• Korean Journal of Veterinary Research
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• v.44 no.4
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• pp.643-648
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• 2004

Efficacy of ciprofloxacin was evaluated in laboratory and field studies for control of streptococcal infection in flounder and eel. In disc diffussion test, all streptococcal strains showed high sensitivity to the ciprofloxacin. Minimum inhibitory concentrations of ciprofloxacin against all streptococcal strains used in this study were less than $0.195{\mu}g/ml/$. In laboratory studies where fishes were challanged with Streptococcus iniae, significant reductions in mortality were observed among fish receiving ciprofloxacin (in fed) at 100 mg/kg/body weight or more daily for 3 d when compared with mortality of non-medicated controls. Similar results were achieved when 100 mg/kg/body weight of ciprofloxacin was used in field trials.

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

• Proceedings of the Korean Aquaculture Society Conference
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• 2004.05a
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• pp.455-456
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• 2004

• Proceedings of the Korean Aquaculture Society Conference
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• 2004.05a
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• pp.457-458
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• 2004

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

• Korean Journal of Veterinary Research
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• v.49 no.4
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• pp.335-343
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• 2009

The pathogenicity and acute toxicity of Lactobacillus (L.) pentosus PL11 from eel (Anguilla japonica) were investigated using male and female Sprague-Dawley rats. The pathogenicity of L. pentosus PL11 was examined after treating the rats with $10^{11}$ CFU/mL, $10^9$ CFU/mL or $10^7$ CFU/mL doses of L. pentosus PL11 culture or 0.85% NaCl (Control) intragastrically. For acute toxicity studies, rats were treated with dried culture broth of L. pentosus PL11 at doses of 5,000 mg/mL, 2,500 mg/mL, 1,250 mg/mL or 625 mg/mL or Lactobacilli MRS broth (Control), and clinical signs or mortalities were monitored for two weeks. The results of the present investigation revealed no mortalities or obvious clinical signs in rats administered with the live bacterial cultures or dried culture broth at any investigated dose level. Also, no significant differences were observed in net body weight gain, gross pathological findings, feed and water consumption and body temperature among the different treatment groups and between the treated and control rats. It can be concluded from the above findings that L. pentosus PL11 is a safe probiotic strain with potential as feed additive to increase the feed efficiency or health of fish.

• Animal cells and systems
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• v.11 no.2
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• pp.117-124
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• 2007

The present study demonstrates the changes in body weight (BW) and plasma sex steroid hormone profiles during artificial maturation induced by human chorionic gonadotropin (HCG) or salmon pituitary extract (SPE) injections in cultured eel, Anguilla japonica, kept in seawater for 3 months. In the weekly SPE-injected female group, BW was relatively stable during vitellogenesis. Following induction of vitellogenesis, females exhibited a rapid increase of BW, and the oocytes were observed to be in the migratory nucleus stage at the end of the experiment. Plasma testosterone (T) and $estradiol-17{\beta}$ ($E_2$) levels increased slightly during vitellogenesis and peaked at an average of 5.82 ng/mL and 4.76 ng/mL, respectively, at the end of the experiment. In the weekly control and HCG-injected female groups, BW slowly decreased during the experimental period, and the oocytes of the two groups were observed to be at the primary yolk globule stage. In the weekly HCG-injected female group, plasma T and $E_2$ levels increased slightly during vitellogenesis and decreased afterward. In the control female group, however, plasma T and $E_2$ levels were not altered during the experimental period. Furthermore, plasma $17{\alpha},20{\beta}-dihydroxy-4-pregnen-3-one$ (DHP) was not detected in all experimental groups. Fertility and hatching rates of SPE-injected females were significantly higher in those that ovulated 15 h after DHP injection than 18 h. These results indicate that long rearing in seawater increases responsiveness to SPE in ovarian maturation of the Japanese eel, resulting in shortened period from completion of vitellogenesis by sex steroid hormone production.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.3
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• pp.237-242
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• 2011

To evaluate the proximate composition and main nutritive ingredients (vitamin A, $V_A$; vitamin E, $V_E$; cholesterol; the composition of fatty acids) between eels cultured in different domestic eel farms, we analyzed edible parts of eels that were cultured in three "Water Recirculation System (WRS)" farms and three "Still-Water System (SWS)" farms. We found differences in crude protein, crude lipids and the ash content of eel meat between the farms, but water content showed no significant difference. $V_A$ and $V_E$ contents did not show meaningful differences between the two culture methods, but there was a noticeable distinction between the eel farms. In particular, $V_E$ content showed significant differences between the eels of each farm (highest farm, about 25 mg/100 g dry wt; lowest farm, about 1 mg/100 g dry wt). The fatty acids of cultured eels were composed of monoenes (MUFA, 55-60%), saturates (SFA, 30-33%), $\omega$-6 highly unsaturates (HUFA, 1.6-2%) and $\omega$-3 HUFA (8-9.2%). The MUFA content of WRS eels ($59.9{\pm}1.97%$) was higher than that of SWS eels ($55.8{\pm}0.48%$). The contents of other fatty acids were higher in SWS eels (SFA, $33.0{\pm}0.52%$; $\omega$-6FUFA, $1.98{\pm}0.2%$; $\omega$-3 HUFA, $9.2{\pm}0.67%$) than in WRS eels (SFA, $30.5{\pm}1.34%$; $\omega$-6 HUFA, $1.62{\pm}0.19%$; $\omega$-3 HUFA, $8.0{\pm}0.5%$).

• Fisheries and Aquatic Sciences
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• v.23 no.8
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• pp.23.1-23.10
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• 2020

This study was conducted to evaluate the acute effects of waterborne cadmium exposure on bioaccumulation and antioxidant enzymes in eels (Anguilla japonica) and to determine the median lethal concentration (LC₅₀). Fish were exposed to different cadmium concentrations (0, 0.15, 0.30, 0.61, 1.83, 3.08, 3.67, 4.29, and 5.51 mg L^-1) for 96 h. The LC₅₀ of A. japonica to cadmium was 3.61 mg L^-1. Cadmium accumulation generally increased in tissues with increasing waterborne cadmium concentrations. At ≥ 1.83 mg L^-1 exposure, all tissues accumulated significant cadmium concentrations compared with the control group, in the order of kidney > liver > gill > spleen > muscle. Measurements of variation in actual cadmium concentrations showed that a reduction of the metal in experimental water was related to cadmium accumulation in tissues. As activity alteration of antioxidant enzymes for reactive oxygen species, superoxide dismutase and catalase activities increased at ≥ 0.61 mg L^-1 significantly, glutathione peroxidase and glutathione S-transferase activities were not significantly changed. The results of this study suggest that acute exposure to waterborne cadmium is potentially fatal to A. japonica due to the metal's major accumulation in various tissues and the effect of antioxidant enzyme activity.

• Fisheries and Aquatic Sciences
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• v.25 no.1
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• pp.12-19
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• 2022

In the present study, we investigated the effects of recombinant eel gonadotropins (rec-GTHs) on maturation induction in immature ovarian culture in vitro and sex steroid hormones in vivo in the Japanese eel Anguilla japonica. To study the in vitro effects of rec-GTHs on estradiol-17β (E2) production in immature ovarian tissues, ovarian tissues were incubated with different doses of rec-follicle-stimulating hormone (rec-FSH) or rec-luteinizing hormone (rec-LH). The results revealed that the E2 levels in the rec-FSH (0.1, 0.5, or 1 ㎍/mL)- and rec-LH (0.1 or 0.5 ㎍/mL)-treated groups were significantly higher than those in the female eels from the control group. Furthermore, to investigate the in vivo effects of rec-GTHs on the gonadosomatic index (GSI) and plasma sex steroid hormone levels, the eels were injected intraperitoneally with eel's ringer (control), salmon pituitary extract (SPE; for female eels), human chorionic gonadotropin (hCG; for male eels), rec-FSH, rec-LH, and rec-FSH + rec-LH once a week. The results revealed that except for the SPE and the hCG groups, none of the groups exhibited a significant difference in GSI values. However, in vivo plasma E2 levels increased at the end of 4 weeks after rec-FSH treatment in female eels. Based on these results, it is suggested that rec-GTHs may have a positive effect on sexual maturation in female eels; however, further studies on complementary rec-protein production systems and additional glycosylation of rec-hormones are needed to elucidate hormone bioactivity in vivo and in vitro.