Growth produces coordination trade-offs in Trichoplax adhaerens, an animal lacking a central nervous system

Coordination between cells is fundamental for multicellular life. The first multicellular animals were capable of growing to indeterminate sizes but lacked nervous systems that could facilitate coordination. We investigate how size variation affects coordination in such organisms by measuring the collective order in the locomotion of Trichoplax adhaerens, the simplest multicellular animal. We find that collective order decreases as such animals grow in size and use a simulation model to determine that this scaling phenomenon occurs at the phase transition between ordered and disordered movement, also known as criticality. Our findings therefore suggest a fundamental trade-off between increasing size and coordination in such a decentralized organism and provide evidence for the necessity of centralized control at larger sizes.