Die Embryonalentwicklung der Paradiesschnecke ... - TOBIAS-lib

Kapitel 2
rather be considered a “conserved stage of anatomical organization rather
than a conserved process of 180 ◦ rotation between two body division” (Page,
2003). In another study (Page, 2006b), she noticed a corotation of a mantle
cell connected with the development of the nervous system together with the
normally rotating cephalopodium. So, there is evidence that not all displacements
of organs or tissues that are supposed to be triggered by torsion are
directly caused by a horizontal rotation by 180 ◦ of the visceropallium relative
to the cephalopodium but that they rather have, at least partly, been falsely
attributed to the easily recognizable and simultaneously occurring event.
We regard our Marisa system a model to disrupt the torsion-like horizontal
rotation of the visceral sac and to separate different, independent developmental
modules which, in their entirety, lead to a post-torsional arrangement
of organs commonly regarded to be typical for prosobranch snails.
Acknowledgments
The authors are grateful to Oliver Betz (Evolutionary Biology of Invertebrates,
University of Tübingen) for the use of his SEM-equipment and to
Karl-Heinz Hellmer for technical help. Furthermore, they thank Irene Gust
and Matthias Hannig for their help with image editing.
Literature cited
Coeurdassier M, De Vaufleury A, Badot P-M. 2003. Bioconcentration of cadmium and toxic effects
on life-history traits of pond snails (Lymnaea palustris and Lymnaea stagnalis) in laboratory
bioassays. Arch Environ Contam Toxicol 45:102–109.
Crofts DR. 1937. The development of Haliotis tuberculata, with special reference to organogenesis
during torsion. Philos Trans R Soc Lond Ser B: Biol Sci 228:219–268.
Crofts DR. 1955. Muscle morphogenesis in primitive gastropods and its relation to torsion.
Proc Zool Soc Lond 125:711–750.
Demian ES, Yousif F. 1973a. Embryonic development and organogenesis in the snail Marisa
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