Phenology of the kelp <Emphasis Type="Italic">Saccharina japonica</Emphasis> and its effect on the gonad index of the sea urchin <Emphasis Type="Italic">Mesocentrotus nudus</Emphasis> across a depth gradient off the Sanriku coast,northeastern Japan

The kelp Saccharina japonica is a dominant seaweed along the Sanriku coast where fisheries for sea urchin and abalone are among the most prosperous in Japan. We investigated the phenology of the kelp at depths of 6, 9 and 12 m from March 2015 to March 2016. The sea urchin Mesocentrotus nudus, a dominant herbivore off the coast, was also monitored with respect to its gonads for fishery use. Juvenile kelp appeared in March and rapidly elongated until May. Weight of the kelp significantly increased from April to July. Sori formation commenced from September and ceased in December. Density and biomass of the kelp were higher in the shallower sites than in the deeper one throughout the year. The highest biomasses recorded between July and October were 3773, 1939 and 501 g dry weight m^?2 at depths of 6, 9 and 12 m, respectively. No regrowth of kelp blades was observed, indicating that S. japonica in this region has an annual life cycle. The gonad index of the sea urchin in the 12-m site was lower than that in the 6- and 9-m sites, indicating the close relation of the gonad index with the biomass of the kelp.     

日本柑橘黄龙病病原体电镜观察及PCR检测

对日本柑橘黄龙病病原体的形态结构进行了电镜观察,结果发现柑橘黄龙病病菌日本株系绝大多数是球形和短椭圆形,极少观察到棒状形态,直径为100～500nm,外被一层胶状物质包围,厚约10～50nm,这与其他地区发现的柑橘黄龙病病原体形态不同．PCR检测表明,以硅藻土法提取的DNA为模板,利用Ready-To-Go^TM PCR bead法可以得到理想结果。