Die Embryonalentwicklung der Paradiesschnecke ... - TOBIAS-lib

Kapitel 4
ready present during torsion, may preserve the streptoneurous structure for
the adult central nervous system that develops later (Dickinson et al., 2000).
In our experiments with M. cornuarietis, the youngest embryos we investigated
were four days old, but we did not observe similar staining patterns
when we investigated FMRFamide. Whether this is due to the advanced
age of the embryos compared to the stages in which such early neurons have
been observed, however, is unclear: it is also possible that such early nervous
structures are simply not present in Marisa.
Still, many unanswered questions remain regarding the development of the
nervous system in experimentally untorted M. cornuarietis. However, our
investigations have shown that a horizontal rotation of the visceral sac, the
hallmark feature for ontogenetic torsion, is not necessary for a streptoneurous
arrangement of the central nervous system to develop in adults. This shows,
along with many other studies that have been conducted, that there is a
need for alternative explanations for streptoneury, e.g. growth factors or
other morphogens, that are expressed independently of the movements of
other organs in ontogeny and that guide the connectives to their respective
destinations.
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