Following our recent observations of contraction waves in the primitive epithelium of Placozoa, we develop a model of tissues as sheets of contractile cells. The simple model assumes only a strain-threshold for contraction, and explains/predicts a variety of unique and surprising phenomena, e.g.: contraction waves in response to external stress, spontaneously-compressed steady-state, emerged limit-cycles, mechanical frustration and active resistance to rupture. In the talk I will present both the experimental observations and the model results. This model of “active cohesion” may be relevant to any epithelial tissue, to manufacturing of synthetic active materials, and to models of evolution of multicellularity.
