The ‘Blob’ of Old Movies Is Really a Slime Mold

Mulches of bark or wood chips become beds of moist decaying plant matter. A variety of mushrooms may grow in those mulches, but organisms that don’t look like mushrooms also may grow there, causing alarm and even calls to professionals such as veterinarians.

Veterinarians get calls because sometimes the substance of concern looks like, to put it bluntly, dog vomit. The mass is slimy in appearance and lies rather flat across the ground, so many people associate it with stomach problems in pets.

The organism is a very strange one called a slime mold. Although some references treat the organism as a member of the Kingdom Fungi, it actually is not that closely related to fungi and now is placed in the Kingdom Protista.

Slime molds are the original “blob” familiar from horror movies. Slime molds move like an amoeba at a slow rate of about 1mm per hour. There is no cell wall, such as would be seen in plants, and a single membrane holds the mass together. In effect, the blob is one enlarged cell that includes a large number of nuclei (in most organisms, one cell contains one nucleus).

The enlarged cell is called a plasmodium because it is a mass of cell contents, or protoplasm. Most plasmodia are only a few millimeters in diameter, but some may reach over 30 cm (12 inches) in width. The plasmodium moves slowly, ingesting organic material and growing. A plasmodium will develop “fruiting bodies” that produce spores, which is the way life begins for a plasmodial slime mold.

Each spore that germinates becomes a single cell that divides and produces large populations of cells, and two cells may join to become a zygote, which eventually becomes a new plasmodium. As nuclei divide, the plasmodium becomes larger (although it remains one cell).

A second group called cellular slime molds has minute cells that travel about singly, then respond to a chemical signal and join to form a structure similar to the plasmodium. This structure, however, contains numerous cells stuck to each other.

Slime molds can be bright colors, such as red, yellow, or orange. They are not harmful and there is no need for control measures (plus there are none that work). Just enjoy their color - usually they are visible for only a few days. The following series of images shows the changes in appearance of the Dog Vomit Slime Mold (Fuligo septica). 

Fuligo septica

Fuligo septica
Dog Vomit Slime Mold

The bright yellow of this early stage of Fuligo septica may last only about a day. 

Fuligo septica
Dog Vomit Slime Mold

The loss of yellow has left this aethalium (reproductive structure similar to that of a mushroom) of Fuligo septica whitish and porous.

Fuligo septica
Fuligo septica3

Fuligo septica
Dog Vomit Slime Mold

Later, breakdown of tissue creates the dark-colored, liquid spots visible in the photo. 

Fuligo septica
Dog Vomit Slime Mold

Finally, the blackish-colored spore mass of Fuligo septica may persist for weeks. 

Fuligo septica4
Ceratiomyxa fruticulosa

Slime molds have other forms and colors. The following are a few examples. Ceratiomyxa fruticulosa Coral Slime Mold

 

 

Ceratiomyxa fruticulosa
Coral Slime Mold

Ceratiomyxa fruticulosa  Coral Slime Mold
Stemonitis

Stemonitis sp.

Known by common names such as Chocolate Tube Slime, Tree hair, and Pipe Cleaner Slime, this slime mold resembles clumps of hair usually growing from decaying tree remains.
 

Stemonitis sp.

Photographs courtesy of Cindy Thornton. 

Stemonitis sp.
Locogala epidendrum

Locogala epidendrum 

 

Wolf's Milk Slime Mold 

Tubifera ferruginosa 

 

Red Raspberry Slime 

Tubifera ferruginosa
Arcyria

Arcyria sp., probably denudata

 

Carnival Candy Slime 

 
 
 
 
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