Canadian researchers have found that fishes exposed to harmful radiation release chemical warning signals to inform other individuals so they can switch on their defenses.

Even since 1921, it was found that cells and animals exposed to radiation produce chemical signals to other cells and animals, respectively. These signals are destined to start defense, repair or restorative functions but sometimes they could lead to DNA disrupting, genetic mutations and chromosome damage, having similar effects with radiation sickness.

But till now, the mechanism behind switching on the defense reaction was unknown. "We are dealing with very small molecules that act like pheromones," said Carmel Mothersill, a radiation biologist at McMaster University in Canada.

The researchers exposed rainbow trouts (photo) to non-lethal doses of radiation produced by an X-ray device in order to check the chemical reactions of the process. The irradiated fishes were put together with unexposed fishes for two hours in the same water tank. The unexposed trouts experimented increased cellular death rates in their gills, fins, skin, spleens and kidneys, like they would have been directly exposed to radiation. "The chemical signals provoked unexposed fishes "to induce appropriate defenses," said Mothersill.

But staying alert and facing the menace come with a cost: damaged and wiped out cells. But few cells loss "may protect an organ from cancer, or loss of a few weak individuals in a group may benefit the group as a whole," Mothersill explained.

Now the team is hunting the chemical compounds involved in the bystander effects. Sometime in the future, fishes might help people monitor radiation leaks. "Detecting these bystander signals in fish could help regulators prove a nuclear plant is leaking radiation," Mothersill added.