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Paramecia (stained prepared slide)
Living paramecium from the hay infusion
This kind of hay infusion produces lots of exciting
objects.
You can keep the pond samples alive for an extended period of time. Cover a
jar or bucket containing the slide and the original water loosely with a piece of
cardboard. This is just to protect against dust. However, oxygen needs to be able
to get in; otherwise your guests from the pond will die! But the water is automati-
cally supplied with fresh oxygen by algae, too. They, however, need light in order
to survive. You should just avoid putting the jar or bucket in full sunlight, since the
water will get too warm, which the organisms don't like. A window sill in a north
or east window is a good place for your micro-aquarium.
The Hay Infusion — A Classic
You can also grow your algae and animals at home on the window sill.
You will need:
• a little hay (or dry grass, wood shavings, and straw for small animals)
• pond water
• a canning jar (0.5 – 1 liter)
• a kitchen hand towel
• a kitchen sieve
• a pipette
• and of course your microscope with accessories (slide, cover slip, ...)
Into a large jelly jar or canning jar that has been rinsed out several times with
hot water, pour some water from a pond, a rain barrel, or an aquarium over
some hay (not more than a small handful) up to about 5 centimeters below
the brim. For the reasons outlined before, cover the jar loosely with a piece
of cardboard. The hay will be used by your guests as a source of nourishment.
Here — as is so often the case — more is not necessarily better: Too much
hay spoils the set-up. Place your hay infusion into a lit place (a north facing
window) and give your guests some time to populate their new living space.
You can take samples at an interval of 3-4 days to check how the living space
is coming along. Are there suddenly new species that you hadn't encountered
before? Do some species eventually disappear from the picture over the course
of time?
A typical inhabitant of such hay infusions is, for example, the paramecium, of
which you will also find a few stained specimens on a prepared slide in your kit.
The name of this creature, which measures from 50 to a maximum of 300 microm-
eters, comes from the Greek word paramekes, meaning oblong or oval. From the
prepared slide, you might be able to guess how these creatures propel themselves.
The entire cell is covered by approximately 10,000 very fine hairs, also known as
cilia. They row together rhythmically like oars on a rowing shell so that the "cili-
ate" (an organism with cilia) is able to move freely through its living space. This
kind of ciliate can of course not see where it's swimming — after all, it is only
composed of a single cell. If it bumps into a barrier, then it simply changes the
direction in which the cilia beat for a while and swims backwards in the "hope" of
going around the barrier when it swims forward again.
Dark spots are often visible on the inside of the cell. These are either the cell
nucleus or the "stomachs" of the paramecium (biologists refer to these as food
vacuoles or vacuoles). It feeds primarily on bacteria that it ingests enclosed by a
little bubble. In these bubbles, the bacteria are digested and all the nutrients are
absorbed into the cell. The paramecium then releases the indigestible waste back
to the outside. One astounding thing here is that the absorption of the nourish-
ment and the excretion of waste take place at very specific places in the cell. So
you could say that a paramecium has what you could call a cell mouth and a cell
anus. Several different types of paramecium live in the indigenous ponds, pools,
or even puddles. So chances are good that you will come across a living specimen
sometime during your research work.
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