Sci-News.com,
Apr 29, 2014
A new
study, reported in the journal Functional Ecology and headed by Dr Ismael
Galván from the Spanish National Research Council, is the first evidence that
wild animals adapt to ionizing radiation and the first to show that birds have
greatest problems coping with radiation exposure.
 |
| A hawfinch, Coccothraustes coccothraustes, from the Chernobyl exclusion zone. Image credit: T.A. Mousseau / A.P. Møller. |
The Chernobyl disaster, which occurred on 26 April 1986 in Ukraine, had
catastrophic environmental consequences. However, because the region remains
heavily contaminated by radiation, it represents an accidental ecological
experiment to study the effects of ionizing radiation on wild animals.
Ionizing radiation produces oxidative stress, but animals can adapt to their exposure
with physiological adaptive responses. However, the role of radioadaptive
responses in wild populations remains poorly known.
Previous
studies of the level of antioxidants and oxidative damage at Chernobyl are
limited to humans, two bird species and one species of fish. Because different
species vary widely in their susceptibility to radiation, this limited data has
made it difficult to study how wild animals adapt to radiation exposure.
At 8 sites
inside and close to the Chernobyl Exclusion Zone, Dr Galván and his colleagues
used mist nets to capture 152 birds from 16 different species: red-backed
shrike; great tit; barn swallow; wood warbler; blackcap; whitethroat; barred
warbler; tree pipit; chaffinch; hawfinch; mistle thrush; song thrush;
blackbird; black redstart; robin and thrush nightingale.
The
scientists measured background radiation levels at each site, and took feather
and blood samples before releasing the birds. They then measured levels of
glutathione, oxidative stress and DNA damage in the blood samples, and levels
of melanin pigments in the feathers.
Levels of
radiation in the study area ranged from 0.02 to 92.90 micro Sieverts per hour.
The
findings show that with increasing background radiation, the birds’ body
condition and glutathione levels increased and oxidative stress and DNA damage
decreased. The birds which produce larger amounts of pheomelanin and lower
amounts of eumelanin pay a cost in terms of poorer body condition, decreased
glutathione and increased oxidative stress and DNA damage.
“The
findings are important because they tell us more about the different species’
ability to adapt to environmental challenges such as Chernobyl and Fukushima,”
Dr Galván concluded.
______
Ismael
Galván et al. Chronic exposure to low-dose radiation at Chernobyl favors
adaptation to oxidative stress in birds. Functional Ecology, published
online April 24, 2014; doi: 10.1111/1365-2435.12283
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