情動行動の起源を探る—魚類をモデルとして—

抄録

Fish is the vertebrate that first appeared on the earth. While it has been found that many fish species are highly social, their brain has less complex organization than mammals. Thus, studying social behavior in fish has a great advantage in understanding of emotion, which is common to all the vertebrates. Among all, Anemonefishes live symbiotically with sea anemones and form a social unit that consists of a breeding pair and several sexually immature individuals. The hierarchy of the social rank is strictly maintained in a group. Agonistic behaviors are observed frequently among the members of a group, which are essential for maintenance of the social structure, as well as for their sex determination. The differences in agonistic behavior according to social status were also detected directed at conspecific intruders. The aggressive behaviors were specifically directed at intruders of the same sexual status, not at those of the opposite sex. These results suggest that sexually mature resident anemonefish perceive intruders of the same sexual status as competitors for reproductive status.