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..

Heat shock protein (HSP) 70, the highly conserved stress protein families, plays important roles in protecting cells against heat and other stresses in most animal species. In the present study, we identified and characterized four Hsp70 (RuHSP4, RuHSC70, RuHSP12A, RuGRP78) family proteins based on the expressed sequence tag (EST) analysis of the Korean rose bitterling R. uyekii cDNA library. The deduced RuHSP70 family has high amino acid identities of 72-99% with those of other species. Phylogenetic analysis revealed that RuHsp70 family clustered with fish groups (HSP4, HSC70, HSP12A, GRP78) proteins. Quantitative RT-PCR analysis showed the specific expression patterns of RuHsp70 family members in the early developmental stages and several tissues in Korean rose bitterling. The expression of 4 groups of Hsp70 family was detected in all tested tissue. Particularly, Hsp70 family of Korean rose bitterling is highly expressed in hepatopancreas and sexual gonad (testis and ovary). The expression of Hsp70 family was differentially regulated in accordance with early development stage of Rhodeus uyekii.

Girella punctata and Girella leonina are economically important species found in the East Sea; along the southern coast of Korea; south of Hokkaido, Japan; around Taiwan; and in the East China sea. In Korea, these two species hold high value, particularly on Jeju Island. These species have similar appearances, and it is challenging to distinguish them, particularly during the seed period. We detected genetic differences in the mtDNA (COI gene) of G. punctata and G. leonina, which are morphologically indistinguishable, and developed species-specific genetic markers for their identification. In total, 16 and 4 haplotypes of the COI genes were obtained from G. punctata (n = 164) and G. leonina (n = 36), respectively. The haplotype diversity (Hd) and nucleotide diversity (Pi, %) of the COI were 0.359 and 0.054 for G. punctata and 0.560 and 0.078 for G. leonina, respectively. We designed a Girella species common primer (control) and species-specific primer sets (experimental) for the two species. Amplicon sizes of 991, 579, and 391 bp were obtained for common primers of the two Girella species G. punctata and G. leonina. To confirm multiple targets in a single reaction, multiplex PCR conditions were optimized to adjust its resolution and accuracy. The detection levels of the multiplex PCR were confirmed to be 0.01 ng/µL for the two Girella species. The multiplex PCR was not associated with cross-reactivity between G. punctata and G. leonina. This multiplex species-specific PCR method provides a simple and rapid technique for the identification of two Girella species, thus increasing the efficiency and quality of Girella species stock management and forensic identification to prevent species misidentification.

Eel populations are globally threatened by overfishing and illegal trade, making accurate species identification essential for resource conservation and regulatory enforcement. Conventional molecular identification methods are generally applied in the laboratory, with limited rapid on-site application. This study developed a field-deployable assay to identify the Japanese eel (Anguilla japonica), by incorporating multienzyme isothermal rapid amplification (MIRA) technology with a visually readable lateral flow assay (LFA). Species-specific primers targeting a 286 bp region within the mitochondrial genome of A. japonica were designed and labeled with fluorescein amidite and biotin, respectively. The performance of the MIRA-LFA was validated by assessing its specificity against four other major eel species and its analytical sensitivity, i.e., limit of detection (LoD), under optimized temperature and reaction-time conditions. The MIRA-LFA demonstrated 100% specificity, generating a positive signal only for A. japonica, with no cross-reactivity. A clear visual result was obtained within 10 min at the optimal reaction temperature of 39 °C. Under these optimal conditions, the assay showed a high sensitivity, with an LoD of 0.1 ng/μL of genomic DNA. The proposed assay is an effective tool for the rapid, specific, and sensitive identification of A. japonica. The ability to obtain fast, equipment-free visual results makes this assay an ideal point-of-care testing solution to combat seafood fraud and support the sustainable management of this economically important and vulnerable species.

Fisheries and Aquatic Sciences

In this study, a multiplex PCR assay was developed for the rapid and accurate identification of three Chionoecetes species (Chionoecetes bairdi, C. opilio, and C. japonicus) available in global seafood markets. The morphological similarity between imported female C. bairdi from Japan and native C. opilio in Korea complicates visual discrimination and raises concerns over potential mislabeling. To address this issue, mitochondrial cytochrome c oxidase subunit I (COI) gene sequences were analyzed to identify species-specific SNPs, and primers were designed accordingly. Singleplex PCR confirmed species-specific amplification among the three target species, and the optimal annealing temperature was determined. The multiplex PCR simultaneously amplified distinct fragments of 598 bp (C. bairdi), 401 bp (C. opilio), and 194 bp (C. japonicus), with no nonspecific amplification or primer–dimer formation. Sensitivity testing revealed a detection limit of 0.01 ng/µL for all three species, defined as the lowest DNA concentration at which species-specific bands were consistently observed in at least two out of three replicates. These results demonstrate that the developed multiplex PCR is a reliable, rapid, and cost-effective tool for accurate species identification, supporting sustainable resource management, preventing seafood fraud, and ensuring safe distribution in both Korea and global seafood markets.