Die Embryonalentwicklung der Paradiesschnecke ... - TOBIAS-lib

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Kapitel 4: No torsion required for streptoneury in the ampullariid snail Marisa cornuarietis 12 Leonie Hannig a , Simon Schwarz a , Heinz-R. Köhler a a Animal Physiological Ecology, Institute of Evolution and Ecology, University of Tübingen, Konrad-Adenauer-Str. 20, D-72072 Tübingen, Germany Abstract The hallmark feature that distinguishes the gastropods from all other molluscs is the horizontal rotation of the visceropallium, the so-called torsion. Torsion is consi<strong>der</strong>ed to be the cause of the anterior position of anus and gills as well as the crossing of the pleurovisceral nerve connectives, a feature that is known as streptoneury. In earlier experiments, we observed that exposure of the caenogastropod Marisa cornuarietis to bivalent platinum ions during embryogenesis does not only prevent the formation of an external mantle and shell but also inhibits the horizontal rotation of the visceral sac. In Platinum 2+ -exposed embryos, immunohistochemical labeling with anti-serotonin antibodies showed the embryonic development of the nervous system to deviate from the typical arrangement. Nevertheless, histological investigations and subsequent 3D modelling of the arrangement of the nervous system in adults revealed Platinum 2+ -exposed individuals to exhibit a streptoneurous arrangement of their nervous system even though the horizontal rotation of the visceropallium had been experimentally suppressed. 12 Unveröffentlichtes Manuskript 108
Kapitel 4 Herewith, we were able to show that torsion is not a prerequisite for the development of a streptoneurous arrangement of the nervous system in M. cornuarietis. Introduction Torsion in gastropods is a difficult topic although the theory behind it is simple enough. It is defined as an anti-clockwise rotation of the visceral sac and mantle by 180 ◦ relative to head and foot, and takes place during the ontogeny of all snails and slugs (e.g. Bieler, 1992) as the so-called “ontogenetic torsion”. It is the common morphological feature of gastropods (e.g. Garstang, 1928) and supposed to be responsible for several anatomical conditions that can be found in snails, some of which are the anterior position of anus and mantle cavity as well as the crossing of the pleurovisceral nerve connectives known as streptoneury or chiastoneury (Bieler, 1992; Haszprunar, 1988; Page, 2006; Raven, 1966). According to the theory, extant gastropods are descendants of an untorted so-called “hypothetical primitive mollusc” (Yonge, 1947) in which the mantle cavity with gills and anus was positioned posteriorly (reviewed in Page, 2006). Supposedly, this untorted “hypothetical primitive mollusc” exhibited a rotation of the visceropallium by about 180 ◦ , leading to a twisting of the internal organs, including the nervous system and the intestine and thus became a torted gastropod (Raven, 1966). We recently reported that exposure to bivalent platinum ions during embryogenesis stops the growth of mantle edge and shell gland in Marisa cornuarietis embryos (Marschner et al., 2012; 2013). As a result, these embryos do not only exhibit no exterior shell but do also not show a horizontal rotation of the visceral sac by 180 ◦ , as can be seen in “normally” developing Marisa embryos (Marschner et al., 2012; 2013). However, the ensuing snails possess an anterior anus which is typical for the torted condition of gastropods while, at the same time, the gills can be found posteriorly on the visceral sac. These individuals both display characteristics typical for torted gastropods (anterior anus) and characteristics that are supposed to apply to the untorted hypothetical ancient mollusc. Another anatomical condition that is, by theory, supposedly 109
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Die Embryonalentwicklung der Paradi
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Inhaltsverzeichnis Zusammenfassung
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Zusammenfassung Hintergrund und Zie
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Hintergrund und Zielsetzung der Arb
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Hintergrund und Zielsetzung der Arb
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Material und Methoden Marisa cornua
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Material und Methoden Hälterung Di
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Material und Methoden lindividuen a
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Ergebnisse lung von Marisa cornuari
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Ergebnisse Kapitel 3: Marschner, L.
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Ergebnisse Wachstum des Columellamu
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Diskussion Naticidae) entwickelt si
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Diskussion engrailed und dpp-BMP2/4
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Diskussion Abb. 4: Vergleich der mi
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Schlussfolgerung perimentell zu unt
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Literatur Engelhardt, W. (2008). Wa
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Literatur Ponder, W. F. und Lindber
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Kapitel 1:Turning snails into slugs
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Kapitel 1 dae). Their ontogeny also
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Kapitel 1 Exposure experiments Test
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Kapitel 1 et al. (2001, 2003) or wi
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Kapitel 1 for 4 × 5 min with PTw (
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Kapitel 1 treatment 29.9 ± 32.78%
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Kapitel 1 Fig. 2 3 : Images of M. c
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Kapitel 1 Fig. 4 4 : Location of th
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Kapitel 1 internal solid circular s
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Kapitel 1 ietis as it was shown for
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Kapitel 1 Burnett, L.E., Woodson, P
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Kapitel 1 Page, L.R., 2002. Ontogen
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Kapitel 2: Arresting mantle formati
Page 61 and 62: Kapitel 2 tropods (Crofts, 1937, su
Page 63 and 64: Kapitel 2 Scanning electron microsc
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Page 67 and 68: Kapitel 2 Fig. 2: M. cornuarietis,
Page 69 and 70: Kapitel 2 and the visceral sac rema
Page 71 and 72: Kapitel 2 Seven-day-old embryos At
Page 73 and 74: Kapitel 2 Fig. 7: M. cornuarietis,
Page 75 and 76: Kapitel 2 gation of internal shells
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Page 79 and 80: Kapitel 2 side of the visceral sac
Page 81 and 82: Kapitel 2 cornuarietis (Mesogastrop
Page 83 and 84: Kapitel 3: External and internal sh
Page 85 and 86: Kapitel 3 during embryonic developm
Page 87 and 88: Kapitel 3 Differential growth of ma
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Page 91 and 92: Kapitel 3 Fig. 4 9 : SEM-images of
Page 93 and 94: Kapitel 3 Fig. 6: Histological sect
Page 95 and 96: Kapitel 3 side of the visceral sac
Page 97 and 98: Kapitel 3 different mechanism that
Page 99 and 100: Kapitel 3 whether the inhibition of
Page 101 and 102: Kapitel 3 tinuum of gradual morphol
Page 103 and 104: Kapitel 3 served one. However, ther
Page 105 and 106: Kapitel 3 hand and modified in Inks
Page 107 and 108: Kapitel 3 ticipated in designing th
Page 109 and 110: Kapitel 3 Demian, E. S. and Yousif,
Page 111: Kapitel 3 Page, L. R. (2003). Gastr
Page 115 and 116: Kapitel 4 Histology and 3D reconstr
Page 117 and 118: Kapitel 4 72 or 96 hours at 6 ◦ C
Page 119 and 120: Kapitel 4 tioned on the ventral sid
Page 121 and 122: Kapitel 4 P2 does not curve backwar
Page 123 and 124: Kapitel 4 which this nerve is attac
Page 125 and 126: Kapitel 4 Fig. 5 13 : 3D reconstruc
Page 127 and 128: Kapitel 4 system in which the right
Page 129 and 130: Kapitel 4 ready present during tors
Page 131 and 132: Kapitel 4 Haydon, P. G., McCobb, D.
Page 133 and 134: Kapitel 5: Quantifikation der Hsp70
Page 135 and 136: Kapitel 5 Die Gesamtproteinmenge wu
Page 137 and 138: Kapitel 5 steigt mit steigendem pro
Page 139 and 140: Kapitel 5 Piano, A., Valbonesi, P.,
Page 141 and 142: Publikationsliste • Marschner, L.
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