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Butterflies and balloons at Fukushima

Nuclear meltdowns make everything depressing, and this week, even butterflies and balloons have seen their normally cheery image marred by radioactivity.

First butterflies. A paper in the open-access journal Scientific Reports shows mutations in butterfly populations around the Fukushima plant, which melted down in March of last year following a major earthquake and tsunami. The paper is impressively thorough: it examined 144 butterflies collected a month after the accident. Although their behaviour was normal, they did suffer from small morphological defects, such as dented eyes and slightly deformed wings (see above). A second examination of butterflies caught six months later showed about twice the rate of mutation.

The researchers also conducted a series of laboratory experiments in which they induced mutations in normal butterflies through radiation exposure. The total dose received by the lab butterflies was 55 millisieverts (mSv) and 125 mSv, and mutations similar to those in the wild samples could be seen in both populations.

The results are consistent with low-dose radiation exposure. As butterflies breed in the radioactive environment, mutations will accumulate in the population. Another study has shown that the number of butterflies around Fukushima has dropped since the accident, and this could be one reason.

It’s bad news for the environment, but should people be worried? Not really. As I reported in May, the vast majority of civilians and workers have received less than 10 mSv of radiation. Those estimates are backed up by a paper out today in the Journal of the American Medical Association showing that 3,286 residents surveyed received less than 1 mSv of internal exposure from caesium-137 six months after the accident (although they admit earlier exposure might be higher).

It is also worth mentioning that people are a lot bigger than butterflies; so even if they do receive higher doses, we wouldn’t expect the same response.

In separate, balloon-related meltdown news, workers have flown a balloon inside the unit 1 reactor in a clever bid to get a better look at it (right, top). By floating it up through an equipment hatch, the crew hoped to get a look at the top of the reactor and the spent fuel pool, which contained used nuclear fuel before the accident and has been the subject of much speculation since. Unfortunately, they couldn’t get all the way to the top because of debris blocking the way. But they did manage to get a look at the fourth floor, and it wasn’t pretty (right, bottom).

There is a very small silver lining to all of this. On the butterfly front, it’s positive that there are scientists carefully examining the ecological impact of Fukushima (this kind of data was absent for years following the Chernobyl accident of 1984). And the balloon shows that the workers at the plant are coming up with creative ideas to try and deal with the situation.

Images: top, Hiyama, A. et al. Scientific Reports 2, 570 (2012); bottom, TEPCO


  1. Report this comment

    Geert Biermans said:

    I think you mean the Chernobyl accident of 1986.

    And while it’s true humans will most likely not show the same response, we should be careful when using size as an indicator of radio-sensitivity. In fact, it’s a very poor predictor of radiation effects. Remember that, in Chernobyl, most of the pine trees died while a lot of small species survived.

    The paper is indeed thorough in the collection of the species, but at no point in the text do they actually indicate the exact measured dose rates at the sample points. Using “distance from the NPP” as a parameter is perhaps not a very good choice, given the irregular deposition pattern of the fall-out.

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    Andrei Sourakov said:

    An abnormal population of a blue butterfly Meleageria daphnis was discovered in 1988 in southern Russia (see ref. 1). Though it was far from Chernobyl, but shortly after the meltdown there, and it is reasonable to suspect a possible fall-out deposition of radioactive materials as a cause. In this butterfly population, gynandromorphy was found in 60% of the females (normally gynandromorphs are rare (1 in 100,000)). A single dominant mutation of a gene responsible for sex differentiation was probably responsible (see ref. 2).

    Other studies showed that mutant butterfly wing patterns can be obtained by X-ray radiation in the lab (see ref. 3). Now, thanks to the Fukushima butterfly study, we know of more mutations in butterflies that can result from a different type of radiation. Butterflies are a great indicator group and should be studied not only for wildlife conservation, but also for human welfare reasons.


    (1) Dantchenko A., Emmel T. C., Sourakov A. 1995. Nuclear pollution and gynandromorphic butterflies in southern Russia. Holactic Lepidoptera 2(2): 77-79.

    (2) Zhao, D. et al. 2010. Somatic sex identity is cell autonomous in the chicken. Nature 464: 237-243.

    (3) Monteiro A, Prijs J, Bax M, Hakkaart T, Brakefield PM. 2003. Mutants highlight the modular control of butterfly eyespot patterns. Evol Dev 5: 180-187.

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    amalina munira said:

    great article..this told us that nuclear crisis will really give a big impacts to all organisms in this earth..

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