Slimy life

In October 2019, a unique exhibition was held at the Paris Zoo in France. In a glass jar on display, a creature without a brain lives. Although it does not have a memory system, it can build an efficient information network. This organism is called slime mold, also known as “slime ball”.

Slime mold is a collection of organisms similar to amoeba, not a single individual. Most slime molds are single-celled microorganisms, so small that they are invisible to the naked eye. But when they are ready to multiply, their body shape will become larger, forming fruit bodies or “sporangia” that can release spores outward. Although the form of spores released is similar to that of fungi, slime molds are far from being related to fungi. Some of the spores released by slime molds will form new single-celled slime molds and start a new life cycle.

Vortex fungus that can transform into super cells.

There are slime molds all over the world. Slime molds like to live on the branches or trunks of dead trees, and also like to live in piles of fallen leaves. Slime molds feed on other microorganisms, such as yeast and bacteria. If there is no slime mold, these microorganisms may lose their restraint and reproduce wildly. Slime molds come in many colors. Some slime molds are very beautiful, such as agglomerates; some slime molds can form gorgeous tree-like spores; and a slime mold commonly known as “dog spit” may not look so attractive. people.

Smart slime mold
“Proteomorph” slime molds are a particularly interesting group, they have evolved a peculiar way to find food. They are usually individual cells most of the time. Under the stimulation of special chemical signals, they fuse into a super cell cluster containing thousands of nuclei, with a maximum radius of up to 10 meters.

Villus fungus is the slime mold star in the Paris exhibition, and it often stretches out finger-like tendrils. In order to find food, this tendril can grow about 1 cm per day. In the past ten years, people have been discovering the “superpowers” possessed by slime molds, the most famous of which is the ability of Verticillium to find a path in a maze: the reason why it can find food in a maze is because it can perceive The trail left by itself, so that it can avoid the previously explored area.

Scientists have discovered that V. vulgaris also has a primitive learning ability. Generally speaking, slime molds tend to gain advantages and avoid disadvantages. If overcoming disadvantages helps to obtain food, slime molds will overcome them. For example, when a tendril of slime mold is negatively stimulated by some substances (such as salt or caffeine) while searching for food, the stimulated part will realize that this is the wrong path, so it quickly retracts and turns to other Path to find food. But if it finds that it can always find a source of food through a beneficial stimulus, it will learn to use this stimulus to obtain food. The slime molds will transmit information and share experiences, and they will also transmit information by fusing with other slime molds that have never encountered risks. What’s more interesting is that even if the lumpy slime mold enters a dry hibernation state, this transmission will continue for several weeks.

Slime molds can find food in the maze.

The sporangia formed during the reproduction period of Villus fungus.

Route designer
The behavior of slime molds shows that even simple organisms can exhibit behaviors that are usually found in animals with brains, which reminds us that we should re-examine single-celled organisms.

Scientists use chemical taste buds to control the movement of slime molds, enabling them to effectively track food. This method has aroused the interest of city planners and traffic engineers. Scientists simulate the locations of towns and cities in the petri dish. By placing the slime mold’s favorite food (oatmeal) at the target location, and let the slime mold autonomously “design” the foraging route, so that researchers can learn from or gain insights How to arrange the most suitable route. For example, through this method they learned that the railway system in Tokyo, Japan is one of the most efficient systems in the world, because when oats are used to map the proportional layout of the city’s railway stations, the slime mold produces tongue-like tongues between food sources The route is very consistent with the actual railway network of the city. In addition, through this method, it can be judged that the road network in the United States is not efficient.

Slime mold can provide a reference for complex route design.

Now, this simple method has even attracted the interest of cosmologists who want to explore the whereabouts of dark matter in the universe. The algorithm generated by observing the growth and connection of slime molds between food sources provides scientists with a useful model for exploring the distribution of dark matter in the universe. Scientists have discovered that the filamentous network of slime mold and dark matter basically overlap. By observing the slime mold network, scientists can roughly guess the distribution of dark matter in the universe. This method has been proven effective many times.

There are currently about 900 known slime molds in the world, but it is likely that more slime molds and their wonderful behaviors are waiting to be discovered. For example, an interesting recent discovery is that some types of slime molds “bring” bacteria in a similar way to leaf-cutting ants. When the slime mold reproduces in a new place, it will carry a kind of bacteria to the new home to “culture” and then feed on it. Perhaps the deeper we study the slime mold, the more we can see our shadow in them.