Meeting Abstract

P3.149  Tuesday, Jan. 6  Effects of progesterone and corticosterone administration on offspring primary sex ratio in the zebra finch (Taeniopygia guttata) GAM, A.E.*; MENDON, M.T.; NAVARA, K.J.; The University of Georgia; Auburn University; Then University of Georgia knavara@uga.edu

Researchers have documented significant skews in the primary sex ratios of avian offspring in relation to a variety of environmental and social cues. Zebra finches, in particular, adjust offspring sex ratio according to both the quality and quantity of available food, as well as the attractiveness of the male. The mechanisms behind such manipulation of offspring sex, however, remain elusive. Recent studies suggest that progesterone may exert influences on the sex of offspring in birds: Progesterone administered to leghorn hens during the segregation of sex chromosomes stimulated the production of significantly more females, and corticosterone implants resulted in a significantly higher ratio of female offspring in Japanese quail. We tested the effects of a administering a pharmacological dose of progesterone or corticosterone to females at the time of sex chromosome segregation on the primary sex ratio of zebra finch offspring. Females were injected intraperitoneally with 20ug of either progesterone or corticosterone dissolved in 100ul of peanut oil, or with a control oil vehicle six hours prior to the predicted time of ovulation. Follicles ovulated immediately after injection were laid two days later, and were marked and returned to the nest. Following three days of incubation and embryonic development, eggs were collected and embryos sexed through PCR amplification of a portion of the W chromosome, after which sexes of eggs injected with progesterone or corticosterone were compared with control eggs. Results and implications will be discussed.