The single-celled mucus fungus has, in recent years, increasingly fascinated researchers. What has surprised scientists most is how an organism without brain and nervous system can behave in a way that seems intelligent.

Usually, only more complex life forms are considered to have what is called "strategic behavior". This makes it unique among single-celled organisms.

- When you see what it can do. It can get through mazes, store enough nutrition, walk around traps and balance its nutritional intake, if you start to wonder if this organism has intelligence, says Audrey Dussutour, ethology researcher at Toulouse University.

The mucus fungus is targeted

The mucus can move and reach the food in an unobstructed way. When hungry, it spreads in the direction of food at a rate of up to 4 centimeters per hour. It extends its network of channels and can double its size by several centimeters per day.

It chooses the best nutrition

It has been found that the mucus fungus does not move randomly but aims at the right target. Researchers in France have studied how it chooses its food and have been able to see that it is moving directly towards the nutrients that are best for it.

- This shows that Physarum is very smart when it comes to getting nutrition. It chose the food that could maximize growth, says Audrey Dussutour

In addition, when it has a nutritional deficiency, it can enter a sleep mode to save energy.

It adapts

The researchers also discovered that the mucus fungus can learn to get used to a certain nutrition that it usually dislikes. This is the first time that researchers have shown that a single-celled organism has adaptability.

- Some were obviously skeptical of the result because it goes against the norm that learning exists only in life forms with brain, says Audrey Dussutour.

Information can be transmitted

When a slurry that was used to salt was then combined with one unfamiliar with salt, the adaptation to salt was transferred to the other slurry.

It showed that in addition to learning to become accustomed to a substance, the mucus can also carry over that habit.

See more about the world's smartest mucus in the world of science. The program airs on SVT2 on Monday 13 January at 20:00 and is available for viewing on SVT Play.