by Mary K. Miller
In his research, Dr. Hayes is particularly interested in the ways in which genes and hormones regulate the developmental changes in frogs. These hormones, many of them similar if not identical to human hormones, orchestrate the development from egg to tadpole, and the metamorphosis from tadpole to adult frog.
As a scientist, Professor Hayes still takes delight in the visible transformation from swimming tadpole to hopping frog, a process that he says is one of the reasons that frogs make such good research subjects. Because they develop inside a clear egg case, amphibian metamorphosis can be seen and monitored more easily than in mammals, which develop inside the mother's body, or in birds, which develop inside a hard-shelled egg. During metamorphosis, frogs are very sensitive to changes in their environment, including chemicals introduced in the water or in their food supply. With frogs as study subjects, scientists can easily see how these chemicals affect every stage of development.
Amphibians are also
relatively easy to raise and handle, another advantage frogs have over
other research animals, such as mice. They don't take up much room --
one frog is so small it can perch on your pinkie finger -- so an average-sized
room can be filled with tens of thousands of them. They're also prolific
parents, with females typically laying 200 eggs every two weeks. For this
reason, Hayes and his students are able to raise 40 species and over 40,000
individual frogs and tadpoles in his lab at Berkeley, an unimaginable
number of subjects for scientists who use mice or other mammals in their
research. Hayes credits his success with raising frogs to the time spent
attending to amphibian care and feeding. "I guess that's the little boy
in me," he says, "I like to figure out what makes them happy, what makes
them want to feed and reproduce."
© 1999, The Exploratorium