Slime Molds: Brainless Intelligence



Slime molds, the yellow, finger-like spongy masses on the sides of rocks and logs, are smarter than they appear. Nova and Scientific American have partnered to produce this video, an excerpt from their series ScienceNow, which premiered November 7th, 2012. It features the Physarum polycephalum, nicknamed "Spongebob Squarepants" for its yellow, spongy appearance.

Unlike the silly, whimsical children's TV show character, this single-celled protist (not fungi, a common misconception) exhibits astonishing signs of intelligence. When placed into the entrance of a maze with food (such as oat flakes) at the exit, it spreads out through every turn and crevice. Then, though it has no central or peripheral nervous system, it exhibits amazing spacial memory, as shown in this study conducted by Chris Reid from the University of Sydney. Slime molds are able to recognize the shortest pathway between the entrance and the exit. The molds secrete a substance into the areas other than this direct pathway, causing these unneeded sections to retract.

What's more is that the slime mold, when placed in models with food sources in areas positioned to simulate Tokyo city, has re-created the Tokyo subway system on its own. It is able to recognize the most efficient pathway between two points, mapping out what took several hundred human engineers to figure out. This experiment has also been successfully applied to highway systems of Canada, the U.K., and Spain. The slime mold spreads out over the entire model at first, then later thins out to form the web between the food sources. 

Slime molds exhibit decision-making capabilities when subjected to unfavorable conditions. One experiment started the slime molds in warm temperatures and humidity, then suddenly decreased the temperature and humidity. In response, the slime mold would crawl slower, saving its energy.

Another experiment by Tanya Latty and Madeleine Beekman from the University of Sydney presented Physarum polycephalum with two food sources, one consisting of 1% oatmeal in darkness and one of 5% oatmeal in bright light, lethal to the slime mold. The slime mold crawled toward both equally, recognizing the trade-off between high food content and unfavorable conditions. However, when a third source containing 3% oatmeal in darkness was introduced, the slime mold showed preference to this food source. Eighty percent of the mold was found to grow toward the 3% solution. 

These single-celled, brainless protists continue to astonish and fascinate the multicellular, fully-developed cerebral cortexes known as human beings. Nature is truly mesmerizing and full of wonderful, hidden talent. What will come next, a fungi that can perform multivariable calculus?