found. The results suggest differential regulatory mechanisms between basal and stress-induced cortisol levels, and context dependence of cortisol modulation in a mammalian species.
authors.affiliation: Instituto de Ecología y Biodiversidad, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile.
authors.forename: Rene
authors.initials: R
authors.lastname: Quispe
authors.affiliation: Instituto de Ecología y Biodiversidad, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile.
authors.forename: Camila P
authors.initials: CP
authors.lastname: Villavicencio
authors.affiliation: Department of Biological Sciences, University of Washington, 24 Kincaid Hall, Box 351800, Seattle, WA 98195, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Addis
authors.affiliation: Department of Biological Sciences, University of Washington, 24 Kincaid Hall, Box 351800, Seattle, WA 98195, USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Wingfield
authors.affiliation: Instituto de Ecología y Biodiversidad, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile. Electronic address: rvasquez@uchile.cl.
authors.forename: Rodrigo A
authors.initials: RA
authors.lastname: Vasquez
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D005260:Female; D005938:Glucocorticoids / Q000097:blood; D006234:Handling, Psychological; D006854:Hydrocortisone / Q000097:blood*; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D008297:Male; D008322:Mammals; D046329:Octodon / Q000502:physiology*; D010913:Pituitary-Adrenal System / Q000502:physiology; D012098:Reproduction / Q000502:physiology; D012621:Seasons; D013312:Stress, Physiological / Q000502:physiology*
chemical_list: D005938:Glucocorticoids; D006854:Hydrocortisone
keywords: Captivity; Cortisol; Degus; Mammals; Season; Stress