Japanese researchers are reporting that in the wake of the Fukushima nuclear disaster they are finding species of mutated butterflies.

Officials at Ryukyu University have found about 12 percent of the species they have monitored have shown signs of genetic changes, or mutations, from radiation released by the plant in March, 2011. The earthquake and resulting tidal wave wreaked havoc on the plant. Unlike American counterparts, Fukushima did not have multiple fail-safe cooling systems, nor did it have a thick concrete containment dome.

The radiation leak caused some types of butterflies to have smaller wings than normal, as well as damaged eyes. However,  in many cases, one of the two parents who joined to create the offspring were unaffected by radiation. The 12 percent affected were taken from sample known conclusively to have been exposed to the radiation.

Researchers said it is too early to tell if the radiation will affect other animals or insects, and said  data from this study cannot be applied directly to, or projected on, other species — including humans.