Fluctuations of cell geometry and their nonequilibrium thermodynamics in living epithelial tissue

We measure different contributions to entropy production in a living functional epithelial tissue. We do this by extracting the functional dynamics of development while at the same time quantifying fluctuations. Using the translucent Drosophila melanogaster pupal epithelium as an ideal tissue for high-resolution live imaging, we measure the entropy associated with the stochastic geometry of cells in the epithelium. This is done using a detailed analysis of the dynamics of the shape and orientation of individual cells which enables separation of local and global aspects of the tissue behavior. Intriguingly, we find that we can observe irreversible dynamics in the cell geometries but without a change in the entropy associated with those degrees of freedom, showing that there is a flow of energy into those degrees of freedom. Hence, the living system is controlling how the entropy is being produced and partitioned into its different parts.

Automated summary

We have measured the contributions to entropy production in a living functional epithelial tissue by studying its functional dynamics and quantifying fluctuations. Using high-resolution live imaging of the translucent Drosophila melanogaster pupal epithelium, we measured the entropy associated with the stochastic geometry of cells. Our analysis of the shape and orientation dynamics of individual cells allowed us to separate local and global aspects of tissue behavior. Interestingly, we observed irreversible dynamics in cell geometries without a change in the entropy associated with those degrees of freedom, indicating a flow of energy into those degrees of freedom and the control of entropy production by the living system.