Superorder Eucarida consists of three orders including Decapoda, Euphausiacea, and Amphionidacea and many of their species have a high economic value. Spatiotemporal distributions of their larvae provide the important ecological information such as reproduction or population, which is useful for the scientific management of their resources. However, it is hard to analyze them from the zooplankton net samples due to the difficulty in the morphological identification and their relatively smaller numbers in the zooplankton samples, which are often dominated by copepods. As the alternative method, metabarcoding analysis is now being widely adopted to study the biodiversity of various taxa. Here, we developed a universal primer set (EUC), which specifically amplify eucarid species from the mixture of the zooplankton sample. In addition, low amount of decapod species were also presented by blocking Euphausia pacifica. The reliability of EUC was tested by next generation sequencing (NGS) analysis of zooplankton net samples collected from Korean waters in 2016 using MiSeq system.
Results/Conclusions
Euc primer successfully amplified a wide range of Eucarid species except copepod species. As the result of NGS analysis of zooplankton samples collected from Korean waters in 2016, Euphausia pacifica was most dominant whose proportion was 79.07% in East/Japan Sea, 95.63% in South/East China Sea, and 92.20% in Yellow Sea. After using a blocking primer of E. pacifica, obtained OTU numbers of the other taxa increased from 51 to 93 at 97 % cutoff identity. However, 46 out of 114 total eucarid OTUs showed low sequence identity to GenBank database (< 90 %), which suggests more eucarid barcode data should be supplemented. Among them, 41 OTUs including Crangon hakodatei were commonly identified in all examined seasons (February, April, August, and November). The numbers of exclusively identified OTU in each sample season were 4 in February, 2 in April, 4 in August, and 5 in November. Three OTUs including Chionoecetes japonicas in East/Japan Sea, 12 in South Sea/East China Sea, and 5 in Yellow Sea were exclusively identified in each sample stations. Interestingly, distinct genotypes of E. pacifica between East/Japan Sea and Yellow Sea were identified suggesting different populations.