The river Isar flood

In the beginning we were puzzled when we came across so many different tardigrade species in the very center of Munich, along the Isar river. At first we had thought that those many tardigrades might have been transported on all kinds of wooden pieces on the river, thus travelling from the Alps to downtown Munich. An other possibility to consider was that the tardigrades might simply be able to swim in the flowing river water. So we were eagerly waiting for one of those Isar floods in order to check whether tardigrades might be able to live within this scenario and to survive it.

Just look how the Isar is like when there is a flood:

Video (~1 MB): Isar river flood, August 7th 2010, as seen in the very center of Munich (so-called Praterinsel area).

Isar flood. View from a bridge (so-called Kabelsteg) southwards.

View from the same bridge northwards. It looks a bit like the Amazonas, doesn't it?

So, keen tardigrade enthusiasts, take care that you do not get drowned in one of those river floods during your research! In fact we found a rather comfortable staircase leading down to the flood scenario:

A safe way to sampling

In order to take a true river water sample we chose a 2 m wooden stick with a 105 µm mesh. The sample was full of earthen particles and plant fibers, the latter probably stemming from plant roots along the river borders.

Microscopic view of the flood water sample filtered through the 105 µm mesh. Note those many (plant root) fibers with vegetable characteristics.

It took some time until we spotted our first tardigrade in the sample. But it fitted our prejudice as it was strongly pigmented which is quite typical for the tardigrades coming from far and from the higher mountain regions.

Tardigrade from the Isar river flood water sample. Quite alive. Total view, length ca. 0.5 mm.

Tardigrade from the Isar river flood water sample, detail view of the last pair of legs. The claws look like Macrobiotus type.

Another detail of the same individuum, backside, detail with eggs.

Same individuum, head region with macroplacoids. Looks like Macrobiotus hufelandi.

So it appears plausible that the tardigrades are actually able to swim in and travel along rivers thus being very effective travellers - on foot it would take them much more time to cover those tremendous distances!

© 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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