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INTRODUCTION
Despite their rather unappealing name, slime
moulds are fascinating and quite beautiful organisms. Known as
Myxomycetes, they exhibit both plant-like and animal-like
characteristics. A particularly interesting type is Physarum
polycephalum, the Many-Headed Slime Mould.
In its growing stage, Physarum
resembles a giant voracious amoeba that spreads out like a fan, enveloping
everything in its path, and digesting any bacteria, spores and decaying
organic matter it encounters. In this plasmodial stage, Physarum
polycephalum is a bright yellow glistening mass that can grow to 30cm
across under the right conditions. In response to environmental changes
such as dry conditions or a scarcity of food, the plasmodium will begin to
shrink and form fruiting bodies or sporangia. Germination of the spores
leads to the formation of a new plasmodium and the cycle can begin again.
A curious variation occurs when the plasmodium
encounters conditions that are too severe for it to continue growing, but
not severe enough to cause it to form sporangia. It goes into a kind of
dry dormant state called sclerotium that can revive itself if it becomes
moist.
MAINTAINING A
CULTURE
Physarum is easy and
inexpensive to obtain and it can be easily cultured in the classroom on a
moist substrate such as a plain agar plate. It can be fed rolled oats as
it grows, and subcultured to a fresh plate when it has fully colonised the
first. Even moist filter paper is suitable, but agar plates are easier to
use because they do not need to be re-hydrated.
OBSERVING
PHYSARUM
A dramatic behavioural characteristic of
Physarum is cytoplasmic streaming. This can be easily seen by placing
the culture plate on the microscope stage and using 40x magnification.
Close down the diaphragm and focus on the bright yellow veins. The rapid
fluid motion of the cytoplasm is easily observed. Note how the flow
pauses every minute or so and reverses direction.
EXPERIMENTS
Physarum polycephalum is well suited to
simple class activities because of its ability to migrate and respond to
its environment. For example:
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Test different food types. Which breakfast
cereal does it prefer? Does it eat fresh fruit?
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Does it prefer light or dark conditions?
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What temperature range suits it best?
Students will learn how to frame their
questions in ways that can be expressed as hypotheses and tested by
controlled experiments.
Aside from scientific study, Physarum
can be a source of inspiration for creative and descriptive writing.
Try brainstorming a list of adjectives to describe the plasmodium.
MORE
INFORMATION
Slime Mould - The Fungus That Walks -
National Geographic, July 1981, page 131.
Chemotaxis in the
Plasmodial Slime Mould, Physarum polycephalum - The American
Biology Teacher, January 1998, page 59
The Fungus That Creeps -
Creepy Crawlies and the Scientific Method, published 1993, chapter 7.
CARE INSTRUCTIONS
Click here to download care instructions (pdf, 0.1M, new window)
Click here to download life cycle notes (pdf, 0.1M, new window)
DOWNLOAD
Cells With Personality: Physarum polycephalum - by D M Bozzone,
PhD (opens in a new window - 0.2M)
MORE
Learn more about the amazing
but little known world of slime moulds in
Like Nothing On Earth, a 43 minute video program produced by the noted
authority in this field, Karlheinz Baumann. |
