Dr. Tyrone Hayes
	Dr. Tyrone Hayes talks about his fascination with frogs , which dates back to his early childhood. [Need help ?]

Story by Mary K. Miller

s a young boy, Tyrone Hayes loved bugs and other creepy-crawly things, but frogs have always held a special fascination for him. "Amphibians do everything in full view," the University of California at Berkeley biologist says, "I loved watching tadpoles turn into frogs ...this is an animal that's really two animals in one. In one tiny little egg, it has the entire genome to make two completely different animals."

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.

One of Dr. Hayes' research subjects, an African reed frog ( Hyperolius mariae ) from Arabuko Sokoke in Kenya. [ Click for a larger image.] Photo by Dante Fenolio.

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.

Dr. Hayes discusses the advantages of frogs as research subjects in a laboratory setting. [Need help ?]

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."