Last egg-day and first life-day of Milnesium tardigradum The tardigrade Milnesium tardigradum can be found almost everywhere on earth and can be easily kept in a micro aquarium for a few weeks. Last December we witnessed how Milnesium babies hatched within their cuticula shelter and made their way out into freedom. The following microphotographs show the develoment of an artifically isolated Milnesium egg. The first four image block shows the egg at the day of hatching, the second the same individuum at its first day of life outside the eggshell. |
Milnesium, egg. | |
Fig. 1 |
Fig. 2 |
Fig. 3 |
Fig. 4 |
When seen from aside the Milnesium babies lie rolled up within their eggs like anxious woodlouses (Fig. 1). When focussing more deeply into the egg (Fig. 2) we will notice the broad mouth tube indicating the carnivore behaviour and the pear shaped pharynx with its radial muscle pattern. Even the normally straight line from mouth tube to pharynx is slightly bent in order to fit tightly into the eggshell. The claws are already fully developped as well but not easily visible in the photograph (Fig. 3). In Fig. 4 two black eye-spots seem to make eye-contact with us. The diameter of a Milnesium egg is about 80 µm. |
Milnesium, 1st day | |
Fig. 5 |
Fig. 6 |
Fig. 7 |
Fig. 8 |
After hatching we will become aware
ot the fact that the cuticula is drastically oversized thus allowing the
baby to grow considerably before a moulting phase will become necessary (Fig. 5).
Otherwise it might have not enough fat resources and starve during
the first moultuing phase. The claws at the last pair of legs are huge
in relation to the overall body size (Abb. 6), the spherical floating
storage cells in the body fluid still very small. A view of the mouth opening
reveals the hexagonal array of mouth papillae (Fig. 7) and it becomes obvious
that they are vary different in size, with Fig. 7 showing only the three upper
(dorsal) papillae. |
© Text, images and video clips by
Martin Mach (webmaster@baertierchen.de).
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