After Fukushima, Generations of Abnormal Butterflies In Japan

A sad, but fascinating scientific report in the journal Nature describes the physiological and genetic damage observed in generations of butterflies following the collapse of the Fukushima Dai-ichi Nuclear Power Plant. While it’s been difficult to study the biological impacts of the accident on animals, scientists have concluded that the pale grass blue Zizeeria maha (a common lycaenid butterfly in Japan) suffered increasingly severe abnormalities over time due to radioactive materials released into the environment.

Representative abnormalities of individuals that ingested contaminated leaves. From the top left to the right bottom, the panels show right antenna malformation (Iitate montane region), right palpus abnormality (Fukushima), dented left compound eye (Iitate flatland), eclosion failure (Fukushima), bent wings (Fukushima), additional bent wings (Hirono), aberrant wing colour patterns (Fukushima), and an ectopic black spot beside the discal spot (Iitate flatland; enlargement in the inset). Arrowheads indicate abnormal parts, and arrows indicate deformed wing spots. Scale bars for the top four panels indicate 1.0 mm, and those for the bottom four panels indicate 5.0 mm.

Although epigenetic effects cannot be entirely excluded, it is most likely that the abnormal phenotypes observed are produced by random mutations caused by the exposure to radiation. This outbreak of abnormal phenotypes in the Fukushima area is very different from the outbreak of wing colour-pattern changes previously observed at the northern range margins of this species, i.e., the Fukaura area, which is located approximately 400 km northwest of the Fukushima Dai-ichi NPP. The Fukaura populations at the time of the outbreak were composed of temperature-shock types that exhibit distinct wing colour-pattern modifications but no other wing modifications or aberrations. Moreover, to the best of our knowledge, no malformations of appendages and other parts have been detected. In contrast, the outbreak in the Fukushima area includes various unexpected abnormal phenotypes. These abnormalities cannot be expressed within the range of phenotypic plasticity exhibited by normal populations. This information and the experimental data obtained in this study allow us to conclude that the present outbreak of abnormal individuals in the Fukushima area was caused by random genetic mutations in addition to physiological effects due to the artificial radionuclides from the Fukushima Dai-ich NPP.

For those interested in heritable genetic damage due to low-dose radioaction exposure, this article is a must-read.