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Evolutionary Change Leapfrogs Over Tadpoles

Date:
March 29, 2000
Source:
University Of Toronto
Summary:
Scientists at the University of Toronto have discovered a species of frog that skips the tadpole phase of development but still requires a thyroid to grow into fully formed adults.

Newly discovered species of frog bypasses the tadpole phase of development

University of Toronto scientists have recently discovered a species of frog that skips the tadpole phase of development but still requires a thyroid to grow into fully formed adults.

"We already knew that many frogs - mostly in tropical zones - bypass the tadpole stage and hatch from eggs as tiny versions of mature adults," says zoology professor Richard Elinson, who co-authored a paper with former doctoral student Elizabeth Callery. "But the question was 'How did they manage to do it?' Since a tadpole requires thyroid hormone to mature into an adult, was the hormone eliminated along with the tadpole phase? It had been assumed that this other species developed without a thyroid hormone but we've shown they still have a thyroid-dependent state."

Elinson calls this a classic case of evolutionary change in development. The theory is that this species, found in the tropics of Puerto Rico, evolved over millions of years to the point where it retained the hormone but lost its tadpole phase. In other words, he says, these frogs devised ways to evade dangerous living conditions in water containing predators - their mating occurs on land, fertilization happens in the body of the female and eggs are laid and hatched on land

The paper, titled Thyroid Hormone-Dependent Metamorphosis in a Direct Developing Frog, is featured in the March 14 issue of Proceedings of the National Academy of Sciences of the United States of America.

CONTACT:
Janet Wong
U of T Public Affairs
(416) 978-6974
jf.wong@utoronto.ca


Story Source:

The above story is based on materials provided by University Of Toronto. Note: Materials may be edited for content and length.


Cite This Page:

University Of Toronto. "Evolutionary Change Leapfrogs Over Tadpoles." ScienceDaily. ScienceDaily, 29 March 2000. <www.sciencedaily.com/releases/2000/03/000328152247.htm>.
University Of Toronto. (2000, March 29). Evolutionary Change Leapfrogs Over Tadpoles. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2000/03/000328152247.htm
University Of Toronto. "Evolutionary Change Leapfrogs Over Tadpoles." ScienceDaily. www.sciencedaily.com/releases/2000/03/000328152247.htm (accessed July 28, 2014).

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