Meeting Abstract

P3.142  Jan. 6  The role of maternal hormones and diet on offspring sex-ratio in the zebra finch Taeniopygia guttata OKEKPE, C.C.*; NAVARA, K.J.; HILL, G. E.; MENDONCA, M.T.; Auburn University; Ohio State University; Auburn University; Auburn University okekpcc@auburn.edu

Sex ratio theory assumes that parents will maximize parental investment and production costs by adjusting offspring sex ratio when fitness returns of sons and daughters are differentially influenced by ecological and social circumstances. Recently, a number of studies on birds have indicated that females (being the heterogametic sex) are capable of using pre-ovulatory mechanisms to skew offspring sex-ratio; however, no one has conclusively identified the mechanism responsible for this phenomenon. An experimental study in chickens found that exogenous progesterone (P) administered during meiosis I results in male-biased offspring ratios as did a low quality, food restricted diet in zebra finches. We investigated whether diet manipulation (N=15-17 pairs/treatment) in zebra finches resulted in significant changes in both circulating P and corticosterone (B) levels at the time of ovulation (i.e. approximately 5 hours before ovulation). Preliminary analyses indicated that a low quality diet was successful in skewing the offspring ratio toward males. The results of the hormone analysis will be discussed.