Plasmodial Slime Molds

Infraphylum Mycetozoa; Class Myxogastria

Plasmodial slime molds, not to be confused with cellular slime molds, are an organism composed of one, blob-like cell, called a plasmodium. In nature they are known for feeding upon dead and decaying plant material. In captivity, many researcher study the feeding and growth behaviors of slime molds since these ancestral organisms have an uncanny ability to find and "solve" spatial puzzles.

Above: macroscopic plasmodium of Physarum polycephalum

Above: Plasmodium of Physarum

Additional Resources

Ecology & Form

  • Fungal-like protists, which are heterotrophic

    • e.g. Physarum

  • Found in open forests, but also in extreme regions such as deserts, under snow blankets, or underwater

    • They also occur on the bark of trees, sometimes high in the canopy

  • The structure is one large cell called a plasmodium, which is a macroscopic coenocytic mass without cells walls

  • When conditions are unfavorable for growth, slime molds create a sclerotium, which is an encrusting phase

Above: Sclerotium of Trichia

Reproduction

  • May represent an ancestral protist with sexual reproduction (diplontic?)

  • Spore cases (sporangia) are produced when conditions become unfavorable such as too warm, dry, or bright

  • Through meiosis, spores are created, which germinates into a unicellular amoeba-like cell or a flagellated cell

  • These "gametes" fuse with another in plasmogamy, and then kayogamy to create a zygote (amoebozygote)

  • Through mitosis, the zygote grows into a plasmodium once again

Above: sporangia of a slime mold

Classification

Unikonta - single-flagellum organisms

└Amoebozoa - amoeba-like organism

└Mycetozoa - slime molds

└Myxomycota - plasmoidal slime molds

Diversity

  • Worldwide distribution; common in temperate regions

  • Over 60 genera and almost 900 species

Geologic Age

  • ??? - present (poor fossil record)