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A pathway to the understanding of mosses? (III)

Mosses do have lots of enemies, in particular in the commercial field. A global player in chemistry products doesn't hesitate to summarize their properties, rather stone-hearted, as follows:

Mosses: Soiling, material degradation and dangerous, slippery surfaces!

Well, there are motives for such statements. The chemical production is providing many, many products which are intended to be sold for an enduring fight against those evil mosses. And, of course, the supplier has a tendency to make profit in this field. Constant demand due to a constant fight - a perfect market situation. So, the statement above is understandable, somehow. But in order to reach a more balanced assessment we must keep in mind that the moss characterization by the suppliers of chemical products is based solely on sales interest. As a consequence the moss positives are being skipped.

We would like to emphasize that the beautiful, ideally (half-)spherical geometry of the moss cushions which is a par excellence support of Darwin's thoughts - a shield and perfect proof of the never-ending fight for existence on earth. No, not only the brute fight against those human individuals who are cleaning their pavement borderlines on a daily basis. Alos the necessity to withstand the extremes of rain and drought. Stone and pavement mosses receive their water supply only from rainfall. So they must be able to defend themselves against this water but at the same time to be able to store it as well.

[ Grimmia pulvinata moss, cross section view ]

Grimmia pulvinata moss cushion, cross section view. Image width ca. 2 cm.

Serious-minded roof tile produces do confirm that a moderate moss growth doesn't cause any harm for the tiles because the rhizoids of the mosses are to weak to penetrate into the tiles. But, of course, thick layers of mosses will cause problems due to permanently increased humidity and microbial growth. As an aside we would like to state that the tardigrades don't like those thicker and smelly moss systems either.

[ Grimmia rhizoids ]

Those ultra fine moss "roots" (the so-called rhizoids) at the underside of a moss cushion will make only soft contact with any substrate and thus not cause any damages. Image width: a few millimeters.

The most important argument to keep a moderate moss landscape goes without saying: the tardigedes love it and need it. So every tardigrade enthusiast should protest against the daily chemical killing of billions of tardigrades all over the world!

[ Grimmia pulvinata scyscraper model ]

Moss cushion in the skyscaper model view

We have already been describing the marvelous properties of those glass hairs in the top layer of the moss cushions. In the scientific literature they are interpreted to function as a kind of climatic buffer volume. This zone can be considered as slightly risky for the tardigrades as it is open to bigger predators (still small in the human understanding of animal size) which can approach directly from top. Moreover the glass hair region has to be charcterized as poor in nutrition content, similar to some kind of plastic bag. As a consequence the tardigrades will prefer green moss areas and green micro organism which are enriched in the deeper regions of the mosses. Furthermore, the glass hairs have to be considered as a difficult substrate with respect to climbing and movement across the moss system.

Mosses don't have a dedicated vertical water pipeline system which might be sufficient for long range water transport, so they have to clinge to the given mineral substrate and will not be able to grow towards the sky. The inner top moss region will typically become dry from time to time and then turn its colour from green to brown. So it is ideal for an organism with a desiccation survival strategy like the tardigrade.

The neighbours within this region (the temporarily brown and sometimes wet region) - nematodes, amoebae and rotifers - normally will not do any harm to the tardigrades. Most of the time they will concentrate on the serach for smaller eatable particles and organisms, simply ignoring the neighbouring tardigrades.

Tardigrade mass murdering nematodes are an invention of journalists and poor internet reports. We have never seen a nematode or a rotifer attacking a tardigrade. Also amoebae will not present a serious risk for healthy tardigrades. Just think of the risk of a human to be devoured by the neighbour's dog. It is possible - but highly improbable.

To sum up we should consider the moss inhabitants as a rather peaceful community, mostly feeding on vegetable particles. Interactions between the various species seem to be scarce and most individuals appear to behave as singles caring only little about their neighbours. The most time of the (wet) day will be spent on searching for nutrition, moulting and laying eggs.

The moss bottom layer with its fine rhizoids will be dense and more wet, less ideal for the tardigrades. In theory, the tardigrades might penetrate though this jungle but the motive to do so will be not very strong. So, as a rule you won't find many tardigrades in this bottom layer of the moss.

When looking onto a dry moss cushion in top view you will not come across many tardigrades. As this location is not ideal for desiccation, the existence of tardigrades in this stratigraphic layer is indicating less than ideal conditions during the desiccation process. Otherwise the tardigrades would have had enough time to crawl back into one of the more moderate inner regions of the moss cushion.

For a direct investigation of dry moss cushions we therefore recommend to section the moss cushion through its vertical (z direction) symmetry axis. On this basis our chances for tardigrade detection will increase dramatically. And, as already reported previously, a blue tinge old fashioned LED light or LED torch will help enormously - as it has a tendency to render the tardigrade tuns in an intensively blue colour:


Echiniscus sp. "tun" (water bear in its dry state) within the brown region of a dry mosscushion. By means of an old-fashioned blue-tinged LED the stereo microscope (dissecting microscope) is showing the water bear as a kind of intensively blue sapphire. Without this optical trick the tardigrade cuticula would appear greyinsh and much more difficult to discern on the brown background.

© 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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