The slime mold, Physarum polycephalum, is an extremely effective forager capable of creating extensive and highly efficient networks between food sources. This single-celled creature, classified as a protist, oozes its way across surfaces in search of bacteria, fungal spores, and other microbes to feed on. As it spreads and grows in search of food, it naturally organizes itself into a network of tube-like structures that quickly and efficiently connect its disparate food sources.
Physarum maximizes its ability to find food by ‘remembering’ and strengthening the portions of its cytoplasm that connect to active food sources. By rhythmically contracting and expanding its body, Physarum is able to move and grow its body in search of food. When it fails to find food or the food source dries up, Physarum retracts its cytoplasm, leaving behind a trail of slime–essentially marking which pathways are useful and which are dead-ends.
By trimming back connections and maintaining only active pathways, Physarum uses the least amount of resources and energy possible while still creating a resilient and fault-tolerant system. Links between food sources are made covering the shortest possible distances, but are connected in such a way that a disruption in one area does not impact the overall health or efficiency of the slime mold’s network.
Check out Physarum in action in this video.
http://www.youtube.com/watch?v=lls27hu03yw#t=110This summary was contributed by Emily Hoehn.
“The body shape of the plasmodium resembles an intricate network of tubular components…During locomotion with a speed of 1 cm/h, the size and mesh of tubes evolve depending on the position within the organism. At the frontal part of the plasmodium, small components of the tube are very densely connected and some of the small tubes gradually become thick, while most of them disappear towards the rear.After several hours, parts of the plasmodial body which extended into the dead ends of the maze retracted and moved to the food sources to wrap around the surfaces of the food source… From the viewpoint of solving a maze, the plasmodial tubes lie only in all possible routes which connect to the food sources, so that all solutions are indicated by the connecting tubes. Several hours later, the connecting tubes were cut off at one place and disconnected, except for the tube in the shortest connecting route.” (Nakagaki 2001:767)“By lying only in the shortest route between two food sources, the plasmodium can deliver much of its own body to the food sources, so that the intake of the nutrient is more efficient. Moreover, since the tube is a channel of protoplasmic streaming, the shortest tube leads to efficient transport of protoplasm.” (Nakagaki 2001:769)