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- An external contribution by the Marien-Gymnasium, Werl, Germany -

Attention please: We are glad to present an external contribution in this issue of the Water Bear web base. And we would like to add that the experiments described here are not the brute, usual ones working with UV light, vacuum, extreme temperatures etc. but insead are more carefully designed, soft investigations. The tardigrades were simply watched walking across a certain distance.
The copyright holders of the following text, images and video are the pupils Julia and Nils supported by their teacher Marco Hagedorn from the Marien-Gymnasium, in Werl, Germany.

Early scientists labelled the water bears as tardigrades (i.e. slow-walking animals). This issue of the Water Bear web base deals with the question whether the tardigrades are actually as slow as their name is suggesting? Julia and Nils, pupils at the Marien-Gymansium in Werl, Germany, had a closer look at this topic. When screening older issues of the Water Bear web base they came across the issue of  February 2005  quoting the famous tardiologists Giuseppe Ramazzotti and Walter Maucci who reported tardigrade on-foot-travelling speeds to reach up to 17 cm per hour.

According to their opinion this statement looked slighty vague, so they decided to perform a thorough measurement themselves. In order to measure the walking speed of the tardigrades they prepared an Agar plate. When the Agar solution had become solid they placed a graph paper with millimeter grid on it and covered it by a second layer of Agar. After this second layer had dried some liquid water was added. The result looked as follows:

[ The tardigrade racetrack ]

The tardigrade racetrack, an area measuring 6 cm x 6 cm, confined in a Petri dish

After this the tardigrades were pipetted from the moss extract Petri dish to the racetrack Petri dish:

[ Nils with pipette ]

Nils with pipette at the stereo microscope (a low mag dissecting microscope)

The following video clip is documenting a typical tardigrade walk-through:

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The broader lines are marking distances of 1 cm, the smaller ones of 1 mm. In the experiment the travelling time for one millimeter racetrack was measured and the respective velocity calculated. The tardigrades had to be watched for rather long periods of time as they didn't run straight forward as hoped by the investigators and sometimes didn't venture to move at all.

The results of the measurements were as follows: Eutardigrades, i.e. tardigrades without armour plates (as shown in the video) reached a maximum velocity of 74.8 cm/h. This value is based on ten individual measurements (of course the tardigrade will not walk straight across 74.8 cm in an hour as the maximum speed was calculated for 1 mm distances only).

Heterotardigrades, i.e. tardigrades with armour plates, reached a maximum speed of 13.3 cm/h . None of the Eutardigrades showed a similar low velocity. The value reported here is based on four measurements. Possibly the armour plates are not good for running?

Now let's come back to the initial topic and re-check whether the label "tardigrade" is justified or not. For this sake we are going to compare the fastest tardigrade with the fasted man on Earth: Usain Bolt measures 195 cm in height. This is equivalent to 1,950,000 Ám. The tardigrade length can be specified as 600 Ám. This means that Usain Bolt is 3,250 times bigger than the tardigrade. In order to compete with Usain Bolt in Usain Bolt's body size our fastest tardigrade would have to cross the 3,250 fold pathway, i.e. 243.100 cm/h which equals 2.4 km/h. But we know from Usain Bolt's world record that he is actually running with a speed of 38 km/h. So it must be admitted that even our fastest tardigrade is much slower than Usain Bolt, possibly not even a fast walker, just a leasurely walker!

© Text, images and video clips by  Martin Mach  (webmaster@baertierchen.de).
Water Bear web base is a licensed and revised version of the German language monthly magazine  Bärtierchen-Journal . Style and grammar amendments by native speakers are warmly welcomed.

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