Slime moulds
Slime moulds were thought to belong to both animal and fungi kingdoms at one time or another. It's now known that they are quite unrelated to animals and fungi and now are classified in the Kingdom Protista.
However slime moulds do exhibit characteristics of both fungi and animals. In the feeding stage, the slime moulds moves about as a mass of protoplasm (the plasmodium) feeding on bacteria, spores, and other organic matter much like an amoeba. When the food supply is exhausted or other unfavourable conditions occur, the plasmodium changes, taking on the appearance of a fungus.
At one stage of their life cycle they can appear as a brightly coloured slimey paint splash on a rotting log, wet grass, or even a fungi. In this state the slime mould is often moving - go back to the same spot some hours llater and you will often see it has moved several inches. The same organism can look totally different in its fruiting state - often as tiny puffballs, or small tufts of hair.
Most slime mould are smaller than a few centimetres, but the very largest reach areas of up to two square metres, making them the largest undivided cells known. Many have bright colours such as yellow, brown, and white.
A common slime mould which forms tiny brown tufts on rotting logs is Stemonitis. Another form which lives in rotting logs and is often used in research is Physarum polycephalum. In logs it has the appearance of a slimy webwork of yellow threads, up to a few inches in size. Fuligo forms yellow crusts.
The Protostelids life cycle is very similar to the above descriptions, but these are much smaller, the fruiting bodies only forming one to a few spores.
The Dictyosteliida, cellular slime moulds, are related to the plasmodial slime moulds but have a very different life style. Their amoeba do not form huge syncytiums and remain individual. They live in similar habitats and also feed on microorganisms. When food runs out and they are ready to form sporangia, they do something radically different. They release signal molecules into their environment, by which they find each other and create huge swarms. These amoeba then join up into a tiny slug like coordinated creature which crawls to an open lit place and grows into a fruiting body. Some of the amoeba become spores to begin the next generation, but some of the amoeba sacrifice themselves to become a dead stalk, lifting the spores up into the air.
The Acrasidae, have a similar life style to Dictyostelids, but their amoeba behave differently and are of uncertain taxonomic position.
The Plasmodiophorids also form syncytia but are internal parasites of plants (e.g., club root disease of cabbages).
Finally the Labyrinthulomycetes are marine and form labyrynthine networks of tubes in which amoebas without pseudopods can travel.
There are two main groups of slime moulds in the Protista Kingdom.
- Plasmodial slime moulds or true slime moulds are a large single-celled mass with thousands of nuclei called a plasmodium. They are formed when individual flagellated cells swarm together and fuse. The result is one large bag of cytoplasm with many diploid nuclei.
- Cellular slime moulds spend most of their lives as separate single-celled amoeboid protists, but upon the release of a chemical signal, the individual cells aggregate into a great swarm, known as a pseudoplasmodia and eventually muticellular slugs.
The plasmodial stage is found in cool, shady, moist places on rotting logs, leaf litter, moist shaded soil, or other organic matter. There are over 500 known species that feed on decaying organic matter, bacteria, protozoa, and other minute organisms, which it engulfs and digests. The plasmodium may reach several 100 millimetres in diameter and is often brightly coloured, although many are also inconspicuous.
Life Cycle
- Once a spore is released from the fruiting body it's dispersed, either by insects, animals, and rain or air movement. On landing on a suitable location with appropriate moisture and temperature, one to four protoplasts are germinated
- The protoplasts once released from the spore's wall through either a pore or fissure will be either a flagellated swarm cell if conditions are wet, or a nonflagellated myxamoebae cell in dryer conditions.
- If conditions for growth are not suitable, the cells can become microcysts to survive long periods of time.
- A diploid zygote is formed when two compatible myxamoebae or swarm cells fuse. This is known as plasmogamy and karyogamy.
- After a time of feeding and growing, the zygote develops into a single celled multinucleate structure known as a plasmodium.
- If environmental conditions are not suitable, then the plasmodium can change into another dormant state known as the sclerotium.
- When the conditions are right, the mature plasmodium produces one to many fruiting bodies containing spores depentding on species.
Included in the photos below are examples of other fungi that have been parasitised by slime moulds.
- This slime mould is shown changing to produce sporangia. Growing on wood, December, Barrington National Park. The log on
- Stemonitis axifera Upper Allyn , late December 2003. This slime mould undergoes considerable changes in form. See
- Slime mould (unidentified) invading unidentified fungus, Fiddens Whard Rd and Beaumont Road after heavy rain, May 2003
- Unidentified slime mould, Lane Cove National Park, Fiddens Wharf Road, July 30, 2006, growing in grass on possum droppin
- On wood, Sheldon Forest, Turramurra, Sydney, April 6, 2007. Dry and soft, top view. This is not a fungus, but a slime mo
- On wood, Sheldon Forest, Turramurra, Sydney, April 6, 2007. Dry and soft, bottom view. This is not a fungus, but a slime
- Unknown bolete in soil and leaf litter Jerusalem Creek Walk, Chichester State Forest, near Chichester Dam. 80mm high, ca
- Cortinarius attxcked by a slime mould, Sheldon's Forest, Pymble, NSW, 24 May 2009
- Vibrissea dura (Fuhrer p340), Rocky Crossing Walk, Barrington Tops National Park, Northern NSW, Australia, on wet wood,
- Vibrissea dura (Fuhrer p340), Barrington Guest House to Rocky Crossing walk, Barrington Tops National Park, Northern NSW
- Physarum polycephalum is the spore stage of a yellowish slime mould which forms purple grape like clusters up to 15mm lo
- Lycogala terrestre is a slime mould which forms globular clusters on very wet dead wood. The soft bodied gobules were ab
- Ceratiomyxa fruticulosa is a slime mould, not technically a fungus. Unlike other myxomcetes, the sporocarps consist of a
- Ceratiomyxa fruticulosa is a slime mould, not technically a fungus. Unlike other myxomcetes, the sporocarps consist of a
