Beautiful Slime

Physarum polycephalum. Photo by Phil Ross.

xkcd comic about slime molds

The peculiar sensibility this comic describes is not the sole province of scientists. Meet artist Phil Ross and his slime molds.

Ross's film Leviathans is on display at the Vast and Undetectable exhibit in the San Francisco Arts Commission Gallery. The gallery isn't large--you can see it all in half an hour--but it's fun.

While we sat on a wooden bench in front of Leviathans, listening to ambient music and watching the gentle expansion of a veined yellow monster, my husband asked, "What are slime molds exactly?"

"Fungi," I answered without thinking, because hey, they're mold, right? Wrong! Slime molds are not true molds, and therefore not fungi, although scientists once thought they were. In fact, slime molds are close cousins to amoebas.


Leviathans features the slime mold Physarum polycephalum, nicknamed the "many-headed slime." P. polycephalum is one of the most popular slime molds, in part because it’s extremely easy to grow, even for artists. Ross notes that his pets enjoyed "oatmeal, this one kind of organic Korean pasta, and an Italian brand of alphabet soup letters."

Slime Mold Physarum polycephalum
Physarum polycephalum. Photo by Phil Ross.

P. polycephalum is also the poster child for plasmodial slime molds. An individual slime mold of a plasmodial species is just one enormous cell with a whole lot of nuclei jostling around inside--which is hard to believe when you see the creature's complex network of veins.

Human veins are made of many cells. So how can you build veins inside a single cell?

The slime mold constructs its veins out of proteins called actin and myosin and fills them with cytosol (basic cell fluid). By rhythmically pumping cytosol through its veins in one direction, the slime mold can expand and move toward food, a more pleasant environment, or anything else that strikes its fancy. This kind of movement is called cytoplasmic shuttle streaming, and a bit of Google Scholar searching will inform you that scientists are not totally sure how it works.

But the mysteries of their movement and their fondness for breakfast cereal aren't the only tricks up the slime molds' veins. They can plan cities! Grow bio-computers! Re-define intelligence! Or at least they might be able to inform human efforts in these directions. Who knows what will come of it all?

One thing's for sure--slime molds will always be beautiful.

Hat tip to Symbiartic for linking Vast and Undetectable!