Mechanisms of Determination in the Development of Gastropods

Raven, Chr. P.

doi:10.1016/b978-1-4831-9950-4.50004-7

Cited by 8 publications

References 29 publications

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Regulative development in the pulmonate gastropod, Lymnaea palustris, as determined by blastomere deletion experiments

1973

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To determine the regulative ability of Lymnaea eggs one or more cells were deleted by puncturing or shaking eggs at the 2-, 4-, 8-and 16-cell stages. Normal snails developed from: oneltwo, three/four, and two/four embryos; from 8-cell embryos in which one, two, or three cells of the first quartet of micromeres or one or two macromeres were deleted; and from 16-cell stage embryos in which one cell of the second quartet of micromeres or one macromere was deleted. Only one/two embryos that cleaved as though they were whole eggs up to the 24-cell stage developed normally. Normal develop ment of other partial embryos was associated with partial cleavage. Developmental abnormalities of partial embryos included death in the cleavage period; arrested gastrulae; trochophores, or veligers; and abnormal snails with head malformations, everted stomodea, or conical shells.Comparing the results with deletion experiments in other molluscs and with deductions from descriptive studies on the Lymnaea egg, we propose that the regulative ability of partial embryos depends on the rearrangement of cells relative to the D macromere before inductive activities begin at or after the 24-cell stage.

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Regulative development in the pulmonate gastropod, Lymnaea palustris, as determined by blastomere deletion experiments

1973

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Die Auspr�gung von Polarit�t und Bilateralsymmetrie in den Oocyten vonGryllus domesticus L.

Netzel

1968

W. Roux' Archiv f. Entwicklungsmechanik

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1. The origin of polarity and bilateral symmetry of oocytes inGryllus domesticus L. has been studied. 2. The histology of the ovary and the process of oogenesis are described. 3. The germinal vesicle shifts into the posterior half of the oocyte, when these cells are 60 to 100 μm in length, thus indicating for the first time oocytic anteroposterior polarity. 4. Bilateral symmetry first appears, when the follicle reaches a length of 450 to 550 μm. This change from radial to bilateral symmetry is the result of the germinal vesicle leaving its position in the long axis of the cell and moving perpendicularly to this axis towards the follicular epithelium. 5. In follicles 60 to 100 μm in length the nucleolus comes to lie, under the influence of gravity, in the geopetal quarter of the germinal vesicle, and remains there. 6. No correlation can be found between geopetal position of the nucleolus and bilateral symmetry of the oocyte. 7. Oogenesis and the establishment of axes in the oocytes are not affected by centrifuging adults and last instars. 8. When the oocyte nucleus touches the follicular epithelium, changes occur in the structure and function of some epithelial cells. Those close to the germinal vesicle, with flattened nuclei, show reduced yolk secretion. Those at the opposite side show enhanced secretory activity. Presumably as a result of this differential secretory activity the shape of the oocyte becomes curved. 9. Only intact vitellogenetic oocytes show a banana-like form. 10. The ultrastructural examination of the previtellogenetic follicle indicates no predisposition for the direction of displacement of the oocyte nucleus, and therefore no predisposition of the plane of bilateral symmetry. 11. The hypothesis is discussed that the germinal vesicle itself initiates and directs the appearance of bilateral symmetry in the oocyte.

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A model of pre-programmed differentiation of the larval head region in limnaea stagnalis

Raven

1968

Acta Biotheor

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Mechanisms of Determination in the Development of Gastropods

Cited by 8 publications

References 29 publications

Regulative development in the pulmonate gastropod, Lymnaea palustris, as determined by blastomere deletion experiments

Regulative development in the pulmonate gastropod, Lymnaea palustris, as determined by blastomere deletion experiments

Die Auspr�gung von Polarit�t und Bilateralsymmetrie in den Oocyten vonGryllus domesticus L.

A model of pre-programmed differentiation of the larval head region in limnaea stagnalis

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