| Abstract: | Laminarialean plants undergo heteromorphic alternation of generations between the macroscopic diploid sporophyte and the microscopic haploid gametophyte. The generations change through the formation and release of asexual or sexual reproductive cells. It is difficult to monitor the release and diffusion of zoospores into the environment. Furthermore, even if zoospores can be detected, species identification remains difficult. This study attempted to develop a sensitive and fast identification method for laminarialean zoospores using quantitative PCR. In addition, we aimed to estimate the density of zoospores in natural seawater. Specific primers for Saccharina japonica and Undaria pinnatifida were designed and used to estimate the quantity of zoospores in seawater. DNA samples (environmental DNA) were collected from seawater once or twice each month for 2 years at the same area, and seasonal variations in the release of zoospores was monitored. The estimated maturation period based on the number of released zoospores in this study was comparable with those of the previously reported maturation periods of S. japonica and U. pinnatifida sporophytes. This supports the validity of our method in estimating zoospore release from laminarialean plants. The method will be a useful tool for ecological studies on these commercially relevant species. |
