Dan Wells, professor of biology and biochemistry at UH, and his team are rummaging the campus undergrowth this summer in search of the Rio Grande chirping frog. The tiny amphibian is the only direct developing frog, meaning it hatches directly to a frog from an egg, outside a tropical climate.

Wells hopes to find out how and why the frog has developed the ability to skip a lifecycle vital to other amphibians. "Amphibians are supposed to lay their eggs in water, hatch, swim around and metamorphose to become terrestrial to a large extent, that defines an amphibian," Wells said. "This frog doesnt like water at all. It buries its eggs in the ground and, in about three weeks, they hatch out as tiny froglets."

Wells believes the source of this unusual lifecycle is a genetic master switch, or a single gene that controls metamorphosis. "Its a quantum leap for our understanding," he said. "Master genes are not a completely far fetched notion they have been found. For example, master genes control sexual development in mammals if the gene is on, you form male structures, if it is off, you form female structures." A key element to a genetic master switch is a protein called a thyroxin receptor, which determines what organs the frog develops at what time. For instance, the Mexican axolotl, an amphibian with a thyroxin deficiency, is water-bound its entire life. The Rio Grande chirping frog may also be used as a guide to the quality of the local environment.

"Amphibians in general can be used as good monitors of environmental pollution," Wells said. "By studying defects, you can monitor what pesticides, pollution or ultraviolet light affect frog embryos." Before major questions can be answered, Wel
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Contact: Amanda Siegfried
asiegfried@uh.edu
713-743-8192
University of Houston
18-Jun-2003