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AbstractThe mitochondrial genome of Cybister brevis Aubé, 1838, is 16,198 bp long and includes 37 genes that are highly conserved in the family Dytiscidae. Phylogenetic analysis revealed that all genera in Dytiscidae, except Hydroporus and Oreodytes, are monophyletic. The Hydroporini tribe was found to be polyphyletic and closely associated with the Hygrotini, Bidessini, and Hyphydrini tribes. Dytiscinae was found to be a highly divergent polyphyletic group comprising three distinct clades. This study also revealed that C. brevis is closely related to Cybister japonicus and that the tribe Cybistrini diverged relatively early compared to other tribes in Hydroporinae. These findings are consistent with those of previous studies and provide new insights into the phylogeny of the Dytiscidae family, which has previously shown discrepancies between morphological characteristics and molecular data. The genome-level analyses conducted in this study serve as a valuable foundation for future investigations into the Dysticidae evolutionary history.

This study introduces one specimen each of the genera Gymnopilus, Marasmius, and Mycena as an unrecorded species found in the Hwasun Gotjawal and Jeju Gotjawal Provincial Park of the Hangyeong-Andeok terrain, South Korea. Morphological analyses of macroscopic and microscopic features, and molecular analysis of the nuclear ribosomal internal transcribed spacer region were conducted to identify the specimens. Our results indicated that the newly identified specimens were Gymnopilus dilepis, Marasmius tenuissimus, and Mycena seminau. Here, we describe these newly identified mushroom species and provide baseline data on their diversity in Gotjawal, South Korea.

Sargassum horneri (SH) and Ulva australis (UA) are marine waste resources that cause environmental and economic problems when entering or multiplying the coastal waters of Jeju Island. We analyzed their anti-diabetic efficacy to assess their reusability as functional additives. The alpha-glucosidase inhibitory activity of SH and UA extracts was confirmed, and the effect of UA extract was higher than that of SH. After the induction of insulin-resistant HepG2 cells, the effects of the two marine extracts on oxidative stress, intracellular glucose uptake, and glycogen content were compared to the positive control, metformin. Treatment of insulin-resistant HepG2 cells with SH and UA resulted in a concentration-dependent decrease in oxidative stress and increased intracellular glucose uptake and glycogen content. Moreover, SH and UA treatment upregulated the expression of IRS-1, AKT, and GLUT4, which are suppressed in insulin resistance, to a similar degree to metformin, and suppressed the expression of FoxO1, PEPCK involved in gluconeogenesis, and GSK-3β involved in glycogen metabolism. The oral administration of these extracts to rats with streptozotocin-induced diabetes led to a higher weight gain than that in the diabetic group. Insulin resistance and oral glucose tolerance are alleviated by the regulation of blood glucose. Thus, the SH and UA extracts may be used in the development of therapeutic agents or supplements to improve insulin resistance.

Eriocheir japonica inhabits rivers flowing into the East Sea, South Sea, and the coastal waters of Jeju-do in South Korea, Japan, and Sakhalin. The larvae migrate to freshwater, mature, and move to estuaries to spawn. Jeju-do has habitats that prevent the migration of aquatic organisms. Populations with low within-group genetic diversity experience increased extinction risk. Industrialization causes climate change and also creates species extinctions. The goal of this study was to investigate the genetic diversity of E. japonica inhabiting Andeok Valley to elucidate their genetic stability and encourage future conservation plans. E. japonica samples used for the study were from the Andeok Valley in South Korea. One walking leg was used for DNA extraction. DNA was amplified using polymerase chain reaction to sequence mitochondrial cytochrome c oxidase subunit 1 (CO1) and cytochrome b (CytB) genes. Haplotype and sequence diversity analyses were performed. Sequencing results for CO1 and CytB genes included 658 and 651 base pairs, respectively. The median network analysis showed that the population inhabiting Andeok Valley had a genetically simple phylogenetic structure. This region provides simple habitat conditions, preventing gene transfer. The probability of extinction of E. japonica that inhabits Andeok Valley is markedly high.

In Jeju-native Citrus, flavonoids are the main contributors to the various types of biological activity, such as antioxidant, antitumor, and anti-inflammatory activity. Thus, we developed simultaneous quantification methods for the analysis of ten bioactive flavonoids in Jeju Citrus fruits (Dangyuja, Gamja, Jigak, Sadugam, and Soyuja) harvested at six different time points using a high-performance liquid chromatography–diode array detector (HPLC-DAD). Separation was performed using a flow rate of 0.8 mL/min, a column temperature of 40 °C, a mobile phase buffer of 0.5% acetic acid, and a detection wavelength of 278 nm. The established analytical method showed good linearity (R2 ≥ 0.9997), precision (inter-day < 0.599%, intra-day < 0.055%), and accuracy (recoveries 92.30–108.80%). The HPLC–DAD method was subsequently applied to analyze flavonoids in Citrus samples. Overall, the quantification results indicated that the compositions and content of flavonoids differed for each Citrus species. The harvesting period also influenced the changes in flavonoid content within each Citrus species. The analytical results with chemometrics revealed that higher flavonoid levels in early-harvested Citrus were derived from the improved fruit size and reduced flavonoid synthesis during maturation. This study provides a practical and reliable method for the analysis of ten flavonoids that can be further utilized in the quality assessment of Jeju Citrus.

The complete mitochondrial genome of Tremoctopus violaceus was sequenced to analyze its organization and phylogenetic status within the order Octopoda. The mitochondrial genome of T. violaceus had a structure and organization similar to that of other Octopoda. The content of the nucleotides A, C, G, and T was 31.68 %, 7.71 %, 20.02 %, and 40.58 %, respectively. All protein-coding genes (PCG) began with the ATG codon, excluding ND4 and ATP6, which began with ATC and ATT, respectively, and terminated with TAG, TAA, TA, or T. Codons for isoleucine were the most used codons, whereas those for arginine were used the least. Two extra tRNAs, trnN and trnL, were found in the control region. These tRNAs have a D-armless structure. The control region had excess A + T content (83.16 %) and a stem-loop structure with two elements, which is reported for the first time in Octopoda by our study. Bayesian inference using 13 PCG revealed that Octopus and Octopodidae were polyphyletic, and that Tremoctopodidae diverged relatively earlier within Octopoda. The mitochondrial genome of T. violaceus and its characteristics may help to understand the evolutionary history of Octopoda and establish a marine biodiversity conservation strategy.

Current research highlights the use of natural products or phytochemicals as drugs and functional additives to treat obesity with few side effects. Sargassum horneri (SH) and Ulva australis (UA) are marine waste resources on Jeju Island, Republic of Korea. In this study, we analyzed their antioxidant and anti-obesity efficacies to confirm their potential as functional additives. We prepared SH and UA extracts using 80% ethanol and observed that free radical scavenging activity and total phenol content were high in SH extracts, and total flavonoid content was elevated in UA extracts. Additionally, 3T3-L1 cells were treated with SH and UA extracts, and the ability of the extracts to inhibit adipocyte differentiation was examined using Oil Red O staining and analysis of neutral fat content. We confirmed that the mRNA expression of the C/EBPα, PPARγ, and SREBP1c genes that act on adipocyte differentiation, and of FAS, a fatty acid synthase, was suppressed. Experiments in a mouse model of obesity showed that 12-week administration of a high-fat diet with 1% extract added to drinking water resulted in lower weight gain compared to the high-fat diet alone. These results suggest that SH and UA extracts have antioxidant properties and are effective in obesity prevention. Therefore, the two marine waste resources are potential functional additive candidates for preventing obesity.