Navigation. Engineering. Multiplication, division, and subdivision. Weighing risks against benefits. Complex tasks require complex anatomy—a suite of bones, muscles, and organs— or at least a central nervous system, right?
A recent experiment, as explained on the Unexplainable podcast, throws stones at that idea. The experiment suggests that the above-mentioned tasks may not need a complex anatomy after all. One cell (yes, one) is enough to do the job.
The investigation focuses on slime molds. If you have ever looked at an amoeba under a microscope, that’s basically what a slime mold is. They “feel like mucus, look like a series of veins,” and come in different shapes and sizes, according to University of Sydney professor Tanya Latty. Latty goes on to describe them as a “brainless yellow goo.” Not much goes on in the goo: it consists of a grand total of one cell.
A cell—that tiny building block of life—usually requires a microscope to see. Humans have over 30 trillion of them. Yet the cell-powered slime mold can ooze out to the size of a bath mat. And it can move around at a rate of four to five centimeters per hour. And that’s not all.
Scientists placed a grain of oatmeal on one end of a labyrinth, and a slime mold on the other. The slime mold oozed its way to the food source, not in fits and starts, but in the shortest line possible. Being thrown into a labyrinth and having to navigate without eyes, nose, or a brain? It’s hard to imagine, right?
Scientists then tried to trick the slime, by placing a pile of bacteria-laden oatmeal at a close distance, and a single “healthy” grain further off in the maze. The slime bypassed the pile, evading potential infection, and oozed its way on to the single grain.
Unexplainable cites other experiments in which slime molds have successfully escaped from traps, controlled robots, and mapped out the entire metro system in Tokyo, Japan. Yet researchers remain stuck on a particularly gooey question: what is it, exactly, that drives the slime mold?
Latty, in investigating the slime, saw collective behavior that looked similar to certain species of ants. When ants identify a food source, they blaze a trail of “messenger chemicals,” effectively saying “Over here! Over here!” to the ants in tow.
OK, so slime molds are a series of pulsating veins. But upon closer examination, not all regions of the slime pulse at the same rate. “If a slime mold finds something it likes, the veins in that region start pumping faster… And it influences the regions around it to also pump faster,” says Latty.
Cut the slime mold into separate pieces, and you will have fully functional independent organisms. Put them back together, the pieces reunite into one. For being such a small creature, the slime mold raises big questions: what is the “individual” versus the “collective”? What, and who, counts as intelligent?
Tardigrades
Speaking of tiny, capable creatures, we would be remiss to leave out tardigrades.
Tardigrades (otherwise known as “water bears” or “moss piglets”) grow no more than 0.5 millimeters and have the honor of being among the smallest known creatures to possess legs. Aside from that, you can dehydrate them into glass, shoot them out of a gun, rehydrate them, and “you still have a living creature,” writes Jacinta Bowler.
Photo: Tardigrade
Research published in the journal PNAS details how tardigrades use their legs on a variety of surfaces. The tardigrades struggled to move around on a smooth, glass surface. But when put on a softer, gel-like substrate, “we found that tardigrades adapt their locomotion to a ‘galloping’ coordination pattern,” said the research team. Their stepping pattern is quite similar to that of insects, despite having no relation and being made of completely different stuff.
To watch tardigrades leg it out, click here .
To listen to the Unexplainable podcast on slime molds, click here .
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