• Fisheries and Aquatic Sciences
• /
• v.12 no.4
• /
• pp.265-275
• /
• 2009

G Protein-coupled receptors (GPCRs) mediating wide ranges of physiological responses is one of the most attractive targets for drug development. Rhodopsin, a dim-light photoreceptor, has been extensively used as a model system for structural and functional study of GPCRs. Fish have rhodopsin finely-tuned to their habitats where the intensity and the wavelength of lights are changed depending on its water-depth. To study the detailed molecular characteristics of GPCR architecture and to understand the fishery light-sensing system, genes encoding rod opsins were isolated from fishes living under different photic environments. Full-length rod opsin genes were obtained by combination of PCR amplification and DNA walking strategy of genomic DNA isolated from olive flounder, P. olivaceus, Japanese eel, A. japonica, and Common carp C. carpio. Deduced amino acid sequences showed a typical feature of rod opsins including the sites for Schiffs base formation (Lys296) and its counter ion (Glu113), disulfide formation (Cys110 and Cys187), and palmitoylation (Cys322 and Cys323) although Cys322 is replaced by Phe in Japanese eel. Comparison of opsins by amino acid sequence alignment indicated the closest similarity between P. olivaceus and H. hippoglossus (94%), A. japonica and A. anguilla (98%), and C. carpio and C. auratus (95%), respectively.

• Journal of Aquaculture
• /
• v.22 no.1
• /
• pp.56-62
• /
• 2009

Effects of Korean mistletoe extracts (KM-110), Viscum album coloratum on the specific and non-specific immune responses of Japanese eel Anguilla japonica were examined. The optimal concentration not showing toxicity of KM-110 was determined to $30-40{\mu}g/ml$ in vitro and $100{\mu}g$/100 g of fish in vivo. Even $1000{\mu}g$ of KM-110/100 g of fish did not show any clinical problem in fish though the levels of toxic parameters were slightly increased. In terms of antibody production, KM-110 significantly elicited more antibody production than FCA or $\beta$-glucan. $\beta$-glucan plus KM-110 group synergistically enhanced antibody production. There was no significant difference between KM-110 and KM-110 plus $\beta$-glucan group. The ROI production by head kidney (HK) leucocytes of eel injected with 500 or $1000{\mu}g$ KM-110 was significantly (P<0.05) enhanced than the control and FCA-treated group. Maximum increase in the NBT reduction value was observed in $1000{\mu}g$ KM-110 group but no significant difference was found between 500 and $1000{\mu}g$ KM group. The level of serum lysozyme activity was significantly (P<0.05) higher in the 500 and $1000{\mu}g$ KM-110- or FCA-treated group than in the control and $200{\mu}g$ KM-110 group. The phagocytic activities of HK leucocytes isolated from eel injected with 500 and $1000{\mu}g$ KM-110 were significantly (P<0.05) higher than $200{\mu}g$ KM-110 and PBS-injected control group. Korean mistletoe appeared to be a good activator of the specific and non-specific immune responses of Japanese eel.

• Journal of fish pathology
• /
• v.36 no.2
• /
• pp.239-250
• /
• 2023

Disease monitoring was conducted to investigate the recent disease occurrence in Japanese eels (Anguilla japonica). Between May 2021 and March 2022, an investigation was conducted on eels from seven farms experiencing mortality. JEECV (Japanese eel endothelial cells-infecting virus) was detected in all examined farms, each exhibiting co-infections with 1 or 2 bacteria, including Edwardsiella anguillarum, E. piscisida, Aeromonas sp., Citrobacter freundii, Lactococcus garviae, or Vibrio sp. From March 2022 to October 2023, monthly periodic inspections were carried out at a farm in Yeonggwang, Jeollanam-do, for a total of 22 times. JEECV was detected in 10 out of 22 times, even when mortality was not recorded. Bacteria such as E. anguillarum, C. freundii, Aeromonas sp., and Vibrio sp. were isolated, but consistent clinical signs of liver abscess and hemorrhagic lesions were only recognized in fish infected with E. anguillarum. Other bacteria were often isolated from apparently healthy fish. In conclusion, mortality in eel farms frequently occurs due to co-infections of JEECV with bacteria rather than JEECV alone. Therefore, to reduce eel mortality, it is crucial to decrease co-infections, with a particular emphasis of JEECV and E. anguillarum.

• Journal of Fisheries and Marine Sciences Education
• /
• v.18 no.3
• /
• pp.374-378
• /
• 2006

Eel is Anguilla japonica and Anguillidae family as a freshwater fish, and Japanese name is Unagi. The content of vitamin A of eel muscle are about 4,000IU/100g and they have many effective components, so it is known as healthy food. Therefore, many people have eel that cooked roast and hot-water extract in Korea. WHO encouraged that daily edible content of vitamin A is 2,000IU. Now, Japan government proposes the weight of roasted eel in lunch basket as 50g. But, Korea government does not proposes in every related aspects. Therefore, we researched content of vitamin A in hot-water extract from eel and optimal processing condition of hot-water extract from eel, in order to determine a proper edible volume. The content of vitamin A in eel hot-water extract sold at a market was about 200 IU. This study resulted from the fact that many eel hot-water extracts lacked the vitamin A. The reason was that the lipids were removed for taste on processing. But, The content of vitamin A in eel hot-water extract which didn't removed lipid on processing was about 800IU. Therefore, in drinking for 3packs per day, eel hot-water extract might have adjusted 100mL per pack which is almost consistent with the recommended dietary allowance of vitamin A in WHO.

• Korean Journal of Ichthyology
• /
• v.27 no.4
• /
• pp.263-274
• /
• 2015

Change in morphological and biological characteristics of Japanese eel, Anguilla japonica, by maturation were determined by examination of 182 individuals collected in Korea waters from September to December 2014. Eels were classified into four stages based on the silvering index. The proportion of silver eels collected from streams and estuaries (34.6%) was higher than that from the freshwater reservoirs (3.8%). The sex ratio between female and male was 1:0.11 (n=182). Mean total length and weight were positively related to the silvering process. The ratios of head and pectoral lengths to total length and the ratio of horizontal and vertical orbital diameters to head length were significantly different between the maturation stages. However the ratio of pre-dorsal and pre-anal lengths to total length were not significantly different between the maturation stages. The gonado-somatic index was the single character that could identify the whole four stages among the indices examined: gonado-somatic index (GSI), condition factor (K), gut index (GI) and eye index (EI) but hepato-somatic index (HSI). One pseudo-silver eel collected. looked like a late silver eel in the S2 stage according to its external body color and morphology, but most of other characteristics suggested that it might be in Y1 (yellow eel) or Y2 stage (late yellow eel).

• Proceedings of the Korean Aquaculture Society Conference
• /
• 2005.05a
• /
• pp.117-117
• /
• 2005

• Proceedings of the Korean Aquaculture Society Conference
• /
• 2004.05a
• /
• pp.360-361
• /
• 2004

• Development and Reproduction
• /
• v.16 no.4
• /
• pp.289-294
• /
• 2012

Gene expressions of cytochrome P4501A (CYP1A), aryl hydrocarbon receptor (AhR) and vitellogenin (Vg) by endocrine disruptors, benzo[${\alpha}$]pyrene (B[a]P) and tributyltin (TBT) were examined in cultured eel hepatocytes which were isolated from eels treated previously with B[a]P (10 mg/kg) or estradiol-$17{\beta}$ (20 mg/kg) in vivo, and the relationship between CYP1A, AhR and Vg genes were studied. When the cultured eel hepatocytes were treated with B[a]P ($10^{-6}-10^{-5}M$) the gene expressions of CYP1A and AhR were enhanced in a concentration-dependent manner. However, when treated with TBT ($10^{-9}-10^{-5}M$) the gene expressions of CYP1A and AhR were suppressed at high concentrations ($10^{-6}-10^{-5}M$), while having no effects at low concentrations ($10^{-9}-10^{-7}M$). Gene expression of Vg was also suppressed by TBT in a concentration-dependent manner in cultured eel hepatocytes which was previously treated in vivo with estradiol-$17{\beta}$.

• Journal of fish pathology
• /
• v.22 no.3
• /
• pp.367-374
• /
• 2009

The effects of extacts of Omae Prunus mume were tested on non-specific immune response of Japanese eel Anguilla japonica. Lysozyme activity in the serum of the administrated group was presented higher than control, whereas no difference was lysozyme in the mucus or bacterial reaction of the serum. The lysozyme activity of the serum was increased 2 weeks after administrated and highest of that was 5 weeks later. Results of the experimental challenge of Edwardsiella tarda and Aeromonas hydrophila were presented administrated group was higher than control. The results of both groups in the growth rate were same.

• Journal of fish pathology
• /
• v.25 no.3
• /
• pp.173-180
• /
• 2012

Vibriosis is one of the most prevalent fish disease belonging to the genus Vibrio. In present study, Vibrio sp. isolated from Japanese eel was confirmed as Vibrio scophthalmi using analysis of the genomic sequence of 16S rRNA. The major signs were hemorrhage of body surface and inner surface of abdomen, severe enteritis and retention of ascitis. Histopathological examination revealed blood cell degenerations in various organs (gills, liver, spleen, kidney, heart, intestine), exfoliate of intestinal epithelium, and congestion and hemorrhage in intestinal lamina propria. This is the first case report on V. scophthalmi infection in Japanese eel Anguilla japonica.