Indirect tardigrade microscopy (the study of the cuticulae)
The tardgrade cuticulae, kind of transparent skins, are left back by the
water bears after a moulting process. As we do really like the tardigrades
we want to point out once more that the microscopic study of a cuticula
doesn't cause any harm to the tardigrade and still can be performed at very low working distance
and extremely high magnification, e.g. by means of an oil immersion objective.
But one obvious obstacle in this endeavour is to find a cuticula at all.
Sometimes you will notice them when slighty stirring the water in the petri dish,
as they behave in a slightly floating manner, like any object of low specific
density. An other possibility is to look out for individuums in the moulting
process - typically with a slightly contracted intestine and temporarily
lying still. After some time (up to two days) they will finally climb out ouf their
cuticula which can then be recovered by means of a pasteur pipette.
The photomicrograph below is illustrating a typical early stage of the moulting process
of a marine tardigrade. It becomes clear that the legs of Halechiniscus are rather long,
stretching out like telescopes. This mechanism comes in handy when the tardigrade
is still standing on its home sand grain and stretching out for the next (target)
Halechiniscus sp. tardigrade
from Craotia, in the starting phase of the moulting process.
Image width ca. 0.3 mm.
In the next photograph the head is already partially detached
from the outer cuticula. As a consequence the overall transparency is enhanced
and we are able to see further detail like a nerve line extending to
the sensory protrusions in the head region.
Halechiniscus sp. tardigrade,
Finally the tardigrade will succeed and hopefully
get rid ot its loose outer 'skin'. It should be kept in mind that the moulting process
is highly risky for the tardigrade as it cannot feed in this time and as it is restricted in its
movements and reactions towards the outer world.
One advantage of the moulting process is that the tardigrade is getting rid of all
marine residues and tiny parasitic organisms clinging to its skin.
Cuticula of a Halechiniscus sp.
tardigrade from Croatia, left back after moulting, with lots of incrustations. Image width ca. 0.3 mm.
Our microscopic advantage is that further anatomic detail becomes visible
as the empty cuticula is an ideal microscopic object: flat like a pancake and highly
transparent. So wie are e.g. able to recognize some kind of 'navel' (which is - of course - not a navel,
just something different ...).
© Text, images and video clips by
Martin Mach (firstname.lastname@example.org).
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