Posts Tagged ‘biology’
Slime mould
some slime mould found at home
Content taken from: Biological Science: the web of life; third edition; Australian Academy of Science, Canberra A.C.T.
Slime moulds are also had to classify into a particular ‘kingdom’. As you may have discovered in the laboratory, a slime mould is a strange and truly remarkable organism. Its structure and behaviour have raised many questions, some of which are still unanswered.
For much of its life a typical slime mould is a creeping mass of living substance with the consistency of raw egg white. It may be orange, yellow, white or colourless. Some are microscopic; others are quite large. The movement of this living thing brings to mind a giant amoeba, for it sends out ‘arms’ which engulf and digest bacteria from rotting logs or leaves. This stage of the slime mould is called a plasmodium.
Most slime moulds live in moist places – in decaying logs, leaves, or other organic matter. A plasmodium can move over grass, creep up the sides of trees or go almost anywhere there is food or moisture.
If you look at a plasmodium through a microscope you will see that it contains many nuclei in a mass of living substance, the cytoplasm. It is not divided up into separate cells. If you watch an active plasmodium you will see the most spectacular exhibition of streaming you can find anywhere. As you watch, the cytoplasm flows rapidly in one direction. After about fifty seconds the flow slows down, stops, then reveres its direction. What causes this rhythmic back-and-forth flow of cytoplasm remains a mystery, despite considerable research.
When a plasmodium is fully grown and well fed, it crawls to a drier and more exposed position (on a dead log in the sunlight, for example) and slowly changes into one of several fruiting bodies, containing spores…
…Looking back at the description of a slime mould, you can see that they are most unusual organisms. Certainly they are not on the border of the living and non-living, like viruses. But they do not have a cellular structure. Nor is there a cell wall around the cytoplasm of a plasmodium, as there is in a bacterium. When it is feeding it looks rather like an animal, but it reproduces by spores like a fungus.
