brainless organisms can learn

Does This Slime Challenge Everything We Know About Evolution? Slime ‘Learns’ Without A Brain Or Nervous System

Scientists researching a seemingly odd subject, yellow tree slime mold, have discovered that the slime has an unprecedented ability to “learn” despite lacking a brain or nervous system. The yellow slime is made up of single-celled organisms that band together to form one unified mass which feeds on fungi and bacteria in the forest. However, scientists studying the slime found that the odd organisms had another previously unheard of ability, they could “learn” to overcome fears of non-harmful substances. While that may seem expected from a living organism, it is anything but usual. In fact, the yellow slime mold is the first organism without a central nervous system that has demonstrated it is capable of learning.

The Proceedings Of The Royal Society B, the Royal Society’s flagship biological research journal, recently published a study performed by researchers at the University of Toulouse involving the mysterious slime behavior. In the study, researchers revealed that the yellow slime mold was able to learn, specifically, the mold was able to perform a type of learning called habituation. This revelation was surprising as the slime provides researchers with the first evidence of an organism without a brain or nervous system capable of performing such a feat.

Learning was defined as “a change in behavior evoked by experience,” and the researchers say that the slime was able to do this by learning to overcome “fear” associated with an unknown substance. According to the Daily Mail, the yellow slime mold is designed to release digestive enzymes and absorb the nutrients when the single cell organisms encounter something that they can eat. However, the slime avoids substances that it is not too keen on. To test the slime’s ability to learn, researchers placed the slime molds in one Petri dish and created an obstacle leading to a second Petri dish of food. In the control group, the first obstacle was a simple bridge that the mold could cross to make its way to the food source. However, in the test group, an undesirable and unknown bitter substance such as caffeine was placed on the bridge.

Researchers discovered that the slime would initially avoid the unknown substance, working its way around the substance to the second dish for the food. However, after six days of performing the same test, the slime “learned” that the substance was not harmful and started performing exactly the same as the control group. Researchers noted that without a brain or nervous system, the mold should not have been able to experience this type of learning behavior.

Interestingly, the mold was only a short-term learner. Researchers say that after two days of no contact with the new substance, the mold “forgot” the old behavior and once again showed fear to the bitter substance. The researchers said they were also able to create fear in the mold samples.

“When they taught the molds to distrust one bitter substance, the researchers found they would automatically distrust another bitter substance.”

Therefore, the team says that this is a clear indicator that the yellow tree slime mold is capable of basic habituation and complex maneuvers that would not be expected in a brainless organism. The Scientific American says it is as if this brainless organism was behaving like “a team of human engineers” and not performing random maneuvers.

“In other words, the single-celled brainless amoebae did not grow living branches between pieces of food in a random manner; rather, they behaved like a team of human engineers, growing the most efficient networks possible.”

The researchers concluded that this specific learning behavior in an organism without a brain could be “centrally important to a comprehensive, phylogenetic understanding of when and where in the tree of life the earliest manifestations of learning evolved. “In fact, it was said that these molds are defying pretty much everything regarding “convoluted brain-based intelligence.”

“They do not accept whatever circumstances they find themselves in, but rather choose conditions most amenable to their survival. They remember, anticipate and decide. By doing so much with so little, slime molds represent a successful and admirable alternative to convoluted brain-based intelligence. You might say that they break the mold.”

What do you think about the idea of a brainless organism showing the capabilities of learning?

[Image via WikiCommons/Slime Mold]