Wastebox mysteries

Do you know what a red ladybug, a red lobster and a red Echiniscus water bear might have in common?

Yes, right, huge quantities of carotinoids in their metabolism. Those strong orange and red hues are said to be caused by the presence of carotinoids.

Montage: Echiniscus tardigrade in various states of movement. Already Ernst Marcus (1929) assumed that those orange substances within the body cavity of Echiniscus are actually carotinoids. Dark field illumination. Image width ca. 1.5 mm.

How could we make plausible that carotinoids are in fact part of the water bear metabolism - without doing harm to the tardigrades, without formaldehyde and other tedious tools which are generally considered as utmost scientific helpers? No problem, as the Echiniscus tardigrades will help us: as already explained a few years ago in a  previous issue  the tardigrades dispose of their stomach/intestine content each time when they undergo a moulting process. They just put a transparent container in front of the door - you just have to pick it up!

Don't worry, as those tardigrades are vegetarians you will not run into health risks or strong odours. If you are lucky you will find one of those bags just when screening soaked moss residues by means of the dissection microscopes at low magnification (30x). They look like pear shaped, green balloons.

Stomach/intestine contents as disposed by an Echiniscus tardigrade during moulting. Total view. Incident light. Image width ca. 0.15 mm.

Once you will have found one of them you will be able to transfer it by pipette to a regular slide for examination under the desktop microscope.

Stomach/intestine contents as disposed by an Echiniscus tardigrade during moulting. Total view. Transmitted light. Image wdth ca. 0.15 mm.

In contrast to the bigger carnivore tardigrades (in particular Milnesium tardigradum ) the vegetarian Echiniscus tardigrades have a slim mouth tube, only suited for some kind of juice transport, normally moss cell juice. As a consequence we do not find remains of potential victims in their stomachs. Also at stronger magnification we will come to the conclusion that the stomach/intestine contents appears to be made up exclusively of very fine, probably liquid or partially solidified material. Some inner structures can be perceived, mostly speroid, orange and olive.

Stomach/intestine content disposed by an Echiniscus tardigrade after moulting. Neat, transparent container. Image width ca. 0.03 mm.

Same situation. Detail. Transmitted light. Image width ca. 0.03 mm.

The contours of those orange regions are strongly variable over time as you will be able to see on the basis of the following picture series taken in one minute intervals:

Same situation. Detail. Transmitted light. Image width ca. 0.03 mm.

Same situation. Detail. Transmitted light. Image width ca. 0.03 mm.

Same situation. Detail. Transmitted light. Image width ca. 0.02 mm.

In this case we will proceed on a classical scientific pathway (knowledge increase by means of total object destruction!) and simply crush the neatly disposed transparent container. It becomes apparent that the contents are liquid but do not mix homogeneously with the surrounding water. As the carotinoids have been proven to be present within the Echiniscus body we assume that we have encountered carotinoids in this case as well.

Same situation - crushed. Transmitted light. Image width ca. 0.02 mm.

Why do the tardgrades dispose of this precious, potential nutrition substance? A possible explanation might be that the carotinoids are used for egg yolk production only - thus becoming useless at the moment when moulting and egg deposition are finished. In case you should have further information or a different opinion on this topic please do not hesitate to contact us via email!

Literature

Ernst Marcus: Tardigrada. p. 21. Leipzig 1929.

© 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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