The well-developed vision of vertebrates possessing camera-type eyes is rapidly established during the early phases of life. Cephalopods, a group of mollusks, possess well-developed camera-type eyes similar to those of vertebrates. Although the anatomy of the cephalopod visual system has been studied as an example of convergent evolution between vertebrates and invertebrates, knowledge of vision and their ontogeny is limited. Therefore, this study focused on the squid (Sepioteuthis lessoniana) t