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The annual rate of ornamental aquatic crustacean importation is increasing globally. The continuous high demand for live ornamental aquatic crustaceans in many countries has also increased the frequency of imported exotic pathogens, which has caused many problems. In the present study, we examined the monthly distribution of viral and bacterial pathogen genes in ornamental aquatic crustaceans imported into South Korea during a 6-month period from February to July 2016. Among the bacterial pathogens identified, Vibrio alginolyticus was detected in cleaner shrimp in June, and Photobacterium damselae was detected in cleaner shrimp in July. Vibrio penaeicida was detected in peppermint shrimp, banded coral shrimp, hinge-beak shrimp, and orange swamp crayfish between February and June. Among the viral pathogens identified, spawner mortality virus was detected in cherry shrimp in May. Finally, hepatopancreatic parvovirus was detected in both cherry shrimp and orange swamp crayfish between February and March. Notably, the genes of two viral pathogens were also detected in cherry shrimp. Although the viruses were not isolated, they are very likely to have been introduced into South Korea and have an influence on Korean aquaculture. In South Korea, HPV is already prevalent and has been reported several times in aquaculture and in the wild; however, SMV infection has not been reported to date. These results demonstrate that many bacterial and viral pathogens are regularly introduced into South Korea via the ornamental aquatic-crustacean trade.

The olive flounder (Paralichthys olivaceus) is an economically important marine fish species in several East Asian countries. Previously, some cell lines have been derived from the olive flounder, which have shown sensitivity to some viral infections that occur in the fish. In this study, we generated a new immortal cell line, named Korea fin Tissue from Sea flounder (KTS), from the fin tissues of olive flounder and successfully subcultured the cells approximately 250 times over 4 years. KTS cells displayed stable growth at temperatures ranging from 25 °C to 31 °C, with optimum growth at 27 °C. Thus, this cell line has a relatively higher and wider range of growth temperatures compared with other reported cell lines. Chromosome analysis showed that the cell line contains 46 chromosomes, which is fewer than those in other cell lines derived from olive flounder. Furthermore, we evaluated the susceptibility of the cell line to infectious viruses such as viral hemorrhagic septicemia virus (VHSV), infectious hematopoietic necrosis virus (IHNV), hirame rhabdovirus (HRRV), and marine birnavirus (MABV). KTS cells showed 100% cytopathic effect (CPE) at 2 weeks. Notably, KTS cells stimulated with CpG-ODN1668 or poly (I:C) showed higher expression of immune genes in the cytoplasm that were recognized by Toll-like receptor 3 (TLR3) or TLR9. These results suggested that the KTS cell line is promising for immune gene expression analysis and other genetic studies. In conclusion, we successfully generated an immortal cell line from the fin tissue of olive flounder. KTS cells have a higher growth temperature range than other reported cell lines, which could prove useful for future cytopathological, genetic, and infectious viral mechanistic studies in this species.