Ecophysiological investigation of the environmental adaptation of Korean mudskippers

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The following points have been clarified through the 3 year project.1. Analysis of mitochondrial DNA of the mudskipper Boleophthalmus pectinirostris collected in Japan, Korea and China demonstrated that the Japanese population had been isolated from the populations of the Asian continent through geological isolation. Most of the Japanese species have been considered to have isolated from the mother populations in the Asian continent approximately 15,000 years ago, however, the isolation of the mudskipper is estimated to have occurred in much earlier time, 240,000-2,650,000 years ago.2. Measurements of endocrine disrupting substances in several locations along Korean coast indicated that lake Shiwa and adjacent locations are heavily contaminated by chemicals that exert female-hormone-like actions contained in sewage water from highly populated and industrialized areas.3. Body composition analysis of the mudskippers collected in Yoesu estuaries shortly before hibernation period demonstrated liver weight and body fat content, which are 2.5 times higher than those observed for Japanese individuals. Hibernation period in Korean south coasts is estimated to be 2 months longer than in Japan, and the high fat content of the Korean fish is an adaptation for the storage of body energy to reduce morality during hibernation periods.