Slime Mold Accurately Simulates Optimal Subway Network

Slime mold is being used to optimize public transportation networks in Japan...and it's really good at it.

...Atsushi Tero from Hokkaido University worked with the slime mould Physarum polycephalum. This amoeba-like creature forages for food by sending out branches (plasmodia) from a central location. Even though it forms vast, sprawling networks, it still remains as a single cell. It's incredibly dynamic. Its various veins change thickness and shape, new ones form while old ones vanish, and the entire network can crawl a few centimetres every hour.

For a mindless organism, the slime mould's skill at creating efficient networks is extraordinary. It can find the most effective way of linking together scattered sources of food, and it can even find the shortest path through a maze. But can it do the same for Tokyo's sprawling cityscape?

Tero grew Physarum in a wet dish at a place corresponding to Tokyo, with oat flakes marking the locations of other major cities in the Greater Tokyo Area. Physarum avoids bright light, so Tero used light to simulate mountains, lakes and other prohibitive terrain on his miniature map. The mould soon filled the space with a densely packed web of plasmodia. Eventually, it thinned out its networks to focus on branches that connected the food sources. Even by eye, these final networks bore a striking similarity to the real Tokyo rail system.

More on Physarum polycephalum.