My research focuses on the role of steroid hormones in amphibian development and I conduct both laboratory and field studies in the U.S. and Africa. The two main areas of interest are metamorphosis and sex differentiation, but I am also interested in growth (larval and adult) and hormonal regulation of aggressive behavior. My work addresses problems on several levels including ecological, organismal, and molecular questions. In my work on metamorphosis, I study a local toad (Bufo boreas). Studies examine the effects of temperature on developmental rates, interactions between the thyroid hormones and steroids, and hormonal regulation of skin gland development. I am also examining the effects of tadpole density on developmental rates and measuring metamorphic rates and hormone levels of tadpoles in the field and in the laboratory. My work on sex differentiation involves the African clawed frog (Xenopus laevis), the Japanese kajika (Buegeria buegeri), and the Pine Barrens treefrog (Hyla femoralis). While Xenopus serves as a good model because of its availability, the latter two species have genetically distinguishable sexes. I can therefore examine early events in gonad differentiation, steroid enzyme activities, steroid receptors, etc., knowing the genetic sex of the individual larvae.
Currently, I am also examining the effects of exogenous steroids on gonadal differentiation and the potential role of endogenous steroids. My main goal is to synthesize ecological/evolutionary, organismal/physiological, and biochemical/molecular studies to learn how an animal translates changes in its external environment to internal changes, how these internal changes are coordinated, what molecular mechanisms are involved, and in turn, how changes at the molecular level affect an animal's ability to adapt to the changes in its external environment.
In the News
The herbicide atrazine, one of the world's most widely used pesticides, screws up the sex lives of adult male frogs, emasculating three-quarters of them and turning one in 10 into females, according to a new study by UC Berkeley's Tyrone Hayes.