1. Otsuchi Marine Research Center, Ocean Research Institute, University of Tokyo, Iwate, Division of Biology, Miyazaki Medical College, Miyazaki, 2 and Department of Biology, Faculty of Science, Kyushu University, Fukuoka 812, 3 Japan, and Sir George Fisher Center for Tropical Marine Studies, James Cook University of North Queensland, 4 and Australian Institute of Marine Science, 5 Townsville, Australia