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
Micscape magazine with a total view
of a running and sniffing water bear accentuated by a little bit of human
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.
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.
(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
So you have one more similarity between waterbear and man.
© 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.