mtDNA MUTATION OBSERVED IN MASU SALMON COLLECTED IN FUKUSHIMA
Fukushima Daiichi Nuclear Power Station accident occurred at March 11, 2011 led the deposition of the radioactive cesium (137Cs) at freshwater fishery grounds. Although more than three years have passed, high level of 137Cs has been detected from the muddy sediment and fishes in rivers of Fukushima. Since the situation of pollution by radioactive materials and its change is still unknown, the pollution will have physiological and genetic effects on freshwater fishes.
Mitochondrial DNA is clonally transferred from maternal parent to its offspring. From this characteristic of mitochondrial DNA, it is possible to survey the genetic change between maternal parent and its offspring and it is good material to consider the genetic effect of radioactive materials on fishes. We examined mitochondrial DNA in maternal parent and produced offspring collected from Mano river in Fukushima and compared with the masu salmon produced in Fukushima prefectural inland water fisheries experimental station (FP). Masu salmon Oncorhynchus masou is popular salmonid fish in this area and this species spend two or three years in the river until maturation.
From two females collected from Mano River, radioactive cesium was detected 632Bq/kg and 212Bq/kg, respectively. On the other hand, it did not detected in the females from FP. Two regions of mitochondrial DNA, Dloop and Cytb, were examined. Different sequences from maternal individual were observed in two sits of Dloop and four sites of Cytb, and calculated mutation rates were 1.76*10-5 in Dloop and 4.9*10-6 to 1.29*10-5 in Cytb. In these mutations, there are two amino acid substitutions was observed, however these change were already observed as polymorphism in masu salmon population. Other mutations were synonymous substitutions. There was no mutation in the individuals produced from PF. These results suggest the effect of radioactive materials on genome of freshwater fishes.