Journal article
Ectoparasite-modulated deposition of maternal androgens in great tit eggs
Proceedings of the Royal Society. B, Biological sciences, Vol.271(1546), pp.1371-1375
07/07/2004
Handle:
https://hdl.handle.net/2376/106810
PMCID: PMC1691743
PMID: 15306335
Abstract
Maternal yolk androgens can promote growth and competitive abilities of nestling birds but are also suggested to increase susceptibility to parasites or suppress immune function. We tested the hypothesis that females exposed to ectoparasites during egg formation will adjust the content of androgens in the yolk. We predicted that when anticipating high levels of parasitism, females deposit (i) less androgens into all eggs of their clutch and (ii) smaller amounts of androgens in eggs late in the laying sequence to facilitate brood reduction. In a field experiment we exposed female great tits (Parus major) to hen fleas (Ceratophyllus gallinae), or kept them free of ectoparasites prior to egg laying. We collected the eggs and measured yolk concentrations of androstenedione (A4), testosterone (T) and 5alpha-dihydrotestosterone (DHT) by radioimmunoassay. Among clutches, eggs of ectoparasite-exposed females contained significantly less A4 and tended to contain less T, whereas DHT content was unaffected. Within clutches, content of A4 and T increased significantly with laying order whereas DHT content significantly decreased. These patterns were unaffected by ectoparasites. In summary, our results provide no evidence for hormone-based facilitation of brood reduction under ectoparasite exposure but support the hypothesis that females exposed to ectoparasites reduce levels of T and its precursor A4 in yolk and might thereby reduce the negative effects of parasites on offspring.
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Details
- Title
- Ectoparasite-modulated deposition of maternal androgens in great tit eggs
- Creators
- Barbara Tschirren - Division of Evolutionary Ecology, Zoological Institute, University of Bern, 3012 Bern, SwitzerlandHeinz Richner - Division of Evolutionary Ecology, Zoological Institute, University of Bern, 3012 Bern, SwitzerlandHubert Schwabl - Division of Evolutionary Ecology, Zoological Institute, University of Bern, 3012 Bern, Switzerland
- Publication Details
- Proceedings of the Royal Society. B, Biological sciences, Vol.271(1546), pp.1371-1375
- Academic Unit
- Biological Sciences, School of
- Identifiers
- 99900546862701842
- Language
- English
- Resource Type
- Journal article