by SM Morgan
The Tohoku Earthquake & Tsunami in March of 2011 caused an unfortunate side effect when it wasted the crap out of a couple nuclear power plants. The nuclear material released into the surrounding environment from the Fukushima Daiichi failures caused a fair bit of panic and we are still only now working out how much of an affect the contamination will prove to have had.
Iodine-131 and Caesium-137 were released into the environment at several estimates of volume, depending on the affiliations of the measurer and sensationalisation of the media. However, it has been estimated (and published here) that the levels of contamination are about one tenth that of Chernobyl.
It is difficult to directly measure the effects of such contamination when they might not be seen for years (for example, cancer incidence rates), however there are some ways in which impact can be visualised in the local fauna; with short lifecycles, ‘vulnerable’ genomes and delicate physical structures.
A paper was published by Hiyama et al last month, investigating this biological impact of the nuclear accident on a local species of butterfly. The butterfly is Zizeeria maha, and looks like this when not in a state of nuclear-mutated contortion:
The authors of the current paper used three main techniques to isolate the aberrations directly caused by the environmental nuclear contamination. Firstly, live adults were collected from the country around the disaster site, and scored for aberrations. These adults were collected at such a time as that they had been exposed to the environmental contamination as larvae, as pupae and as adults: about a 2 month radiation exposure. From the sites that these adults were collected, radiation measures were taken from ground level, 30 cm above ground and 100 cm above ground. This was, of course, to identify the radiation at the level of the butterflies diet – leaves.
Two slightly different mating and rearing experiments were carried out with these collections; ‘healthy and vigorous’ males and females were mated and the offspring scored for aberrations, and then ‘abnormal’ males and females were mated and their offspring scored for aberrations. The first group was given 9-10 days to lay and the second 7-8 days, though ]the reason for the difference is unclear. The offspring were also observed for pupation and hatching data, to see if those processes had changed.
The scoring of aberration, or ‘decision of abnormality’ was carried out by two people, separately, who then debated a feature if they both disagreed on its score. The kind of things they were looking for were differences in wing morphology, colour patterns, appendages and the classic ‘other’ category; which covered eyes, thoraces and abdomens.
The second of the three techniques investigated the effect of external radiation exposure. This was achieved by collecting 200 normal larvae, 150 of which were zapped with Caesium-137 (I say ‘zapped’: they were put in a plastic container and exposed to the radiation source) for either 180-280 hours or 177-387 hours, and the remaining 50 raised as controls. The reason for the range is unclear. However, these larvae were later also scored for aberrations as adults.
The final experiment investigated the effect of internal radiation exposure and this was achieved by feeding with wild leaves collected from the contaminated environment.
The authors found that of the native butterflies collected after being exposed to the environmental radiation in both larval and pupal stages, about 18.3 % of collected adults showed (overall) aberrations, but the second generation jumped to (overall) 33.5 %. In the laboratory radiation exposure study, they claim to have replicated these data, with aberration occurrence increasing after both kinds of radiation exposure (either external exposure or internal leaf ingestion), but without giving overall aberration percentages.
Being the jaded skeptic that I am, I would have liked to have seen genetic evidence of mutation, however it does appear that the environmental radiation contamination is causing an effect in this species, most notably in wing size and pigment pattern, so we can perhaps conclude that the meltdown of the Fukushima Daiichi power plant was indeed bad, and that measurable effects are visable in the surrounding areas species now. Whilst a terrible catastrophe, this event will provide fascinating science study subjects for quite a while yet. It is also interesting that the media have been showing severely mutated butterfly photos, of which do not appear in the paper itself.
And least you get too worried, the senior researcher on the paper was quoted in a newspaper as saying, “Humans are totally different from butterflies and they should be far more resistant [to radiation]”. Totally different…