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The Big Feast  or  The Feast of the Big Ones (I)

When diving into the micro world we are encountering very different scenarios: e.g. there are complex mixtures of interesting species, like the ones found on the bordering concrete walls of the Munich city river Isar - in fact most of those tardigrades are immigrants coming afloat from a southern mountain area. But there are also much more simple scenarios, like those found within the moss of old roof tiles where we come across red Echiniscus tardigrades and nothing else.

Both scenarios have their advantages and disadvantages. Complex mixtures of many species are providing insight into the complexity of tardigrade populations and we can make use of them in order to present a tardigrade universe to a visitor or a friend. Nevertheless there are problems as well: E.g. we cannot be sure which tardigrade egg has been deposited by which adult tardigrade. As a consequence simple populations can be easier to understand.

This and two upcoming issues of our magazine are focusing on feeding behaviour, in particular on the feeding behaviour of big tardograde species, namely Macrobiotus richtersi. Macrobiotus richtersi is quite abundant and well known to science since more than a decade. So we conclude that the following depiction of "Macrobiotus schultzei" might as well represent an individuum of what we call Macrobiotus richtersi today. Species names have a tendency to appear and to vanish - so we cannot really count on them.

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Fig. 1: Macrobiotus schultzei alias Macrobiotus richtersi. This wonderful drawing is a copy from a publication by [Shipley 1909] published more than 100 years ago. But we think that it is actually going back even further, to works by GREEF (in 1865 or 1866).

Recently, we found an impressive monoculture of Macrobiotus richtersi under an old maple tree, in moss cushions, apparently harvested by blackbirds and woodpeckers.

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Fig. 2: Stem and roots of an old maple tree with lots (though invisible lots) of Macrobiotus richtersi inhabitants.

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Fig. 3: This is by no means the result of our sampling but instead the avid work of blackbirds and woodpeckers searching for food on the maple tree.

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Fig. 4: At first glance, the loose moss cushions don't look like living organisms ...

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Fig. 5: ... but just by adding water the moss color is quickly turning into a vivid green!

Now we can proceed as usual: the tardigrades are transferred to a slide by means of a Pasteur pipette and studied under the microscope. A short glance at fig. 6 might help to understand why Macrobiotus richtersi is commonly considered as one of the less attractive tardigrades - possibly even being partially responsible for the fact that the whole family of tardigrades is sometimes described as "worm-like"! Macrobiotus richtersi has a massive, lengthy body and rather small legs, barely visible below its body. So it cannot be abused for a photomicrography contest. And it goes without saying that the historic drawing in fig. 1 is much superior to our photomicrograph.

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Fig. 6: Macrobiotus richtersi from the thoroughly bruised maple tree. Image width ca. 0.3 mm. Please note that the drawing in fig. 1 is much superior with respect to anatomic detail! And there are no visible eye pigment spots. How on earth are those animals able to spot their food?

In the next two issues of the magazine we will explain why these tardigrades have to be classified as Macrobiotus richtersi and we will discuss their terrible table manners!

Image source

A.E. Shipley: Tardigrada. In: Smith, Geoffrey et al., Crustacea and Arachnids. p. 480. London 1909.

© 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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