1987 Fiscal Year Final Research Report Summary
Mechanism of individuality establishment in developing ascidian buds.
| Project/Area Number |
61540522
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
動物発生・生理学
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| Research Institution | Kochi University |
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Principal Investigator |
NAKAUCHI Mitsuaki Faculty of Science, Kochi Univ., Professor, 理学部, 教授 (00036526)
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| Co-Investigator(Kenkyū-buntansha) |
KAWAMURA Kazuo Faculty of Science, Kochi Univ., Associate Professor, 理学部, 助教授 (30136361)
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| Project Period (FY) |
1986 – 1987
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| Keywords | Ascidian / Tunicate / Asexual reproduction / Budding of ascidians |
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| Research Abstract |
In asexual reproduction the development of an individual starts form a bud which consisits of many cells which are able to give rise to a variety of tissues. From the view point of individuality, the bud does not have an established individuality in the beginning of bud development. The inidividuality seems to be established during the course of development. Employing the stolonic buds of the colonial ascidian, Polyzoa vesiculiphora, we studied the mechanism by which the individuality is established. Stolons artificially isolated from their parent each develop into an individual. But, if such a stolon is kept ligated at its middle part two individuals are formed, while if the ligature is removed within 20 hours only one zooid is formed. By varing the beginning and duration of ligation we determined the stage in which the organizing center (which will control the individuality) was established. The results showed that the center was established 30-40 hours after isolation of stonons from their parents. Histological study showed that the stage at which the center forms corresponds roughly to the stage in which the formation of gut rudiment occurs. it was also revealed that the accumulation of free cells in the distal side (which then caused the formation of the center in the proximal side) was not caused by the stimulation of cutting, but caused by an intrinsic proximo-distal polarity of the stolons. It was suggested that only the stolons in which two inner vesicles of formative tissues were formed by ligation were able to form two individuals. It was shown that the position of the gut rudiment on the epithelium of the inner visicle depended on the site at which the epithelium had been cut off from that of the parental or sister zooid.
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