The Hairy Fungus That Wasn’t

Myxogastria stemonitis, or Hairy Brown Slime Mold

I found this interesting, hairy fungus during a trek at Tillie K. Fowler Regional Park. Except it isn’t a fungus. It’s Myxogastria stemonitis, or Hairy Brown Slime Mold, or Chocolate Tube Slime Mold, or Pipe Cleaner Slime.

 Hmm. But molds are fungi!

True, but slime molds were only differentiated from fungi in the late 1800s. We now know that they are protists, single-celled life forms having organelles with assigned functions (just as the organs in our own bodies play certain roles).

Stemonitis begins life as a microscopic spore. It then develops into a single-celled organism that slowly crawls until it finds one or more mates. The mates fuse into a zygote containing thousands of nuclei. As the nuclei simultaneously divide, the zygote morphs into a plasmodium.

The plasmodium looks like a white, yellow, or orange clump of insect eggs or oatmeal, and may grow to be a few centimeters across (1.2 inches). It moves very slowly, roughly two and a half centimeters (1 inch) a day, looking for food. When it finds bacteria, fungal spores, protozoa, or dead organic matter, it engulfs the food with its body and digests it.

 As a plasmodium, Stemonitis appears to be aware of its surroundings. In the laboratory, it can navigate a maze in its quest for food and avoid obstacles. If it is separated into pieces, and the pieces are in close proximity, it reassembles. The plasmodium can also combine with another plasmodium and acquire the knowledge of the newcomer.

 Scientists are gradually learning what feeds on plasmodia. So far the list includes beetles, mites, snails, slugs, and occasionally birds.

Stemonitis plasmodium stops growing when it encounters an environmental stressor, such as hot, humid weather. It then positions itself on a piece of decaying wood and, over a period of 48 hours, transforms into its reproductive form (pictured above). It should be noted that Stemonitis does not damage wood it grows on.

The hairlike strands of the reproductive (or fruiting) body emerge from thin, black filaments. The projections are brown because they are filled with millions of spores. As the fruiting body dries, the spores are dispersed by wind, rain, or passing animals, and the cycle renews.


REFERENCES
19 Type of Mold Commonly Found at Home, Rock Environmental.
Pike, Sue, Nature News: Slime molds are beautiful and smart. Fosters.com, August 14, 2018.
Roehl, Thomas, #111: Stemonitis spp., Chocolate Tube Slime Molds or Tree Hair. Fungus Fact Friday, October 16, 2016.
Stevenson, Carrie, Weekly “What is it?”: Chocolate Tube Slime Mold. UF/IFAS University of Florida.
Cullington, Penny, The amazing development of a slime mould (Myxomycete) recorded over the space of just 40 hours. Buckinghamshire Fungus Group.
Conover, Adele, Hunting Slim Molds. Smithsonian Magazine, March 2001.
Stemonitis spp., Messiah.edu.
The Blog: Slime Molds. Department of Biology, Intermountain Herbarium.
Vidyasagar, Aparna, What are Protists? LiveScience.
Keller, Harold W., Snell, Kenneth L., Feeding activities of slugs on Myxomycetes and macrofungi. Mycologia, Volume 94, Issue 5, 2002.
Greenberg, Alissa, Eight smart things slime molds can do without a brain. PBS, NOVA, September 21, 2020.
Resnick, Brian, Trump doesn’t have a science adviser. This slime mold is available. Vox, April 5, 2018.
Bonner, John Tyler, A Brief History of the Cellular Slime Molds, Department of Ecology and Evolutionary Biology, Princeton University.

Published by cafsamsel

Carol Fullerton-Samsel is a nearly-native Floridian who lives with her husband of 25 years and three rescue animals. She is a [mostly] vegan, alcohol-free, [relatively] caffeine-free, Buddhist writer and day-hiker. Her novel, The Clones of Langston, was a Reader’s Favorite medalist and a New Century Writer Awards finalist. It tells the story of cloned workers who are abandoned to form their own society. As the facility housing them erodes, they discover a challenging new world—our own.

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