The physiological similarities between humans and amphibians make frogs ideal subjects for research, according to Dr. Hayes. [Need help ?]

ecause much of the physiology of humans and amphibians is so similar, frogs can be stand-ins for basic research into human development and diseases, such as cancer. "Testosterone is testosterone is testosterone," Hayes says. "The hormone that caused my larynx to develop is the same hormone that causes development of vocal sacs in these frogs."

The current star in Hayes' lab is an African reed frog ( Hyperolius argus ) that is especially sensitive to estrogen. Named after the sentinel Argus, a 100-eyed monster from Greek mythology, the female of this tiny frog species sports colorful spots on its back while the male is solid green. "Out of 4,000 frogs species in the world," says Hayes, "this is one in only five frogs we know about where females and males have different colors."

Male (left) and female (right) African reed frogs ( Hyperolius argus. ) [ Click for a larger image.] Photo courtesy of Dr. Tyrone Hayes.
In this RealAudio clip, hear the call of the African reed frog ( Hyperolius argus ) pictured above. [Need help ?]

  
Professor Hayes would like to understand the ecological and evolutionary reasons for the sexual color differences in reedfrogs, why they developed this strategy for survival. "Are they like the poison dart frog," he questions, "where the females are out in the open more so they have a warning coloration, while the males rely more on camouflage?"

While the sexual coloration is intriguing in itself, another related discovery makes this frog especially valuable for research. During a critical period in the frog's development, one of the students in Hayes lab introduced low doses of estradiol and other estrogen-like substances in the water. Instead of remaining their characteristic green, the male reed frogs exposed to females hormones developed female coloration.

"This is very exciting for our research, but one of the troubling things about this," says Hayes, "is if you go into the environment and see these animals they look like perfectly normal females, except they shouldn't be females because some of them are males."