Fisheries and Aquatic Sciences

In order to assess the high value-added use of the alginate-free residue of sea tangle, an animal study was performed to evaluate the functional activities and key compounds present. In the animal study, sea tangle and the alginate-free residue demonstrated good anti-hyperlipidemic and anti-arteriosclerotic abilities. The functional compounds in the alginate-free residue of the sea tangle were effectively extracted by supercritical fluid extraction (SFE). The optimum extraction temperature and pressure were 40 °C and 6500 psi (M1) in the SFE, a better method in comparison to the conditions of 70 °C and 4500 psi (M2), respectively. The anti-atherosclerotic effects of the alginate-free residue of sea tangle (M1, M2) were investigated in Sprague-Dawley rats treated with poloxamer 407, Triton WR 1339, corn oil, and a high-fat diet. The M1 fraction reduced the serum lipid levels with greater efficacy than the M2 fraction. In the hyperlipidemic rats, treatment with M1 decreased the serum triglyceride (TG), total cholesterol (TC), and low-density lipoprotein-cholesterol (LDL-C) levels when compared to the levels in normal rats. Our results demonstrated that the alginate-free residue of sea tangle reduces serum TC, TG, and LDL-C. These results suggest that the alginate-free residue of sea tangle contains physiologically active components, such as fucosterol, that may exert beneficial effects in the prevention of atherosclerosis.

Assemblages of juvenile fish and associated abiotic parameters were investigated inside and outside Jinju Bay in southern Korea, on a monthly basis from December 2014 to November 2015. Fluctuations in water temperature and salinity were larger inside than outside the bay. In total, 534,657 individuals per square kilometre from 81 fish species and 47 families were collected during the study period. The most dominant species was Nuchequula nuchalis both inside (25.6%) and outside (26.9%) the bay. The next dominant species were Thryssa kammalensis (17.9%) and Zoarces gillii (16.0%) inside the bay and Liparis tanakae (16.9%) and T. kammalensis (9.0%) outside the bay. Forty species (33% of total number of individuals) of young fish were recorded inside the bay and 47 species (52%) outside the bay. Therefore, it appears that a diversity of fish use nursery grounds inside and outside Jinju Bay. In particular, the following six species appeared: Z. gillii, Pleuronichthys cornutus, L. tanakae, Hemitripterus villosus, Pennahia argentata, and Xenocephalus elongates. Due to assemblage differences for fishes within Jinju Bay and outside the bay, management of both areas is required to maintain current diversity of species in the region.

The objective of this study was to develop an efficient selectable marker for transgenic Dunaliella salina. Tests of the sensitivity of D. salina to the antibiotic chloramphenicol and the herbicide Basta® showed that cells (1.0 × 106 cells/ml) treated with 1000 or 1500 μg/ml chloramphenicol died in 8 or 6 days, respectively, whereas D. salina cells (1.0 × 106 cells/ml) treated with 5, 10, 20, or 40 μg/ml Basta® died in 2 days. Therefore, D. salina is more sensitive to Basta® than to chloramphenicol. To examine the possibility of using the phosphinothricin N-acetyltransferase (pat) gene as a selectable marker gene, we introduced the pat genes into D. salina with particle bombardment system under the condition of helium pressure of 900 psi from a distance of 3 cm. PCR analysis confirmed that the gene was stably inserted into the cells and that the cells survived in 5 μg/ml Basta®, the medium used to select the transformed cells. The findings of this study suggest that the pat gene can be used as an efficient selectable marker when producing transgenic D. salina.

The nematode species belonging to genus Anisakis occur at their third larval stage in numerous marine teleost fish species worldwide and known to cause accidental human infection through the ingestion of raw or undercooked fish or squids. They may also draw the attention of consumers because of the visual impact of both alive and dead worms. Therefore, the information on their geographical distribution and clear species identification is important for epidemiological survey and further prevention of human infection. For identification of anisakid nematodes species isolated from largehead hairtail (Trichiurus japonicus), polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of internal transcribed spacers of ribosomal DNA were conducted. Mitochondrial cytochrome c oxidase subunit 2 gene was also sequenced, and phylogenetic analysis was conducted. From the largehead hairtail (n = 9), 1259 nematodes were isolated in total. Most of the nematodes were found encapsulated throughout the viscera (56.2 %, 708/1259) or moving freely in the body cavity (41.5 %, 523/1259), and only 0.3 % (4/1259) was found in the muscles. By PCR-RFLP, three different nematode species were identified. Anisakis pegreffii was the most dominantly found (98.7 %, 1243/1259) from the largehead hairtail, occupying 98.7 % (699/708) of the nematodes in the mesenteries and 98.1 % (513/523) in the body cavity. Hybrid genotype (Anisakis simplex × A. pegreffii) occupied 0.5 %, and Hysterothylacium sp. occupied 0.2 % of the nematodes isolated in this study. The largehead hairtail may not significantly contribute accidental human infection of anisakid nematode third stage larvae because most of the nematodes were found from the viscera or body cavity, which are not consumed raw. But, a high prevalence of anisakid nematode larvae in the largehead hairtail is still in concern because they may raise food safety problems to consumers. Immediate evisceration or freezing of fish after catch will be necessary before consumption.

Live fish import may lead to the unintended introduction of pathogens. We examined the monthly distribution of microbial pathogens in ornamental finfish imported into South Korea over a 6-month period. Vibrio alginolyticus was detected in one lemon damsel in June and July; V. vulnificus was detected in one lemon damsel, one caerulean damsel, and one pearl-spot chromis and one ocellaris clownfish in July, April, and May, respectively; Photobacterium damselae was detected in one ocellaris clownfish and one caerulean damsel in June and July, respectively; V. anguillarum was detected in one pearl-spot chromis in February; V. harveyi was detected in one ocellaris clownfish and two mandarin fish in February and April, respectively; Yersinia ruckeri was detected in a pearlscale goldfish group in June and July and in two colored carp groups in July; and Lactococcus garvieae was detected in a lemon damsel group and a sutchi catfish group in July and May, respectively. European catfish virus, the only viral pathogen detected, was found in two sutchi catfish groups in May. This study is the first to identify pathogenic species and the presence or absence of pathogens (non-quarantine diseases) in imported ornamental finfish. These results demonstrate that various pathogens with the potential to harm indigenous fish populations can accompany ornamental finfish imported into South Korea.

Metallothionein (MT) is a multifunctional protein playing important roles in homeostatic regulation and detoxification of metals. Mollusk species have been considered as useful sentinel platforms for MT-based biomarker approaches, and they have been reported to display an extraordinary structural diversity of MT proteins. However, potential diversity of molluskan MTs has not been fully explored and recent updates have suggested the need of revision of evolutionary hypothesis for molluskan MTs. Based on bioinformatic analysis and phylogenetic evidences, novel divergence mechanisms and paths were hypothesized in both gastropod and bivalve MT groups. Our analyses are suggestive of the taxon- or lineage-specific domain multiplication/duplication from the ancestral or prototypic MT. Diversification and selection of molluskan MTs might be driven by the needs for acquiring metal selectiveness, specialized novel function, and improved capacity of metal detoxification under environmentally stressed conditions. The structural diversity and variations of molluskan MTs are significantly larger than previously understood. Undoubtedly, molluskan MTs have undergone dynamic divergent processes in their evolutionary histories, giving rise to the great diversity of domain structures in extant MT isoforms. Novel evolutionary paths for molluskan MTs newly proposed in this review could shed additional light onto the revision of the hypothesis for evolutionary differentiation of MTs in the molluskan lineage.