Interstitial live, within the sand in the oceans (I)
We have already learnt that the waterbear Batillipes mirus lives
in the so-called interstitial water volume between sand grains. This is by no means
a cosy habitat. In order to survive the tardigrade must be able to crawl
on the sand grain surfaces and to move through between the sand grains.
It can do this because it is so extremely small. Furthermore the tardigrades
must be able to cope with dead end routes between the sand grains.
All animals living within the sand grain system are specialists and they have
developed different strategies to survive. E.g. the worm shown below has a kind
of route "testing head" and a hind part safeguarding the previous position:
a part of it remains in place and another part is checking the situation
in front. Furthermore its body is extremely flexible and elastic:
The Batillipes tardigrades have a different strategy in order
to cope with difficult pathways. In contrast to their terrestrial brothers and sisters
they can move backwards. We hve seen this ability in a
previous issue .
Funny enough Batillipes has eight legs and 48 toes all of which - at least in theory -
might be quenched by one of those many huge sand grains. But everyday
experience has taught us that those small animals seemingly encounter
relatively softer physics - surviving deep falls and developing tremendous power in movement
and when working against obstacles.
Though there are many, many sand grains within the ocean and though they might
be even moving from time to time, the tardigrade feels safe and healthy
between them and as a rule will not be quenched.
In contrast to the worm which is passing trough the holes between the sand grains,
avoiding the contact with the sand grain surfaces, the tardigrade is seeking
close contact with the sand grains - it appears to be sand grain loving.
According to tardiologist Ernst Marcus maritime tardigrades without
sand grain might become so desperate that they will commit suicide (but
don't become nervous, actually we never did come across this behaviour)!
But, in any case the close clinging to the sand grain is obvious:
Batillipes sitting on sand grain.
There is no space between belly and substrate.
In particular when seen from top Batillipes looks
like a very inconspicuous animal, it is a kind of microscopic, faint shadow.
Only the stomach content does interfere with the camouflage - so hungry tardigrades
will remain invisible.
Batillipes mirus on a big
sand grain. In the center of the image you will see the nice glass housing
of a maritime diatom living on the sand grain as well.
Batillipes mirus on sand grain
Lateral lobes at the sides of the Batillipes body make
contact with the sand grain like a coat. As a consequence the bruteness of
waves will not be able to pass between tardigrade and sand grain surface area.
The lobes can be best seen without the sand grain:
Batillipes - stabilising lateral lobes
What are the advantages for tardigrades living within
this miraculous "apartment sand"? We will try to explain in our
next issue. See you in December!
© Text, images and video clips by
Martin Mach (email@example.com).
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