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Transgenerational immunity in a bird–ectoparasite system: do maternally transferred antibodies affect parasite fecundity or the offspring's susceptibility to fleas?

Authors

  • BARBARA TSCHIRREN,

    Corresponding author
    1. Centre for the Integrative Study of Animal Behaviour, Macquarie University, Sydney, NSW 2109, Australia
    2. Evolutionary Ecology Group, Zoological Institute, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland
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  • HELI SIITARI,

    1. Department of Biological and Environmental Science, University of Jyväskylä, PO Box 35, 40014 Jyväskylä, Finland
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  • VERENA SALADIN,

    1. Evolutionary Ecology Group, Zoological Institute, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland
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  • HEINZ RICHNER

    1. Evolutionary Ecology Group, Zoological Institute, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland
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*Corresponding author.
Email: barbara.tschirren@mq.edu.au

Abstract

During egg formation, female birds deposit antibodies against parasites and pathogens they were exposed to before egg laying into the yolk. In captive bird species, it has been shown that these maternal immunoglobulins (maternal yolk IgGs) can protect newly hatched offspring against infection. However, direct evidence for such benefits in wild birds is hitherto lacking. We investigated (1) if nestling Great Tits Parus major originating from eggs with naturally high levels of maternal yolk IgG are less susceptible to a common, nest-based ectoparasite, (2) if maternal yolk IgGs influence nestling development and in particular, their own immune defence, and (3) if there is a negative correlation between levels of maternal yolk IgG in host eggs and the reproductive success of ectoparasitic fleas feeding on the nestlings. Counter to expectations, we found no indication that maternally transferred yolk IgGs have direct beneficial effects on nestling development, nestling immune response or nestling resistance or tolerance to fleas. Furthermore, we found no negative correlation between host yolk IgG levels and parasite fecundity. Thus, whereas previous work has unequivocally shown that prenatal maternal effects play a crucial role in shaping the parasite resistance of nestling birds, our study indicates that other egg components, such as hormones, carotenoids or other immuno-active substances, which bird females can adjust more quickly than yolk IgG, might mediate these effects.

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