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

Raj D Gurung,Wataru Taira,Ko Sakauchi,Masaki Iwata,Atsuki Hiyama,Joji M Otaki

doi:10.3390/insects10090290

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.

Highlights

Field observations of the possible biological effects of radioactive contamination after the Fukushima nuclear accident have been reported in various organisms, including bird and arthropod populations [1,2], gall-forming aphids [3], Japanese monkeys [4,5,6], barn swallows [7], goshawks [8], rice plants [9,10], fir trees [11], red pine trees [12], and intertidal species populations, including the rock shells [13]
The original survival rate for the improved diet was not very high, mostly less than 80%, as observed in the control groups C0 and H0, but these results were likely because the larvae were reared in small dishes within an airtight container to prevent water evaporation from the small patches of artificial diet
Small-sized adults were obtained in this rearing system with the artificial diet, as shown in Figure 1C, this did not harm the quality of the experimental system, either; small size adults have been known in entomological studies with artificial diets [43], this fact indicates a room for further improvement

Summary

Introduction

Field observations of the possible biological effects of radioactive contamination after the Fukushima nuclear accident have been reported in various organisms, including bird and arthropod populations [1,2], gall-forming aphids [3], Japanese monkeys [4,5,6], barn swallows [7], goshawks [8], rice plants [9,10], fir trees [11], red pine trees [12], and intertidal species populations, including the rock shells [13]. Additional cases include DNA damage in bovine lymphocytes [16], enhanced spermatogenesis [17], and chromosomal aberrations [18,19] in large Japanese field mice. Changes in the genome-wide DNA methylation levels have been detected in plants from Chernobyl but not from Fukushima [21]. Mammalian testes collected from bulls, bore, inobuta, and large Japanese field mice in the contaminated

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Discussion

Conclusion