Ethological dynamics in diorama environments

The utero-vaginal junction in the avian oviduct contains microscale tubular structures called sperm-storage tubules (SSTs), where sperm is stored for long periods before fertilization. Although sperm entry into SSTs is an essential event in avian fertilization, the details of this process are still unknown. Previous observations have shown that low-motility sperm and immotile particles such as beads cannot enter the SSTs, suggesting sperm enter the SSTs actively rather than passively. We believe that sperm enter the SSTs via "proto-intelligence," in which they sense any differences in the microenvironment arising from the presence of SSTs while swimming in the oviduct and change their movement accordingly. In this study, we aim to reveal the mechanism of sperm entry into SSTs in Japanese quail by characterizing the microenvironment surrounding SSTs and observing sperm movement patterns in the diorama environment, emulating the minute region around SSTs.