Leucocyte profiles and corticosterone in chicks of southern rockhopper penguins |
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Authors: | Nina Dehnhard Maud Poisbleau Laurent Demongin Olivier Chastel Hendrika J van Noordwijk Petra Quillfeldt |
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Institution: | 1.Max Planck Institute for Ornithology,Vogelwarte Radolfzell,Radolfzell,Germany;2.Department of Biology-Ethology,University of Antwerp,Antwerp (Wilrijk),Belgium;3.Centre d’études Biologiques de Chizé,CNRS UPR 1934,Beauvoir-sur-Niort,France |
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Abstract: | The immune system is essential for health and survival of vertebrates, yet still little is known about the ontogeny of the
immune system in wild birds. The southern rockhopper penguin (Eudyptes chrysocome chrysocome) is a semi-altricial seabird with a long developmental period and reversed hatching asynchrony, favouring the survival of
B-chicks. We compared leucocyte counts and baseline corticosterone levels of southern rockhopper penguin chicks under different
preconditions such as sex and origin from an A- or B-egg from 4 to 51 days of age. We conducted an experiment to compare leucocyte
profiles and baseline corticosterone levels in A- and B-chicks in single-egg clutches as well as in B-chicks from normal two
egg-clutches (one A- and one B-egg). None of these treatments influenced leucocyte counts or corticosterone levels, indicating
a similar investment in the immune system. Our main finding was an increase of leucocytes/10,000 erythrocytes with age, which
was mainly caused by an increase in lymphocyte numbers. This suggests differential investment into acquired immunity at this
stage of development. As the granulocyte/lymphocyte (G/L) ratio did not change with age or body condition, G/L ratios seem
not to reflect stress caused by poor provisioning of penguin chicks. This was also reinforced by the decrease of plasma corticosterone
levels with age. Body condition was negatively correlated with monocyte numbers, suggesting a poorer health status of penguin
chicks in poorer body condition. Yet, there was no link between body condition and other leucocyte parameters, indicating
that chicks in a good body condition did not additionally invest into their immune system. |
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