Effects Of Temperature And Irradiance On Filament Development Of Grateloupia Turuturu And Early Development Of Silvetia Babingtonii

Grateloupia C. Agardh belongs to Halymeniaceae, Cryptonemiales, Rhodophyta. It is the biggest genera of Halymeniaceae. It is reported that there are total of about80species throughout the world, including32species in China. Grateloupia turuturu Yamada is an economically valuable red alga and is considered native to Japan and Korea. Because it is a common invasive species, its biological range is still expanding. G. turuturu has potential to be used in nutraceuticals, Pharmaceuticals, industry and so on. Considering the promising applications of this species, wild stocks at present could not satisfy the commercial needs. Therefore, the sporeling culture and cultivation of G. turuturu must be developed. At present, although there are several approaches to make the artificial seedling culture possible, the constraints exist respectively. Filaments of G. turuturu are very important in germoplasm preservation and sporeling culture. But the optimal culture conditions, including temperature and irradiance, on filament development have not been documented.In this study, we observed the filament development in detail using microscope at20℃with60μmol photons·m-2·s-1and obtain the juvenile thalli of G. turuturu. The filament development included three stages:filament stage, discoid crust stage and upright thalli stage. After the filaments settled on immersed cover slips, cells started to divide to form radiating structures, and eventually developed into discoid crusts after5days. The discoid crusts had uneven distribution of pigment and there was high concentration pigment in the center. When the discoid crust diameters were more than200-300μm, coalescences of two or more discoid crusts were observed. The center area of discoid crusts arched slightly and one or more upright thalli developed gradually. The time for filaments to develop into juvenile thalli was21days. Simultaneously, we made the filaments settled on the palm ropes and cultivated in the same condition. After7-8weeks, juvenile thalli were visible without magnification and were cultivated in the sea. Juvenile thalli reached2-5cm after being cultivated3months.In addition, the effects of temperature (10,15,20,25,30℃) and irradiance (10,30,60,90μmol photons·m-2·s-1) on filament development were investigated. Temperature was an important factor for the formation of discoid crusts, while irradiance had little or no effects.25℃was the optimal temperature for discoid crust formation and no discoid crusts formed at30℃. There were synergistic interactions between temperature and irradiance during the development from discoid crusts to upright thalli. With the development of discoid crusts, high temperature (25℃) and irradiance (90μmol·m-2·s-1) seemed to inhibit the development. The combination of20℃and60μmol photons·m-2·s-1was optimal for discoid crust development. The earliest formation of a few (1-2) upright thalli were observed at25℃with90μmol photons·m-2·s-1. However, the thalli died after the first week. Considering more biomass of upright thalli,20℃and60μmol photons·m-2·s-1were the best condition. Silvetia belongs to Fucaceae, Fucales, Cyclosporeace, Phaeophyta and has5species. Silvetia babingtonii is a cartilaginous brown alga and distributes in Japan, Korea and Russia except for China. The life cycle only has sporophytic life stage and gametangia are attached to the sporophytes. The species has a potential for use as a raw material for nutraceuticals and pharmaceuticals because of its high content of fucoidan, lipids and bioactive compounds. At present, there are many papers related to Silvetia, but the investigations about S. babingtonii rarely have been reported, especially in the domestic. Therefore, the knowledge about the internal structure, early development and life cycle needed to be further studied. These can provide information for future cultivation and prospective utilization.In this study, we observed the internal structure of conceptacles. The conceptacles were spherical, monoecious and composed of antheridia, oogonia and paraphyses.In addition, the early development of S. babingtonii from zygotes to juvenile sporelings was investigated under room temperature (20℃) and natural light (60-100μmol photons·m-2·s-1) using microscope. After attachment, zygotes germinated and divided into two cells:thallus cell and rhizoidal cell in2days. The larger thallus cell then divided further and developed into juvenile stipe and fronds until the5th day, while the small rhizoidal cell formed germ tubes firstly. The germ tubes elongated, branched and developed into rhizoidal hairs. When the juvenile sporelings were visible with bare eyes, they were observed under a dissecting microscope. They had two growth pattern:single and in cluster. The basal portion of juvenile sporelings elongated and developed continually and more branches were generated from rhizoid hairs. Moreover, we summarized the life cycle of S. babingtonii, which provides the foundation for future sporeling culture.