Thaindian News

Toronto, Oct 28 (IANS) A fish predator’s mere presence can trigger enough stress to kill a dragonfly. Scientists suggest that the finding could be used as a model for studies on the lethal effects of stress on all organisms.

“How prey respond to the fear of being eaten is an important topic in ecology,” says Locke Rowe, professor of ecology and evolutionary biology and co-principal investigator of a study conducted by the University of Toronto’s Koffler Scientific Reserve.

“As we learn more about how animals respond to stressful conditions… we increasingly find that stress brings a greater risk of death, presumably from things such as infections that normally wouldn’t kill them,” says Rowe.

Shannon McCauley, post-doctoral fellow and ecology and evolutionary biology professors Marie-Josee Fortin and Rowe raised juvenile dragonfly larvae in aquariums or tanks along with their predators, the journals Ecology and Nature reported.

The two groups were separated so that while the dragonflies could see and smell their predators, the predators could not actually eat them, according to a university statement.

“What we found was unexpected - more of the dragonflies died when predators shared their habitat,” says Rowe. Larvae exposed to predatory fish or aquatic insects had survival rates 2.5 to 4.3 times less than those not exposed.

In a second experiment, 11 percent of larvae exposed to fish died as they attempted to metamorphose into their adult stage, compared to only two percent of those growing in a fish-free environment.

“We allowed the juvenile dragonflies to go through metamorphosis to become adult dragonflies and found those that had grown up around predators were more likely to fail to complete metamorphosis successfully, more often dying in the process,” says Rowe.

The scientists suggest that their findings could apply to all organisms facing any amount of stress, and that the experiment could be used as a model for future studies on the lethal effects of stress.