両生類卵形成過程の研究 : VI. ヤマアカガエルの脂肪卵黄

概要

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Electron microscope studies have demonstrated that the fatty yolk formation in the oocytes of Rana ornativentris begins at the same time as the proteinaceous yolk formation and that it occurs in vesicular structures, fatty yolk precursors, surrounded by single membranes and enclosing varying amounts of myelin structures arranged in concentric layers or in stacks between granular and fibrillar components. Fatty yolk begins to appear in clusters near the subcortical regions of the oocytes which reach the diameter of 300-400 μ. The sequence proposed for the fatty yolk production in this amphibian species is as follows: First, fatty yolk precursor formation; second, appearance of myelin structures arranged in concentric layers or in stacks within the fatty yolk precursors and their increase in number; third, transformation of the myelin structures into homogeneous lipid material. Fatty yolk accumulation occurs multicentrically in the fatty yolk precursors and this is followed by a release of fatty yolk into the ooplasm through breaks in the limiting membranes resulting in the formation of groups of fatty yolk globules. The present findings are compared with the data and interpretations of other authors. It appears that there are considerable differences in the mode of fatty yolk formation even in related species of anuran amphibians.
社団法人日本動物学会の論文
1968-06-15