Physarum polycephalum is one of those organisms that generates disbelief the more you learn about it. A single cell you can see with the naked eye, spreading over tens of centimeters. No brain, but it can solve mazes. No stomach, but it selects a balanced diet. This fact sheet compiles the most important data points about slime mold into a structured, science-backed reference.
Identity Card
| Field | Data |
|---|---|
| Scientific name | Physarum polycephalum |
| Common names | Slime mold, many-headed slime, "le blob" in France |
| Name meaning | "Bellows with many heads" (Greek/Latin) |
| Supergroup | Amoebozoa |
| Class | Myxomycetes (Myxogastria) |
| Order | Physarales |
| Family | Physaraceae |
| First described | 1822 by Lewis David de Schweinitz |
Physical Characteristics
| Trait | Details |
|---|---|
| Color (plasmodium) | Bright yellow to orange |
| Color (sclerotium) | Orange-brown, turning darker with age |
| Texture | Moist, gel-like, slightly spongy |
| Visible structure | Network of interconnected veins and fan-shaped fronts |
| Size | A few millimeters to a few tens of centimeters in the wild. No verified size record has been published |
| Thickness | Veins: 0.1 to 1 mm; growth fronts: thinner |
| Smell | Faintly earthy, similar to forest floor |
Biology at a Glance
| Feature | Details |
|---|---|
| Cell structure | Syncytium: one giant cell with no internal walls |
| Number of nuclei | Millions to billions, depending on size |
| DNA | Diploid genome, approximately 210 Mb |
| Mating types | 720, from three genes (matA, matB, matC) |
| Cytoplasmic streaming | Rhythmic back-and-forth shuttle flow (period: about 100 seconds) |
| Cell division | All nuclei divide at the same time without the cell dividing |
| Immortality? | Theoretically, the plasmodium does not age. No known biological limit to its lifespan. |
720 Mating Types
While most animals have two sexes, Physarum polycephalum has 720 mating types. They come from three genes: matA has 16 known versions, matB 15 and matC 3, and 16 × 15 × 3 = 720. Two reproductive cells can only pair if their combinations differ, so almost any partner will do. Its other feats, measured and sourced, are gathered in slime mold records.
Movement and Speed
| Measurement | Value |
|---|---|
| Typical speed | Around 1 cm per hour in a home culture |
| Maximum recorded speed | About 4 cm per hour in ideal lab conditions |
| Movement mechanism | Cytoplasmic streaming drives extension of growth fronts |
| Streaming speed (internal) | Up to 1.35 mm per second inside veins |
| Direction changes | Responds to chemical gradients (chemotaxis), light (phototaxis), gravity (gravitaxis) |
| Obstacle response | Explores multiple paths simultaneously, reinforces the most efficient one |
For a detailed look at the mechanics behind slime mold locomotion, see How Slime Mold Moves.
Diet and Feeding
| Aspect | Details |
|---|---|
| Feeding method | Phagocytosis (engulfing food particles) |
| Primary food sources | Bacteria, fungal spores, yeast, decaying organic matter |
| Laboratory diet | Oat flakes (most common), agar supplemented with nutrients |
| Food detection | Chemotaxis: detects chemical signals from food at a distance |
| Nutritional balance | Actively selects a 2:1 ratio of protein to carbohydrates |
| Toxic avoidance | Can detect and avoid salt, quinine, and other repellent substances |
Learn about the fascinating research on slime mold nutrition in our article on how slime mold eats.
Habitat
| Factor | Preferred Range |
|---|---|
| Biome | Temperate deciduous forests |
| Substrate | Decaying logs, leaf litter, bark, soil |
| Temperature | 22 to 25 degrees Celsius (optimal growth) |
| Humidity | High (above 80% relative humidity) |
| Light | Prefers dark or shaded conditions; avoids UV and blue light |
| Geographic range | All continents except Antarctica |
Life Cycle Stages
| Stage | Size | Duration | Key Feature |
|---|---|---|---|
| Spore | 8-12 micrometers | Years (dormant) | Resistant to desiccation, heat, cold |
| Amoeba | ~10 micrometers | Hours to days | Free-living, feeds on bacteria |
| Swarm cell | ~10 micrometers | Hours to days | Flagellated, free-swimming form |
| Zygote | ~20 micrometers | Hours | Fusion of two compatible cells |
| Plasmodium | Millimeters to meters | Days to months | Active feeding, moving, learning phase |
| Sclerotium | Same as plasmodium | Months to years | Dormant, dried, can be revived |
| Fruiting body | 1-3 mm tall | Days | Spore-producing reproductive structure |
Remarkable Abilities
What sets slime mold apart from virtually every other single-celled organism is its repertoire of complex behaviors. Each of these has been documented in peer-reviewed research.
| Ability | Description | Key Research |
|---|---|---|
| Maze solving | Finds the shortest path between two food sources through a maze | Nakagaki et al., 2000 |
| Network optimization | Creates transport networks comparable to human-engineered ones | Tero et al., 2010 |
| Habituation learning | Learns to ignore harmless but repellent substances over time | Boisseau, Vogel and Dussutour, 2016 |
| Memory transfer | Passes a learned behavior to another individual through cell fusion | Vogel and Dussutour, 2016 |
| Anticipatory behavior | Anticipates periodic events based on past experience | Saigusa et al., 2008 |
| Nutritional balancing | Selects an optimal protein-to-carbohydrate ratio | Dussutour et al., 2010 |
| Unconventional computing | Used to solve graph theory and optimization problems | Adamatzky, 2010 |
| Spatial memory | Avoids areas already covered by its own slime trail | Reid et al., 2012 |
Explore the science behind these abilities in our articles on slime mold memory and slime mold movement.
Key Numbers
| Metric | Number |
|---|---|
| Known myxomycete species worldwide | Approximately 1,000 |
| Mating types in P. polycephalum | 720 |
| Genome size | ~210 megabases |
| Cytoplasmic streaming period | About 100 seconds per cycle |
| Maximum internal flow speed | About 1 mm/s |
| Optimal growth temperature | 22 to 25 degrees Celsius |
| Sclerotium survival | Two years and more if dried and stored properly |
| Sclerotium revival time | About 24 to 48 hours on a damp substrate |
| Year of Nakagaki's maze experiment | 2000 |
| Year of Dussutour's memory paper | 2016 |
| Year sent to ISS | 2021 |
Still Growing
Research on slime mold has accelerated dramatically since the early 2000s. New papers appear every month, and new abilities continue to be discovered. This fact sheet will be updated as new findings are published.
This page on a single sheet
Its classification, the key numbers, its three states and what we still do not know fit on a printable fact sheet (PDF, A4), handy for a school project or a classroom wall. To check what you remember, take the ten-question slime mold quiz.
Slime Mold vs. Common Misconceptions
Given how unusual slime mold is, misconceptions are widespread. Here are the most common ones, corrected. Twelve of them are taken apart in more detail on our page about slime mold myths.
| Misconception | Reality |
|---|---|
| "It's a type of fungus" | No. Slime molds were reclassified out of fungi decades ago. They are protists. |
| "It's dangerous or toxic" | No. Physarum polycephalum is harmless to humans, animals, and plants. |
| "It's intelligent like an animal" | It exhibits intelligent behavior, but through entirely different mechanisms than animal brains. |
| "It's microscopic" | The plasmodium is easily visible and can spread over tens of centimeters. |
| "It only exists in labs" | It is found in forests on every continent except Antarctica. |
| "It has a short lifespan" | The plasmodium shows no programmed aging. Lab strains have been kept going for decades by regular subculturing. |
For a complete introduction to this organism, start with What Is Slime Mold? or explore the history of slime mold research to understand how scientists uncovered these abilities one by one.