Movie 1

0:00-0:07: Dorsal view of Thoracophelia mucronata burrowing in cryolite (sequence in Figure 2A-H). 0:08-0:26: Dorsal view of Thoracophelia mucronata burrowing in cryolite (sequence in Figure 2I-K). Forward gut movements accompanied by anterior region expansions occur at 2, 3, 5, 7 11, and 16 s.