Tolerance of High Oral Doses of Nonradioactive and Radioactive Caesium Chloride in the Pale Grass Blue Butterfly Zizeeria maha

Abstract

The biological effects of the Fukushima nuclear accident have been examined in the pale grass blue butterfly, Zizeeria maha (Lepidoptera: Lycaenidae). In previous internal exposure experiments, larvae were given field-collected contaminated host plant leaves that contained up to 43.5 kBq/kg (leaf) of radioactive caesium. Larvae ingested up to 480 kBq/kg (larva), resulting in high mortality and abnormality rates. However, these results need to be compared with the toxicological data of caesium. Here, we examined the toxicity of both nonradioactive and radioactive caesium chloride on the pale grass blue butterfly. Larvae were fed a caesium-containing artificial diet, ingesting up to 149 MBq/kg (larva) of radioactive caesium (137Cs) or a much higher amount of nonradioactive caesium. We examined the pupation rate, eclosion rate, survival rate up to the adult stage, and the forewing size. In contrast to previous internal exposure experiments using field-collected contaminated leaves, we could not detect any effect. We conclude that the butterfly is tolerant to ionising radiation from 137Cs in the range tested but is vulnerable to radioactive contamination in the field. These results suggest that the biological effects in the field may be mediated through ecological systems and cannot be estimated solely based on radiation doses.

Nutrient Imbalance of the Host Plant for Larvae of the Pale Grass Blue Butterfly May Mediate the Field Effect of Low-Dose Radiation Exposure in Fukushima: Dose-Dependent Changes in the Sodium Content

“…Among insects, the pale grass blue butterfly Zizeeria maha (Lepidoptera, Lycaenidae) is an important organism that has been studied since immediately after the Fukushima nuclear accident [ 38 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 ]. This butterfly has many advantages both as a sampling animal for field work and as a laboratory animal [ 77 ].…”

“…Although the exposure level of the pale grass blue butterfly has not been rigorously determined, the butterfly’s vulnerability to radioactive contaminants does not fit the conventional dosimetric view that insects are highly tolerant to radioactive exposure. Remarkably, our “laboratory-based” data have revealed that the pale grass blue butterfly was highly tolerant to radioactive cesium ( 137 Cs), the major radioactive contaminant in leaves from Fukushima, when fed an artificial diet [ 72 ]. This result is reminiscent of the case of gall-forming aphids [ 39 , 40 ].…”

Observation of morphological abnormalities in silkworm pupae after feeding 137CsCl-supplemented diet to evaluate the effects of low dose-rate exposure

“…If nutritional changes occurred in host plants at low-dose radiation, noticeable consequences on the butterfly can be expected. Recently, an internal exposure experiment in the pale grass blue butterfly, Z. maha, did not show any morphological abnormalities when Z. maha was fed an artificial diet, with a high concentration of 137 CsCl 39 . This result is in line with the results of this study and negates the direct effects of radiation.…”

Overwintering States of the Pale Grass Blue Butterfly Zizeeria maha (Lepidoptera: Lycaenidae) at the Time of the Fukushima Nuclear Accident in March 2011

“…This information is required for accurate dosimetric estimates of the absorbed radiation doses, which will make us understand the relationship between field absorbed doses and their biological impacts on the pale grass blue butterfly. Additionally, dosimetric calculations likely contribute to the understanding of transgenerational effects [47,76,77] and the field–laboratory paradox of the biological effects of radioactive pollution, at least in this butterfly [78,79,80,81].…”