About Myxomycetes

This web site is about MYXOMYCETES. Even if these are usually known by the less attractive common name “slime moulds”, the fruiting bodies produced by the myxomycetes exhibit incredibly diverse forms and colours and may be astonishingly beautiful. Apart from their interesting biology, their beauty is the main inspiration behind this web site.
Myxomycetes, or slime moulds, is a unique group of organisms, very different from all other organisms. They are not plants, not animals, and not fungi – in modern classification systems, they are placed in a separate Kingdom (Protozoa), along with other “primitive” unicellular organisms, like the amoeba. The group treated here is the so-called plasmodial slime moulds which comprises around 1000 species worldwide, approximately 330 of which have so far been found in Norway.
Myxomycetes have traditionally been classified as primitive animals by zoologists and as fungi by mycologists. The reason for this is that their life cycle include stages where they move around (up to 2,5 mm per hour!) to eat and grow (the vegetative stage), as well as a spore- producing stage, similar to fungi (the reproductive stage). The spores germinate to produce either amoeba or swarm cells. These cells will eventually fuse in pairs, forming a zygote – this is what we generally refer to as mating. This zygote move around and grow into a so-called plasmodium, thus the name plasmodial myxomycetes. This blob of slime can grow to considerable sizes, in some species up to several square decimetres. In extreme cases specimens of a few meters have been found, making these organisms the inspiration for a group of horror films named “The Blob”. These plasmodia are what can often be seen in the forests or elsewhere as yellow or white slime patterns on e.g. dead tree trunks or stumps or among mosses. When conditions are suitable these plasmodia will develop into fruiting bodies, producing large numbers of spores. And the cycle is closed.
During the two stages when the myxomycetes eat and grow, bacteria represent the primary food resource but plasmodia are also known to feed upon yeasts, cyanobacteria, and fungal spores and hyphae, sometimes even consuming whole fruiting bodies of mushrooms.
Under favourable conditions, the plasmodium gives rise to one or more fruiting bodies. The fruiting bodies produced by myxomycetes somewhat resemble those produced by mushrooms, although they are considerably smaller, usually no more than 1–2 mm tall, some even a fraction of a millimetre.
Identification of myxomycetes is based almost entirely upon features of the fruiting bodies and the spores. Fruiting bodies (also referred to as “sporophores” or “sporocarps”) occur in different forms or types, some free standing (sporangia), often in groups derived from the same lump of plasmodium, stalked or sessile, some in cushion-like structures as aethalia or plasmodiocarps, usually sessile. There is great variation in form and colour and also in the internal structure of these fruiting bodies.
The majority of species of myxomycetes are probably cosmopolitan. Temperature and moisture are thought to be the main limiting factors for myxomycetes, and species diversity tend to increase with increasing biodiversity and also depend on the biomass of organic material that support the bacteria and other microorganisms upon which the myxomycetes feed.
The ability of a plasmodium to move and to migrate some distance from the substrate within which it developed has the potential of obscuring myxomycete-substrate relationships, but there are indications that the fruiting bodies of particular species of myxomycetes tend to be rather consistently associated with certain types of substrates, such as dead wood, bark, dead leaves and other plant debris, and mosses and liverworts.
Since many of the myxomycete species achieve macroscopic dimensions, they can be collected and preserved for study in the same way as the fruiting bodies of fungi or even specimens of mosses, lichens, and vascular plants. If handled carefully and properly stored, myxomycete fruiting bodies will remain suitable for study for many years.
Biologically, the most unique feature of the plasmodial myxomycetes is the fact that the plasmodium is one single, large cell where all the cell nuclei are found. The implication is that all these nuclei divide simultaneously (mitosis). This fact renders these organisms a unique tool for the scientific study of the process of mitosis.
Myxomycetes are also known for their “intelligent behaviour”, like finding the shortest way through a maze, operating robots, showing capability for learning and memorising, choosing optimal composition of food, and also being candidates for bio-computing devices. They are known to produce sound, although outside the range of the human ear.
The purpose of this web site is, however, to show the beauty and perhaps unsurpassed variation in colour and shape displayed by fruiting bodies of these plasmodial myxomycetes from the “Slimy Kingdom”.

Helge G. Gundersen