When placed at the perimeter of a maze with food in the center, the plasmodial slime mold Physarum polycephalum explores the maze, retracts branches from dead-end corridors, and then grows exclusively along the shortest path possible to the food. How does Physarum do this? One theory is that it leaves behind slime deposits—an externalized 'memory' that 'reminds' it not to retry dead ends. Propose an experiment that would test whether the coating of extracellular slime changed the speed at which the slime mold moved across the substrate.

Verified step by step guidance

1. Step 1: Design the experiment with two groups of Physarum polycephalum. One group will move in an environment where the substrate is pre-coated with extracellular slime, and the other group will move in a clean environment without any pre-coated slime.
2. Step 2: Prepare identical maze setups for both groups, ensuring that the only variable that differs is the presence of the slime coating on the substrate. Use a controlled environment to maintain consistent conditions such as temperature, humidity, and light.
3. Step 3: Introduce food at the center of each maze and place equal amounts of Physarum polycephalum at the start point of each maze. Start a timer to record the time taken for the slime mold to reach the food.
4. Step 4: Observe and record the movement of the slime mold in both setups. Note the speed of movement, the path efficiency, and whether the slime mold retraces its steps or avoids paths with pre-existing slime.
5. Step 5: Analyze the data to compare the speed and path efficiency between the two groups. Use statistical methods to determine if the presence of extracellular slime significantly affects the movement behavior of Physarum polycephalum.

Key Concepts

Plasmodial Slime Mold Behavior

Plasmodial slime molds, such as Physarum polycephalum, exhibit unique behaviors that allow them to navigate complex environments. They can explore mazes and optimize their paths to food sources by retracting from unproductive routes. This behavior is driven by their ability to sense environmental cues and adapt their growth patterns accordingly, showcasing a form of intelligence despite lacking a nervous system.

Extracellular Slime and Memory

The extracellular slime produced by Physarum polycephalum serves as a form of externalized memory. When the slime mold moves, it leaves behind a trail of slime that can influence its future movements. This slime may contain chemical signals that help the organism avoid previously explored dead ends, effectively 'reminding' it of the paths that did not lead to food, thus enhancing its efficiency in navigating mazes.

Experimental Design in Biology

Designing an experiment to test the effect of extracellular slime on the movement speed of Physarum involves establishing controlled conditions to isolate variables. One could compare the movement speed of slime molds on substrates with varying amounts of slime deposits. By measuring the time taken to reach food in different scenarios, researchers can determine if the presence of slime significantly alters the slime mold's navigation efficiency.