When being chased by predators, it’s best to move quickly. I remember a scene in the movie, “Jurassic Park”, where the characters were being chased by a Tyrannosaurus Rex. As the jeep sped down a dirt road, Jeff Goldblum kept repeating, “Must go faster”. And then there was a scene in the movie, “Independence Day”, where Will Smith and Jeff Goldblum were fleeing from the bowels of the alien mother ship. Jeff’s words of advice to Will Smith: “Must go faster.”
But human beings are not the only creatures who are chased by predators. So are frog tadpoles; they are hunted by a number of predators such as racoons, fish, snapping turtles and birds and even dragonfly larvae. To stand any chance of escape, the tadpoles must swim faster.
And what will help frog tadpoles swim faster? How about larger tail? In their experiments with tadpoles, University of Michigan researchers found “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.”
Here’s how they conducted the experiments. Researchers placed tadpoles in a tank of water. Then they placed dragonfly larvae (tadpole predators) in small cages inside the tank. Inside the cages, the larvae were fed live tadpoles. “When under attack, tadpoles, release chemical signals called pheromones that travel through the water to alert other tadpoles to the presence of predators. The researchers found that tadpoles repeatedly exposed to the alarm pheromone over several days showed elevated whole-body levels of corticosterone.”
Meanwhile, 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.
The stess hormone produced by tadpoles, corticosterone, is chemically similar to cortisol, the stress hormone produced by humans. So it appears that no matter whether you’re being chased by dragonfly larvae, T-rex’s or space aliens, the body’s chemical stress response is similar and the goal is the same: must go faster.
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Trail Maintenance Schedule. Come join our volunteers as they help maintain our trails. Contact Steve at firstname.lastname@example.org for time and place.
Wednesday mornings, September 4, 11, 18 & 25.
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Ask Dr. Norm: Do you have questions about the flora, fauna, animals, rocks, etc. in our Santa Clarita Valley? Here’s a place for you to ask your questions. Dr. Norman Herr, Ph.D., is a professor of science and computer education at California State University, Northridge.
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Source: Santa Clarita News