Myxomycetes are a class of slime molds that contains 5 orders, 14 families, 62 genera, and 888 species. They pass through several morphologic phases (in biology, form, or structure) like microscopic individual cells, slimy amorphous organisms visible with the naked eye, and conspicuously shaped fruit bodies.
They are monocellular but in extreme cases, they can grow to be as much as 3 ft 3 in across and weigh up to 44 lbs. They are found worldwide but are more common in temperate regions. Look for them in open forests but can be in deserts, under snow, or underwater. They are found on the bark of trees, sometimes high in the canopy.
The name comes from the Ancient Greek words myxa, which means “mucus”, and mykes, which means “fungus”. This name for them was introduced in 1970 by Lindsay Shepherd Olive to describe the family Myxogastridae, which was introduced in 1899 by Thomas Huston Macbride. The spores of Myxogastria are haploid, mainly round and measure between 5 μm and 20 μm, rarely up to 24 μm in diameter. Their surface is generally reticular, sharp, warty, or spiky and very rarely smooth.
Important factors for the germination of spores are mainly moisture and temperature. The spores usually remain germinable after several years and some have been known to germinate after 75 years.
They exist in nature as a plasmodium – a blob of protoplasm without cell walls and only a cell membrane to keep everything in. True fungi have a cell wall and digest their food with exoenzymes before ingesting it.
When the plasmodium runs out of food, it can form fruiting bodies. Most slime mold-fruiting bodies are quite beautiful, especially under a dissecting microscope.
Myxogastria are found in the soil of moist environments, typically forests. A few species can be found in almost any ecosystem. During the plasmodial stage, they can be found in shady environments such as decaying wood. Myxogastria plays a role in the carbon cycle because they help decompose decaying plant matter. It is believed that individual cells aggregate only when they lack sufficient nutrients.