Jesse Ritcey took these pictures of a very common slime mold found on bark mulch and woody debris. Slime molds are fascinating organisms. Even though they are called molds, they are not fungi. In fact, they are not animals, plants, or bacteria either.

If you learned your biology in the 1970s or later, you probably learned the five-kingdom system of Robert Whittaker that was proposed in 1969 and has been widely adopted in biology curricula. In this system, the Kingdom Protista was erected as a group of unrelated left-over organisms that do not fit in any other kingdom. They are eukaryotic with organized nuclei, unicellular or unicellular-colonial and they don’t form structured internal tissues (but many do form distinctive reproductive structures). It is a mixed bag of unrelated organisms with no common ancestor that are put together for convenience. The classification of the protists is unsettled, and DNA sequencing is yielding changes. They encompass such organisms as protozoa and single celled algae.

Slime molds (or moulds) are a group of unrelated organisms that can live freely as single cells or aggregate together to form a gelatinous amoeboid mass that moves slowly over organic matter in search of their food sources of bacteria, yeasts and other fungi. This is the phase shown in the image of the yellow mass. When conditions dry, they form spores either as a single, dark mass or on distinctive structures. The second picture is probably a mass that is beginning to dry out, however, the wet mass is sometimes a dull yellow-gray colour.

Fuligo septica beginning to dry and convert into dark spores. Jesse Ritcey photo

Over 900 species have been described globally and they are divided into three groups called the cellular slime molds (the nuclei are surrounded by cell membranes), the acellular slime molds (form a multi-nucleate plasmodium), and protosteloids (very small organisms).

Jesse’s pictures are of Fuligo septica (Dog vomit). It falls in the acellular category as a plasmodial slime mold. It occurs world-wide and is particularly common on wet bark mulch. The plasmodial mass moves in an amoeboid-fashion. If you are patient and look carefully, you can see it moving, they can speed along at a few millimetres an hour! When they dry, they form the largest spore mass of any known slime mold. Its spores are known to be dispersed by beetles in the family Latridiidae.

Here it is completely dry as photographed on May 27. It looks and feels like dry ash. It is all dry spores at this stage.

For more information, see the following Wikipedia pages.

• Fuligo septica
• Slime molds
• Protists

This article was recently updated to replace the code errors, but the author may choose to edit this more.   10/25/DAS