Whether you are growing slime mold at home, studying for a biology class, or simply reading about these organisms, you will run into specialized terms. This glossary groups them by theme so you can quickly find and understand each concept.
Classification and Taxonomy
| Term | Definition |
|---|
| Amoebozoa | The supergroup of eukaryotic organisms that includes slime molds. Amoebozoa are characterized by their amoeba-like movement using pseudopods. This group is distinct from fungi, plants, and animals. |
| Myxomycetes | The class of "true" slime molds, also called myxogastrids. These are plasmodial slime molds that form large, visible, multinucleate cells. There are roughly 1,000 known myxomycete species worldwide. |
| Dictyostelids | Cellular slime molds. Unlike myxomycetes, dictyostelid cells remain individual until they aggregate into a multicellular slug for reproduction. Dictyostelium discoideum is the most studied species. |
| Protostelids | A small, relatively obscure group of slime molds that produce simple fruiting bodies. They are often microscopic and live on dead plant material and animal dung. |
| Physarum polycephalum | The most commonly studied and cultivated species of plasmodial slime mold. Its name means "many-headed slime," referring to the branching network it forms. This is the species most people mean when they say "the blob." |
| Protist | A broad, informal term for eukaryotic organisms that are not animals, plants, or fungi. Slime molds are protists, though the category itself is not a formal taxonomic group. |
Life Stages
| Term | Definition |
|---|
| Plasmodium | The vegetative, feeding stage of a myxomycete. A plasmodium is a single giant cell containing thousands or millions of nuclei, with no internal cell walls. It is the yellow, vein-like network you see when growing Physarum. Not to be confused with the malaria parasite Plasmodium, which shares the name but is entirely unrelated. |
| Sclerotium | The dormant, hardened state of a plasmodium. When conditions become unfavorable (too dry, too cold, no food), the plasmodium dehydrates into a tough, paper-like structure that can survive for months or even years. See slime mold dormancy for details. |
| Spore | A reproductive cell produced inside the fruiting body. Slime mold spores are microscopic, resistant to environmental stress, and can remain viable for decades. They germinate into either amoebae or flagellated swarm cells depending on conditions. |
| Swarm cell | A flagellated cell that emerges when a spore germinates in wet conditions. Swarm cells swim through water films and can convert back and forth into amoebae depending on moisture levels. |
| Myxamoeba | An amoeba-like cell that emerges from a germinating spore in drier conditions. Myxamoebae feed on bacteria and eventually fuse with compatible cells to form a new plasmodium. |
| Fruiting body (sporangium) | The spore-bearing reproductive structure produced by a mature plasmodium. Fruiting bodies come in a spectacular variety of shapes: stalked spheres, tufted clusters, net-like structures, and more. They are the main feature used to identify myxomycete species. |
| Aethalium | A large, cushion-shaped fruiting body formed when the entire plasmodium transforms at once, rather than dividing into many small sporangia. Fuligo septica ("dog vomit slime mold") produces a characteristic yellow aethalium. |
Cell Biology
| Term | Definition |
|---|
| Syncytium | A cell containing multiple nuclei within a shared cytoplasm, with no internal cell membranes separating them. The plasmodium of Physarum is a syncytium, and this is what makes it a "single giant cell" despite sometimes reaching meters in size. Learn more about this unique single-cell biology. |
| Cytoplasmic streaming | The rhythmic, back-and-forth flow of cytoplasm inside the plasmodium's veins. This shuttle streaming distributes nutrients, signals, and organelles throughout the organism. The flow reverses direction roughly every 1-2 minutes and is driven by actin-myosin contractions. |
| Pseudopod | A temporary extension of the cell membrane used for movement and feeding. The leading edge of a plasmodium advances by pushing out pseudopods. The word means "false foot." |
| Phagocytosis | The process of engulfing food particles (bacteria, yeast, organic debris) by wrapping the cell membrane around them. This is how slime mold eats. |
| Actin / Myosin | Proteins responsible for cell contraction and movement. The same actin-myosin system that powers human muscles drives cytoplasmic streaming in slime mold, though without any muscle cells or nervous system. |
| Multinucleate | Containing many nuclei. A mature Physarum plasmodium can contain millions of nuclei, all dividing synchronously. This synchronized nuclear division is one of the reasons Physarum became an important model organism in cell biology research. |
Behavior and Intelligence
| Term | Definition |
|---|
| Chemotaxis | Movement toward or away from chemical signals. Slime mold uses chemotaxis to locate food sources (moving toward nutrients) and avoid harmful substances (moving away from salt, light, or toxins). This is the primary way it navigates its environment. |
| Phototaxis | Movement in response to light. Physarum polycephalum is generally negatively phototactic, meaning it moves away from light, especially UV light. This behavior helps it stay in moist, shaded habitats. |
| Habituation | A form of learning where an organism stops responding to a repeated, harmless stimulus. In 2016, Audrey Dussutour demonstrated that Physarum can habituate to substances like caffeine and quinine, showing a form of memory without a brain. |
| Network optimization | The ability of a plasmodium to build efficient transport networks between food sources. The resulting network often mirrors optimal human-designed infrastructure, as demonstrated in the famous Tokyo rail experiment. |
| Distributed intelligence | Problem-solving ability that emerges from the collective activity of many simple components, rather than from a central controller like a brain. Slime mold intelligence is distributed across its entire body. |
| Decision-making | The process by which a slime mold chooses between options (food sources, paths, environments). Research has shown that Physarum can make consistent, rational choices and even exhibit a form of risk assessment. |
Reproduction
| Term | Definition |
|---|
| Sporulation | The process of forming spores. In myxomycetes, sporulation occurs when the plasmodium transforms into one or more fruiting bodies. This usually happens when food becomes scarce or the environment deteriorates. See slime mold reproduction. |
| Meiosis | A type of cell division that reduces the chromosome number by half. Meiosis occurs during spore formation in myxomycetes, producing haploid spores from a diploid plasmodium. |
| Plasmogamy | The fusion of two compatible myxamoebae or swarm cells to form a diploid cell, which then grows into a new plasmodium. This is the sexual reproduction phase of the slime mold life cycle. |
| Mating types | Slime molds do not have "male" and "female" sexes. Instead, Physarum polycephalum has over 720 different mating types. Two cells can fuse only if they have different mating types, which promotes genetic diversity. |
| Fragmentation | Asexual reproduction by physically dividing the plasmodium into pieces. Each fragment can grow into a complete, independent organism. This is how slime mold is typically propagated in home and lab cultures. |
| Capillitium | A network of thread-like structures inside the fruiting body that helps with spore dispersal. When the sporangium wall breaks open, the capillitium expands and contracts with humidity changes, scattering spores into the air. |
Ecology and Environment
| Term | Definition |
|---|
| Saprophyte | An organism that feeds on dead or decaying organic matter. Slime molds are saprophytic during their feeding stage, consuming bacteria and organic debris on decomposing wood and leaf litter. See ecological role. |
| Substrate | The surface or material on which a slime mold grows. In nature, common substrates include dead wood, leaf litter, and bark. In captivity, agar gel, damp paper towels, or moistened filter paper serve as substrates. |
| Nivicolous | Literally "snow-loving." Refers to myxomycete species that fruit exclusively near melting snow in alpine or boreal environments. These are among the most specialized and least-studied slime mold species. |
| Corticolous | Growing on the bark of living trees. Some myxomycete species specialize in this habitat, developing on bark surfaces without harming the tree. |
| Coprophilous | Growing on animal dung. Several myxomycete species specialize in this nutrient-rich substrate, particularly the dung of herbivores. |
Quick Reference: Life Cycle Stages at a Glance
Understanding slime mold terminology is much easier when you can see how the terms connect in the organism's life cycle:
- Spore germinates into a myxamoeba (dry conditions) or swarm cell (wet conditions).
- Two compatible cells undergo plasmogamy to fuse into a diploid cell.
- This cell grows into a plasmodium (a syncytium) through repeated nuclear division without cell division.
- The plasmodium feeds via phagocytosis and moves using cytoplasmic streaming and pseudopods.
- It navigates using chemotaxis and phototaxis, demonstrating distributed intelligence.
- Under stress, it may enter dormancy as a sclerotium.
- When ready to reproduce, it undergoes sporulation, forming fruiting bodies that release new spores.
Laboratory and Culture Terms
| Term | Definition |
|---|
| Agar | A gel-like substance derived from seaweed, used as a substrate for growing slime mold in Petri dishes. Non-nutritive (plain) agar is preferred because it does not encourage contaminant growth. See our growing guide for preparation instructions. |
| Culture | A population of slime mold maintained in a controlled environment (Petri dish, container). Cultures are started from live plasmodium fragments or rehydrated sclerotia. |
| Contamination | The unwanted growth of bacteria, fungi, or other organisms in a slime mold culture. Green, black, or white fuzzy patches on the substrate indicate contamination. The most common contaminants are Penicillium and Trichoderma mold species. |
| Subculture | The process of transferring a piece of an existing slime mold culture to a fresh Petri dish with new substrate and food. Regular subculturing (every 5-7 days) keeps cultures healthy and free from contamination. |
| Phototaxis experiment | An experiment that uses light to direct slime mold movement. Since Physarum avoids light, shining a light on one side of the dish drives the plasmodium toward the dark side. This is a common classroom demonstration. |
This glossary covers the terminology you will encounter most frequently. For deeper exploration of any topic, follow the internal links to our dedicated articles on slime mold biology, reproduction, and intelligence.