Androgens and carotenoids circulating in plasma affect the physiology and behavior of vertebrates. Much is known about control mechanisms and functions of each of these substances, yet their interactive effects are not well understood. Here we examine possible additive, multiplicative, and interactive effects of testosterone and carotenoids on female endocrine physiology, immunocompetence, and investment in eggs by simultaneously manipulating levels of testosterone [via gonadotropin releasing hormone (GnRH) challenges] and carotenoids (via diet supplementation) in captive female Japanese quail (Coturnix japonica). Females were randomly assigned to one of four treatments: carotenoid supplementation, GnRH challenge, GnRH challenge + carotenoid supplementation, or control. Carotenoid supplementation significantly increased circulating plasma carotenoid levels and acquired immune system performance, but not innate immunity. GnRH challenges elevated circulating testosterone and carotenoid levels, and induced immunosuppression in females. However, females in the GnRH challenge + carotenoid supplementation treatment had higher cell-mediated immune responses than control females and similar responses to those of carotenoid-supplemented females. Hence, availability of carotenoids in female quail seemed to counteract immunosuppressive effects of GnRH challenges. Our results provide further evidence for synergistic effects of carotenoids and testosterone on endocrine physiology and immune function in female birds. Elevated plasma testosterone or carotenoids levels resulted in increased deposition of those compounds to eggs, respectively. Furthermore, because we found that concentrations of testosterone and carotenoids in yolks were correlated within each treatment group, differential deposition of hormones and carotenoids in eggs may not only respond to surrounding social and environmental conditions, but also to other components of the egg.
|Original language||English (US)|
|Number of pages||16|
|Journal||Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology|
|State||Published - Jul 2012|
Bibliographical noteFunding Information:
Acknowledgments All procedures were conducted under the guidelines for ethical animal care and use approved by the NDSU IACUC. We thank S. WeissenXuh and M. Gastecki for valuable comments on the manuscript; J. Froehlich, S. WeissenXuh, M. Doucette, V. Nagel and a number of volunteers for assistance with animal care and laboratory procedures; E. Davenport and W. Clark for help running the immune assays; and DSM Nutritional Products Ltd. for donating carotenoid beadlets. We also thank Julio Di Rienzo for invaluable help with statistical analysis, and three anonymous reviewers for improving the manuscript. S.I.P. was supported by a postdoctoral fellowship from the Department of Biological Sciences, North Dakota State University. This work was funded by North Dakota State University AES/CSM collaborative grant program to W.L.R. and P.G.
- Acquired immunity
- Innate immunity
- Maternal effects
- Vitamin E
- Yolk carotenoids
- Yolk steroids