Die Embryonalentwicklung der Paradiesschnecke ... - TOBIAS-lib

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an “intermediate” between the already described “sluggish” snails which develop
internal shells after platinum exposure and “normal” control snails. We
called these animals “partly-shelled”, since they developed a partial external
shell, covering the ventral part of the visceral sac but which often do not
extend to the dorsal part.
In order to elucidate the differences in the development of the “partlyshelled”
animals and those with internal shells, we investigated adult “sluggish”
and control individuals as well as “partly-shelled” and normally developing
embryos histologically. As well, the course of development of platinumplus-heat-exposed
embryos was studied by scanning electron microscopy.
Results
Figure 1 shows selected individuals which have developed the different types
of shells that we found in our experiments, ranging from completely “shellless”
or “sluggish”, i.e. snails with fully internal shells (Figure 1A), and
“partly-shelled” individuals with small external shells, covering varying parts
of the visceral sac (Figures 1B-D), to normally shelled animals (Figure 1E).
Fig. 1: Marisa cornuarietis individuals after hatching with different types of shells. Arrows
indicate the mantle edge, “partial” shells are encircled in white; A: “sluggish” snail without
an external mantle and with an internal shell (about 3 weeks old); B, C: snails with “partial”
shells, D: snail with an almost normally developed “partial” shell; E: normally developed
snail from the control; H: head, SH: shell, VS: visceral sac.
The normal embryonic development of Marisa cornuarietis has been thoroughly
described by Demian and Yousif (1973a,b,c,d, 1975).
An analysis
of the embryonic development of platinum-exposed “sluggish” snails can be
found in Marschner et al. (2012). All this work will be used to compare the
development of “partly-shelled” snails with.
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