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We will have a short look at water bear anatomy in this issue.
Of course, one might wonder how much anatomy in fact will be necessary for a microscope amateur: it is possibly to enjoy microscopic life without any knowledge in anatomy, same as it is possible to enjoy a talk with a friend without being so much interested in the bone structure of this person. And you will agree that only very brute people would cut their dog into pieces just in order to have a look into its interior anatomic details.
So we will try to restrict our studies to those details in anatomy which can be studied at the living water bear without doing any harm to it.
So, what do you perceive in the photography below?

[Echiniscus legs]

Echiniscus water bear, time: 00 sec.
Detail: Hind part of the body
with the fourth pair of legs (1).
As seen from above.
Image width about 100 µm.

Right - this is the backside of a water bear. But let's focus our attention to the legs. A comparison between the left and the right hind leg reveals the presence of a water inhabitant. The water bear is able to align its legs either in streamline shape (left leg) or can form a web-foot with its claws (right leg). Those tools are important in order to move actively through a dense medium. Remember, water is about 1000 times more dense than air. Just have a look at the  Film Gallery II  to get a better understanding how forcefully the water bear shovels its way through the water droplet.

Perhaps you have already noticed a further remarkable detail of the water bear legs in the image above: a fine dentated collar decorates each leg!
Is it just a fashionable decoration, possibly even a weapon or just a tool to get rid of some water troublesome water vegetable sticking to the legs? Do the water bear men appreciate those ornaments? Are those water bear men actually able to see those tiny details? ... you understand, we do not know too much about all this.

Four seconds later (see below): in addition to claw motion the water bear is able to stretch its legs in a telescope manner and is able to retract them until to the level of the dentated collar:

[Echiniscus legs]

Echiniscus water bear, time: 04 sec.
Detail: Hind part of the body
with the fourth pair of legs (2).

Possibly the dentated collar comes into action in this moment. Perhaps it works like a spike tyre and prevents the water bear from sliding off a slippery moss plant surface.
A few seconds later the water bear shows a real muscle, here in the relaxed state (see gray circle):

Echiniscus water bear, time: 08 sec.
Detail: Hind part of the body
with the fourth pair of legs (3).

Would you like to seem some  muscle action  (avi-Animation, 1 MB, takes some time to load)?

So we have completed our first studies in water bear anatomy. In the next issue we will see the feeding equipment of the water bears. Curious? Well, come in again next month.

© 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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