The blob: 10 fascinating facts you didn't know about Physarum polycephalum
720 sexes, capable of solving mazes without a brain, and from a lineage over a billion years old. Here are 10 sourced facts that will blow your mind — along with the myths we’re setting straight.
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720 sex types, capable of solving mazes without a brain, born from a lineage over a billion years old... The blob is the strangest organism on the planet. Here are 10 facts that will amaze you — each one sourced, and when data is uncertain, we tell you.
1. The blob has 720 sex types
Where humans have 2 sexes, Physarum polycephalum has 720 different sex types. To reproduce, any type can unite with any other, except its own.
The figure comes from three independent compatibility loci: matA (16 alleles) × matB (15) × matC (3) = 720 combinations. Important nuance: these are compatibility types, not 720 "sexes" in the animal sense — matB governs cell fusion, matA governs the fusion of nuclei.
Source: Kawano, S., Kuroiwa, T. & Anderson, R.W. (1987). A third multiallelic mating-type locus in Physarum polycephalum. Journal of General Microbiology, 133(9), 2539-2546.
2. It has no brain, but it makes decisions
The blob is unicellular — a single giant cell containing millions of nuclei, all dividing at the same time without ever separating the cell. Yet, it makes real decisions: it chooses the richest food source, flees from light, and finds an efficient path between two points.
Faced with several food sources, the blob distributes its network of veins to maximize nutrients while minimizing the distance traveled — a trade-off that engineers take weeks to calculate.
Source: Nakagaki, T., Yamada, H. & Tóth, Á. (2000). Maze-solving by an amoeboid organism. Nature, 407, 470.
3. It belongs to an extremely ancient lineage
The blob is part of the Amoebozoa, one of the major eukaryotic groups, whose molecular clocks place its diversification over a billion years ago. Long before the dinosaurs, long before land plants.
4. It solves mazes
Placed in a maze with food at both ends, the blob retracts from dead ends and eventually keeps only one efficient path — within a few hours in the original experiment.
Japanese researchers arranged oat flakes according to the map of cities around Tokyo. Within 26 hours, the blob formed a network whose efficiency is comparable to the actual railway network of the region — which itself was built over more than a century.
Source: Tero, A. et al. (2010). Rules for biologically inspired adaptive network design. Science, 327(5964), 439-442.
"In 26 hours, a brainless cell replicates what a century of railway engineering had built."
5. It moves — and moves faster when hungry
The blob advances by a few millimeters to a few centimeters per hour by deploying its plasmodium. The speed depends heavily on its state: a well-fed blob spreads out calmly, while a hungry blob sets off to explore much faster.
6. It sleeps for a very long time
When conditions become unfavorable (drought, cold), the blob transforms into a sclerotium: a dormant and dehydrated crust. Kept dry and away from light, a sclerotium remains viable for at least a year, often much longer. This is the form in which we send it to you.
7. It has been to space
In 2021, four sclerotia reached the International Space Station via the Cygnus cargo ship, and Thomas Pesquet woke them up on September 2 during his Alpha mission. On the ground, about 2,000 schools performed the same experiment in parallel, as part of the Raise your blob operation.
→ The full story, with exact timeline
8. It fuses and separates
Two compatible blobs that meet fuse into one. And a blob cut in two becomes two autonomous blobs, each going its own way. This is the most spectacular experiment to do in class.
9. It loves oats
In nature, it engulfs bacteria, yeast, and spores, and also absorbs dissolved nutrients. In your kit, stick to oat flakes: it is what works best, by far.
10. It exists in several strains
There are hundreds of strains worldwide. At BlobFarm, you can choose from two strains, at the same price: Major Tom (reference LU352, the exact strain sent to the ISS) and an Australian Physarum polycephalum, an isolate of the same species from the other hemisphere. Each has its own history.
