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
"Sure, they're cute, but this
might be a bit much:
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
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).
Typical terrestrial eutardigrade.
Body length ca. 400 µm.
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
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.
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!
Eutardigrade Ramazzottius oberhaeuseri
leaving its old skin.
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 (firstname.lastname@example.org).
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.