• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.6
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• pp.466-471
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• 2006

We investigated the changes in body weight (BW), plasma sex steroid hormone profiles, and testicular development of cultured male eel Anguilla japonica during an artificial maturation process. Eels that received weekly intraperitoneal injections of eel's ringer solution containing human chronic gonadotropin (HCG) were examined. In the ringer-treated control, BW changes decreased slowly during the experimental period. Plasma testosterone (T), 11-ketotestosterone (11-KT) and $17{\alpha},\;20{\beta}$-dihydroxy-4-pregnen-3-one (DHP) levels In the control remained low and did not show significant changes. Moreover, all germ cells in the testes of the control were spermatogonia. In the HCG-treated male eels, however, BW changes increased gradually from the fifth week and then decreased slowly. The plasma T level increased rapidly (p<0.05) in the second week and then decreased slowly. The plasma 11-KT level increased dramatically (p<0.05) in the second week and was maintained until the end of the experiment. The plasma DHP level increased progressively from the second week and peaked in the eighth week (p<0.05). The testes of HCG-treated male eels were more developed than those of the control; most were at the spermatozoa and spermatid stages and showed active spermiation. Thus, spermatogenesis and spermiation in the cultured eel can be induced by repeated injections of HCG.

• Journal of fish pathology
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• v.15 no.2
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• pp.49-56
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• 2002

Effects of Temperature on the Pharmacokinetics of norfloxecin (NFX) were studied in the cultured carp,Cyprinus carpio, and cel, Anguilla japonica, using high performance liquid chromatography (HPLC) originally developed for quinolone determination in livesrocks. Pharmacokinetics of NFX was apparently affected by ambiem water temperature. In a two-compaament model for carp after oral dosage of 20 mg/K01 at $13^{\circ}C$ and $23^{\circ}C$ and 5.20/hr, respectively. In carp the $K_{\iota\nu}$, $T_{max}$and $C_{max}$ for carp at $13^{\circ}C$ were 13.30/hr, 17.44 ${\mu}g$/$m\ell$ and 7.00 ${\mu}g$/$m\ell$, respectively. The" correspoeding values at $23^{\circ}C$ were 3.93/hr, 15.40 ${\mu}g$/$m\ell$ and 9.44 ${\mu}g$/$m\ell$, respectively. The AUC and T were 355.66 ${\mu}g$ hr/$m\ell$, and 12.70 hr at $13^{\circ}C$ and 417,24 ${\mu}g$ hr/$m\ell$ and 13.86 hrs at $23^{\circ}C$, respectively. Similar trends were revealed in the NFX pharmacokinetics of eel kept under the two water temperature regimes aftee oral NFX dosage of 20 mg/kg. These pharmacokinetkal results have some implication in the optimal usage of recently introduced antibacterials in farmed fish, which were originally adapted for poultry and mammalian species.

• Journal of fish pathology
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• v.22 no.3
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• pp.367-374
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• 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 Fisheries and Marine Sciences Education
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• v.28 no.6
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• pp.1573-1580
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• 2016

The disease occurred in cultured eel (Anguilla japonica) in a recirculatory culture system without any separated filtration apparatus. As the pond had a high level of nitrite with $60mg/{\ell}$, 1% NaCl was added to reduce nitrite toxicity to eel. The first outbreak was observed a week after the NaCl treatment and continued for 10 days. Accumulated mortality was about 0.2-0.5%. Affected fish ranged from 150-350 g were usually anorexic and exhibited yellow colour in the skin of the abdominal region and at the base of pectoral fins, as well as in the eyes. In a few individuals with severe symptoms, the lateral skin was also yellowish. The spleen, kidney, muscle and gall bladder were yellowish and the liver was pale-yellow colour but green on the posterior part. The gall bladder was shrunken without bile. Some abnormal erythrocytes such as "tear drop" cells (dacrocyte) were observed in peripheral blood smears stained with May-Grunwald Giemsa. Hematocrit values and hemoglobin contents in the jaundiced eel were significantly lower compared with apparently heathy eel. Severe haemosiderosis accompanied by erythrophagocytosis was found in the kidney and spleen. Haemosiderin deposits were observed in macrophages of the haematopoietic tissue of the kidney and in the splenocytes. But no significant alterations were found in the hepatic cells. In this study we report the first outbreak of jaundice in cultured eel in Korea. Pathological and hematological investigations suggested that severe hemolysis may resulted in jaundice in eel although the cause of hemolytic jaundice was not identified in this study.

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

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.4
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• pp.418-425
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• 2021

The effects of an aquaponic system based on biofloc technology (BFT-AP) were analyzed for eel Anguilla japonica as aquaculture species and caipira Lactuca sativa as the cultivated crops. The rate of weight gain rate by the eels was 178% (BFT-AP 200 head) > 136% (BFT-AP 100 head) > 100% (BFT). The eel body weight in the BFT-AP (200 head) significantly increased when compared to the BFT only eel group (P<0.05). The weight of the upper layer of caipira was 91±8.5 g (200 head) > 90±8.9 g (100 head) > 48±8.3 g (Hydroponic crop, HP). The crop growth in all BFT-AP groups was higher than the control, the hydroponic group. The total ammonia nitrogen (TAN) and NO₂^--N concentrations decreased in the BFT-AP group when compared to the BFT group. It was possible to remove nitric acid from the aquaponics system and reuse it as eel rearing water. Although some nutrient concentrations were low in BFT when compared to HP, the nutrient concentration was sufficient for plant growth. The results show that BFT has the potentially to provide a sustainable aquaponic system.

• Journal of fish pathology
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• v.33 no.2
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• pp.153-161
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• 2020

Cytochrome P450(CYP) gene is involved in the biotransformation of drugs and environmental pollutants. In this study, we analyzed the nucleotide sequence of the Anguilla japonica CYP1(AjCYP1) family gene and examined the relative expression of AjCYP1A, AjCYP1B and AjCYP1C1 in response to the exposure to environmental pollutants. After exposure to B[a]P 20mg/kg bw, the expression of AjCYP1 family gene increased over time. Among four tissues examined (liver, spleen, gill and kidney), AjCYP1 family gene was expressed significantly in the kidney. Compared with the control group, AjCYP1A was expressed about 5-fold at 48 hr, AjCYP1B about 6-fold at 24 hr, and AjCYP1C1 about 4-fold at 24 hr. However, after exposure to B[a]P 200mg/kg bw, AjCYP1A did not change in all tissues. On the other hand, AjCYP1B was expressed at about 4-fold at 24 hr in the spleen and 4-fold at 48 hr in the gill. Finally AjCYP1C1 was expressed 3.7-fold and 4.3-fold in the spleen and kidneys at 48 hr, respectively. Taken together, our results suggest that the expression of AjCYP1 gene in eel tissues might be used as a useful tool to assess the exposure to environmental pollutants in aquaculture system.

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

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.2
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• pp.104-108
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• 2009

Glycation and oxidation induce formation of carbonyl (CO) groups in proteins, which can be used to develop an index of cellular aging. Methyl glyoxal (MG) and hypochlorite anions are deleterious products of oxygen free-radical reaction. The effects of eel carnosine on protein modification mediated by MG and hypochlorite were studied. MG and hypochlorite induced formation of carbonyl groups with high molecular weight and cross-linked forms of ovalbumin. The presence of eel carnosine effectively inhibited these modifications in a concentration-dependent manner. Imidazole ring in eel carnosine might have a primary role in inhibition of protein glycation. Our data suggests that the eel carnosine may be useful as a "natural" anti-glycating agents.

• Fisheries and Aquatic Sciences
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• v.18 no.4
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• pp.387-393
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• 2015

Biotyping of Vibrio vulnificus strains isolated from marine environments along the south coast of Korea showed that the majority of the isolates (94.7%) belonged to biotype 1 and the remaining isolates (5.3%) belonged to biotype 2. Analysis of 16S rRNA V. vulnificus strains isolated from marine environments using a multiplex polymerase chain reaction (PCR) revealed that 78.7% were type A and 21.3% were type B. Random amplified polymorphic DNA (RAPD) was used to analyze the genomic differences in V. vulnificus among the biotype 2 strains isolated from marine environments (newly isolated strains group) and reference strains obtained from infected eels (reference strains group). The two groups had distinctly different profiles of the amplicons produced from RAPD. Additionally, biochemical comparison of these strains revealed that all four strains isolated from marine environments differed from the strains isolated from eels in their ability to promote D-mannitol fermentation. Two (NH 1 and NH 2) out of four isolates of biotype 2 from marine environments showed pathogenicity in eels Anguilla japonica in a challenge test. These isolates did not agglutinate with antisera against V. vulnificus NCIMB 2137 (serovar E), ATCC 27562 (non-serovar E), and ATCC 33816 (atypical serovar E).