Made up of just a single cell and lacking any brain, or even any neurons and connections for that matter, you wouldn’t think much of the humble slime mold. But these creatures seem to display quite incredible levels of intelligence. Even though they lack grey matter, they were found to learn from their experiences, and now researchers have found that different colonies can teach other colonies.
The slim mold is composed of lots of individual single-celled organisms that come together to form a single large entity that acts as one. They move around by putting out tendrils, testing the environment as they search for food and avoid anything damaging. Working in this way, they become incredibly efficient, working out the shortest routes to food, for example.
But it was back in April this year that French scientists found that there was more to the slime mold than just impressive efficiency. They put the mold in agar on one side of a “bridge” and then placed their food on the other side. The bridge was then laced with caffeine or quinine, which tastes bitter to the microorganisms. After a while, the mold learned to find the route free of caffeine, and over time got better at crossing the obstacle, showing that they had some capacity for learning.
But in a new series of experiments, published in Proceedings of the Royal Society B, researchers placed one colony of mold in the agar alongside another colony who had never experienced the bridge, and therefore did not know the solution. They found that the experienced colony would fuse with the naïve mold and together they would move over the bridge while avoiding the harmful chemicals, which was salt this time.
What’s more, they then repeated the experiment by seeing if the one educated mold could teach multiple naïve colonies. They found that even when there were three inexperienced molds placed with just one experienced colony, all four would merge together and the resulting single mold would then know which path to take. This, the researchers suggest, shows that the “knowledge” gained by the first group is not diluted down, but somehow spread out within the single organism.
No one is quite sure how the slime is managing this, but the results may not be that surprising. There seems to be some sort of biophysical change in the slime molds cells, which it then seemingly passes on. This is not that unexpected, considering a similar thing presumably happens in our own brains with memories. Despite the human body turning over cells constantly through our lifetime, we still remember things from our past, even when the original cells that “remembered” them no longer exist.