Physarum polycephalum is one of those organisms that generates disbelief the more you learn about it. A single cell that can grow to several square meters. 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, the blob, many-headed slime |
| Name meaning | "Bellows with many heads" (Greek/Latin) |
| Kingdom | Protista |
| Phylum | Mycetozoa |
| Class | Myxomycetes (Myxogastria) |
| Order | Physarales |
| Family | Physaraceae |
| First described | 1822 by Lewis David de Schweinitz |
| Estimated age of group | Over 500 million years (myxomycetes as a clade) |
Physical Characteristics
| Trait | Details |
|---|---|
| Color (plasmodium) | Bright yellow to orange |
| Color (sclerotium) | Dark brown to black |
| Texture | Moist, gel-like, slightly spongy |
| Visible structure | Network of interconnected veins and fan-shaped fronts |
| Maximum recorded size | Over 10 square meters (in laboratory conditions) |
| 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 |
| Number of sexes | Over 720 known mating types |
| Cytoplasmic streaming | Rhythmic back-and-forth shuttle flow (period: ~90 seconds) |
| Cell division | Nuclear division without cell division (endomitosis) |
| Immortality? | Theoretically, the plasmodium does not age. No known biological limit to its lifespan. |
720+ Sexes
While most organisms have two sexes, Physarum polycephalum has over 720 mating types. Any two individuals of different mating types can fuse to form a new plasmodium. This extraordinary genetic diversity helps the species adapt rapidly to changing environments.
Movement and Speed
| Measurement | Value |
|---|---|
| Average speed | 1 to 4 cm per hour |
| Maximum recorded speed | Up to 5 cm per hour under optimal 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 | 19 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 | Dussutour et al., 2016 |
| Memory transfer | Transmits learned information to another individual through cell fusion | Dussutour et al., 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 |
| Risk assessment | Adjusts exploration strategy based on environmental threats | 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 | Over 720 |
| Genome size | ~210 megabases |
| Cytoplasmic streaming period | ~90 seconds per cycle |
| Maximum internal flow speed | 1.35 mm/s |
| Optimal growth temperature | 22 to 25 degrees Celsius |
| Spore viability | Decades under proper storage |
| Sclerotium revival time | 12 to 24 hours with water and food |
| Largest recorded specimen | Over 10 square meters (lab) |
| Year of Nakagaki's maze experiment | 2000 |
| Year of Dussutour's memory paper | 2016 |
| Year sent to ISS | 2021 |
| Published scientific papers on Physarum | Over 3,000 |
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.
Slime Mold vs. Common Misconceptions
Given how unusual slime mold is, misconceptions are widespread. Here are the most common ones, corrected.
| 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 stage can grow to several square meters. |
| "It only exists in labs" | It is found in forests on every continent except Antarctica. |
| "It has a short lifespan" | The plasmodium shows no signs of biological aging. Lab cultures have been maintained for decades. |
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.