Fukushima Fallout: Scads of Mutant Butterflies

The radiation that poured out of the Fukushima Dai-ichi nuclear reactor last year looks like it's doing a number on Japan's animal populations, researchers warn, after discovering rampant mutations among butterflies. Scientists collected 144 adult pale grass blue butterflies—which would have been overwintering as larvae during the disaster—from around Japan, and found that those from the most irradiated regions had stunted wings and irregularly developed eyes, according to a new study spotted by the BBC.

"It has been believed that insects are very resistant to radiation," the lead researcher says. "In that sense our results were unexpected." And the effects are still being felt. Researchers found that breeding those butterflies resulted in all new mutations, and a second set of Fukushima-area butterflies, collected six months later, showed twice the mutation rate of their predecessors. "This study is important and overwhelming in its implications," one biologist says. These mutations "can only be explained as having resulted from exposure to radioactive contaminants." (More Fukushima Daiichi stories.)