| Project/Area Number |
06660230
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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 |
General fisheries
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| Research Institution | Tokyo University of Fisheries |
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Principal Investigator |
OMORI Makoto Tokyo University of Fisheries, Dept.of Aquatic Biosciences, Professor, 水産学部, 教授 (10013567)
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| Co-Investigator(Kenkyū-buntansha) |
ISHII Haruto Tokyo University of Fisheries, Dept.of Aquatic Biosciences, Assistant, 水産学部, 助手 (30251680)
YAMAKAWA Hiroshi Tokyo University of Fisheries, Dept.of Aquatic Biosciences, Assistant Professor, 水産学部, 助教授 (80017061)
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| Project Period (FY) |
1995 – 1996
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1995: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1994: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | moon jellyfish / Aurelia aurita / polyp / ephyla / strobilation / eutrophication / mass occurrence / 生態学 / 海分生物学 |
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| Research Abstract |
Factors and conditions to relate mass occurrence of the moon jelly Aurelia aurita in the upper part of Tokyo Bay have been examined through field survey and laboratory experiment. In the field sampling of the jelly and measurement of hydrographic conditions were carried out once or twice a month during three consecutive years from April 1993. Seasonal variation of the size of medusae and occurrence of planulae and ephyrae were determined. Based on these information, rearing experiments of planulae and polyps were carried out under different temperature and food regimes during a few months in each year. As the result, processes of formation of the strobilation and a sexual reproduction by budding were revealed. Other findings included the size of polyps to commence strobilation, duration of strobilation, production rate of strobilae, and number and size of ephyrae.
Growth of polyps and timing of the ephyla's liberation are strongly influenced with temperature and feeding condition.Number of buds of polyps increase with increasing feeding duration after the temperature lowered. The polyps settled before autumn of the previous year liberate ephyrae in January, whereas those settled in autumn produce ephyrae in February to April.
With favorable higher temperature and food density during the early polyp stage, the polyps growth and increase the number rapidly. The strobilation is induced when the temperature lowered to 15ﾟC or less. If food condition is still preferable after the lowering temperature, large size ephylae are liberated from large numbers of polyps. The population explosion of A.aurita could be attributed to its high reproductive potential under these special conditions.
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