The adaptive strategies of marine organisms—such as osmoregulation and reproduction—differ significantly from those of terrestrial animals like ourselves. What mechanisms underlie these adaptations, and how have they evolved? To address these questions, we employ a wide range of approaches, from molecular and cellular studies—including cell culture and genetic manipulation—to research at the levels of whole organisms and behavioral physiology. Our work involves the rearing and analysis of diverse fish species, including sharks and rays with distinctive osmoregulatory and reproductive systems, medaka (which are highly suited for reverse genetic analysis), and basal species such as hagfish and gars. We also maintain active collaborations with aquariums and research institutions both in Japan and internationally.