This advanced quiz is for those who think they already know everything about Physarum polycephalum. Prepare for some challenging questions.
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The full answer key, question by question. Expand a question to see the correct answer and why.
Answer : Actin-myosin shuttle streaming driven by rhythmic contractions
Physarum moves its cytoplasm through shuttle streaming, powered by actin-myosin contractions that create rhythmic oscillations (a cycle of about 100 seconds). This generates a pressure differential that pushes cytoplasm back and forth, with net movement toward favorable stimuli.
Answer : Nature, 2000
Nakagaki's groundbreaking paper 'Maze-solving by an amoeboid organism' was published in Nature in September 2000 (Volume 407). It demonstrated that Physarum polycephalum could find the shortest path through a maze connecting two food sources.
Answer : Habituation to a non-harmful aversive stimulus
Dussutour's 2016 paper demonstrated habituation, the simplest form of learning. Physarum learned to cross bridges coated with quinine or caffeine (unpleasant but harmless) after repeated exposure. This was the first demonstration of habituation in a non-neural organism.
Answer : matA
matA decides whether the union of two reproductive cells gives rise to a new plasmodium. It has 16 known versions. Combined with matB (15 versions) and matC (3), it produces the 720 mating types of Physarum polycephalum (16 × 15 × 3 = 720).
Answer : An unconventional biological logic gate and network optimizer
Adamatzky (University of the West of England) has extensively studied Physarum as an unconventional computing medium. His work includes implementing logic gates (AND, OR, NOT) using slime mold tubes, solving graph-theoretic problems, and creating Physarum-based sensor arrays.
Answer : Physarum polycephalum
The 2010 Science paper by Tero, Takagi, Saigusa, Ito, Bebber, Fricker, Yumiki, Kobayashi, and Nakagaki used Physarum polycephalum. The researchers placed oat flakes on a map of the Tokyo area and showed that the slime mold formed a network comparable in efficiency, fault tolerance, and cost to the actual rail system.
Answer : Sclerotium
The sclerotium is the dehydrated, dormant form that Physarum adopts under unfavorable conditions (desiccation, cold, starvation). The plasmodium hardens into a crusty mass that can survive for years and reactivate when conditions improve.
Answer : Myxamoebae and swarm cells
Physarum spores can hatch into either myxamoebae (amoeboid cells that move on surfaces) or swarm cells (biflagellated cells that swim in water), depending on moisture levels. Both forms are interconvertible and can fuse with a compatible mating type to form a new plasmodium.
Answer : About ten times more salt than in untrained slime molds
Boussard and colleagues showed that slime molds trained to cross salt had absorbed it, ending up with about ten times more salt inside their cell than untrained ones. The salt stayed in the sclerotium during a month of dormancy, and the habituation was still there on waking. The absorbed substance itself may act as the memory.
Answer : Yellow pigments specific to the organism, called physarochromes
The yellow of Physarum polycephalum comes from its own pigments, the physarochromes. It has no chlorophyll and does not photosynthesize. Other myxomycetes come in white, pink, red, brown or iridescent blue, each with different pigments.
Answer : It is a cellular slime mold where individual amoebae aggregate, unlike Physarum's true multinucleate plasmodium
Dictyostelium discoideum is a cellular slime mold (Dictyosteliida). Its amoebae live independently and only aggregate into a multicellular slug when starving. Physarum, by contrast, is an acellular (plasmodial) slime mold: it forms a single giant multinucleate cell. They belong to different branches of the Amoebozoa.
Answer : A conductivity reinforcement model based on Hagen-Poiseuille flow
The Tero-Kobayashi model describes tube dynamics using Hagen-Poiseuille flow equations: tubes carrying more cytoplasm increase in conductivity (positive feedback), while underused tubes shrink and vanish. This creates an efficient, self-optimizing transport network that can approximate Steiner tree solutions.
Answer : 1 to 2 minutes
The cytoplasm oscillates with a period of roughly 1 to 2 minutes. These rhythmic contractions are coordinated across the entire plasmodium and serve as both the locomotion mechanism and a rudimentary form of information processing, as the oscillation frequency changes in response to stimuli.
Answer : By controlling the geometry of channels and food placement to guide tube formation
Adamatzky implemented logic gates by carefully designing the spatial arrangement of food sources and physical constraints (channels, barriers). The presence or absence of a Physarum tube connecting specific points represented binary outputs. By engineering the geometry, he created functional AND, OR, and NOT gates.
Answer : A common large yellow slime mold known as 'dog vomit,' one of the most visible wild species
Fuligo septica, commonly called 'dog vomit slime mold' or 'scrambled egg slime,' is one of the most frequently encountered myxomycetes worldwide. It forms large, conspicuous yellow or white aethalia (fruiting bodies) on mulch, lawns, and rotting wood, and is completely harmless despite its alarming appearance.
