Slime Molds

What is a slime mold?

At first they were thought to be fungi. So mycologists studied them and included slime molds in mycology books and texts. However, slime molds exhibit characteristics of fungi and animals. Currently slime molds are taxonomically placed in the Kingdom Protoctisa, a catchall group of eucaryotic (have enclosed cellular nuclei) organisms that are not plants, animals or fungi.

Slime molds are often found on decaying forest litter and rotting wood. No matter where found, slime molds feed on bacteria, yeasts and fungi that feed on decomposing matter and are important in returning nutrients to the soil. Slime molds communicate by chemical signals to others of their kind.

There are three types of slime molds:

Cellular slime molds stay as single cells that can form a mass that is capable of amoeba-like movement. The aggregation occurs when food is scarce. These organisms are rarely visible to the naked eye.

Another type of microscopic slime mold are protosteloid slime molds. These are amoeboid and capable of forming fruiting bodies.

Slime molds that are visible are acellular and are called plasmodial slime molds, also known as myxomycetes. They too start out as single cells and join together forming a mass with a single cellular membrane and many nuclei.

Pictured is one example of a plasmodial slime mold known commonly as wolf’s milk (Lycogala epidendrum). The reproductive stage is a stalkless “cushion”. When immature and first formed, these spore cases are pink and exude a pink paste when broken. When mature, they turn dark and crusty and eventually split open to release spores. My 12-01-11 post, “Wolf’s Milk Slime”, discusses this species and is illustrated with mature spore cases.

This wolf’s milk slime mold was photographed along the PSEA Trail at McArthur Burney Falls State Park (Shasta County CA).

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