Slime Mold

at 11:35 PM
Save ArticleSave Article

Failed to save article

Please try again

At last the rains have begun, hopefully ushering in a full-blown wet-winter season. A couple of days ago on a stroll in a soggy redwood forest, I came across a bright yellow mass of a slime mold. I vaguely recalled reading that you could grow slime molds on a medium of oatmeal. So I brought a bit of the yellow goo home and tried it. My experiment failed miserably -- the slime mold shriveled and died horribly. My calling as a pet owner was over.

Slime molds are weird, but not uncommon. The kind I saw was a plasmodial slime mold, which is nothing more than a gigantic single-celled life form with thousands of nuclei. They develop when tens of thousands of single cells, all with a whip-like appendage called a flagellum, throng together and fuse into one giant cell with a single membrane. Worldwide there are about 500 species: they are often orange or yellow and are probably the easiest single-celled organisms to see with the unaided eye. They can be several inches across and cruise around on the forest floor like giant amoebas engulfing microorganisms such as bacteria and yeast. They also devour decaying vegetation, but apparently not oatmeal!

Slime molds reproduce with spores, which led biologists to lump them with fungi, along with familiar household molds. But things are not so simple. Slime molds behave like animals when they are feeding and growing, and then more like plants or fungi when in the immobile, reproductive phase. So now they are classified in the Kingdom Protista. This diverse group includes many "leftover" organisms that just do not fit into other kingdoms. They are mostly single-celled, like amoebas and dinoflagellates, but also include the multicellular seaweeds.

So on your next winter walk in any deep, damp forest watch for bright yellow or orange blobs. Just don't try to feed them oatmeal.

This is Michael Ellis with a Perspective.


Michael Ellis is a naturalist who leads trips throughout the world. He lives in Santa Rosa.