ショウジョウバエ棒眼の個眼前駆体形成の組織学的観察
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概要
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The histological changes in the cluster formation process of the wild-typeds imaginal eye disc and the bar-eyed imaginal disc during the third larval stage were studied. Normal developmental process of the wild-typed eye disc observed in Drosophila melanogaster is almost the same as that observed in Drosophila virilis. In the early third instar, the cells of the eye disc divide gardually as a whole and no remarkable histological change was observed. About the middle of the third instar, however, rapid cell divisions begin in the disc, and the clusters of the cells, which are supposed to change into the facets of the imaginal compound eye, are formed. Both the rapid cell division and the cluster formation occur at the posterior end of the disc and gradually proceed to the anterior end where the eye stalk is attached. Each cluster contains 10 or more cells. The number of cells forming a cluster is almost equal to that which constructs a imaginal facet. The clusters are regularly arranged in the same manner as the facets in the imaginal compound eye. In the bar-eyed disc the developmental process is in itseld similar to that observed in the wild-typed eye disc. But a difference between them is found at the stage when raped cell divisions occur in the discs. At this stage of the bar-eyed disc, degenerations or lysis of the cells are found here and there in the region where the clusters are formed at the next stage. These degenerated cells are more frequently found in the anterior part than in the posterior part of the disc. In the nuclei of these degenerated cells, bead-like chramatin connecting the large granules or Feulgen positive spherical bodies are found. These cells frequently fuse and result in a irregular mass. At the end of the third instar these degenerated cell groups move to the underlayer of the disc, while the remaining normal cells form the culsters. On account of the degeneration of the cells, the bar-eyed imaginal disc becomes smaller in size and contains fower clusters than that in the normal. At the end of the larval stage, a distribution of the clusters shows the characteristic "Bar" feature of the imaginal compound eye. From these observations, it is shown that the diminution of facets in the bar eye is not based upon the degeneration of the completly formed clusters, but upon the degeneration or Jysis of the cells found in the rapid cell division which occurs at the middle stage of the third instar. There are many reports showing that the sensitive period for temperature or chemical effect upon the bar eye series exists at the early and middle larval stages, disappearing at the later stage when the clusters are being formed. It is shown from the author's data that the sensitive period begins at about or somewhat prior to the time when the rapid cell division begins in the imaginal disc. And it is during this stage that lysis of cells occur in the bar-eyed disc. It is reasonablel to consider that sensitivity to temperature or other factors are due to the cellular or developmental mechanisms in the rapid cell multiplicating process during this stage.
- 社団法人日本動物学会の論文
- 1956-06-15
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