Newly deposited maternal hormones can be detected in the yolks of oviductal eggs in the green anole lizard

Abstract

Studies often examine egg yolks after oviposition with the goal of drawing conclusions about maternal allocation of gonadal steroid hormones and how it may affect offspring development. However, these hormones might originate from a few sources, including the ovary, blood plasma, or the embryo itself. The goal of this study was to investigate whether maternal steroids can enter oviductal eggs. In Experiment 1, gravid female green anole lizards were injected with 1 microCi 3H-T. Plasma, ovarian follicles (separated into yolking and non-yolking samples), and shelled oviductal eggs were collected at times ranging from 15 min to 24 hr after treatment. Main effects of tissue, time, and an interaction between them all existed on recovered 3H-hormone corrected for tissue mass. Of particular interest, there was a decrease in plasma with coincident increase in eggs. In Experiment 2, females were injected with doses ranging from 0.01 to 0.45 microCi of 3H-T per gram body weight. Across tissues, 3H-hormone levels corrected for mass were greater with increasing doses. Values also differed among tissues and an interaction was detected. Within each dose, plasma and non-yolking follicles generally had higher concentrations of 3H-hormone than did yolking follicles and oviductal eggs. However, at and after 6 hr, eggs had higher total radioactivity levels than both yolking and non-yolking follicles had (not corrected for mass). The results indicate that steroids can cross through relatively well-formed shells before oviposition, suggesting a way in which maternal hormones might influence developmental factors after yolk deposition.