• 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.

• Development and Reproduction
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• v.22 no.3
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• pp.225-234
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• 2018

A new embryonic cell line (OFEC-17FEN) derived from olive flounder Paralichthys olivaceus was developed. OFEC-17FEN cells were subcultured for <30 passages over ~200 days. OFEC-17FEN cells had a doubling time of 114.34 h and modal diploid chromosome number was 48. The pluripotency genes POU5f1 and NANOG were expressed in OFEC-17FEN cells. However, the lack of several pluripotency-related genes expression indicates that OFEC-17FEN cells are not stem cells. OFEC-17FEN cells transfected with plasmid pEGFP-c1 exhibited a strong green fluorescent signal at 48 h after transfection. Accordingly, OFEC-17FEN cells may be useful for both basic research and biotechnological application.

• Journal of fish pathology
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• v.37 no.1
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• pp.9-15
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• 2024

An enzyme-linked immunosorbent assay (ELISA) with two Novirhabdovirus antigens (viral hemorrhagic septicemia virus, VHSV and infectious hematopoietic necrosis virus, IHNV) was used to detect specific antibodies against VHSV from olive flounder (Paralichthys olivaceus) sera. In ELISA plates with VHSV culture supernatants (VHSV-Ag plate), optical density (OD) values for sera from olive flounder with VHS history (VHS sera) ranged from 0.64±0.36, and those of sera from fish without VHS history (non-VHS sera) ranged from 0.26±0.26. In IHNV-Ag plate, the OD values (0.43±0.28) for VHS sera were quite low compared to those in VHSV-Ag plates, while the OD values for non-VHS sera were almost similar. When the OD values for each serum were calculated by subtracting the OD values in the IHNV-Ag plate from those in the VHSV-Ag plate, the corrected OD values were significantly different between VHS sera and non-VHS sera. The results were completely in line with fish histories of VHS epizootics. It was considered that the corrected OD values may represent the true values recognized by VHSV-specific antibodies.

• Development and Reproduction
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• v.24 no.3
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• pp.207-214
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• 2020

Primary cell culture is a sufficient method frequently used to study the cellular properties and mechanisms of isolated cells in a controlled environment. In this study, an embryonic cell line (FGBC8) derived from the blastula stages of embryos of olive flounder Paralichthys olivaceus was developed. Furthermore, conditions for optimal long-term maintenance of this primary embryonic cell culture were investigated. Morphologically, FGBC8 cells were composed primarily of epithelial-like cells. FGBC8 cells were subcultured for >160 passages over ~830 days. The doubling time of FGBC8 cells was 73.8 h, and the modal diploid chromosome number was 48. FGBC8 cells transfected with green fluorescence protein (GFP)-expression plasmid exhibited a strong signal 48 h after transfection. Consequently, we demonstrated that fish serum is a crucial supplement for the long-term survival and maintenance of comparable morphology in these primary embryonic cells. Our results can be used as a guide for primary embryonic cell cultures for other fish species and may be useful for cell biotechnological applications.

• Journal of fish pathology
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• v.34 no.2
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• pp.225-231
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• 2021

In biofloc culture for olive flounder, Paralichthys olivaceus, the possibility of antibiotics treatment was investigated against edwardsiellosis. After inducing edwardsiellosis by immersion in Edwardsiella tarda 1.2 × 10⁵/mL suspension, the survival trends on various biofloc water management and some physiological changes were observed. For biofloc water management, six types of water treatments were carried out, which were no exchange without antibiotics as negative control, the exchange to stored biofloc water, the exchange to stored biofloc water with 20% flow-through, the exchange to fresh biofloc water, half fresh biofloc water and half sea water, and the complete flow-through. There was no significant physicochemical change on water qualities in any type. The exchange to fresh biofloc water was shown the highest survival ratio as 72.3%, and in case of stored biofloc water with 20% flow-through, the survival ratio was also significantly high as 62%. Plasma glucose, cholesterol, total protein, calcium, and magnesium were analyzed as physiological index. Mostly, there was no significant change, but plasma cholesterol showed an initial decrease in low survival group, and an initial increase with high survival group. Consequently, antibiotic treatment against a bacterial disease during biofloc culture is possible as long as the biofloc water management follow along properly.

• Journal of Aquaculture
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• v.7 no.2
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• pp.109-122
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• 1994

The cultured olive flounder larvae given nutrient enriched rotifer, Artemia nauplii and commertial micro diet were investigated the changes of lipid content, fatty acid composition and vitamin E content in whole body with growth stages in order to compare with those of the wild one. The results obtained are as follows. 1) Lipid and vitamin E contents of the cultured larvae were higher than those of the wild one. 2) Clear differences of fatty acid composition with growth stages, especially 18: 2n-6 and 22 : 6n-3, were recognized between the wild and cultured olive flounder larvae. 3) Changes of lipid content, fatty acid composition and vitamin E content were found to be affected by dietary composition given to fish. 4) The wild olive flounder larvae were found to obtain natural live foods containing of low lipid content and high concentration 22: 6n-3 based on the fatty acid composition of the fish.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.57 no.1
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• pp.23-31
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• 2024

This study evaluated the utilization of a low fish meal (LFM) diet and black soldier fly (BSF) Hermetia illucens meal and oil as a fish meal (FM) substitute or functional additive for juvenile olive flounder Paralichthys olivaceus at the Jeju fish farm. Two experimental diets replaced FM using animal (tankage, poultry byproduct and tuna byproduct meal) and plant (wheat gluten and soy protein concentrate) protein sources, containing 45% (FM45) and 35% (FM35) of FM, respectively. One experimental diet replaced FM with animal, plant, and BSF meal, fish oil using insect meal and oil (FM35+). After the feeding trial ended, no differences in growth performance, feed utilization, survival and biological indices were observed among all experimental groups. Aspartate aminotransferase and cholesterol levels in the FM35 and FM35+ groups were significantly higher than that in the FM70 group. The linoleic acid level in the muscle was significantly higher in the fish fed with the FM70 diet than in those fed with the FM45, FM35, and FM35+ diets. Thus, the LFM diet is suitable for juvenile olive flounder farming during six months.

• Journal of Aquaculture
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• v.13 no.3
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• pp.223-230
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• 2000

A rearing experiment of the olive flounder was performed in a set of water-reuse system to test the reusability of the water in culture system with (i) a foam fractionator to separate particles from water and (ii) a culture tank contain mineral particles to filter the metabolic wastes by adsorption and/or decomposition. Two kinds of commercially processed loess particles and a dolomite particle (all 50 ${\mu}$diameter) were tested. The mineral particles were suspended in the culture tank and the water was pumped into the foam fractionator, where the particles were separated and drained out with foam from the system. In a circular culture tank of 4.8 m in diameter with 10 d water, the juvenile olive flounders (23.1 g/fish, 5,555 fish, 128 kg total body weight) were stocked. 90 % of the rearing water was reused and turnover rate of the water in the tank was two times per hour. Water temperature was maintained 17${\pm}$1$^{\circ}C$. At the end of 75 day-experimental rearing, 5,532 flounders, weighing 468 kg, were harvested. An individual flounder grew to 84.6 g of body weight. The final stocking density was 26.0 kg/$m^2$. No diseases were observed during the experiment.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.5
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• pp.1470-1478
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• 2015

Adjuvant is an immune enhancer commonly used during vaccination to enhance the host immune response. In the present study, we produced the several recombinant protein from immune related gene of olive flounder (Paralichthys olivaceus). Especially, to produce the soluble type of recombinant protein, we constructed the MBP (Maltose binding protein) fusion G-CSF (Granulocyte colony stimulating factor) recombinant protein among the flounder immune related genes. To verify the immune stimulatory effect and safety of this recombinant protein (rPoGCSF), expression changes of several immune genes were tested using quantitative real-time PCR method with gene specific primer from flounder head kidney leukocytes. As a result, we confirmed that the rPoGCSF has an ability of immune stimulatory effect, also it has broad range of pH and temperature.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.3
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• pp.300-308
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• 2023

This study aimed to evaluate the utilization of low fish meal (LFM) diet and black soldier fly (BSF) Hermetia illucens meal supplementation in LFM diet as a fish meal (FM) replacer or functional additive for juvenile olive flounder Paralichthys olivaceus. Three LFM diets were prepared to contain 30, 25, and 20% FM, respectively (designated as F30, F25, and F20). Three BSF diets were prepared by adding 2.0, 2.5, and 3.0% BSF in the LFM diets, respectively (designated as F30B2.0, F25B2.5, and F20B3.0). A total of 540 fish (initial mean body weight: 22.3±0.01g) were randomly distributed into 18 tanks (240 L) in triplicate groups and fed the experimental diets twice daily for 12 weeks. Results showed that there were no significant differences in the growth performance, feed utilization and survival among all the groups. Lysozyme activity significantly increased in F30B2.0 and F25B2.5 groups compared to their respective LFM groups. Total immunoglobulin was significantly higher in F30 group than in F20 group. Anti-protease and myeloperoxidase activities were significantly higher in F30B2.0 group than in F20 group. Innate immunity gradually decreased with decreasing FM level in all the groups. BSF supplementation significantly improved immunity compared to their respective LFM diets. Therefore, BSF could be used as an immuno-stimulant supplement in LFM diets for P. olivaceus.