Die Embryonalentwicklung der Paradiesschnecke ... - TOBIAS-lib

Kapitel 2
called “mantle anlage”.
One-day-old embryos
Figure 1A shows an embryo from the water control in the gastrula stage. In
1-day-old embryos, there is no visible difference between Pt-exposed embryos
and the control.
Fig. 1: M. cornuarietis, 1- and 2-day-old embryos; A: control embryo in gastrula stage; B:
Pt-exposed embryo in Stage IV, left lateral view. f, foot; pt, prototroch; shgr, rudimentary
shell gland; vs, visceral sac.
Two-day-old embryos
Figure 1B shows a 2-day-old embryo from the platinum exposure group. It
matches the description given by Demian and Yousif (1973a) for embryos at
about 48 h after oviposition (Stage IV). The foot rudiment and the developing
visceral sac are clearly distinguishable. The rudimentary shell gland forms
a depression on the visceral sac. The prototroch marks the region where
the head will develop. Up to this timepoint, the embryos from the platinum
exposure do not differ from those from the water control (not shown).
Three-day-old embryos
After 3 days of development, the control embryo in Figure 2A matches what
Demian and Yousif (1973a) named Stage VII: head, foot, and visceral sac
can clearly be distinguished. The foot has elongated, and the visceral sac
61