Keeping pets has gradually become an important part of the lives of many young people. Following the trend of keeping "stinky water," "cardboard box dogs," and "mango pits," many people are now keeping slime mold. Unlike the black alien life form in the movie "Venom," this is a slippery, yellow slime.
Yellow slime mold is looking for food.
Slime molds are among the most peculiar life forms on Earth. They are neither plants nor animals, and although their name includes "mold," they are not fungi or bacteria, but rather belong to a class of protists.
Protozoa (or Protista) are a group of eukaryotic organisms primarily composed of single cells. Unlike plants and animals, they do not belong to the typical multicellular taxa, but they possess independent life activities. Protozoa are widely distributed in aquatic environments, soil, and within or on the surface of plants and animals, forming a highly diverse group of organisms.
Slime molds, as a type of protozoa, typically live in moist environments, such as decaying wood, soil surfaces, or on leaves. They lack the photosynthetic capacity of plants and do not possess the complex tissue structures of typical animals, but they play an important role in ecosystems, especially in the decomposition of organic matter.
Just how fun are slime molds that they've become a new favorite among young people?
It can find food on its own even without a brain or eyes.
The saying goes, "Give a foodie food, and he'll work miracles," and many studies on slime molds are based on this idea. Recent research has discovered that *Vorticella multicephala* (also known as *Vorticella multicephala*) uses its body to sense its surroundings before "deciding" where to go. This is the latest surprise this single-celled organism has given us.
Please watch the video:
Slime molds will go to places with more food.
Researchers placed slime mold samples in petri dishes using ordinary agar gel as the culture medium. A small glass slide was placed on one side of the dish, and three glass slides were placed side-by-side on the other side. Each glass slide contained food for the slime mold. The petri dishes were placed in a dark room, which is the light environment preferred by slime molds. For the first 12 hours, the slime mold grew evenly in all directions. However, by 24 hours, 70% of the samples were growing towards the three side-by-side glass slides, rather than a single slide.
Further experiments revealed more interesting phenomena. When the three glass slides were stacked together rather than placed side by side, the slime mold's preference disappeared, and the probability of growing to both sides was almost equal. This indicates that the quality of the glass slides did not cause the slime mold to choose three side by side.
Using computer models, researchers discovered the cause lies in the deformation of the agarose gel. When glass slides are placed side-by-side, they deform in a different way than when stacked, similar to how placing multiple weights side-by-side on a trampoline creates a different pressure pattern than stacking weights. The research team determined that the slime mold migrates towards this deformation pattern.
It can navigate a maze without a brain.
The slime mold maze puzzle experiment also utilizes the above approach. This is a famous study conducted in 2000 by Toshiyuki Nakagaki and his team at Hokkaido University in Japan. Slime molds are single-celled organisms without a nervous system, yet the researchers' experiment demonstrated their ability to find food in complex environments. They designed a complex maze, with oatmeal placed at the exit as food, and the slime molds initially placed at one of the maze's entrances.
During the experiment, slime molds spread through the maze using pseudopodia, gradually covering each passage. As they explored, they sensed changes in their environment and adjusted their expansion direction. When they found food, cytoplasmic flow gradually concentrated on the shortest path, while the remaining pseudopodia gradually contracted and disappeared. The experimental results demonstrate that slime molds can efficiently find the shortest path from the entrance to food.
Slime molds find the shortest path to food in a maze.
This behavior is surprising because slime molds, lacking a nervous system or brain, exhibit abilities similar to distributed computing. Scientists believe this is related to the slime mold's cytoplasmic flow and chemosensory mechanisms, enabling it to find optimal solutions in complex environments through continuous trial and error and feedback. This research provides inspiration for biologists and computer scientists, particularly in the design of nature-inspired algorithms and the study of distributed intelligent systems.
Slime molds can optimize complex traffic routes
In subsequent experiments, scientists further investigated the performance of slime molds in other complex problems, such as the optimization of simulated urban traffic networks.
The slime mold simulation of the Tokyo subway network optimization experiment was an innovative study conducted in 2010. The aim of the experiment was to explore the potential of slime molds in optimizing complex transportation systems by leveraging their network-building capabilities. Researchers chose Tokyo and its surrounding areas as models, a region with a highly complex transportation network that needed to be both efficient and robust. To simulate this environment, scientists placed oat flakes on agar plates resembling a map of Tokyo, simulating major transportation hubs in Tokyo, and observed how the slime molds established connections between these points.
In the experiment, slime mold was placed at a central point (simulating Tokyo's core transportation hub) and began to grow on a culture medium, gradually expanding its pseudopodia to connect various "cities" (oatmeal flakes). Over time, the slime mold's network gradually optimized: it eliminated redundant channels while maintaining the stability and efficiency of the connections. The network eventually formed by the slime mold bore a striking resemblance in some aspects to the actual Tokyo subway system. The slime mold's network layout not only efficiently connected all the hubs but also exhibited strong robustness, quickly adjusting through other channels even if some paths were disrupted.
Slime mold network simulating urban traffic
This research demonstrates that although slime molds lack a brain or central control system, they are able to optimize their networks through simple physical and chemical reactions. The performance of this distributed intelligent system offers important insights for urban planning and transportation network design. The slime mold network not only exhibits strong adaptability but also finds the shortest path under limited resources, which is similar to many optimization problems in practical engineering. Researchers believe that this behavior of slime molds can be used to design more efficient and sustainable transportation systems, especially those that require consideration of redundancy and disaster recovery capabilities.
Do slime molds have memory and learning abilities?
In 2016, a research team at the French National Centre for Scientific Research, led by Audrey Dussutour, discovered that slime molds can adapt to environmental changes through habituation learning.
Habituation refers to the gradual reduction in an organism's response to a harmless stimulus after repeated exposure. In experiments, researchers used bitter-tasting chemicals (such as quinine or caffeine) to block the movement paths of slime molds. Although these substances were harmless to the slime molds, they initially avoided these areas.
In the early stages of the experiment, slime molds exhibited avoidance behavior when encountering these chemicals, choosing to bypass these areas in search of food. However, over time, researchers observed that the slime molds gradually "got used" to these chemicals and increasingly preferred to pass directly through these areas.
Behavioral responses of two groups of slime molds when crossing agar bridges containing quinine and those without quinine. The slime molds in the figure represent the control group (C) and the experimental group (EXP), respectively.
Experiments showed that slime mold significantly reduced its avoidance response to these harmless chemicals after 4-6 exposures. This behavior demonstrates that slime mold possesses a simple form of learning ability, namely, the ability to remember harmless stimuli in the environment and adjust its behavior to improve efficiency.
Even more surprisingly, this habituated learning behavior of slime molds can persist for days, even being "preserved" during dormancy. When reactivated, the slime mold continues to exhibit familiar and adaptive behavior towards these chemicals. This persistent memory has led scientists to further consider the memory mechanisms of slime molds, demonstrating how they can remember and adapt to environmental changes through molecular and cellular responses, even without a brain or nervous system.
This is incredible for an organism without a brain or nervous system! The learning mechanisms of slime molds demonstrate how simple organisms in nature can solve complex problems through environmental adaptation.
Are there any risks associated with playing with slime mold?
Slime molds themselves are not harmful to humans. As a common laboratory organism, they are neither toxic nor do they cause disease, making them safe for humans and pets.
However, maintaining a moderately humid environment is crucial for cultivating slime mold. In such a humid environment, poor hygiene can easily lead to mold growth and the production of numerous spores, posing a threat to human health. In poorly ventilated conditions, these mold spores associated with slime mold can potentially enter our trachea and lungs through respiration, causing respiratory problems, allergic reactions, and other health risks.
Therefore, when cultivating slime mold, it is essential to regularly check the culture environment, keep it clean and well-ventilated, and try to prevent excessive mold growth.
