Fukushima radiation still poisoning insects news.sciencemag.org/asiapacific/2014/09/fukushima-radiation-still-poisoning-insects Eating food contaminated with radioactive particles may be more perilous than thought—at least for insects. Butterfly larvae fed even slightly tainted leaves collected near the Fukushima Daiichi Nuclear Power Station were more likely to suffer physical abnormalities and low survival rates than those fed uncontaminated foliage, a new study finds. The research suggests that the environment in the Fukushima region, particularly in areas off-limits to humans because of safety concerns, will remain dangerous for wildlife for some time. The 2011 Fukushima Daiichi Nuclear Power Station disaster (Fukushima report urges U.S. plant operators to take heed - news.sciencemag.org/asiapacific/2014/07/fukushima-report-urges-u-s-plant-operators-take-heed) released massive amounts of radiation, much of which drifted out to sea. Humans were evacuated to safety and their exposure to radiation was minimal. But local wildlife were exposed both externally to radiation in the environment and internally from contaminated food sources. Joji Otaki, a biologist at University of the Ryukyus in Nishihara, Japan, and his colleagues have been conducting field studies and lab experiments on how such radiation affected the pale grass blue butterfly (Zizeeria maha), a species found throughout most of Japan. In a previous experiment, Otaki’s group fed butterfly larvae leaves of the creeping woodsorrel (Oxalis corniculata) with radiation in the thousands of becquerels per kilogram (Bq/kg) gathered near the power plant within a few months after the accident. (For comparison, the Japanese government set a limit of 100 Bq/kg for human consumption of rice, meat, and fish, and 50 Bq/kg for milk and infant formula.) Larvae that dined on the radiation-drenched leaves had low survival rates and high incidences of physical abnormalities such as unusually small forewings. These results corroborated field surveys by others that turned up fewer butterflies in contaminated areas than would normally be expected. The new study shows that radiation can damage larvae even at much lower concentrations. Otaki and colleagues collected leaves 16 to 20 months after the accident, after short-lived radioactive contamination had decayed, but this time from locations ranging from 59 to 1760 kilometers from the power plant; contamination levels ranged from 161 to 0.2 Bq/kg. They found that as contamination increased, mortality rates and incidences of abnormalities increased. These results suggest that low-dose ingestion of approximately 100 Bq/kg may be seriously toxic to certain organisms, the team writes in a paper published today in BMC Evolutionary Biology. In another experiment, the researchers divided offspring of the butterflies into two groups, feeding larvae either the same contaminated leaves their parents had eaten or uncontaminated leaves. Larvae fed the contaminated leaves had even lower survival rates and more abnormalities than their parents (1), whereas those feeding on clean leaves largely reverted to near-normal in both mortality rates and frequency of abnormalities. The findings from Otaki’s group are “groundbreaking,” says Timothy Mousseau, a biologist at the University of South Carolina, Columbia, who also studies the effects of radiation on wildlife near Fukushima and Chernobyl. He notes that there have been “almost no studies” on how ingestion of radiation-tainted foods affect wildlife. Still, Mousseau cautions that the results should not be directly extrapolated to humans. “I think butterflies as a group are likely to be much more sensitive than humans to radiocontaminants,” he says. He adds that Otakis findings suggest that insects that survive after eating contaminated leaves might evolve tolerance to the low levels of radiation likely to persist in the Fukushima region for decades. Reference Ingestion of radioactively contaminated diets for two generations in the pale grass blue butterfly BMC Evolutionary Biology 2014, 14:193, doi:10.1186/s12862-014-0193-0 biomedcentral/1471-2148/14/193 PDF: biomedcentral/content/pdf/s12862-014-0193-0.pdf Abstract Background: The release of radioactive materials due to the Fukushima nuclear accident has raised concern regarding the biological impacts of ingesting radioactively contaminated diets on organisms. We previously performed an internal exposure experiment in which contaminated leaves collected from polluted areas were fed to larvae of the pale grass blue butterfly, Zizeeria maha, from Okinawa, which is one of the least polluted localities in Japan. Using the same experimental system, in the present study, we further examined the effects of low-level-contaminated diets on this butterfly. Leaves were collected from two localities in Tohoku (Motomiya (161 Bq/kg) and Koriyama (117 Bq/kg)); two in Kanto (Kashiwa (47.6 Bq/kg) and Musashino (6.4 Bq/kg)); one in Tokai (Atami (2.5 Bq/kg)); and from Okinawa (0.2 Bq/kg). In addition to the effects on the first generation, we examined the possible transgenerational effects of the diets on the next generation. Results: In the first generation, the Tohoku groups showed higher rates of mortality and abnormalities and a smaller forewing size than the Okinawa group. The mortality rates were largely dependent on the ingested dose of caesium. The survival rates of the Kanto-Tokai groups were greater than 80%, but the rates in the Tohoku groups were much lower. In the next generation, the survival rates in the Tohoku groups were below 20%, whereas those of the Okinawa groups were above 70%. The survival rates in the second generation were independent of the locality of the leaves ingested by the first generation, indicating that the diet in the second generation was the determinant of their survival. Moreover, a smaller forewing size was observed in the Tohoku groups in the second generation. However, the forewing size was inversely correlated with the cumulative caesium dose ingested throughout the first and second generations, indicating that the diet in the first generation also influenced the forewing size of the second generation. Conclusions: Biological effects are detectable under a low ingested dose of radioactivity from a contaminated diet. The effects are transgenerational but can be overcome by ingesting a non-contaminated diet, suggesting that at least some of the observed effects are attributable to non-genetic physiological changes. Photo: Larvae of pale grass blue butterflies died prematurely or developed abnormalities when fed radioactive leaves from the Fukushima region.
Posted on: Sun, 28 Sep 2014 23:51:31 +0000
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