Lichens - a tardigrade paradise!

External contribution by Marien-Gymnasium, Werl, Germany

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Annotation: We are glad to present a third-party experiment here once more. The authors would like to emphasize that the tardigrades were not maltreated in order to perform the experiments.
The copyright owners of the text and the images are the pupils Jule and Maike and their teacher Marco Hagedorn from Marien-Gymnasium, Werl, Germany.
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When asked about typical tardigrade habitats some time age, Chat GPT 3.5 delivered the following environments: moss, foliage, soil, roof gutters and house walls. But it didn't mention freshwater and marine sediment and apparently wasn't aware of lichens. Moreover, house walls and gutters should have been explained and linked to the existence of moss cushions on walls and in gutters. These were tiny flaws in the answer but they provided a little bit of consolation for the endangered human brains!

The pupils Jule and Maike took part in a German science contest ("Jugend forscht") in 2016. The aim of their scientific work was to find out which tardigrade species were living on lichens. For this sake lichen samples were taken from the surface of steel bridges, tree barks (fig. 1) and stones. Most of the samples were dominated by the tardigrade Ramazzottius oberhaeuseri (see fig. 2 and fig. 3).

Fig. 1: Most people probably would not expect to find tardigrades within those lichens!

Fig. 2: The tardigrade Ramazzottius oberhaeuseri shown here is clinging to a small alga, possibly considering to use it as a meal in order to take profit of is sugar water cell content.

Fig. 3: The same Ramazzottius oberhaeuseri, now abandoning the alga, possibly trying to find back into its lichen environment

The Ramazzottius oberhaeuseri tardigrade can be recognized easily, already at low magnification, by its brown stripe pattern. For those among you who are interested in their abundance within the lichen environment we are going to list a few numbers:

Futhermore two lichen samples found on stones were investigated. But they were not inhabited by tardigrades.


Resume
Even though the number of samples and individuals was comparatively small, it appears that Ramazzottius oberhaeuseri is the dominating lichen tardigrade. Further investigations (after 2016) confirmed this result.
Besides, lichen samples have a tremendous advantage over moss samples: lichen sample water as a rule will remain clear and transparent whereas moss sample water normally will look rather murky. You might take advantage of this fact when setting out for your first tardigrade expedition!

© Text, images and video clips by  Martin Mach  (webmaster@baertierchen.de).
The 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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