1991 Fiscal Year Final Research Report Summary
Physiology and ecology of ciguatera causative dinoflagellates
| Project/Area Number |
02660192
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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 |
ISHIMARU Takashi Tokyo Univ. Fisheries, Associate Professor, 水産学部, 助教授 (90114371)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Ciguatera / Benthic dinoflagellates / Integrating-sphere-fluorometer / In vivo fluorescence |
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| Research Abstract |
Distribution of benthic dinoflagellates including ciguatera causative organisms were examined in Akajima Island, Kerama Islands, Okinawa, Japan. Prorocentrum species including a new species occupied high percentage of density compared with others. Gambierdiscus toxicus known as a main producer of CTX and MTX was rater low in the density, but its maximum cell density was a thousand times higher than that examined at Okinawa Island and Ishigaki Island. The new species recembles Prorocentrum emarginatum but the difference in the valval shape and depression on the valve surface were confirmed by scanning electron microscopic observations.
A new type of fluorometer was made to monitor the growth of benthic dinoflagellates. A culture tube is placed in the integrating sphere which diffuse both excitation light and in vivo fluorescence. Thus the fluorescence is monitored without agitation. The performance of integrating-sphere-fluorometer (ISF) was tested for cultures of a benthic diatom and dinoflagellates, and good correlations were obtained between in vivo fluorescence and extracted chlorophyll amounts.
Effects of light, temperature and exudate of macroalgae on growth of benthic Prorocentrum species were examined. Their optimum growth were observed between 1.1-1.4x10^<16>quanta cm^<-2> sec^<-1> and 25.5-30.7 ﾟC, respectively. The exudate released from the surface of Zonaria stipitata and Distromium decumbens (Phaeophyceae) promoted the growth of P. lima, P. sp. and P. emarginatum but P. concavum. On the contrary, the exudate of Turbinaria ornata, on which abundant adhesion of Prorocentrum was observed in the field, rather disturbed the growth of four species. From these results, benefits of their adhesion to the host macroalge were thought as a shading from high irradiance besides the supply of growth promoting substances.
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