Iksookimia yongdokensis (Actinopterygii, Cypriniformes, Cobitidae) is known as endemic freshwater fish species in Korea. The total length of I. yongdokensis mitogenome is 16,640 bp, consisting of 13 protein-coding genes (PCGs), 22 tRNAs, 2 rRNAs, and 1 control region (D-loop). The gene arrangement and content were identical with previously recorded mitogenomes of Iksookimia species. Phylogenetic analysis using PCGs and rRNA was examined by maximum likelihood method indicated that genus Iksookimia is taxonomically not stable status according to Iksookimia species and Cobitis species were grouped together.

In this study, the complete mitochondrial genome sequences of Iksookimia hugowolfeldi, Korean loach species, was determined using next-generation sequencing analysis. The complete mitogenome of I. hugowolfeldi has 16,634 bp in length and consists of 13 protein-coding genes (PCGs), 22 tRNAs, two rRNAs, and one control region (D-loop). Both gene orders and characteristics were exactly accord with mitochondrial genome of other species those belong to the family Cobitidae. Phylogenetic analysis revealed that the establishment of taxonomic relationship between Iksookimia and Cobitis has still uncompleted because of the not distinguished as monophyletic status.

In marine environments, environmental DNA (eDNA) can be effectively detected and possibly quantified when combined with molecular techniques, as demonstrated by several recent studies. In this study, we developed a species-specific primer set and a probe to detect the distribution and biomass of an invasive hydrozoan in South Korea, Ectopleura crocea. These molecular markers were designed to amplify a 187 bp region based on mitochondrial cytochrome c oxidase subunit I (COI) of E. crocea and were tested on seawater samples from 35 Korean harbors in 2017. Of the 35 sites we investigated, only nine harbors returned positive detections when using traditional survey methods, while surveys based on the use of eDNA techniques detected E. crocea DNA in all seawater samples. These results suggest that eDNA surveys based on molecular techniques are more effective at identifying species distribution and estimating biomass than traditional surveys based on visual assessment of morphology.

Environmental DNA (eDNA) method used by many ecologists as effective investigation tool can detect endangered species, rare species, and invasive species. In case of invasive species, eDNA method help to monitor the target species when the species was hard to detect through the traditional survey such as the early stage of invasion, low abundance, and larva or juvenile stage. The bryozoan, Bugulina californica, was known as a marine fouling invasive species in Korea since its first reported in 1978. This species expanded nationwide, and damages to ascidian aquaculture through attached on the ship hulls and artificial facilities. To monitor the distribution and biomass of invasive bryozoan, B. californica, the qPCR analysis of environmental DNA was performed on seawater samples from 12 harbors. In this study, we designed species-specific markers which can calculate the detected DNA copies of B. californica, and the presence and monitoring of this species can be more accurately estimated by environmental DNA analysis than by traditional survey, in which it is difficult to identify the species. Real-time PCR analysis using environmental DNA is an effective monitoring method that can determine both the distribution and the monthly change in biomass of B. californica in Korea.

Genus Zacco specimens collected in this study were classified genetically as five species, Zacco platypus, Z. temminckii, Z. koreanus and two unidentified species, using DNA barcoding analysis based on 655 bp of mitochondrial cytochrome c oxidase subunit I (COI) gene. Two of unidentified species (Z. sp.1 and Z. sp.2) were considered to be unrecorded or new species of genus Zacco according to genetic distances between Zacco species. In addition, we determined a natural hybrid based on polymorphic base at the diagnostic positions displayed on nuclear recombination activating gene 1 (RAG1) gene (965 bp), and estimated paternal and maternal species of natural hybrid comparing phylogenetic tree between COI and RAG1, and Z. sp.1♀ × Z. koreanus♂, Z. sp.2♀ × Z. koreanus♂ and Z. koreanus♀ × Z. sp.1♂ individuals were confirmed. The habitat of natural hybrids of Z. koreanus between Z. sp.1 and Z. sp.2 was identified as Geum and Yeongsan River, respectively. In our data, only F1 hybrid generation was identified; however, generations after F1 hybrid or backcross were not demonstrated.

A new species of the genus Henricia Gray, 1840 that belongs to the family Echinasteridae is described from South Korea. Henricia epiphysialis sp. nov. has epiphyseal ossicles at the ends of the abactinal and lateral plates, and the abactinal and lateral spines form a hooked crown. The partial sequence of the mitochondrial COXI gene (537 bp) of H. epiphysialis sp. nov. was obtained, and the new species was morphologically and genetically compared with other related Henricia species.