"A telescope can resolve a faint spot
down to crisp, individual stars - but this is a rather weak pleasure when
compared to the delight of a microsocope resolving everything around us
into this fabulous world of cells ..." |
Gustav Jäger (1867) |
... the fabulous world of cells - some among you will be reminded of their childhood and in particular of those biology lessons where an onion (allium cepa) was brutally torn into pieces and investigated under a microscope in order to demonstrate the existence of ubiquituous cell structures which are common to all so-called higher organisms: |
Original, temporary preparation of
an onion shell, prepared for a school lesson in biology.
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The discovery of the cell as an elementary biological unit is commonly
attributed to Robert Hooke (1635-1703). In his famous 'Micrographia' (1667)
Hooke described typical vegetable cells, using cork cells as an example. |
Stomach region of an eutardigrade
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Detail from the image above,
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In other cases we are often not able to distinguish those cell structures. We do notice marvelous, fine details like legs with delicate claws, cute noses and much more but there might be a complete lack of any kind of cell characteristics: |
Echiniscus tardigrade, dark field illumination. The complex and optically dense structure doesn't reveal any cell structures. |
Well, what should we do now? Should we stop all tardigrade cell investigations
and return ruefully to the onion shells? |
Exuvium (group of deposited eggs) by an Echiniscus tardigrade. The first cell divisions have happenend simultaneously ending up in two cells of the same size each. |
Single echiniscus egg, after the second cell division, with four cells. |
Single echiniscus egg, after the third cell division, with eight cells. |
The cell divisions continue, 16, 32, 64 and 128 cell stages follow, possibly not always exactly simultaneously, until it is no more possible to tell the exact number of cells. This stage is called a "Morula" which is the Latin term for 'mulberry'. |
Single egg of an Echiniscus tardigrade, multi cell stage 'Morula'. |
Once you will have seen one of those multi-cell stages you will be able to recognize it in other situations as well: |
Eggs of an Echiniscus tardigrade, in multi-cell stage. |
Of course, at some moment the development of cells must turn into differentiation. Otherwise we would end up with a stupid snowball of identical cells and not with a fully developped tardigrade. But this will be the subject of a latter issue of our magazine. In any case this miraculous process seems to happen in a perfect manner billions of times per year, without asking the advice of one of our constantly wise business consultants - strange, isn't it? |
Literature
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© Text, images and video clips by
Martin Mach (webmaster@baertierchen.de).
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