Anemia: A physiological mechanism underlying the cost of egg production

The ‘cost of reproduction’ (i.e. trade-offs between current reproduction and future fecundity and/or survival) is a central concept in life history theory, yet the physiological mechanisms underlying such costs remain unknown. Recently it has been recognised that physiological mechanisms regulating reproduction might result in costs, for example, hormones may have antagonistic pleiotropic effects in non-reproductive organs and tissues. Here we investigate the development of anemia during egg production, which may be due to estrogenic inhibition of erythropoiesis. Anemia could function as a cost via reducing oxygen carrying-capacity of the blood, compromising aerobic performance during subsequent reproductive stages. In this thesis, we provide evidence that the development of anemia is not strictly dependent on resource level (e.g. diet quality), but is directly dependent on endogenous estrogens. Therefore, this mechanism is a good candidate for a regulatory-network based trade-off involving antagonistic pleiotropic effects of estrogens, which otherwise have essential reproductive functions.