Meeting Abstract
The herbicide atrazine is one of the most commonly used agrichemicals in the world. It is also a potent endocrine disruptor that is active at low, ecologically relevant doses. Among other mechanisms, atrazine induces aromatase and results in increased estrogen production. Exposure to atrazine during larval development in African clawed frogs (Xenopus laevis) results in demasculinized and feminized gonadal and laryngeal morphology. Here, we examined the effects of atrazine and exogenous estradiol on the size of the dilator laryngis muscle in male Xenopus laevis. Larvae from two different sources of Xenopus laevis exhibited dissimilarities in the ratio of females to males produced in response to each treatment, indicating a difference in sensitivity to estrogenic compounds between different sources. Thirty percent of the genetically male larvae from one source (San Diego) developed ovaries in response to estrogen (3 ng/ml), but the second source (Xenopus Express) showed no response. There was no indication of an interaction between atrazine and estradiol, and laryngeal morphology appeared unaffected in both sources. Preliminary observations of female-typical laryngeal morphology in genetically male frogs with testes suggest that there are tissue-specific responses within individuals to endocrine disruptors, prompting further investigation into their causal mechanisms. These data demonstrate the importance of examining variability in response to estrogen and endocrine disruptors in the species, especially if Xenopus laevis is to be used as the accepted model for studying endocrine disruption and for predicting impacts on free-ranging amphibians.
