Slime molds are not plants or animals. Neither are they fungi, though they were long classed as such. These life forms are like animals in many ways. They move, for example, but they also have characteristics of plants and fungi. Slime molds have eukaryotic cells, that is, cells with clearly defined nuclei, but are not nearly as organized and differentiated as the organisms they evolved to become.
Acellular Slime molds
Plasmodial slime molds, of class Myxomycetes, are giant cells with many nuclei dispersed throughout them. In a sense, each organism is a giant bag of stuff that acts like one cell.
These slimy lumps can be as large as a turkey platter. Some are even larger, but most are tiny, or hidden. They often live in damp to wet shade, and feed by engulfing bacteria, yeasts, and decaying vegetation. When times are tough, they can go dormant, retreating within a resistant structure called a sclerotium. When mature, spurred perhaps by food shortage, perhaps by changes in light, they move (in a flowing motion worthy of nightmare) to a drier and sunnier place where they form spores. The spores are protected inside cell walls containing cellulose, and in time, some of them produce myxamoebae.
The tiny mxyamoebae feed by engulfing their food. In harsh conditions, they can retreat within a sort of shell. In better times, they have sex. To reproduce, a myxamoeba must join with a myxamoeba of a different strain. It is sterile with its own near relatives.
Once mating occurs, the genetic material of the two strains will form a zygote. The zygote will divide and subdivide, until an acellular slime mold comes to be.
The website Wayne’s Word was my source. It has great slime mold photos as well as information. Another source was online class notes from a botany class taught by Dr. George Wong at the University of Hawaii. He lucidly explains slime molds along with his main topic, fungi.
Cellular Slime molds
Cellular slime molds, Acrasidae, may be a kingdom unto themselves. They spend most of their life cycle as single-celled amoebae, which swarm together in response to chemical signals, including the pheromone acrasin, which is probably activated by scarcity. They form a mass called a grex. It reproduces sexually, and that results in spores which become amoeba.
A facebook group is devoted to sharing knowledge about the cellular slime molds, and was my source for information about them.
Slime Nets
Slime nets are sometimes considered slime molds, but they are probably only distantly related to the “true” slime molds.
Slime molds are interesting. They come in vivid colors and strange forms. Get a paperback guidebook (slime molds will probably still be included in a fungus guide) and look for them in the woods after a rain. Some live in the forest litter, some on fallen logs, leaves, or inside or upon living plants.
