1. Department of Biotechnology, Akita Prefectural University, Shimoshinjo-Nakano, Akita-shi, Akita, Japan
2. Department of Animal Health Technology, Yamazaki Gakuen University, Minami-Osawa, Hachiouji, Tokyo, Japan
3. Marine Biology Section. Department of Biology, University of Copenhagen, Universitetsparken, Copenhagen, Denmark
4. Tateyama Marine Laboratory, Marine and Coastal Research Center, Ochanomizu University, Kou-yatsu, Tateyama, Chiba, Japan