#22 Secretive Slime Moulds

If you've ever spied strange slimy stuff creeping through your garden, or tiny baubles or blobs adorning mulch or foliage, and thought it too odd to be any life-form you're familiar with, there's every chance it could be a slime mould.

#1 Slime mould on Birds Nest Fungi in my herb garden

The Myxomycota, commonly known as slime moulds do not belong to the fungi kingdom, but in many aspects they are fungi-like and are studied by mycologists. Slime moulds belong to the kingdom Protoctista.

What are slime moulds?

Exhibiting some characteristics of both plants and animals, it is little wonder that slime moulds have a history of confusing classification. They move and feed like animals, engulfing bacteria and other micro-organisms, fungi, and decaying organic matter. But slime moulds contain cellulose, the stuff of plants. Cellulose is not found in fungi.

#2 Pink stalked sporangia of a slime mould

Slime moulds live in damp terrestrial habitats such as below garden mulch or forest-floor debris, and inside decaying logs.

Life cycle of a slime mould

When conditions are ideal for reproduction (warm and moist), the plasmodium (a mass containing many nuclei) moves to a drier, better-lit place. The plasmodium can be white, grey, yellow, orange, brown or grey jelly-like or frothy patches on the lawn, logs, mulch or leaf litter.

The slimy plasmodium can move up to a metre, or more, and can climb objects in order to reach a site which will be suitable to spore dispersal. Thousands of individual cells congregate and flow together in a mass called a pseudo-plasmodium often resembling a slug, until it settles in a position with suitable light and warmth for transformation into reproductive structures.

#3 Fruiting bodies of slime mould in my garden

The creeping stages often look alike, making identification difficult. When they fruit they take on more individual characteristics. Positive identification, however, is difficult, even for the experts.

Identification

There are four main types of fruiting bodies. The most common fruit body is the sporangium where the protoplasm separates to form tiny fruit bodies usually only a couple of mm in height, each with its own peridium (protective covering for spores) - examples in images #1, #2 and #7.

The aethalium is a relative large, but variable fruiting body, that forms crusty masses. Each cushion-like structure has a single peridium containing the reproductive spores - examples in images #3 and #4.

The plasmodiocarp consists of a fat network of veins on the surface of decaying logs. The peridium is laid down on the outside of the fat veins - example Pretzel Slime Mould (Hemitrichia serpula).

The fourth is pseudoaethalium where the fruiting body consists of sporangia closely crowded together - example Tubifera ferruginosa.

#4 When damaged, the crust breaks to reveal spores

Of the three slime moulds I am featuring here, the first two were found in my backyard mulched herb garden, while the third was found in a moist alpine environment in New England National Park (north of the Hunter Valley).

Image #1 shows the sporangia of a slime mould that has fruited on Birds Nest Fungi, Cyathus stercoreus, in a mulched garden in my backyard in April 2007. The fungi are only 5 to 8mm in diameter, so the tiny size of the slime mould fruiting bodies is evident.

Image #2 is a pale pink version of the same fruiting bodies as in image #1, photographed on the same day on mulch.

#5 Plasmodium in active mobile phase

Image #3 shows the fruiting stage of a slime mould that could possibly be a Fuligo species. I found this in February 2005 on fallen chile leaves and straw mulch in my backyard herb garden.

Image #4 is the same species with the crusty exterior cracked to expose spores.

#6 The same species as pic 5, plasmodium separating

Images #5, #6 and #7 are the same slime mould photographed in May 2007 on leaf litter in alpine woodland. Pic 5 shows the active mobile stage, pic 6 shows the separating stage, and pic 7 shows the sporangium formed. The sporangia will dry out and crack to expose spores to be dispersed by the wind. Fifteen hours elapsed between picture 6 and 7.

#7 Sporangium (spore bearing capsules) of the slime mould of previous two images

There is no cause for alarm if you find these creeping slimy growths in your lawn or garden. They will not harm your pets if injested, and there is no evidence that they cause harm to plants.

Although some slime moulds can look quite disgusting and bear such names as "Dog Vomit Slime Mould", most are exquisitely beautiful when studied up close. Next time you encounter a slime mould in its reproductive stage, take a look at the intricate detail, and I feel sure you will agree with me about their beauty.

More Slime Mould reading

Slime Mould basics

Structural characteristics

Anatomy and life cycle

More biology