Environmental Protection

Tadpoles Grow Bigger Tails to Elude Predators

University of Mighican researchers have demonstrated that stress hormones can alter the body shape of developing animals, such as the tadpole, in order to better defend themselves against predator attacks.

Researchers at the University of Michigan conducted a series of experiments in the laboratory and out at field sites in order to observe how tadpoles that were exposed to a stress hormone for a prolonged amount of time were able to increase the size of their tales, thus improving their ability to avoid 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 Robert Denver, a professor of molecular, cellular and developmental biology and of ecology and evolutionary biology.

In the laboratory, other tadpoles were exposed either to the alarm pheromone, to corticosterone or to a chemical that blocks the synthesis of the stress hormone. Over the course of several days, tadpoles treated with either the pheromone or the stress hormone developed deeper tails and shorter trunks than control animals, while tadpoles treated with the pheromone and the hormone inhibitor had shallower tails and longer trunks than those exposed to the pheromone alone.

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