Summer mortality, caused by thermal conditions, is the biggest threat to abalone aquaculture production industries. Various measures have been taken to mitigate this issue by adjusting the environment; however, the cellular processes of Pacific abalone (Haliotis discus hannai) have been overlooked due to the paucity of genetic information. The draft genome of H. discus hannai has recently been reported, prompting exploration of the genes responsible for thermal regulation in Pacific abalone. In this study, 413 proteins were systematically annotated as members of the heat shock protein (HSP) super families, and among them 26 HSP genes from four Pacific abalone tissues (hemocytes, gill, mantle, and muscle) were differentially expressed under cold and heat stress conditions. The co-expression network revealed that HSP expression patterns were tissue-specific and similar to those of other shellfish inhabiting intertidal zones. Finally, representative HSPs were selected at random and their expression patterns were identified by RNA sequencing and validated by qRT-PCR to assess expression significance. The HSPs expressed in hemocytes were highly similar in both analyses, suggesting that hemocytes could be more reliable samples for validating thermal condition markers compared to other tissues.

Primary cell culture is a sufficient method frequently used to study the cellular properties and mechanisms of isolated cells in a controlled environment. In this study, an embryonic cell line (FGBC8) derived from the blastula stages of embryos of olive flounder Paralichthys olivaceus was developed. Furthermore, conditions for optimal long-term maintenance of this primary embryonic cell culture were investigated. Morphologically, FGBC8 cells were composed primarily of epithelial-like cells. FGBC8 cells were subcultured for >160 passages over ~830 days. The doubling time of FGBC8 cells was 73.8 h, and the modal diploid chromosome number was 48. FGBC8 cells transfected with green fluorescence protein (GFP)-expression plasmid exhibited a strong signal 48 h after transfection. Consequently, we demonstrated that fish serum is a crucial supplement for the long-term survival and maintenance of comparable morphology in these primary embryonic cells. Our results can be used as a guide for primary embryonic cell cultures for other fish species and may be useful for cell biotechnological applications.

Fisheries and Aquatic Sciences

Accurate origin determination of seafood is crucial for consumer trust and safety. This study was performed to develop a machine learning-based single-nucleotide polymorphism (SNP) analysis technique to determine the origin of Acetes species in salted small-shrimp products. Mitochondrial DNA (COI and 16S rRNA) analysis revealed genetic variations among species and origins. Eight candidate SNPs were identified, six of which were developed into markers for genotyping analysis. Using the developed markers, an SNP array was created and SNP data from salted small-shrimp samples were obtained. Machine learning analysis using a supervised learning algorithm achieved 100% accuracy in classifying the origin of Acetes based on SNP data. This method offers a reliable method for regulatory bodies to combat food fraud and ensure product integrity. The approach can be further improved by expanding the data set to encompass a wider range of species and origins. This study highlights the potential of SNP analysis and machine learning for ensuring seafood authenticity and promoting sustainable practices.

Pufferfish (Takifugu spp.) are economically important edible marine fish. Mistakes in pufferfish classification can lead to poisoning; therefore, accurate species identification is critical. In this study, we used the mtDNA cytochrome c oxidase subunit I gene (COI) to design specific primers for six Takifugu species among the 21 domestic or imported pufferfish species legally sold for consumption in Korea. We rapidly and simultaneously identified these pufferfish species using a highly efficient, multiplex polymerase chain reaction (PCR) system with the six species-specific primers. The results showed that species-specific multiplex PCR (multiplex species-specific polymerase chain reaction; MSS-PCR) either specifically amplified PCR products of a unique size or failed. MSS-PCR yielded amplification fragment lengths of 897 bp for Takifugu pardalis, 822 bp for T. porphyreus, 667 bp for T. niphobles, 454 bp for T. poecilonotus, 366 bp for T. rubripes, and 230 bp for T. xanthpterus using the species-specific primers and a control primer (ca. 1,200 bp). We visualized the results using agarose gel electrophoresis to obtain accurate contrasts of the six Takifugu species. MSS-PCR analysis is easily performed and provides identification results within 6 h. This technique is a powerful tool for the discrimination of Takifugu species and will help prevent falsified labeling, protect consumer rights, and reduce the risk of pufferfish poisoning..

Olive flounder (Paralichthys olivaceus) is a commercially important fish species in Japan, China, and the Republic of Korea. Despite numerous attempts to improve productivity, there have been no studies of in vitro germline stem cell (GSC) culture in this species. Here, olive flounder testicular and ovarian cell lines (OFT and OFO, respectively) were established and characterized. RT-PCR demonstrated that OFT and OFO expressed several gonadal somatic cell markers, including wt1 and fgf2, but lacked expression of germ cell markers, such as vasa, nanos2, and scp3. In addition, SNP analysis revealed that OFT originated from XY male P. olivaceus and OFO originated from XX female P. olivaceus. These results suggest that OFT was composed of Sertoli cells and OFO was composed of granulosa cells and theca cells. Finally, coculture of OFT or OFO with enriched male P. olivaceus GSCs isolated from the top 20% and 20–30% Percoll density gradient layers showed that GSCs were attached on both cell lines. In conclusion, we established P. olivaceus testicular and ovarian cell lines, which were expected to use for development of an in vitro GSC culture system.