Wolf’s milk slime mold or pink slime mold

Lycogala epidendrum

Wolf's milk slime mold is a beautiful slime mold that is commonly found growing on rotting logs in shady, moist forests. The slime mold, when in its fruiting body form, can be identified by clumps of smaller, round balls that range in color from pink to coral to gray. The bright, paste-like fluid that is seen oozing out of the small balls when they are pressed is actually Lycogala epidendrum in its youth. As the slime mold matures, the moist, vivid fluid dries up to a powdery mass of spores, and the small balls turn gray or brown [1][2].

Lycogala epidendrum is actually more of a protist than a fungus, specifically a myxogastrid protist. As this species of slime mold cannot be classified as a fungus, it is representative of life that straddles the line between animal-like movement and fungus-like fruiting. While in its plasmodial, motile phase, the slime mold creeps ever so slightly across the wood surface and ingests bacteria and decaying organic matter as it goes. Environmental stressors like changes in pH, temperature, and moisture cause the plasmodium to enter its spore-producing, sessile phase, during which it forms the soft globes that, when dry, crack apart to release the spores into the air [1][3].

Ecologically, Lycogala epidendrum plays a role in forest decomposition and nutrient cycling. By growing on decaying wood, it helps to decompose microbes and redistribute nutrients in the layer of detritus on the forest floor. Beyond being a cool forest organism, the wolf's milk slime mold is a fascinating example of a long evolutionary lineage of life that moves across and through decay [1][3].

Glistening on rotting logs after a rain, the wolf's milk slime mold is a reminder that all of forest life is not contained by our definitions of animals, fungi, and bacteria. It lives and pulses quietly on the boundaries between movement and cognition, between predator and prey, and between health and decay.

[1] Stephenson, Steven L. “Past and Ongoing Field-Based Studies of Myxomycetes.” Microorganisms 11, no. 9 (2023): 2283. https://doi.org/10.3390/microorganisms11092283

[2] MushroomExpert.com. “Lycogala epidendrum — MushroomExpert.com.” https://mushroomexpert.com/lycogala_epidendrum.html

[3] Missouri Department of Conservation. “Wolf’s Milk Slime (Toothpaste Slime) – Lycogala epidendrum.” https://mdc.mo.gov/discover-nature/field-guide/wolfs-milk-slime-toothpaste-slime