Symmetry breaking and inter-clonal behavioural variability in a slime mould.

Cells are dynamic systems capable of switching from isotropic growth to polarized growth even in the absence of any pre-existing external asymmetry. Here, we study this process of symmetry breaking in the acellular slime mould Physarum polycephalum. In these experiments, slime moulds could grow on two identical opposed sources of calcium. We highlighted a positive correlation between growth dynamic, level of symmetry breaking and calcium concentration. We identified three populations of slime moulds within our clonal lineage with similar symmetry breaking behaviours but different motility characteristics. These behavioural differences between slime moulds emerged in the absence of any environmental differences. Such behavioural plasticity could generate cellular diversity, which can be critical for survival.