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Slime Molds on the Move

8-21-15  431As usual, Naturally Curious readers submitted unbelievably creative ideas about the identity of yesterday’s Mystery Photo. Kudos to those of you who recognized that it was a slime mold. Slime molds look like a fungus, and reproduce with spores like fungi do, but are no longer classified as fungi. Slime molds are made up of individual organisms that form a mass called plasmodium. They can be bright orange, red, yellow, brown, black, blue, or white. These large masses act like giant amoebas, creeping slowly along and engulfing food particles (decaying vegetation, bacteria, fungi, and even other slime molds) along the way. If a slime mold is cut up into pieces, the pieces will pull themselves back together.

The most common species are in a group called plasmodial slime molds. They share one big cell wall that surrounds thousands of nuclei. Proteins called microfilaments act like tiny muscles that enable the mass to crawl at rates of about 1/25th of an inch per hour. A slime mold mass can actually navigate and avoid obstacles. If a food source is placed nearby, it seems to sense it and head unerringly for it.

As long as conditions are good, (enough food and moisture and favorable pH), the mass thrives. But when food and water are scarce, the mass transforms itself into spore-bearing fruiting structures. These typically form stalks topped by sphere-like fruiting bodies called sporangia that contain spores that are carried by the rain or wind to new locations. After they have been dispersed, each of these spores will germinate and release a tiny amoeba-like organism which, if it successfully finds and fuses with another similar organism, can then begin to feed and develop into a new plasmodium.

The pictured slime mold, Coral Slime (Ceratiomyxa fruticulosa), is one of the more common slime molds. It is unusual in that it produces its spores externally on small stalks, not in sporangia, which gives it a fuzzy appearance.

To watch a time-lapse video of slime mold moving, go to

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15 responses

  1. fascinating!! thanks, Ellen

    August 21, 2015 at 8:41 am

  2. Marilyn

    Yes, fascinating!

    August 21, 2015 at 8:44 am

    • Thanks so much, Marilyn. I am flabbergasted at this amount of new knowledge!

      August 23, 2015 at 12:55 pm

  3. Carlene Squires


    August 21, 2015 at 8:44 am

  4. Wow! This is why I love getting your emails Mary! Now I will look for it in the woods.

    August 21, 2015 at 9:09 am

  5. Thanks, Mary! The video reminds me of the 1958 movie, “The Blob” with Steve McQueen!

    August 21, 2015 at 9:35 am

  6. Evergreen Erb

    This is just way too cool! I loved the video…..thanks!

    August 21, 2015 at 10:00 am

  7. Penny

    Check out this British film I found– Scary cool.

    August 21, 2015 at 10:07 am

    • Hi Penny,
      I think that’s the very same one I mentioned at the end of my post! Amazing, isn’t it?

      August 21, 2015 at 10:26 am

  8. Treah

    This posting & the YouTube video totally blew my mind! There is something like intelligence here.

    August 21, 2015 at 10:41 am

  9. This was so incredibly fascinating! I watched both videos thinking all the while about a sci-fi movie I saw in the 60’s that was so scary to me as a child… and then the british scientist references the very same movie! …The Blob! What a very cool post Mary, thank you!

    August 21, 2015 at 11:13 am

  10. Elizabeth Christie

    Mary, this is really timely for me. Yesterday morning I found a rope-like circle, maybe 6″ in diameter, of tiny whitish cells about 1/4″ wide, circling around and around and around counter-clockwise on my sidewalk. Could this have been a slime mold? It was gone by the time I returned home.



    August 21, 2015 at 1:36 pm

    • Elizabeth, I’m not all that familiar with the different species of slime mold…a mycologist (at a nearby college?) might be able to give you an answer. Did you photograph it? Interesting that it disappeared so quickly. Sorry not to be able to solve this mystery for you!

      August 21, 2015 at 5:21 pm

  11. Wow! SO cool! I saw some patches on the trail at Indian Brook Reservoir yesterday. I’m going back with a magnifying glass!

    August 22, 2015 at 6:12 am

  12. Fascinating stuff, slime mould! Thanks for sharing this interesting post.

    August 22, 2015 at 10:37 pm

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