1997 Fiscal Year Final Research Report Summary
Studies on the obstracting mechanism of Protozoa in Mass Culture of Food Organisms and its Control
| Project/Area Number |
08660224
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | The University of Tokyo |
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Principal Investigator |
HINO Akinori The university of Tokyo. Graduate School of Agricultural and Life Sciences, Professor, 大学院・農学生命科学研究科, 教授 (90012012)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Brachionus rotundiformis / Protozoa / lethality / growth obstraction / Heliozoa / stable isotope / ciliate |
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| Research Abstract |
1. Succession of protozoal fauna in mass culture of the marine rotifer Brachionus rotundiformis : Ciliates, Euplotes vannus and Uronema sp. were dominant in food rations from 1/2 to 2/1 of normal level.
2. Function of Protozoa in food web :
The larger ciliates E.vannus was isolated and artificially cultured as the representative protozoon which competes with the marine rotifer. The propagation exceeding 1000 cells/ml obstracted the growth of the rotifer when inoculated into rotifer cultures. The mechamism that the ciliate dominates in rotifer culture was postulated from experiments using ^<15>N tracer as follows.
(1) In lag phase of rotifer culture, the ciliate can fed those dead and bacteria-attached algae which exist as the result of excessive feeding for the rotifer, though the ciliates can not utilize live algea. (2) In log phase, rotifer faeces, which are excellent food for the ciliate, produced enough. Scatrophagy of the rotifer, however, competes it. (3) In stationary phase, rotifer activity comes to decrease because of too much accumulation of organic substances, which makes bacteria production vigorously and the ciliate "enjoy" it.
3. Killing protozoa isolated from a mass culture tank
A mass culture technique of the killing Heliozoa which appeared in a rotifer tank was established. The 24hrs'LD_<50> was only 10^4-10^5 cells/ml to the rotifer. From inspections using TEM etc, it was identified as Oxnerella maritima. It is the first record of lethal Protozoa to marine rotifer. A specific fraction of MeOH extract by the Sephadex colum had strong lethality.
4. The probability of Protozoa-control by antibiotics
The remaining of four antibiotics in rotifer culturing water was examined by HPLC.
5. Publication
The results of two years'experiment are published.
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