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Our website access statistics show that there has been a constant increase in page hits (i.e. page clicks) over the years. At present we do have about 30,000 page hits per month. This is, of course, nothing when compared to a weather forecast website or an erotic site. But it is quite competitive for an internet domain dealing with a very special kind of microscopic beings only. So, once again, welcome to you all as your are definitely members of a rare but persistent minority group, possibly even an endangered species variant of homo sapiens ;-)

From time to time there are mysterious peaks in our user statistics, e.g. the one caused by a discussion thread in the U.S. website "www.metafilter.com" from which we want to quote a funny statement concerning the emotional relations between tardigrades and humans:

"Sure, they're cute, but  this  might be a bit much:
« when I have children, I'll definitely be calling them 'moss bears' » "

But now we will return to the moulting of tardigrades. In the last issue of the Water Bear web base we had seen an eutardigrade striving in order to get rid of its old skin.

But you will rarely come across pictures of moulting heterotardigrades in the scientific literature.

For those who have joined us recently we should perhaps explain a little bit what we mean by terms like "heterotardigrades" and "eutardigrades": here we call heterotardigrades those often red to orange tardigrades which have armour plates and appendices with a hair-like or thorn-like appearance whereas eutardigrades are "naked", normally have no appendices and no intense colour (whitish in incident light, transparent in transmitted light, with some brown or yellow or rose tinge at most).

[ eutardigrade ]

Typical terrestrial eutardigrade.
Body length ca. 400 µm.

[ heterotardigrade ]

Typical terrestrial heterotardigrade. The armour plates are present here but visible only when the microscope is exactly focusing on them.
Body length ca. 300 µm.

The moulting of an eutardigrade can be easily recognized by its erratic movements. The cuticula remains fully transparent throughout the process, similar to those modern transparent foils for flower bouquets.
In contrary the moulting of heterotardigrades is rather inconspicuous. The animals remain still and it is very difficult to visually follow the moulting. It is a real challenge for micrometer screw artists and ingenious illuminators.

[ Echiniscus tardigrade during moulting ]

Heterotardigrade during moulting.
At a first glance one might think that the animal is dead, as it looks so much different from normal. The legs are retracted, sometimes (in the beginning of the moulting process) the cuticula might appear cloudy. But during the process of moulting it turns transparent again and sometimes minor movements of the heterotardigrade are perceivable.

The moulting of heterotardigrades is a difficult scenario for photomicrography as the animals are optically dense (opaque). Also our CCD has become a little bit angry and has produced some noise which doesn't show up here due to the modest image size.

[ Tardigrade (tardigrada) during moulting ]

Heterotardigrade during moulting. Ventral view. The contracted shape ot the "newly born" animal and its intestine within the body are clearly visible.

And, no matter whether eutardigrade or heterotardigrade, after many hours the animals leave their old skin. Some of them deposit their eggs in the cuticula during the last stage of moulting.
By this the old, seemingly useless cuticula is in fact re-used as a shelter for the eggs. This is true recycling, ideal biological packaging and shelter at the same time. A true Tupper® type miracle!

[ Moulting, final stage ]

Eutardigrade  Ramazzottius oberhaeuseri  leaving its old skin.

[ Heterotardigrade(Echiniscus) ]

Heterotardigrade (genus echiniscus) eggs in otherwise empty cuticula.
The eggs have been deposited by the female during the moulting phase. Incident light. Some borderlines of the cuticula armour plates are visible.

© 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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