• Fisheries and Aquatic Sciences
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• v.9 no.3
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• pp.123-128
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• 2006

An epizootic causing mortality among cultured marine finfishes occurred in 1999 in the province of Kyoungsang, Korea. The disease was characterized by the presence of enterocele, abdominal swelling, and gastroenteritis. The causative bacteria were isolated from olive flounder (Paralichthys olivaceus), black rockfish (Sebastes schlegeli), turbot (Scophthalmus maximus) and the rearing water. These bacteria showed swarming activity on agar plates and yellowish or greenish colonies on thiosulfate-citrate-bile salts-sucrose (TCBS) agar plates, but no luminescence. The pathogen was identified as Vibrio harveyi based on morphological and biochemical characteristics and the sequence of l6S rDNA. The lethal doses (LD$_{50}$) of olive flounder and black rockfish were estimated to be $1.24\times10^6-1.36\times10^8$ and $3.24\times10^5-5.8\times10^7$ CFU/fish respectively following intraperitoneal injection.

• Journal of fish pathology
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• v.17 no.3
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• pp.179-189
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• 2004

Morphological structure and sporogenesis of myxosporean parasite, Parvicapsula anisocaudata from cultured olive flounder, Paralichthys olivaceus were examined by light and transmission electron microscopies. Numerous round early stages, spindle-shaped disporic or monosporic pseudoplasmodia, asymmetrical thin-walled mature spores were found inthe lumen of renal tubule and urinary bladder. Long pseudopodia or short projections from cytoplasm of pseudoplasmodia make the parasite attach firmly to host tissues. Spore development was mono- or disporous with no pansporoblast formation. Sporoplasmic cell was partially surrounded by two capsulogenic cells, and capsulogenic cells were enveloped by two flattened valvogenic cells. Capsulogenesis and valvogenesis followed general patterns seen in that of other myxosporean.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.6
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• pp.785-790
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• 2011

This study investigated the nutritive quality of olive flounder Paralichthys olivaceus fed either moist pellet (MP) or moist pellet mixed with mushroom extract (MPME) for 6 months. There was no significant difference in crude protein or extractive nitrogen in the muscle of flounder fed MP versus MPME (P > 0.05). The total amino acid content in the muscle of flounder fed MP was $15.22{\pm}5.24$ g/100 g, compared to $19.90{\pm}2.90$ g/100 g for flounder fed MPME. Essential amino acid content was $7.04{\pm}2.21$ g/100 g in the muscle of flounder fed MP versus $8.94{\pm}2.50$ g/100 g for MPME. Total amino acid content was higher in the muscle of olive flounder fed MPME, while essential amino acid content was higher in flounder fed MP. The ratio of non-essential amino acids to essential amino acids was $0.86{\pm}0.07$ for flounder fed MP and $0.81{\pm}0.08$ for flounder fed MPME. There was no significant difference in free amino acid content and fatty acid composition. The breaking strength of muscle of olive flounder fed MP was higher ($1.44{\pm}0.51\;kg/cm^2$) than in flounder fed MPME ($1.29{\pm}0.30\;kg/cm^2$). There was no evidence that dietary additives, such as mushroom extract, increase growth rate or nutritive quality of olive flounder.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.4
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• pp.447-453
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• 2015

We determined the optimal culture conditions for obtaining the maximum number of intestinal bacteria from the olive flounder Paralichthys olivaceus, and studied bacterial diversity using both culture-dependent and culture-independent methods. Using six culture conditions, mean bacterial numbers were greater than $10^6$ per gram of gut mucus, regardless of the medium. However, the bacterial diversity, based on colony morphology, appeared much higher on Marine agar (MA) and Zobell 2216 agar than on other media. We found eight and 17 cultured bacterial phylotypes with 99% minimum similarity in gut mucus grown on MA and tryptic soy agar, respectively. Furthermore, we used genomic DNA extracted from gut mucus to generate 78 random clones, which were grouped into 25 phylotypes. Of these, six were affiliated with Firmicutes, Actinobacteria, and Verrucomicrobia, and were not found using our culture-dependent methods. Consequently, we believe that Marine agar and Zobell 2216 agar are optimal media for culturing diverse intestinal microbes; we also discovered several novel sequences not previously recognized as part of the gut microbiota of olive flounder.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.4
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• pp.397-403
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• 2018

We determined the resistance rates of pathogenic bacteria isolated from cultured olive flounder Paralichthys olivaceus to erythromycin (Em), antibiotic typically used in aquaculture and analyzed the genotypes of resistant bacteria using polymerase chain reaction (PCR). We isolated and utilized 160 isolates of Streptococcus parauberis, 1 of S. iniae, 66 of Edwardsiella tarda, 56 of Vibrio sp. and 23 of unidentified bacteria from presumed infected olive flounder from Jeju Island from March 2016 to October 2017. Of the 306 isolated strains, Em-resistant strains included 33 of S. parauberis, 39 of E. tarda and 2 of Vibrio sp. We conducted PCR to assess the resistance determination of Em-resistant strains. Five different types of Em-resistance genes were detected in the 74 Em-resistant strains: erm (A), erm (B), erm (C), mef (A) and mef (E); erm (A) and erm (B) were detected in 1 (3%) and 24 (72.7%) S. parauberis isolates, respectively. In E. tarda, erm (B) was detected in five isolates (12.8 %) and no Em-resistance genes were detected in the two Vibrio sp. isolates.

• Fisheries and Aquatic Sciences
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• v.26 no.3
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• pp.234-240
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• 2023

Enteromyxum leei has been identified as the causative agent of emaciation disease in a wide range of marine fish hosts. In this study, we aimed to determine the effect of the parasitic infection of Enteromyxum species on starry flounder that were cultured in aquaculture farms of Jeju island in Korea. As the mortality of cultured olive flounder Paralichthys olivaceus because of E. leei infection increased, some fish farms on Jeju island attempted to culture the starry flounder Platichthys stellatus, as an alternative. Myxosporeans with a developmental stage similar to E. leei were found in the intestines of cultured starry flounders. The partial 18S rDNA of myxosporeans showed 100% similarity with E. leei. To reveal the effect of E. leei infection on starry flounder, the intensity of E. leei infection measured using quantitative polymerase chain reaction, and the condition factor (CF) of fish were measured and analyzed statistically. The results showed that high-intensity E. leei infection significantly decreased the CF of the starry flounder. However, the pathogenicity of E. leei to starry flounder is low, considering its mortality and clinical signs.

• Journal of fish pathology
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• v.15 no.2
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• pp.93-97
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• 2002

The scuticociliate, a histophagous ciliate, is known to cause high cumulative mortalities in juvenile olive flounder Paralichthys olivaceus rearing in land-based tank facilities. This study examined effects of bath treatment of 3 chemical agents including formalin, hydrogen peroxide and sodium chloride. and freshwater against scnricociliates infected olive flounder. Although 100 ppm formalin and freshwater did not completeIy eliminale ue scuticociliates within the internal organ of fish, chemicals were effective to prevent scuticociliatosis from spreading. It confirms the efficacy of the chemical with treating the diseased fish for at least 4 consecutive days.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.3
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• pp.337-345
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• 2015

To investigate the causes of emaciation in cultured olive flounder Paralichthys olivaceus in Korea. We performed histological examinations and polymerase chain reaction (PCR) with a new primer set. In most cases, the most severe emaciation was observed in the abdominal area Using PCR on extracted livers, kidneys, spleens, gills, brains, and intestines, we found that areas around the kidneys and intestines were as almost always positive. In significantly emaciated fish, PCR was positive in all internal organs except the gills. In addition, the homology of 812-bp nucleotide sequences of the 28S rRNA gene was more than 99% in emaciated fish. Partial homology with Myxobolus spp. and Cystodiscus axonis, whose data were obtained from GenBank was 86% and 88%, respectively. Histological examinations detected spores in kidneys and intestines but not in other organs. We also performed cohabitation experiments to determine whether infections could be exchanged among species or only within species. Uninfected olive flounder and red sea bream, Pagrus major, cohabitating with emaciated olive flounder showed 100% and 0% cumulative mortality, respectively. Thus the cause of emaciation in cultured olive flounder of Korea is likely due to a new parasite.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.3
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• pp.879-889
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• 2015

The outbreak of viral diseases caused by viral haemorrhagic septicaemia virus (VHSV) and red seabream iridovirus (RSIV) have been reported in cultured olive flounder, Paralichthys olivaceus. VHSV has been a serious viral disease that infects the olive flounders in South Korea. Clinical signs of VHSV infection are skin darkening, abdominal distension and haemorrhages. Outbreaks of fish iridoviral disease was first reported from red seabream, Pagrus major farms in Japan. Recently, iridovirus infection have occurred frequently from olive flounder farms in South Korea. In this study, disease surveillance was performed to monitor the prevalence of VHSV and RSIV in olive flounder in 2014. The samples were collected from 60 different olive flounder farms in Jeju from April, May, September, November and December in 2014. RT-PCR (VHSV) or PCR (RSIV) results showed that VHSV were detected in 5 farms, but RSIV has not been detected in any farms. The migration of olive flounder was restricted for the quarantine in 5 farms of VHS outbreak. The nucleocapsid protein (N) gene and glycoprotein (G) gene sequences of the 5 Korean VHSV isolates were successfully amplified and sequenced. Phylogenetic analysis was performed using the VHSV sequences reported here together comparison with the nucleotide sequences available from the GenBank database. Phylogenetic analysis indicated that most of Korea VHSV belong to the genotype IVa and closely related to the strains from Japan and China.

• Development and Reproduction
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• v.18 no.4
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• pp.275-286
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• 2014

To successful molecular breeding, identification and functional characterization of breeding related genes and development of molecular breeding techniques using DNA markers are essential. Although the development of a useful marker is difficult in the aspect of time, cost and effort, many markers are being developed to be used in molecular breeding and developed markers have been used in many fields. Single nucleotide polymorphisms (SNPs) markers were widely used for genomic research and breeding, but has hardly been validated for screening functional genes in olive flounder. We identified single nucleotide polymorphisms (SNPs) from expressed sequence tag (EST) database in olive flounder; out of a total 4,327 ESTs, 693 contigs and 514 SNPs were detected in total EST, and these substitutions include 297 transitions and 217 transversions. As a result, 144 SNP markers were developed on the basis of 514 SNP to selection of useful gene region, and then applied to each of eight wild and culture olive flounder (total 16 samples). In our experimental result, only 32 markers had detected polymorphism in sample, also identified 21 transitions and 11 transversions, whereas indel was not detected in polymorphic SNPs. Heterozygosity of wild and cultured olive flounder using the 32 SNP markers is 0.34 and 0.29, respectively. In conclusion, we identified SNP and polymorphism in olive flounder using newly designed marker, it supports that developed markers are suitable for SNP detection and diversity analysis in olive flounder. The outcome of this study can be basic data for researches for immunity gene and characteristic with SNP.