A Slime Mold and a Parasitic Fungus in the California Woods - Observation of the Week, 4/6/21

Our Observation of the Week is this Trichia botrytis slime mold (and a Polycephalomyces tomentosus fungus), seen in the United States by @alison_pollack!

The name “slime mold” is a bit misleading, as slime molds belong to their own polyphyletic group, Phylum Mycetozoa. But Alison Pollack beautifully captured both the fruiting body of a slime mold and a fungal parasite in the photo you see above. It wasn’t her first attempt, however. “Trichia botrytis is a very pretty slime mold, and I had seen it only a few times before,” she explains.

The fungus, Polycephalomyces tomentosus, parasitizes slime molds of the genus Trichia. I had seen and photographed that fungus on various Trichia species several times, but I really wanted to find a specimen where there was not so much of it so that you couldn’t see the detail. In the woods a few weeks ago, I turned a log over and saw something that looked like it might be nice, and when I looked at it with the magnifying glass I was thrilled at what I saw - not only a formation of the fungus of exactly the kind I had been looking for, but also a clean Trichia botrytis, clearly showing the characteristic bands of that species.  A wonderful and photogenic combination!

Alison’s image isn’t just one photo - at macro distances an image’s depth of field is razor thin - but rather a series of about forty-five photos, each focusing on a slightly different part of the subject. She then used software to focus stack the images, combining the parts in focus to make  a single image with greater depth of field. That’s why both the slime mold and fungus are in razor sharp focus. 

Fittingly, it was photography that sparked Alison’s recent interest in slime molds, fungi, and other tiny organisms. As a child in the suburbs of New York City she wasn’t particularly into nature, but graduate school in Wisconsin and then hikes around the Bay Area opened her eyes to it. She carried her camera with her and began to photograph mushrooms. One day, however, she came across something new.

I took a photo, and when I got home I did a Google reverse image search to figure out what it was. I quickly figured out that it was a Myxomycete, Leocarpus fragilis. I stayed up all night looking at photos of various slime molds and reading about these fascinating organisms; I was completely smitten by their beauty and their amazing life cycle. Shortly after that I bought a DSLR camera and a macro lens so I could take better photos of myxos.  And while looking for myxos, I also found many fascinating tiny fungi. 

When I am in the woods, I am often on my hands and knees, looking very closely. What I am looking for usually cannot be seen while walking. I use a light and a magnifying lens to look for my tiny subjects. The smaller they are, the more they fascinate me! I love finding and photographing myxos and tiny fungi and sharing them with people who might otherwise never see them. My goal is to inspire people to go into the woods and look for them themselves.  

Alison (above, in Alaska) previously only posted her photos on Instagram, but an acquaintance suggested she also add them to iNat, where she tries to post most of her photos now. “It's great when experts chime in and identify what I have captured,” she says, 

and I also feel like I am contributing to science because not too many people are looking for and posting things so tiny. These days I also use iNat all the time to look for where people are finding myxos and fungi; the combination of iNat and NOAA precipitation maps helps me to plan my trips to the woods. 

Photo of Alison by Bruce Welkovich (@bwelko).

- This isn’t Observation of the Week’s first slime mo(u)ld rodeo!

- Slime molds can solve mazes?

- Check out some of the most-faved slime mold observations on iNat!

Posted on April 6, 2021 10:17 PM by tiwane