Slime Mold: Diet

Ten Things I Like About... Podcast

Summary: Slime mold eats some pretty interesting stuff, but how it finds it’s food is they really fascinating part. Join Kiersten as she talks about who slime mold eats.

For my hearing impaired listeners, a complete transcript of this podcast follows the show notes on Podbean

Show Notes:

“Slime Molds” by Dr. Sharon M. Douglas, Department of Plant Pathology and Ecology, The Connecticut Agricultural Experiment Station. https://portal.ct.gov

“Slime Mould,” by Thomas J. Volk, in Encyclopedia of Biodiversity, 2001. https://www.sciencedirect.com

“Slime Mold Nutrition” Brad Renner, University of Wisconsin-La Crosse. bioweb.uwlax.edu

“Eight smart things slime molds can do without a brain,” by Alissa Greenberg, Nova, Monday, September 21, 2020. https://www.pbs.org

Slime Mold: Diet

Transcript

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Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.

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Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating.

This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.

On to number four, listeners, and we’re talking diet. I’m learning so much researching this series and the fourth thing I like about slime mold is what it eats!

Slime mold was thought to be a fungus for quite some time, so people were amazed to find out that it ingests it food, then digests. That doesn’t sound so odd to me, since that’s what I did with my breakfast this morning, but that’s not how fungus does it. Fungus digests its food externally before absorbing it. So, this is what researchers expected when they looked at how slime mold eats.

To say the least, they were surprised. Let’s take a closer look at how slime mold eats. We’re going to investigate how Myxomycota, the true slime molds, eat their food.

As a quick reminder, Myxomycota are the plasmodial slime molds. They exist as a plasmodium. A plasmodium is a blob of protoplasm without cell walls and only a cell membrane to keep everything together. (I see why this inspired a 1950s horror movie.)

They are essentially an amoeba and amoebas eat their food well, like the Blob. They engulf their food and then digest it. By engulf I mean completely surround it with their amoeba body. This process is called pseudopodia. The definition of pseudopodia is a temporary protrusion of the surface of an amoeboid cell for movement and feeding. This is what slime mold does when it is preparing to eat.

The next step is phagocytosis. Phagocytosis is the act of eating or damaging foreign components in cells. According to Science Direct phagocytosis is a universal cell function, which starts with the recognition and binding of a particle, generally in a receptor-dependent manner, and leads to its internalization and degradation. Sounds pretty complicated to me but, I guess it’s essentially digestion. Some organisms may use it for other things besides digestion such as defending against invading pathogens, it is also important during development and in adulthood for normal turnover, remodeling, and disposal of tissues, but that’s a whole other podcast.

The important part of this definition is that this is the process that helps slime mold digest its food.

Alright! We know how slime mold eats, let’s look at what slime mold eats. Bacteria is a big favorite of slime mold, but they can also eat decaying leaves, decaying logs, yeasts, other protists, and poo. Hey, somebody’s gotta do it, right?!

So far the diet and eating habits of slime molds don’t seem too unusual compared to other creatures, expect for maybe the poo, but we’re just getting to the really mind blowing part.

First of all, slime mold can smell its food. I know what you’re thinking, how can a blob of cells with no detectable olfactory system smell food? The answer is that they have olfactory receptors all over the cells connected into the amoeba. These receptors are similar to the receptors that mammals, including humans, have lining their nasal passages. I’ll pause a moment while you let this information sink in…

Hold on to your hat though, it’s about to get even more amazing! Some mold actually shows preferences for food. That’s right! If given the choice between two potential food sources they will chose the one that has the best nutritional value.

Ecologist and entomologist Tanya Latty has studied slime molds extensively and in her research she’s discovered that slime molds make smart decisions about their nutritional needs. To be successful slime molds need sugars and proteins. In a laboratory setting, Latty and colleagues offered Physarum polycephalum, also know as the many-headed slime, 35 different recipes made of different ratios of the nutrients slime mold needs to survive. The slime mold chose to engulf the foods that offered the best balance of elements and avoided the recipes that would harm them or weren’t worth the effort to ingest. You heard me correctly, they chose the food themselves. If nothing else blows your mind about slime mold, I just said a living entity that has no brain or any detectable ganglia is making a decision!

Need another example? Latty also tested whether slime mold could make trade-offs between quality of food and risk. (I can’t even believe I’m reporting this, it’s so amazing!) The researchers set up an experiment where they put the preferred food under a bright light and less desirable food in the dark. Slime mold doesn’t like bright light, so you’d expect it to stay in the dark and eat what it can get, right? But from what we’ve just learned you may be thinking it took the chance and ate the food in the light because it was worth the risk. The results were not this simple.

What actually happened I that the slime mold only took the risk to enter the bright light to engulf the food if the food was fives times more nutritious than what was in the dark. That is crazy amazing! This entity that is a blob of simple cells kept together by a common wall is processing information from olfactory receptors and choosing to make a calculated trade-offs to ensure it’s survival. Holy Cow!!

Quoting from an article from PBS Nova Latty says, “If you’re a basic system, you’d expect you always choose one. You have a simple rule that always works. If you’re sophisticated, you get some information about quality of food and intensity of light and do some calculations to figure out if it’s worth it.” End quote. Looks like slime mold is in the second category. Latty continues, “That implies some molds are able to process information between two different attributes of a food source, which seems pretty sophisticated thing for, well, mucus.” End quote.

I have no words for this…it’s truly amazing.

Stick with me listeners because it only gets cooler from here. The diet and feeding behavior of slime mold is my fourth favorite thing about this mind-blowing creature.

If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change.

Join me next week for another episode about slime mold.

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This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.