Byssal thread secretion behavior of the mussel Mytilus coruscus.

This video shows the complete process of byssal thread formation. The mussel extends its foot to explore the substrate. Once a specific site is selected, the tip of the foot touches the surface and begins to secrete byssal thread. As the foot retracts, a newly secreted byssal thread (labelled “byssal thread”) is visible attached to the substrate. The video is played at 1×speed.