S5-1.1 Friday, Jan. 4 Maternal Yolk Steroid Effects on Offspring: Questions and Answers from Galliform Birds ADKINS-REGAN, E*; VAN VEEN, SC; JOHNSON, P; Cornell University email@example.com
The first part of the talk will summarize results of experiments with Japanese quail and chickens supporting the hypothesis that maternal yolk steroids, especially progesterone, may be a mechanism allowing female birds to produce biased offspring primary sex ratios. In chickens, experimental elevation of maternal progesterone during meiosis (when the chromosomal sex of the ovum is determined) produced female biased sex ratios. Progesterone levels of treated hens predicted offspring sex better than either estradiol or testosterone. In female Japanese quail, increases in progesterone levels following a mating interaction predicted offspring sex ratio but changes in corticosterone levels did not. The second part of the talk will discuss some questions that need to be answered in order for progress to be made understanding maternal yolk steroid effects on later offspring phenotype, especially behavioral phenotype. Are such effects mediated by the central nervous system (CNS) directly or by peripheral consequences that then impact behavior? How do yolk steroids affect the CNS? Are such effects activational or organizational? Are there effects on offspring sexual differentiation that are part of the costs and benefits of maternal yolk steroids? Progress in answering these questions would be aided by more extensive experimental designs, by methods to reduce as well as enhance maternal yolk steroids, and by capitalizing on established avian models for hormonally based sexual differentiation, especially galliform birds.