Males and females differ in many aspects of behavior and physiology. In most animal species, males typically choose females as mates, and conversely, females typically choose males. Courtship is usually performed by males, while female-initiated courtship is rare. Males also tend to display higher levels of aggression than females and frequently compete over territory and mates. In vertebrates, such differences between males and females are largely driven by the actions of sex steroid hormones—namely androgens and estrogens—released from the testes and ovaries and acting on the brain. However, it remains unclear how these hormones shape the brain to generate sex-specific behaviors and physiological traits. Among vertebrates, fish are particularly sensitive to sex steroids. In fact, simply blocking the synthesis of androgens or estrogens can readily reverse sex-specific behaviors and physiological traits. Taking advantage of this feature, our lab uses medaka fish as a model to explore the brain mechanisms through which sex steroids generate sex-specific behaviors and physiological traits.
Educational content
For students interested in how the brain shapes sex-specific behavior and sexual orientation
My fascination with fish began in childhood and eventually led me into this field of research. Fish possess a remarkable ability to change sex—and with it, they can switch patterns of mating behavior, aggression, and even sexual orientation (that is, which sex they choose as a mate). This fluidity sparked my curiosity about how sex and behavior can change so dramatically, laying the foundation for my current research. As my work progressed, my interests expanded beyond fish. I became captivated by broader biological questions—namely, how behavioral sex differences and sexual orientation are determined across animal species, including in humans. Our lab welcomes undergraduate and graduate students who are curious about these topics. If you are interested, we are always happy to answer your questions or arrange a lab visit. In our training, we emphasize the development of strong logical thinking skills. Through regular seminars and discussions, students are encouraged to hone their reasoning abilities and formulate well-founded hypotheses. The moment your own hypothesis—born from deep, logical thought―is validated through experiment is profoundly rewarding. It is an experience unlike any other: exhilarating, unforgettable, and truly addictive.
Prospects for joint research and industry-academia collaboration
Exploring sex differences and their lability
Our research aims to uncover not only the mechanisms underlying sex differences in fish but also the broader principles that explain how such differences arise and vary across the animal kingdom, including in humans. As public awareness and discussion of sex and gender grow, there is a global movement to dispel myths and biases surrounding these issues. Central to that effort is the widespread communication of accurate, science-based understanding of sex differences. We are committed to advancing rigorous scientific knowledge and sharing our findings with the broader community. We also hope our research will contribute to improvements in aquaculture. Traits such as mating behavior, aggression, and sexual maturation—core areas of our research—have direct implications for fish farming productivity. Common challenges in aquaculture, such as delayed sexual maturation, unsuccessful spawning, or excessive aggression toward conspecifics, can be addressed more effectively when we understand the brain mechanisms controlling these traits. Our goal is to develop precise, targeted methods to regulate these traits without causing unintended side effects.
