The above is a 1cm section of slime mold Physarum polycephalum plasmodium (think ‘ectoplasm’, it’s really gooey) lit from below. It has something like muscles and also a kind of equivalent to blood flowing along veins. When the plasmodium is contracted it appears light grey and looks darker where it is relaxed. At the beginning of the movie a drop of delicious sugary liquid is placed at the bottom left. You can see Physarum‘s contractions become more rapid and chaotic. How do these responses spread to the rest of the plasmodium? How are these signals processed and coordinated into an appropriate behaviour such as directed movement?
Here is the paper’s significance statement:
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.
A short guide to Physarum polycephalum aimed at a scientific audience can be found here:
Here the yellow P. polycephalum plasmodium oozes over the pores of a turkey tail mushroom (Trametes versicolor). The elapsed time is around 3 hours.