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Slime Molds!

What PEI creature looks like a fungus, has cells like a plant, behaves like an animal, and has relatives that inspired the creation of at least one science fiction alien? Meet one of our slime molds: Wolf’s Milk (Lycogala epidendrum).

Wolf's Milk Slime Mold (Lycogala epidendrum). And yes, part of this one DOES look like a rubber ducky!

There are hundreds of species of slime molds globally, and dozens known from PEI. They’re often mistaken for fungi – and were once classified as such – but have cell walls composed of cellulose (as plants do) rather than the chitin of fungi. But unlike plants, slime molds can’t make their own food and must eat other organisms to survive (they are heterotrophs rather than autotrophs).

Slime molds spend much of their lives as independent, single-celled organisms but can also combine into groups called plasmodia that work together very much like the multiple cells of an animal. They do this when food is scarce, enabling them to move across the landscape (often at rates of several feet per day) to search in a very efficient way. So efficient that they’ve been used to map the best transportation corridors: place a food source (such as oatmeal) on a map at your key cities and a barrier (such as salt) in places you need to avoid, and a slime mold will map the fastest and safest routes with its plasmodia. Slime mold plasmodia can solve complex mazes, learn, and share what they learn with other slime molds. They are being used to map optimum electrical circuits, computer and communications networks, and even the cosmic web of the universe!

Mapping the universe seems appropriate, as slime molds have some decidedly out-of-this-world traits. If you separate the plasmodia, each part will continue to grow in sync with the others as if they were still connected. This has made slime molds of interest to cancer researchers, enabling them to test how various drugs affect cell growth and division on multiple identical samples at once. One can see why the cult classic sci-fi movie The Blob was modelled on a slime mold.

Slime mold plasmodia are thread-like and inconspicuous, so rarely noticed by people (although they’re common on forest floors, decaying wood and even in garden mulch). It’s their reproductive stalks – such as those shown here – that usually catch our eye. They come in a wide range of often vibrant colours, including these pink stalks of Wolf’s Milk. (I’m particularly fond of the bright yellow and aptly named Dog Vomit Slime Mold [Fuligo septica]).

Wolf’s Milk is one of the Island’s most common and easily recognized slime molds, found on dead wood in summer and fall. Its little pink balls are filled with a darker pink toothpaste-like substance that is essentially immature spores. As these reproductive stalks mature, they turn grey and this inner paste becomes powdery. They’ll eventually break open to release millions of spores that will germinate and grow into new single-celled slime molds.

Slime molds can do some things better than we big-brained humans with our complex computers can. If that’s not cool, I don’t know what is.

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