title: Variable effects of yolk androgens on growth, survival, and immunity in eastern bluebird nestlings.
abstract: Female birds allocate androgens differentially within and among clutches, and it has been suggested that this is a strategy to maximize reproductive success. Only a few studies, however, have examined the effects of yolk testosterone (T) on the growth and development of nestlings, and none have reported on the immunological effects of yolk T nor have they examined several different effects in the same nestlings. To examine the effects of yolk T on nestling eastern bluebirds, we administered two doses of exogenous T to bluebird eggs and measured the growth and immunological responsiveness in the resulting nestlings. We found that yolk T is detrimental to developing embryos, with hatching success decreasing with increasing doses of yolk T. Moderate doses of yolk T stimulated skeletal growth during the embryonic period, while high doses of yolk T resulted in nestlings that weighed more and were more mature at fledging but had a compromised T-cell immune response to phytohemagglutinin. These data suggest that the alteration of reproductive success through the allocation of yolk T is a complicated phenomenon that involves the integration of several physiological effects.
authors.affiliation: Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA. navarkr@auburn.edu
authors.forename: Kristen J
authors.initials: KJ
authors.lastname: Navara
authors.forename: Geoffrey E
authors.initials: GE
authors.lastname: Hill
authors.forename: Mary T
authors.initials: MT
authors.lastname: Mendonca
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development* / Q000276:immunology; D000906:Antibodies / Q000097:blood; D000917:Antibody Formation / Q000187:drug effects; D001837:Body Weights and Measures; D004527:Egg Proteins / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000187:drug effects; D005260:Female; D007111:Immunity, Cellular / Q000187:drug effects*; D007958:Leukocyte Count; D010063:Ovum / Q000187:drug effects / Q000502:physiology; D046109:Passeriformes / Q000196:embryology* / Q000254:growth & development* / Q000276:immunology; D010835:Phytohemagglutinins; D013739:Testosterone / Q000494:pharmacology* / Q000502:physiology
chemical_list: D000906:Antibodies; D004527:Egg Proteins; D010835:Phytohemagglutinins; D013739:Testosterone