The Effects of Ionizing radiation on bank vole in Chernobyl Exclusion Zone

Abstract

The Chernobyl disaster in 1986 created an environment that provides unique opportunity to explore the eco-evolutionary impacts of chronic exposure to low-dose radioactive contaminants on wild animals. Studying the key species in the area could help determine the effects of radiation on species interactions and thus improve the radiation impact assessment. The bank vole (Myodes glareolus) was chosen as study species as it combines ecological relevance with laboratory tractability. Multi-generational experiments were conducted to test the wild populations exposed to long-term low-level ionizing radiation by analysing: the impact of added food sources on population sizes, the effects of radiation on reproduction of males and females, and radiation induced effects on organs. In the first study, bank vole abundances decreased with increasing radiation. Adding food sources to the field increased vole abundances only in low radiation environments. To find out whether lower abundances result from problems in male reproduction, in the second study, properties of the bank vole sperm were investigated. Sperm mid-pieces got shorter with increasing radiation. In addition, the proportion of static sperm increased in higher radiation areas. Thus, there were some negative effects on male reproduction. In the third study, reciprocal transplant experimental design was used to find study female reproduction. Females tended to survive better when moved to similar type of radiation environment indicating a possible adaptation to radiation in the environments. However, their pups survived better if the female was pregnant when living in the clean sites. Finally, in the fourth study, differences in various organ masses between the contaminated and clean sites were investigated. Results revealed smaller brain mass in the contaminated sites, and increased heart and spleen masses in the contaminated sites. In this thesis many correlative radiation effects were found, however the strength of the radiation in large areas of Chernobyl are very low. It is still unclear whether these effects are really radiation induced or do they come from combined stress effects in the area.