1. Laboratory of Animal Breeding and Genetics, Graduate School of Agricultural Science, Kobe University, Nada, Kobe 657-8501, Japan
2. Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima 739-8528, Japan
3. Mention Zoologie et Biodiversité Animale, Faculty of Sciences, Antananarivo University, BP 906 Ankatso, Antananarivo 101, Madagascar
4. Faculty of Agriculture, Tokyo University of Agriculture, 1737 Funako, Atsugi, Kanagawa 243-0034, Japan