Supplementary Movie 2

Exhalant siphon of one mussel sample is shown in this 4-second movie. Exhalant siphon is indicated with a red arrow. Exhalant siphon changes its shape and area in the movie. Edge of mantle, which has plus shaped fringes, can be observed above the exhalant siphon and at the upper end of the mussels' shell. In the far background the PIV alignment apparatus is also shown that does not interfere with the mussel and located away from the sample.