Slime Mold Form a Map of the Tokyo-area Railway System

Slime molds are one of the smartest among lower organisms. These gooey, slimy blobs form veins as they spread along dead logs or leaves, or anything that they deem as food. Slime molds are unique and do not fit well into the current system of classification. When it comes to research on slime molds, bright, yellow-colored Physarum is the lab rat. It can detect food, changes in humidity, pH, and even light using receptors. Receptors are similar to sense organs like eyes or ears. Within a blob of slime mold, one can find veins. Long proteins are associated with these veins. Jelly-like protoplasm runs through these veins, and on smelling food, these veins grow outwards. The proteins squeeze and relax, pushing the protoplasm towards the growing end.

Slime molds don’t travel mindlessly, but choose the best route to reach a source of food. In a famous experiment by Toshiyuki Nakagaki, he placed oat flakes to represent key towns and cities of Japan, with a blob of slime mold in the center to represent Tokyo. As the slime mold branched out towards the oat flakes, the network of veins that formed looked an awful lot like the Tokyo rail system.


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