Die Embryonalentwicklung der Paradiesschnecke ... - TOBIAS-lib

Kapitel 2
Seven-day-old embryos
At the age of 7 days, the embryos from the control almost completely resemble
adult snails in shape (Fig. 6A). The tissue covering the dorsal side of the
visceral sac usually forms the lining of the mantle cavity, whereas the tissue
on its ventral side, the mantle anlage under the shell, covers the visceral
sac. In contrast to this conventional anatomy, Figure 6B shows a sagittal
section of the visceral sac of a Pt-exposed embryo. The distal parts of the
mantle edge and shell gland shown in Figure 6B (Pt-exposed) correspond to
the parts of the mantle edge and shell gland that are located above the head
in controls (Fig. 6A). The proximal part of the shell gland in Pt-exposed
animals (Fig. 6B) is found at exactly the same position right above the foot
as in controls (Fig. 6A).
Fig. 6: M. cornuarietis, 7-day-old embryos, asterisks indicate corresponding structures;
A: control embryo, sagittal section, plane of section indicated by dashed lines in sketch
(left lateral view), HE-staining and B: Pt-exposed embryo, sagittal section through the
visceral sac and foot; detail and plane of section indicated by dashed lines in sketch (left
lateral view), methylene blue staining. cn, ctenidium; f, foot; h, head; ls, larval stomach;
mtc, mantle cavity; mte, mantle edge; oe, oesophagus; op, operculum; sh, shell; shg, shell
gland; vs, visceral sac. [Color figure can be viewed in the online issue, which is available
at wileyonlinelibrary.com.]
Nine-day-old embryos
Figure 7A shows the shell of a 9-day-old control embryo. The soft tissue
is not visible here, because the animal is completely retracted into its shell
in response to the fixation procedure. In Figure 7B, a transverse section
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