In this issue we will have a look at the in-built feeding equipment used by the waterbears. The species under consideration is  Milnesium tardigradum , a cosmopolitan tardigrade which can be recognized easily.

Waterbear Milnesium tardigradum:
looking for some food ...

Please note the characteristic "Milnesium claw".

This video clip doesn't need so many comments. It goes without saying that somebody is sniffing there, trying to explore (or devour) the rest of the world. When still in doubt you might have a look at our parallel presentation in the   Micscape magazine  with a total view of a running and sniffing water bear accentuated by a little bit of human musical interpretation.

The small lobes around the mouth are called  oral papillae . There are two further papillae on both cheeks called lateral papillae . Tardigrade scientists have created a new term for this complex system of whiskers and further (invisible) chemo-sensors: they call it a circum-oral sensory area . Of course it is extremely difficult to tell what kind of sensory information actually is aquired there as we cannot ask the waterbears.

Nevertheless one early German author, Ernst Marcus, concluded that the tardigrades "must have an ample sensory world".

The photograph below presents the characteristic pear-shaped pharyngeal bulb of Milnesium tardigradum the function of which might be compared to a micro nut-cracker in combination with a high power micro vacuum-cleaner engine.

Milnesium tardigradum,
anterior part of the body

The pharyngeal bulb is packed with strong muscles (horizontal structure within the bulb). Buccal tube, pharyngeal bulb and stylets form the so-called  pharyngeal apparatus  which can be easily perceived under the microscope and is among the most important criteria to distinguish between the different species.
The midgut (in the upper left edge of the image) is linked to the pharyngeal bulb by a narrow elastic tube called oesophagus.

The video below shows the movement of the stylets on both sides of the buccal tube. The stylet tips can be retracted into sheaths. When the water bear wants plans to pierce a plant the stylets are pushed forwards out through the sheath slits and furtheron through the mouth opening.
The stylet bases are fixed to the elastic stylet holders which guide the stylet movement. The mouth opening can be closed by very minute skin lobes which serve to open and close the tube as needed. On the right side of the image you can see the black pigment of the right eye.

In a later issue we will discuss the menu card of the water bears in detail, but as a preliminary information we would like to indicate that most of the water bear food is strictly vegetarian. Only a few species, among those also "Milnesium tardigradum", are said to be carnivorous and in fact you will sometimes observe those animals eating tiny rotifers.

So you have one more similarity between waterbear and man.

© 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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