We study benthic animals in various aquatic ecosystems from intertidal rocky shores to hadal trenches to tropical streams. Our current research projects include 1) ecology, evolution and systematics of deep-sea animals, with special focuses on species’ distributions at 7,000–10,000 m deep and larval connection between hydrothermal vent fields, 2) diversity, population genetics and larval ecology of benthic invertebrates on tidal flats and rocky shores along Japan’s coasts, and 3) oceanic dispersal and upstream migration of amphidromous snails in low-latitude regions.