LAUSR

Abstract Morphological abnormalities of the pale grass blue butterfly, Zizeeria maha (Kollar) (Lepidoptera: Lycaenidae), have been successfully used as an environmental indicator to assess the biological impacts of the Fukushima Dai-ichi Nuclear Power Plant accident. To prepare for future nuclear accidents or other human and natural disasters, we examined the morphological abnormality rate of this butterfly in southwestern Japan and built a pre-disaster reference data set. We collected butterfly samples, primarily in summer 2015 from 52 localities, which were categorized into three regional groups associated with the Sendai, Ikata, or Takahama Nuclear Power Plant. Mean values of the abnormality rate and the wing color pattern modification rate for localities were 3.8% and 0.8%, respectively, indicating that butterflies were not under severe anthropogenic stress. Using all collected samples, the abnormality rate of females (7.4%) was significantly higher than that of males (2.8%). We did not detect any significant correlations of the abnormality rate or modification rate with latitude, ground radiation dose, or distance from the nuclear power plants. Based on logistic regression analyses, sex, annual average temperature, and monthly average temperature might have influenced morphological abnormalities, suggesting possible direct and epigenetic temperature effects on morphogenesis. These data serve as a reference data set for future nuclear accidents or other artificial or natural environmental disasters in southwestern Japan.