Effects of estrogenic contamination on anuran amphibians with varying life histories

Amphibian decline is affected by several causes, all of which are widespread.  However, the response by amphibian species is not uniform.  Contamination, for example, is prevalent not only from point sources but is also available worldwide via atmospheric deposition.  My thesis research examines the role that estrogenic contaminants play in the varied response of amphibian species to decline.  I am investigating the influence of life-history characteristics especially sensitive to estrogenic endocrine disrupting contaminants on factors important to population persistence.  In particular I am interested in the effect of 17-β-estradiol and atrazine, a widespread estrogenic contaminant, on sex ratio, survival, time and size at metamorphosis, and mating behavior in true toads (Bufonidae), true frogs (Ranidae) and treefrogs (Hylidae). 

The representatives I have chosen from these families vary in their length of larval periods and stage of gonad differentiation at metamorphosis.  American toads (B. americanus) and gray treefrogs (H. versicolor) have relatively short larval periods as compared to Southern leopard frogs (R. sphenocephala).  Further, all representatives experience varied gonad developmental rates (Ogielska and Kotusz, 2004; personal observation).  Thus, when estrogens appear in the water, each species is exposed for different lengths of time and during different stages of development. 

Storrs, S.I., and R.D. Semlitsch. 2008. Species variation in somatic and ovarian development: predicting susceptibility of amphibians to estrogenic contaminants. General & Comparative Endocrinology 156:524-530.

Storrs, S.I. and J.M. Kiesecker.  2004  Survivorship patterns of larval amphibians exposed to low concentrations of atrazine.  Environ Health Perspect  112:1054-1057.