Slime mold memorizes foreign substances by absorbing them

April 22 (UPI) -- The slime mold Physarum polycephalum doesn't have a nervous system, yet the single-celled organism is capable of learning and communicating.

According to a new study, published this week in the journal Philosophical Transaction of the Royal Society B, the mold learns via fusion.

A team of biologists at the French National Center for Scientific Research determined the molds learn by absorbing the foreign substance. After researchers had the slime molds move across salty environments for six days, the molds contained ten times more salt than molds in a control group.

When researchers placed the salty slime molds back in a salt-free environment, the single-celled organisms expelled the salt within two days -- purging the "memory" of the foreign substance.

In a followup test, scientists injected a salt concentration into molds previously unexposed to salty environs. When placed in a salty environment, the molds behaved just like the molds that had become conditioned to the foreign substance.

Slime molds enter a dormant stage when environmental conditions worsen, but researchers found the dormant molds held onto their memories.

"We showed that information acquired during the training was preserved through the dormant stage as slime molds still showed habituation after a one-month dormancy period," researchers wrote.

Scientists are currently conducting additional experiments to determine whether slime molds can memorize multiple foreign substances at once.