When people or animals are thrust into threatening situations such as combat or attack by a predator, stress hormones are released to help prepare the organism to defend itself or to rapidly escape from danger—the so-called fight-or-flight response.

Now U-M researchers have demonstrated for the first time that stress hormones are also responsible for altering the body shape of developing animals, in this case the humble tadpole, so they are better equipped to survive predator attacks.

Through a series of experiments conducted at field sites and in the laboratory, Professors Robert Denver and Earl Werner, director of the E.S. George Reserve, demonstrated that prolonged exposure to a stress hormone enabled tadpoles to increase the size of their tails, which improved their ability to avoid lethal predator attacks.

"This is the first clear demonstration that a stress hormone produced by the animal can actually cause a morphological change, a change in body shape that improves their survival in the presence of lethal predators. It's a survival response," said Denver.

The team's surprising findings are detailed in a paper published online March 5, 2013 in the journal Proceedings of the Royal Society B. First author of the paper is Jessica Middlemis Maher, a former U-M doctoral student, now at Michigan State University, who conducted the work for her dissertation.

U-M News Service press release

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