A rock wall (I) - or: holiday time

About 10 years ago we presented instructions about How to find tardigrades . We didn't go much into detail with respect to the recommended locations, just mentioned that the typical tardigrade home is a moss cushion.

Starting from 2008 we described marine tardigrade species and the respective locations, e.g. Echiniscoides sigismundi  living on Enteromorpha algae at a Lissabon beach, Batillipes mirus  from a sand sample of the Kieler Föhrde, Germany, and some bizarre marine tardigrades from a beach in Croatia, e.g. Florarctus sp. , living at a few meters depth at the ground of the ocean.

This issue will provide some supplementary hints which will hopefully help the beginner to collect "good", i.e. densely inhabited, moss samples. But in any case it must be pointed out before that there is no need to devastate the landscape. The volume of a walnut is perfectly sufficent in order to gain an overview about the tardigrade population of given location. This sample size will cover the ground area of several petri dishes. Please keep in mind that the mosses are growing slowly - so by taking bigger samples you are in danger of leaving ugly traces at some locations which might remain visible for years.

As a rule the most suited mosses will be those which undergo a regular wet/dry cycle, either becoming wet by dew or rain. Furthermore they should become thoroughly dry from time to time - so sun-lit locations should be preferred. A good choice are mosses on the walls of cemented brooks and rivers, mosses on old roof tiles - the older the better, mosses on stone or rock surfaces. It is well known that the tardigrade diversity is increasing when moving from the aequatorial regions to the south or north pole of the earth. And it is important to keep in mind that tardigrades have no blood circulation, just rely on oxygen diffusion. So oxygen lack is omnipresent. Tardigrades enjoy cool areas (high oxygen content in water) and windy areas (much oxygen and few bacteria). As a consequence locations with constantly high humidity or high temperature will be less ideal as a tardigrade home. Those of you who are not willing to travel to the poles can be consoled. You will find lots of tardigrades on most mountains:

An ideal tardigrade collecting area

Even if you shouldn't be the sportive type you might ask your friends to collect a moss sample for you. But tell them to transport all moss samples in a perfectly dry condition only. Otherwise funghi and bacteria will destroy your sample and kill all tardigrades. Sometimes the rock wall locations will be difficult to access, see e.g. the secenario below where most of the moss appears to be located at about 10 m height above ground level:

Small rock wall in Austria, extending to a height of about 10 m.

In the detail view below it becomes clear that most mosses are clever enough not to settle in reach of the mountaineers. When seen from below, the most interesting mosses often seem to be located far away, close to the top of the rock walls:

Rock wall in Austria, detail showing the upper part with promising moss cushions.

In this situation our moss grabber (from the electronics discounter) doesn't reach out far enough - even though it serves well in many other situations:

The moss grabber, an ideal tool to take samples from a distance of about 1 m. But not very helpful with respect to the rock wall!

But instead of climbing up and possibly risking your life you should simply look out for fallen mosses. In particular after rain and storm or after periods of continued dryness you will find many mosses from top areas that have fallen to the ground and can be easily collected from there. Furthermore you needn't have a bad conscience with respect to the tardigrades as their castrophe has already happened before (the tardigrades' living conditions are drastically deteriorated at the moment when the moss has lost its contact to the rock and comes down!)

One additional advice: look out for large moss areas but do not neglect very tiny patches of moss either. We will discuss one of our moss samples in the upcoming issues. See you!

© 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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