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In the Water Bear web base issue #17 we had learnt how to photograph those too-thick water bear eggs by means of a  computer trick  :

[tardigrade egg]

Tardigrade egg,
maximum diameter ca. 85 µm.

You might ask now who the parents are and what the exact name of their species might be. Here is the borderline to professional science. We should be aware that an exact water bear species determination normally is beyond the scope of us amateurs. Nevertheless we will discuss some general ideas of species determination here  .
The egg on the photograph above is being shown in some of the more modern water bear monographs, e.g. those by Walter Maucci and Ian M. Kinchin (see literature). "Our" egg has an identical shape and an identical surface. Polygon areole rows are grouped around the tips (chorions) and there is a characteristical pair grouping of those polygons. Maucci mentions an overall diameter of 80 to 100 µm which fits our egg, too. Also the vertical lining of the protrusions can be found in Maucci's drawing. Maucci and Kinchin state that this type of egg is an egg by  Macrobiotus areolatus  . Perhaps we should better stay modest and state that there is a certain probability that our egg is an   Macrobiotus areolatus  egg.
The grown-up animals close to the egg looked as shown in the photomicrograph below. Possibly those were the parents ... but you never know when the egg is just lying there.

[Macrobiotus sp.]

Eutardigrade, possibly
Macrobiotus areolatus.
Image width ca. 100 µm.

In any case we can be rather sure that the grown-up animals belong to the genus Macrobiotus.   Number and form of the macroplacoids within the oval pharyngeal bulb fit to the descriptions of   Macrobiotus areolatus   in literature but one might determine those grown-up water bears as   Macrobiotus richtersi  as well.
So it is more safe and certainly more fun just to enjoy those marvels of nature in a less intellectual way and   n o t   to kill and preserve them just for species determination:

[Macrobiotus areolatus ?]

Eutardigrade  water bear,
possibly Macrobiotus areolatus. Dark field illumination.

There are cases where the eggs are not very helpful in species determination. E.g. the egg shown below gives only the rough direction for genus determination. We will discuss it in the next issue. In any case you will notice that the water bear within this egg is already fully devolopped. You will perceive the buccal tube, the two stylets and even the pores of the skin within the eggshell. Everything is packed tightly within a very restricted volume.

[tardigrade egg]

Water bear egg,
by a heterotardigrade,
diameter ca. 40 µm.

BTW: Do not miss the video clip "The Water Bear: a living sweet?" within the  MICSCAPE website  !


SEM photomicrographs of  Macrobiotus areolatus  eggs are shown within:
Ian M. Kinchin: The Biology of Tardigrades. p. 63. London 1994.
Walter Maucci: Tardigrada (volume XXIV of the series Fauna d'Italia). p. 19. Bologna 1986.

© Text, images, and video clips by  Martin Mach  (webmaster@baertierchen.de).
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.

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