Ho-Seop Han

The starry flounder (Platichthys stellatus) and the spotted halibut (Verasper variegatus) are economically important flatfish species in Korea. The hybrid P. stellatus (♀) × V. variegatus (♂) has attracted attention in aquaculture. In this study, we report the first complete mitochondrial genome sequence of this hybrid flatfish, obtained using next-generation sequencing. The mitogenome is 16,874 bp in length and comprises 13 protein-coding genes, 22 tRNAs, and two rRNAs. Phylogenetic analysis revealed that the hybrid clusters with its maternal species, P. stellatus, confirming strict maternal inheritance of mitochondrial DNA. These findings provide genomic resources for phylogenetics and hybrid flatfish breeding.

Two generations were hatched after artificially crossing Paralichthys olivaceus and Verasper variegatus, commercially valuable species of Pleuronectidae. Here, we report the complete mitochondrial genome and phylogenetic relationships of P. olivaceus (♀) × V. variegatus (♂). The mitogenome is 16,946 bp long and contains 13 protein-coding genes (PCGs), 22 tRNA genes, and 2 rRNA genes. Phylogenetically, it clustered with P. olivaceus within Pleuronectidae, providing a justification for the lack of information on flounder hybrids. Analysis of genetic information and genetic mapping studies of individuals with intermediate traits between the parents support previous research suggesting that it has economic value.

Background The freshwater sculpin Cottus koreanus is endemic to the Korean Peninsula and has a fluvial life history. However, its population has been greatly reduced and it is now listed as an endangered class II species. Objective To obtain important information for its conservation, we examine the genetic diversity, population structure, and demographic history of C. koreanus through mitochondrial cytochrome c oxidase subunit I (CO1) gene sequence analysis. Methods We analyzed the CO1 gene sequences of 430 individuals of C. koreanus from 23 populations in South Korea. Results In all, 32 haplotypes were defined by 124 variable nucleotide sites, of which 28 were unique haplotypes not shared with other regional populations. All sampled populations had high haplotype diversity (H_d = 0.941) and low nucleotide diversity (π = 0.0146). Median-joining network analysis identified two divergent clusters: cluster I that had unique haplotype patterns assigned to each population and cluster II that had a star-like pattern. Each was supported by pairwise F_ST values and hierarchical analysis of molecular variance. The results of the mismatch distribution, goodness-of-fit test, and extended Bayesian skyline plot analysis showed that cluster I has experienced a gradual population expansion since the last glacial maximum, while cluster II experienced a sudden one. The results of neutrality testing supported the results for cluster II but the signal was weak. Conclusions C. koreanus inhabits the upper reaches of rivers and has extremely low dispersal ability, resulting in unique genetic structure patterns among populations. Therefore, all populations should be managed and conserved separately.