Slime Mold: Senses

Summary: Are you telling me a brainless protists has senses? You bet! Join Kiersten as she discusses slime mols senses.

 

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

 

Show Notes:

“Slime Mould Senses” Warwick Life Sciences. https://warwick.ac.uk/fac/sci/lifesci

“Phototaxis and Photomorphogenesis in Physarum polycephalum Plasmodia”, by Th. Schereckenbach. Blue Light Effects in Biological Systems pp 463-475. Proceedings in Life Sciences, Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-69767-8_51

“The Intelligence of Slime Mold,” by Hannah Gillespie, The Appalachian Voice. October 11, 2019. https://appvoices.org

“Can Slime Molds Think?” By Nancy Walecki. Harvard Magazine, November-December 2021. https://www.harvardmagazine.com

 

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.

This is episode six of slime mold and today we’re talking senses. I know it sounds a little odd to talk about senses in a life form that doesn’t even have a brain but the fact that slime mold has senses is the sixth thing I like about it.

To be honest, slime mold doesn’t have all the traditional senses that we think about creatures having, such as sight, hearing, taste, touch, and smell, but the senses they have are pretty mind-blowing for such a simple organism.

Let’s look at sight first. He-he, see what I did there? On boy! I’m stuck in a pun-cycle! Seriously, slime mold can’t actually see, there is no evidence of an optical nerve or any kind of optical receptors in slime mold. They do have the ability to sense light. Most of the time, slime mold will avoid light. Blue light and UV light can damage DNA and the slime mold consistently moved away from these wavelengths. On the other end of the spectrum, red light influenced the movements of slime mold but to a lesser degree than blue and UV. 

Light affects slime mold in various ways. In laboratory experiments, visible light has been shown to inhibit growth, induce a light avoidance response in mobile slime mold, control the change of plasmodial slime mold into resting structures, and trigger a formation of fruiting bodies. Movement influenced by light is called phototaxis. It looks like slime mold may not be able to see light in the traditional sense, but it defiantly has quite the impact on this organism.

In the diet episode we already sniffed out slime molds sense of smell, but let’s revisit it quickly here. Slime mold doesn’t possess an olfactory system in the traditional sense. In mammalians we have a centralized olfactory system that concentrates the cells that collect scent. It’s our nose!

Slime mold does not have a nose, but it does have olfactory cells all over its form. So, it’s kind of like one big nose. It is able to determine, by smell, which direction it wants to go to find high-quality food. It can, somehow make decisions based on the scents in the environment. Chemotaxis is movement influenced by chemical scents in the environment. Slime mold has this ability. In laboratory experiments, slime mold moved toward oats and paprika, both a good source of acceptable food, and moved away from black pepper and turmeric.

Sense of smell often goes hand in hand with a sense of taste. Slime mold definitely behaves like it has a sense of taste as well as smell, because it avoids engulfing certain types of food.  Items high in salt, caffeine, and items with a high pH level are all commonly avoided by slime mold. Oats, sugar, and high protein foods all attract slime mold. Now, of course, these items all give off a chemical scent that we know the slime mold can sense, but it’s reasonable to believe that it may also have a sense of taste. We’ll have to wait for future research to see if it’s true.

Moving on to the sense of touch. There is really no way for use to truly understand what slime mold feels, but there is research that shows slime mold has preferences for certain surfaces. Like Goldilocks, slime mold wants a surface that is just right. They want something hard but not too hard. They will pick wood over a rock or over a loose patch of moss. 

There is no evidence, yet, that slime mold is capable of hearing, but give it some time. I don’t think we should rule anything out when it come to slime mold.

We do know that slime mold employs mechanosensation to judge objects in the distance without coming into physical contact with them. Researchers at Harvard’s Wyss Institute for Biologically Inspired Engineering and the Allen Discovery Center at Tufts University presented challenges to the slime mold in a laboratory setting to see what it was capable of. They placed the slime mold in the center of a petrie dish and placed glass discs on opposite sides of the dish. One side held one disc and the other side held three discs. They turned off the lights and left the slime mold for approximately 12 hours. When they checked on the slime mold, it consistently traveled toward the side contains three discs.

Now, they filmed the progression of the slime mold to make sure it hadn’t  reached all the way out to each side touching the discs and then determined which way to go. The slime mold never touched any of the discs before it favored the side with the three discs. 

To make this even crazier, the slime mold showed a preference for discs that took up more horizontal space than discs that were closer together or stacked on top of one another. They are still not sure how the slime mold is processing this information, but the presence of protein channels called TRP have been found in slime mold. The human brain uses these TRP channels to process mechanosensation input. Notice I said the human brain, and as we know by now, slime mold does not have a brain. So , how is slime mold processing the information that helps it determine the mass of objects on the horizon?

I don’t know about you, but each episode of this slime mold series amazes me. Slime mold senses is mu sixth favorite thing bout this under appreciated organism.

 

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.