Developmentally driven order-disorder transition in chiral living crystals*

Living matter exhibits complex non-equilibrium behavior. Here, we report on the formation of chiral crystals of starfish embryos which undergo autonomous order-disorder transitions. Embryos form a stable bound state at the water-air interface and hydrodynamically self-assemble into 2D crystals with hexagonal order. Time reversal asymmetry leads to emergence of chiral waves and dissipationless mechanical response. Remarkably, as a function of developmental time, these 2D crystals undergo an order-disorder transition characterized by progressive loss of translational and orientational order. Our hydrodynamic model elucidates how near field interactions can lead to the experimentally observed emergent dynamics.