Meeting Abstract

P1.151  Sunday, Jan. 4  Early testosterone exposure in amphibian eggs: no effects on development, growth, or behavior WIDDER, P.D.; Virginia Tech widder@vt.edu

In a variety of egg-laying taxa, steroid hormones have been found to be maternally transferred to the yolk of eggs. Furthermore, additional studies, especially in birds, have found that early exposure of the developing embryo to testosterone can influence development, growth and behavior. I recently verified that amphibian eggs also contain steroid hormones at laying and that the amounts of testosterone vary by female; however, the influence of this early exposure to testosterone on amphibian development, growth, and behavior is not known. I collected four clutches of freshly laid Rana sylvatica (Wood frog) eggs and exposed each of them to three different levels of testosterone for 48 hours. At the end of 48 hours, I sampled a subset of eggs and, using a radioimmunoassay, verified that the egg hormone levels were elevated, yet remained within physiological limits. The remaining eggs were raised to hatching, and time-to and stage-at hatching were recorded, as well as several morphological variables. After one month of development, at Gosner (1960) stages 26-27, I measured tadpole activity level, fast start behavior, and again assessed tadpole morphological variables. Finally, after two months of development (Gosner stages 30-36), morphology was assessed a third time. Throughout the experiment, changes in development, growth, or behavior were never observed relative to testosterone treatments; however, significant clutch effects were observed in most measures. Thus, the significance of maternally-derived testosterone in amphibian eggs remains unclear.