A tardigrade petri dish misadventure

At the moment your are reading issue #199 (one hundred and ninety-nine). 15 years of monthly tardigrade news - isn't that way too much? You see, we have already gone through most of the topics one might think of: practical hints for tardigrade microscopy, literature recommendations, the human philosophy behind the tiny life, tardigrade anatomy, experimental carotinoid evidence in the tardigrade dry state, egg developement, portraits of unusual species, the marine tardigrades etc.

On the other hand we are encountering new tardigrade situations from time to time when looking through the microscope. So, why not make use of them?

Only with extreme technical restrictions it is possible to take photos of tardigrades under perfectly natural conditions. Well, just look around in the internet: who is actually photographing microscopic critters in their true enviroment? The most typical tardigrades are living within a jungle of moss plants, so their activities will be hidden anyway when looking on a moss cushion in top view. The usual petri dish is far away from a natural situation and also the nano marine aquarium with its 200 cm³ of sea water (our so-called "Rocharium") can't conceal its tragical similarity to a sand grain in relation to the Sahara desert.

But without the use of petri dishes, pasteur pipettes, microscopy slides and cover glasses we would not be able to understand the tardigrades at all. Nevertheless one should keep in mind that some tools might turn out as the wrong tools. Once you will have seen how a Batillipes sp. tardigrade is clinging to a glass slide you will end up with the conclusion that glass substrates might cause problems in some cases. As a consequence one should consider to use plastics for this particular scenario instead.

But with respect to terrestrial tardigrades we recently learnt that plastic materials might be dangerous as well. Just have a look at the following video showing a Macrobiotus tardigrade which is clinging to the bottom of a polystyrene coin container micro aquarium:

video html by EasyHtml5Video.com v3.5

Obviously the video is showing that a tardigrade might make contact with the plastics surface in a most tragical manner. It sticks to the petri dish surface in a similar way as the car owner who is accidentally making lip contact with a frosted metal door pull.

So, please try to avoid those nasty tardigrade traps. Tragedies might also happen unnoticed, in times when you are not looking through your microscope, just when keeping tardigrades temporarily in containers made up of inappropriate material. As we have learnt from other animal species, many of them have difficulties to deal with perfectly transparent, man-made materials like glass and transparent plastics. Just think about those desperate wasps trying to find their way around glass panes of open windows, fishes jumping out of aquaria, birds flying against glass etc.

Ceterum censeo: try to avoid all those primitive articles in the internet which are reducing the tardigrades to tiny supermen and superwomen. And do not end up with primitive "percentage alive / percentage killed" experiments. Tardigrades are closer to you than you might think at first glance. They can feel pain and desperation. You disagree? Well, are you able to prove your opinion? Tardigrades might even show suicidal tendencies like the ones pointed out by Ernst Marcus: he describes how Batillipes tardigrades were crawling across the waterline of a watch glass thus ending up in tragic desiccation and death.

Literature

Ernst Marcus: Zur Anatomie und Ökologie mariner Tardigraden. Zoologische Jahrbücher, Abteilung für Systematik, Ökologie und Geographie der Tiere  53 (1927) 487-558.
[The remakrs referring to suicidal tendencies of Batillipes can be found on page 522]

© 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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