Developmentally-driven self-assembly and dynamics of living chiral crystals*

Active crystals are highly symmetric ordered structures that emerge from the nonequilibrium self-organization of motile objects. Here, we show that swimming starfish embryos spontaneously assemble into highly ordered rotating active crystals that span thousands of spinning organisms and persist for tens of hours. Our experiments show that the formation, dynamics, and dissolution of these living chiral crystals are controlled by the natural development of the embryos. As a function of developmental time, these crystals undergo an order-disorder transition characterized by progressive loss of translational and orientational order. Remarkably, non-reciprocal force and torque exchanges between the embryos lead to emergence of chiral waves and signatures of odd elasticity. Our work shows how autonomous morphological development at the single-embryo level can control emergent collective nonequilibrium dynamics and symmetry breaking at the macroscale.