Think you know slime mold? Take this 10-question quiz to find out how much you really know about Physarum polycephalum.
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This quiz also comes on paper, with every answer explained, in the slime mold quiz booklet (PDF, 14 pages), handy for a classroom or a family evening.
The full answer key, question by question. Expand a question to see the correct answer and why.
Answer : Myxomycete (protist)
The blob is a myxomycete. It was long filed among the protists, a catch-all for organisms that are neither animals, plants nor fungi, and DNA now places it among the Amoebozoa. It is not a fungus, nor a bacterium, nor an alga.
Answer : By rhythmic contractions of its cytoplasm (shuttle streaming)
Slime mold moves through cytoplasmic shuttle streaming: rhythmic back-and-forth contractions push the cytoplasm toward the leading edge. In ideal lab conditions it can advance up to about 4 cm an hour, closer to 1 cm an hour at home.
Answer : By showing it could learn to ignore a repulsive but harmless substance
In 2016, Romain Boisseau, David Vogel and Audrey Dussutour (CNRS) showed that Physarum polycephalum learns to cross a bridge laced with quinine or caffeine once it has found the substance harmless. Later that year, Vogel and Dussutour showed that a slime mold trained this way could pass the behavior on to an untrained one by fusing with it.
Answer : By releasing spores that hatch into gamete cells which fuse
Under stress, the plasmodium forms fruiting bodies that release spores. These spores hatch into myxamoebae or swarm cells, which then fuse in compatible pairs to form a new diploid plasmodium.
Answer : Slime mold built a network matching Tokyo's rail system
Researchers placed oat flakes on a map at the positions of the cities around Tokyo. The network the slime mold grew between them was comparable to the real rail system in cost, efficiency and resistance to breakdowns, showing it can solve a hard optimization problem without a brain.
Answer : Bacteria, fungal spores, and yeasts
Slime mold feeds by phagocytosis, engulfing bacteria, fungal spores, yeasts, and other microorganisms. It plays an important ecological role as a decomposer in moist forest environments.
Answer : No verified record exists: it grows as long as it is fed
A plasmodium has no known size limit and roughly doubles its area every day when well fed. Figures of several square meters circulate online, but no size record has been measured and published in a verifiable way. In the wild, a few tens of centimeters is already a big one.
Answer : 4 cm/h
Slime mold can advance up to about 4 cm per hour in ideal lab conditions on smooth agar. In a home culture, expect around 1 cm per hour. That is slow for us, but its whole body flows forward through its network.
Answer : An educational experiment run in parallel with thousands of French schools
In September 2021, Thomas Pesquet woke four slime molds aboard the ISS, while 4,500 French schools were invited to run the same experiment on Earth. All four revived and grew in orbit, but four specimens are too few for scientific conclusions, and the project was educational from the start.
Answer : 720
Mating type in Physarum polycephalum is set by three genes: matA (16 known versions), matB (15) and matC (3). That gives 16 × 15 × 3 = 720 combinations, so 720 mating types, and two reproductive cells can only pair if their combinations differ.
