DISSERTATION RESEARCH: Assessment of Endocrine Disruptor Effects in Anurans

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Amphibians have been proposed as bio-indicators of environmental change. Amphibian populations may be in rapid worldwide decline for reasons that are still unclear. One proposed contributor to this decline is widespread contamination with chemicals that disrupt hormone systems. This study is designed to evaluate ways of testing the effects that eco-estrogens have on frogs and toads (anurans). Eco-estrogens include chemicals mostly designed for agricultural and industrial use and that have been proposed to mimic the effects of estrogens. The PIs will use anurans to examine the effects of naturally produced (endogenous) estrogens and compare the effects of endogenous estrogens to the effects of eco-estrogens. The PIs found that the endogenous estrogen effects vary according to species and developmental stage. The PIs are testing multiple species and multiple life stages to determine if specific eco-estrogens consistently act like endogenous estrogens throughout all of our tests.Endogenous estrogens cause adult female frogs and toads to produce egg yolk components (vitellogenin). Males do not normally produce vitellogenin because they do not normally make eggs. However, vitellogenin production can be induced in males exposed to both endogenous and eco-estrogens. Before vitellogenin can be produced, the genetic instructions to produce vitellogenin (vitellogenin mRNA) must be made. The PIs will survey wild male frogs and toads at sites throughout California to determine if their vitellogenin genes are turned on. The PIs shall use this information as the first step in developing a reliable system for detecting estrogen exposure in non-laboratory animals.