Immune response covaries with corticosterone plasma levels under experimentally stressful conditions in nestling barn swallows (Hirundo rustica) |
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Authors: | Saino Nicola; Suffritti Chiara; Martinelli Roberta; Rubolini Diego; Moller Anders Pape |
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Institution: | a Dipartimento di Biologia, Università degli Studi di Milano, via Celoria 26, I-20133 Milano, Italy
b Laboratoire d'Ecologie Evolutive Parasitaire, CNRS FRE 2365, Université Pierre et Marie Curie, 7 quai St. Bernard, Case 237, F-75252 Paris Cedex 05, France |
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Abstract: | Traits related to fitness are often pleiotropically linked orotherwise constrained in their expression. Organisms thereforetrade between fitness components such as number and viabilityof their offspring. The physiological mechanisms mediating suchtrade-offs, however, have been poorly investigated. We manipulatedbrood size and satiation of nestling barn swallows, Hirundorustica, to simulate the effect of two kinds of natural stresses,i.e., long-term intense competition in a large brood and acutefood deprivation, and we measured their effect on body condition,T cellmediated immune response, and corticosterone, themain hormone mediating the adrenocortical stress-response. Broodenlargement increased corticosterone levels compared with thosefor brood reduction, and brood enlargement depressed immuneresponse, body mass, and condition. Corticosterone levels markedlyincreased after food deprivation. Immune response negativelycovaried with corticosterone levels measured after long-termstress. Hence, living in a crowded nest and with food deprivationelicited a stress response mediated by corticosterone, and depressedan important component of offspring fitness such as T cellmediatedimmunity. The negative covariation between circulating corticosteroneand immunity suggests that the trade-off between offspring numberand quality is mediated by variation in plasma levels of corticosterone,which has immunosuppressive effects. |
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Keywords: | body mass brood size competition corticosterone food availability Hirundo rustica immunity stress trade-off |
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