1. Department of Biotechnological Science, School of Biology-Oriented Science and Technology, Kinki University, 930 Nishimitani, Kinokawa, Wakayama 649-6493, Japan, Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan, and Department of Biology, Graduate School of Science, Kobe University, 1-1 Rokkodai-cho, Kobe, Hyogo 657-8501, Japan