Mechanism of signal propagation in Physarum polycephalum

Significance How do apparently simple organisms coordinate sophisticated behaviors? The slime mold Physarum polycephalum solves complex problems, for example finding the shortest route between food sources, despite growing as a single cell and the lack of any neural circuitry. By carefully observing P. polycephalum’s response to a nutrient stimulus and using the data to develop a mathematical model, we identify a simple mechanism underpinning the slime mold’s behaviors: A stimulus triggers the release of a signaling molecule. The molecule is initially advected by fluid flows but also increases fluid flows, generating a feedback loop and enabling the movement of information throughout the organism’s body. This simple mechanism is sufficient to explain P. polycephalum’s emergent, complex behaviors.