Physiology and ecology of ciguatera causative dinoflagellates

调查了日本冲绳庆良间群岛赤岛底栖甲藻的分布。原甲藻属的种和一新种在各种中所占比例较高。毒性干盘菌是CTX和MTX的主要生产菌，其密度较低，但其最大细胞密度比在冲绳和石垣岛检测到的细胞密度高1000倍。通过扫描电镜观察，证实了新种为原甲藻（Prorocentrum embryatum），但其瓣的形状和瓣表面凹陷的差异。将培养管放置在积分球中，其漫射激发光和体内荧光。因此，在不搅拌的情况下监测荧光。利用积分球荧光计（ISF）对一种底栖硅藻和甲藻进行了活体荧光测定，结果表明，活体荧光与提取的叶绿素含量具有良好的相关性，并研究了光照、温度和大型藻类分泌物对底栖原甲藻生长的影响。它们的最适生长温度分别为1.1- 1.4 × 10 ~（<16>-1）cm ~（-1）sec <-2>~（-1<-1>）和25.5-30.7 ℃。具柄带藻和斜卧盘藻表面分泌物促进了利马原甲藻、假单胞菌和新月原甲藻的生长，但对凹原甲藻的生长没有促进作用。而在野外观察到大量附着原甲藻的装饰喇叭藻分泌物则对4种植物的生长有一定的干扰作用。从这些结果来看，除了提供生长促进物质外，它们粘附到宿主大型藻类的益处被认为是对高辐照的遮蔽。

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.