Backyard Nature: Slime mold brings people together

by Marlene Berlin

On my many hikes in Rock Creek Park, I often get to meet wonderful and interesting people who teach me wonderful and interesting things. That’s what happened one day in July. I happened upon a trio of hikers who had stepped off the trail a bit. They were examining something – yellow in color – on the ground. My curiosity piqued, I asked if they were looking at mushrooms.

“No, said the woman in the middle of the group. “Slime mold.” She bent down to touch it, and then stood to show us a yellow substance on her finger. She introduced herself as Cathy Hokshul, of the Smithsonian Research Center outside of Annapolis. She had been telling the rest of her group about slime molds, and said she is no expert, but finds them fascinating.

Suddenly, I was seeing them everywhere. Later that week, I even found a similar yellow substance in my backyard.

Naturally, I needed to know more.

My first stop, Wikipedia, left me more confused about these strange… creatures? So I ordered a book: Myxomycetes: A Handbook of Slime Molds.

What I learned are that slime molds “possess characteristics of both animals and fungi.” They have a fruiting body – like the mushrooms’ mycelium – that produce spores. And, they move.

Another example of slime mold, seen on my travels.

Also, there are two kinds of slime molds. Myxomycetes, or plasmodial slime molds, are found in greater numbers and have been studied more. They are amoeba-like creatures that mate and produce zygotes that then merge into a plasmodium, a giant cell with many nuclei.

Dictyostelids, or cellular slime molds, are the other kind. When their cells come together, they maintain their integrity.

In both cases, after their cells merge, they have the capacity to move over a surface. And, they need moisture to sustain them. Slime molds change form and lie dormant when conditions are dry.

And when moisture returns to their environment, they return to their shape and continue their travels until they spread out like mycelium, or the root-like structure of fungi. At this stage, they form their fruiting bodies and produce spores.

The life cycle of plasmodial slime mold (graphic from plantscience4u.com)

The myxomycetes feed on and are most often found on moist and rotting wood. Cellular slime molds are mostly found in the humus layer of soil.