title: Seasonal redistribution of immune function in a migrant shorebird: annual-cycle effects override adjustments to thermal regime.
abstract: Throughout the annual cycle, demands on competing physiological systems change, and animals must allocate resources to maximize fitness. Immune function is one such system and is important for survival. Yet detailed empirical data tracking immune function over the entire annual cycle are lacking for most wild animals. We measured constitutive immune indices once a month for a year on captive red knots (Calidris canutus). We also examined temperature as an environmental contributor to immune variation by manipulating ambient temperature to vary energy expenditure. To identify relationships among immune indices, we performed principal-component analysis. We found significant repeatability in immune indices over the annual cycle and covariation of immune indices within and among individuals. This covariation suggests immune strategies as individual traits among individuals and the use of different immune strategies during different annual-cycle stages within individuals. Over the annual cycle, both higher-cost phagocyte-based immunity and lower-cost lymphocyte-based immunity were high during mass change, but there was a clear shift toward lower-cost lymphocyte-based immunity during peak molt. Experimental manipulation of temperature had little effect on annual variation in immune function. This suggests that other environmental factors, such as food availability and disease, should also be examined in the future.
authors.affiliation: Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, P.O. Box 14, 9750 AA, Haren, The Netherlands. d.m.buehler@rug.nl
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Buehler
authors.forename: Theunis
authors.initials: T
authors.lastname: Piersma
authors.forename: Kevin
authors.initials: K
authors.lastname: Matson
authors.forename: B Irene
authors.initials: BI
authors.lastname: Tieleman
mesh_terms: D000220:Adaptation, Biological / Q000502:physiology*; D000818:Animals; D001835:Body Weight; D002176:Candida albicans / Q000276:immunology; D046091:Charadriiformes / Q000276:immunology*; D004926:Escherichia coli / Q000276:immunology; D008214:Lymphocytes / Q000097:blood; D009426:Netherlands; D010507:Periodicity; D010586:Phagocytes / Q000166:cytology; D025341:Principal Component Analysis; D012621:Seasons; D013211:Staphylococcus aureus / Q000276:immunology; D013696:Temperature