Slime Mold: The Next Middle School Trend?
Slime is all the rage among middle school students. (You can find my favorite recipe here.) As a science teacher, though, you may be more captivated by slime mold. And, hopefully, your enthusiasm for this living slime will spread to your students like Physarum polycephalum on the forest floor.
Although slime mold resembles the colorful goop that students mix up by the batch, the living mold consists of single-celled amoeba-like organisms that may join together to form large masses that can measure meters across. They form these masses to make the most of available resources, often when food is scarce. It’s an example of altruism in nature, when an individual cell sacrifices individuality for the overall good of the community.
You might not expect much from a brainless, spineless protist with no apparent internal command center, but slime molds are capable of moving, learning, and mapping efficient routes.
Sure, your students’ lumps of slime may appear to melt and spread, leaving a goopy mess, but blobs of slime mold pulsate and move with a purpose, usually to find food or reproduce.
The bright yellow Physarum polycephalum is one of the most studied slime molds. It’s shown a remarkable ability to solve maze puzzles and to map out efficient routes. For example, in one oft-noted study, flakes of oatmeal (one of its favorite foods in the lab) were placed around the slime mold in a manner that mimicked a map of Tokyo’s subway system stations. In its slow, pseudocephalopodic way, within a few hours the slime mold spread out and found the food. As it did,, it created shortest-distance pathways that looked like the train routes. Human engineers, by contrast, had spent years planning those railway routes around Japan.
In other experiments, samples of Physarum polycephalum were taught to cross bridges covered in distasteful chemicals in order to reach a desirable food source. Although the slimy massees initially reacted to the salty or bitter substances by slowing their movements across the bridges, they eventually habituated to the off-putting materials and increased their speed in pursuit of their goal.
Even more interesting, when samples from “educated” supercells fused with new groups, the newly “inoculated” masses crossed the salty and bitter bridges without slowing down.
How Do They Do It?
Scientists are trying to understand how Physarum polycephalum learns and communicates. And more importantly, what human society can learn from this creature that is typically found on forest floors breaking down rotting materials. What we’ve discovered about slime mold so far has inspired engineers, city planners, computer scientists, social scientists, and artists.
Show Your Students
A Slimey Wish
I hope that the mysteries of slime mold will intrigue your students as much as the goop that the kids are currently making at home. (And, by the way, it’s pretty easy to grow slime mold at home or in your classroom.) If your students are inspired, remind them that that all they need to enter the 2018 Young Scientist Challenge is a good idea and a short video. Entries are open through April 19.