Immune response of male barn swallows in relation to parental effort, corticosterone plasma levels, and sexual ornamentation |
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Authors: | Saino Nicola; Incagli Michele; Martinelli Roberta; Moller Anders Pape |
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Institution: | a
Dipartimento di Scienze dell' Ambiente e del Territorio, Università di
Milano-Bicocca, via Emanueli 15, I-20126 Milano, Italy
b
Dipartimento di Biologia, Università degli Studi di Milano, via Celoria
26, I-20133 Milano, Italy
c
Dipartimento di Etologia, Ecologia ed Evoluzione, Università di Pisa,
via Volta 6, I-56126 Pisa, Italy
d
Laboratoire d'Ecologie, CNRS UMR 7625, Université Pierre et Marie
Curie, 7 quai St. Bernard, Case 237, F-75252 Paris Cedex 05, France |
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Abstract: | Life-history theory posits trade-offs between fitness components.
Reproduction negatively affects physiology and immune systemfunctioning, and the effect of this form of stress may be mediatedby glucocorticosteroids. We manipulated brood size of barnswallows (Hirundo rustica) to study the effect of stress arisingfrom reproductive effort on corticosterone levels of males.We also measured T-cellmediated immunocompetence by
intradermally injecting birds with phytohemagglutinin, whichis mitogenic to T-lymphocytes. The results confirmed the predictionof a negative effect of parental effort on lymphoproliferativeresponse. We found no covariation between immune response andcorticosterone levels. Males with long tails, an ornament currentlyunder directional sexual selection, had a relatively large
T-cell response to the mitogen, consistent with models of parasite-mediated
sexual selection predicting higher levels of immune defensein highly ornamented males. In addition, males with large sexualornaments had relatively low corticosterone levels at the endof the parental period. These results can be reconciled withthe hypothesis proposing a trade-off between parental activitiesand adaptive immunity and suggest that highly ornamented malesare less exposed or less susceptible to stress arising fromparental effort. |
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Keywords: | barn swallows corticosterone Hirundo rustica immunity parental effort secondary sexual characters stress |
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