Plasmodio

A slime mold redraws Italy

How it works

Everything you see is computed live on your graphics card. Nothing is pre-recorded and no server is involved.

The organism

Physarum polycephalum is a single-celled slime mold with no brain, no eyes and no plan. It explores by pushing out a network of veins, then thickens the veins that carry food and lets the others wither.

The Tokyo experiment

In 2010 Atsushi Tero and colleagues placed the mold on a map of Japan with oat flakes on the main cities. In about a day it had grown a network with the efficiency, cost and resilience of the real Tokyo rail system. Tero et al., Science 327 (2010).

The rules

This is the agent model of Jeff Jones (2010). Every agent, every step:

smells the trail at three points ahead: left, front, right;
turns toward the strongest smell;
moves one step and leaves a drop of trail.

The trail spreads to neighbouring cells and fades. Towns emit trail as food, weighted by population. The sea is a wall; ferry corridors are the only way across water. From these rules alone the veins appear, compete and prune themselves.

What is real here

Coastline and borders: geoBoundaries (CC BY 4.0), with Natural Earth as fallback.
Towns and populations: GeoNames (CC BY 4.0).
High-speed rail, main railways, motorways and ferries: OpenStreetMap contributors (ODbL).
Roman roads: Itiner-e, de Soto et al. 2025 (CC BY 4.0).

Projection is equirectangular around 41.9° N, so distances are true to about 8% at the extremes of the map. The Pelagie islands are outside the frame.

Keys

Space pause · R reset · F fit · L labels · drag to pan · wheel or pinch to zoom · Esc close

Made by

Alberto Barnabo. Source and data pipeline are in the Files tab of this Space. The simulation is a WebGL2 program: three textures and five shaders.

This is a slime mold.

Physarum polycephalum has no brain and no eyes. In 2010, placed on a map of Japan with oat flakes on the cities, it regrew the Tokyo rail network in about a day.

Real experiment. Tero et al., Science, 2010.

Waking the organism…