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Are tardigrades able to smell? --------------------------------------------------------------------------------------------------------------------- |
Mosses are by no means the only rewarding tardigrade habitat. When looking for
tardigrades you might as well have a closer look at litter. Within the framework of the
German year 2017 "Jugend forscht" competition it could be demonstrated
that the tardigrades are able to migrate from soil into litter.
And we think that they are following this pathway in order to look out for nutrition.
Possibly they feed on tiny fungi on the leaf surfaces. |
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Fig. 1: Filter paper was used for this experiment in order to create some kind of artifical litter. One liter of leaf juice was used to wet the filter papers on the left side whereas the filter papers on the right side were merely treated with pure water. |
For this experiment we used 16 filter papers (two groups of 8)
and fixed them to the soil by means of toothpicks.The first group was soaked
with leaf litter water, the second group with pure water. The leaf litter water
was prepared as follows: a 5 liter container was filled with litter and
two liters of water were added. This mixture was stirred for 5 minutes taking care
that the leaves were actually quenched. After those 5 minutes the leaves were removed
and the mixture poured through a 20 µm sieve (this mesh size will make sure
that no live tardigrades are transported into the solution). |
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Diagram 1: Percentages of tardigrades on pure water treated filters (left, marked as "mit Leitungswasser") and leaf juice filters (right, marked as "mit Laubwasser"). |
2. The Agar experiment |
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Fig. 2: Agar plates for experiment 2 |
For the Agar experiment one Petri dish is filled with 2% Agar solution (in water).
For this sake 1 g of Agar is mixed with 50 ml of water. The mixture has to be boiled
for a short moment in order to become homogeneous. A second Petri dish is prepared in
the same manner, but this time with leaf litter water instead of pure water (same as in experiment 1).
The two Petri dish preparations are then cooled down to room temperature. Now a
"combination plate" with two halves of Agar can be built (cf. fig. 2, on
the very right side). In case of a gap between those halves one can apply
additional liquid Agar solution in order to properly bridge
between the two areas. Now as many tardigrades as possible are collected
from litter (we had about ten in each experiment) and then pipetted to the
center of the split Agar preparation. We waited until the next day and
performed an evaluation (we had made sure in preliminary tests that the tardigrades are in fact able to
move on the Agar surface area). A previous "Jugend forscht" experiment
in the year 2014 had revealed that the tardigrades are able to move with a speed of up to
74 cm/h. So there should be enough time for the tardigrades - at least in theory -
to walk along on the 5 cm diameter Petri dish. |
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Diagram 2: Percentage of tardigrades on the pure water Agar side (left) and the leaf litter water Agar side (right). |
Discussion |
© Text, images and video clips by
Martin Mach (webmaster@baertierchen.de). |