Even slime moulds have ‘brains’: a series of tubes that expand and contract to provide a memory of where food is located.
Slime molds (Physarum polycephalum) are single-celled organisms that can remember where they’ve been and can even find the shortest route through a maze. The moulds lack conventional brains, leaving scientists mystified about how their memory works.
Watching slime moulds through a microscope, Mirna Kramar at the Max Planck Institute for Dynamics and Self-Organization in Gottingen, Germany, and Karen Alim at Munich Technical University in Garching, Germany, saw that the organisms contained a network of variously sized tubes with gel-like walls. The diameter of the tubes changed when the mould sensed food nearby, creating an ‘imprint’ of the food’s location that lasted for half an hour.
The researchers think that a chemical signal from the food softened the walls of tubes close to it. This allowed the structures to fill with fluid and expand, while other tubes contracted. The authors say that this type of memory could be copied when building soft robots and other technologies that rely on hydraulics.