Physarum polycephalum, often called a “slime mold,” is a unique organism that challenges traditional notions of biological complexity. Its behaviors have captivated scientists, hinting at sophisticated processes within a seemingly simple life form.
Meet Physarum
Physarum polycephalum is a single-celled organism, a type of plasmodial slime mold, belonging to the protist kingdom. In its active, feeding stage, it appears as a bright yellow, glistening, multinucleated mass that can spread across surfaces. It can grow to over 30 centimeters in diameter.
It thrives in cool, humid, and dark environments like forest floors. Its movement involves cytoplasmic streaming, where internal protoplasm rhythmically flows back and forth within a network of vein-like tubes. This shuttle streaming, which changes direction roughly every 60-100 seconds, distributes nutrients throughout its body. Physarum consumes food by engulfing small particles like bacteria, fungal spores, and decaying organic material through phagocytosis.
Physarum’s Surprising Abilities
Despite lacking a brain or central nervous system, Physarum polycephalum exhibits sophisticated behaviors. Researchers have observed its ability to navigate complex mazes. When presented with multiple food options, it explores its surroundings by extending its protoplasmic network, then retracts from less promising areas, focusing its biomass on the most efficient connections.
This organism can also demonstrate a form of “memory” regarding its environment. It avoids previously explored areas by leaving a trail of extracellular slime, which deters future movement. Its internal network morphology can also encode memory about nutrient locations, with thicker tubes forming around consumed food sources. Physarum has even been shown to optimize network connections, mimicking the efficiency of man-made transport systems. A notable example involved arranging food sources to represent major cities around Tokyo, and Physarum created a network of protoplasmic tubes that closely resembled the actual Tokyo railway system, demonstrating similar efficiency in connecting nodes.
Why Scientists Study Physarum
Physarum polycephalum is a model organism across various scientific disciplines. Its ability to solve complex optimization problems without a central brain offers profound insights into decentralized computing and artificial intelligence algorithms. Researchers study Physarum’s self-organizing network formation to understand how simple local interactions can lead to efficient global solutions.
The organism’s strategies for finding optimal paths and building resilient networks are being explored for applications in network theory, urban planning, and logistics. For instance, its capacity to adapt and reconfigure its network in response to changing conditions holds promise for designing more adaptive and self-healing infrastructure, such as smart cities or energy grids. By studying Physarum’s simple yet effective problem-solving, scientists aim to develop bio-inspired engineering solutions.