Slime molds are unique organisms, often mistaken for fungi due to their appearance. Historically grouped with fungi, modern biology places them in the kingdom Protista. These entities exhibit distinct forms throughout their existence, making them challenging to identify. This article clarifies what slime molds look like in their different stages, providing a visual guide.
The Basic Visuals of Slime Mold
Slime molds are diverse in their visual forms. Their colors range from vibrant yellows, oranges, and reds, like the common “dog vomit” slime mold (Fuligo septica), to subdued whites, grays, browns, and even purplish-black hues. Texturally, they can appear as gooey, slimy masses, often described as lumpy or gelatinous, especially in actively feeding stages. Some forms also exhibit a powdery, crusty, or frothy surface as they mature or dry. Their shapes vary from amorphous, amoeba-like blobs spreading across surfaces to intricate, fan-like patterns or delicate networks of interconnected veins.
Plasmodial slime molds, also known as acellular slime molds, are often the most noticeable type due to their size. They manifest as a single, large cell containing many nuclei, forming a macroscopic, creeping mass. This mass can be an amorphous blob, resembling scrambled eggs, and can spread over significant areas, sometimes reaching several square meters. In contrast, cellular slime molds typically remain as individual, microscopic amoeboid cells for most of their lives, making them less commonly observed.
How Slime Mold’s Appearance Changes Through Its Life Cycle
The appearance of slime molds undergoes dramatic transformations across their life cycle. They begin as microscopic, single-celled amoeboid forms, known as myxamoebae, typically invisible to the naked eye. These individual cells move by extending pseudopods, actively consuming bacteria and other small organic particles.
For plasmodial slime molds, these amoeboid cells fuse to form a larger, often brightly colored, macroscopic structure called a plasmodium. This plasmodium is a single, giant cell containing many nuclei, and can spread as a thin, creeping sheet or an intricate network of veins across surfaces. It exhibits slow, observable movement, actively engulfing food as it glides.
When environmental conditions become less favorable, such as a decline in moisture or food, the plasmodium ceases its creeping movement and transforms into spore-producing structures. These structures, known as fruiting bodies or sporangia, vary widely in form and color depending on the species. They can appear as small, stalked spheres, delicate goblets, or cushion-like masses, often changing from a vibrant color to a dry, powdery texture as they mature and release their microscopic spores. Cellular slime molds, after their individual cells aggregate into a slug-like form, also develop into fruiting bodies with a stalk and a spore-filled cap.
Where to Spot Slime Mold
Slime molds thrive in moist, shady environments, making them common inhabitants of forest floors, gardens, and mulched areas. They are frequently observed on decaying organic matter such as rotting logs, stumps, and leaf litter, which provide an abundant food source. Their diverse appearances can be striking against these natural backdrops; vibrant yellow or orange plasmodial forms often stand out on dark wood chips or soil. Conversely, some species may blend in, resembling a bluish-gray or purple-brown discoloration on lawns or appearing as subtle crusts on plant surfaces. Slime molds often appear suddenly, sometimes overnight, particularly after periods of wet, moderate temperatures.