Maritime tardigrades (V) - the Batillipes adhesive toes
Just think about "Blitzeis" - sudden slippery ice glaze being formed on pathways and streets,
when rain drops are suddenly coming in contact with cold ground. All of us are
in constant danger of slipping under those circumstances, no matter whether we are travelling on foot,
on bicycle or by car.
Do you know who would have no problems? Yes, the Batillipes tardigrade.
It has to cope with huge amounts of water, working destructively on its
constantly wet maritime sand grain world. We have learnt in a previous issue
that Batillipes can easily 'anchor' on glass slides and that we will
not be able to remove it even by a very brute Pasteur pipette water flow.
Perhaps some of our splendid nano engineers should have a glance at Batillipes
in order to learn how to produce non slippery shoes for elderly people?
We are terribly sorry to report that we didn't find much in literature apart
from the apparently wrong internet statement that Batillipes had sucking discs.
Earlier scientists were more cautious stating wisely that it had adhesive discs,
which is a quite different principle, of course.
As there are only few traces of all this in literature we will have to investigate ourselves.
One major problem is that Batillipes is really tiny, its legs are even smaller,
an its toes therefore must be terribly tiny-tiny.
Batillipes sp. tardigrade, leg with six toes,
each equipped with a tiny adhesive disc.
We will be using a more primitive model for study and visualisation.
It contains only those elements which we must assume to be constructive parts of the
Batillipes toe system: a stiff (probably hollow) cylindrical toe stick ending excentrically at the edge of the toe disc
which has the form of a leaf and a central ripple. The 'leaf' appears to be elastic
and thin. This sounds more like an ordinary cleaning cloth, not so much like
a highly sophisticated transportation and anchoring mechanism!
Batillipes toe, schematically.
It becomes apparent why Prof. Ferdinand Richters called 'his' new species
Batillipes (i.e. "shovel foot")
Sucker type elements are not visible in this design.
So we might consider other adhesive mechanisms and we can use
a bigger model in order to check the physical effects, like this:
Simple spring balance which can be used in
order to estimate forces necessary to loosen a plate from a surface
(via Ebay, very cheap)
Demonstration of the adhesion caused by direct contact
with a very thin water film between toe plate and ground surface. With this model
you will get a good feeling for the forces necessary to lift the toes and you will
see that a horizontal, sliding motion is much easier to perform than a vertical lift.
The experimental setup is easily prepared, as you can see
in the images, with a cover glass and a wet slide. Just fix the spring balance
to the red stick and try to lift the cover glass in vertical direction.
You will note that this is difficult to perform, whereas the cover glass can be
better moved in horizontal direction. When there is a thicker water layer the
adhesive forces become weaker.
We can conclude that adhesive forces might be present in a system based
merely on physical contact but that there would be still some danger of
horizontal sliding. We know that the tardigrade can do better in practice.
Of course one might add that 8 legs multiplied by 6
toes makes up for 48 adhesive spots which is definitely more than a single spot.
But there is still a further trick:
In extreme raking light it becomes obvious from its traces that a tardigrade is
using sticky glue when needed. Of course all this must happen within
fractions of sections and an overdose of glue would possibly be detrimental
for the tardigrade as well. Intelligent glue like Spiderman - not fiction but reality.
Already in the 1920s Ernst Marcus suspected glue mechanisms as he noted
that some tardigrades appeared to trail sand grains linked to them with tiny
fibers, similar to spider net fibers. He reported as well that the tardigrades
used the sand grains to clean their body from surplus glue. So the sand grains
are not only forming the maritime tardigrade living room but also serve as
indispensible cleaning media.
© Text, images and video clips by
Martin Mach (firstname.lastname@example.org).
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