• 현장농수산연구지
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• 제22권2호
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• pp.51-58
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• 2020

2019년 11월, 국내의 뱀장어 양식장에서 양식 중이던 뱀장어가 피부궤양 및 피부의 점상출혈 소견을 보이며 지속적으로 폐사하였다. 일련의 폐사는 2019년 11월부터 12월까지 지속되었다. Vibrio 속 균주 1E1-2는 첫 번째 폐사 사례에서 폐사한 뱀장어의 출혈성 복수에서 분리되었고 균주 2A3-1는 두 번째 폐사 사례에서 폐사한 뱀장어의 복수에서 분리되었으며 균주 3K1-2는 세 번째 폐사 사례에서 폐사한 뱀장어의 신장에서 분리되었다. 16S rRNA gene 시퀀스 분석으로, 분리균주 1E1-2와 3K1-2가 V. fluvialis NBRC 103150T와 가장 높은 유사도를 나타내며 V. fluvialis로 동정되었으며, 균주 2A3-1는 V. plantisponsor NBRC103148T와 가장 높은 유사도를 나타내며 V. plantisponsor로 확인되었다. 항생제 감수성 실험 결과로, V. fluvialis 1E1-2는 tetracycline과 chloramphenicol에 대하여 중등도의 감수성을 보였고 trimethoprim-sulfamethoxazole에 대하여 내성을 나타내었다. V. plantisponsor 2A3-1는 ciprofloxacin과 levofloxacin에 대하여 중등도의 감수성을 나타내었고 trimethoprim-sulfamethoxazole에 대하여 내성을 나타내었다. V. fluvialis 3K1-2는 tetracycline에 대하여 중등도의 감수성을 나타내었고 ampicillin과 trimethoprim-sulfamethoxazole에 대하여 내성을 나타내었다. 이는 국내 양식 뱀장어에서의 항생제 내성 비브리오 감염증 사례로, 의미 깊은 보고라고 할 수 있다.

• Fisheries and Aquatic Sciences
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• 제24권7호
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• pp.260-275
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• 2021

Aquaponics is a cultivation system that combines aquaculture and agricultural hydroponics. This study investigated the productivity of leafy vegetables cultivated in the hybrid biofloc technology-aquaponics (HBFT-AP) using Japanese eel fed two kinds of diets (Mash, commercial powdered feed and extruded pellet [EP]) and hydroponics (HP).The mash was fed to the fish in a type of a dough mixed with water for 6 weeks (Exp1) and switched to the EP containing 2.7% monobasic potassium phosphate (MKP) for subsequent 6 weeks (Exp2). Leafy vegetables of 8 cultivar were employed in the experiment and water quality [dissolved oxygen (DO, mg/L), pH, water temperature (℃), electrical conductivity (EC; ㎲/cm), turbidity (NTU), TAN (NH₃ + NH₄⁺) (mg /L), NO₂-N (mg/L), NO₃-N (mg/L) and PO₄-P (mg/L)] was measured 6 times a week. Leafy vegetable productivity (HBFT-AP vs HP) was compared in respective experiment, which was similar or somewhat higher in HBFT-AP. During the 12-week feeding trial, concentrations of nitrite (NO₂-N) and phosphorus (PO₄-P) were kept low in variability while total ammonia nitrogen (TAN) and NO₃-N levels increased with time in HBFT-AP. At the end of two feeding trials, values of weight gain (WG, %), feed efficiency (FE, %), specific growth rate (SGR, %) and protein efficiency ratio (PER) were higher in Exp2 than in Exp1. As well, higher values in hematocrit (PCV, %), plasma K (mEq/L) and inorganic phosphorus (mg/dL) were found (p < 0.05) in Exp2 where fish were fed the EP (EP: 38.60%, 2.80 mEq/L and 7.04 g/dL; Mash: 33.20%, 1.95 mEq/L and 5.50 g/dL). Leafy vegetables in HBFT-AP using Japanese eel fed the EP with MKP 2.7% had a productivity similar (4 kinds of cultivar) or somewhat higher (4 kinds of cultivar) compared to those in HP. Also, Japanese eel fed the EP showed higher values of Pi (m/dL) and K (mEq/L) in plasma compared to those fed commercial powder diet.

• 한국동물생명공학회지
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• 제36권4호
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• pp.169-174
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• 2021

Mutations in the luteinizing hormone/chorionic gonadotropin receptors (LH/CGRs), representatives of the G protein-coupled receptor family, have been rapidly identified over the last 20 years. This review aims to compare and analyze the data reported the activating and inactivating mutations of the LH/CGRs between human, rat, equine and fish, specifically (Japanese eel Anguilla japonica). Insights obtained through detailed study of these naturally-occurring mutations provide a further update of structure-function relationship of these receptors. Specifically, we present a variety of data on eel LH/CGR. These results provide important information about LH/CGR function in fish and the regulation of mutations of the highly conserved amino acids in glycoprotein hormone receptors.

• 한국양식학회지
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• 제18권3호
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• pp.135-141
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• 2005

본 실험은 치어기 Japanese eel (A. japonica)의 에너지 수준에 대한 사료내 적정 단백질 비를 평가하기 위하여 갈색어분(Brownfish meal)과 혈분(Blood meal)을 사용하여 조단백질 함량은 에너지에 대해 각각 45%와 50%,그리고 총에너지 함량은 각각 3800, 4150, 4500 kcal/kg의 반정제사료(semipurified)를 제조하여 16주간 사육실험을 실시하였다. 본 연구는 사료내 에너지 수준에 따라 단백질 함량을 달리 조절하여 사육실험을 실시하여 에너지 수준에 따른 적정 단백질 함량을 규명하는데, %증체율(WG), 일간성장률(SGR) 등의 성장평가와 사료효율(FE), 단백질효율(PER) 등의 사료영양학적 평가 및 혈액성상학적 평가와 연관해서 수행하였으며 실험 종료 후 어체내 일반성분 및 혈청 내 생화학적 조성을 비교 조사하였다. WG과 SCR에 있어서 $_{100}P_{45}$실험구가 다른 실험구들에 비해서 유의적으로 높게 나타났다(P<0.05). FE에 있어서 $_{100}P_{45}$실험구가 $_{100}P_{45}$ 실험구를 제외한 다른 실험구들에 비해서 유의하게 높은 것으로 나타났으며(P<0.05), SGR 역시 $_{100}P_{45}$ 실험구가 다른 실험구들에 비하여 유의적으로 높게 나타는데 $_{100}P_{45}$ 실험구와는 유의적인 차이가 없었으며, 이들을 제외한 나머지 실험구들간에 있어서 유의한 차이는 나타나지 않았다(P<0.05). 따라서, 본 결과를 통하여 치어기 Japanese eel (A. japonica)에 있어서 사료내 단백질 함량 45%, 에너지 4500 kcal/g가 최적의 성장을 나타낼 것으로 예측되며, 이때 단백질과 에너지 비율(P/E ratio)은 100mg protein/kcal가 적합한 것으로 판단된다.

• Fisheries and Aquatic Sciences
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• 제25권1호
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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.

• 한국발생생물학회지:발생과생식
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• 제25권4호
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• pp.225-234
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• 2021

The present study aimed to investigate the mechanism of cell surface receptor loss by two constitutively activating mutants (designated L469R, and D590Y) and two inactivating mutants (D417N and Y558F) of the luteinizing hormone receptor (LHR) in the Japanese eel Anguilla japonica, known to naturally occur in human LHR transmembrane domains. We investigated cell surface receptor loss using an enzyme-linked immunosorbent assay in HEK 293 cells. The expression level of wild-type eel LHR was considered to be 100%, and the expression levels of L469R and D417N were 97% and 101%, respectively, whereas the expression levels of D590Y and Y558F slightly increased to approximately 110% and 106%, respectively. The constitutively activating mutants L469R and D590Y exhibited a decrease in cell surface loss in a manner similar to that of wild-type eel LHR. The rates of loss of cell surface agonist-receptor complexes were observed to be very rapid (2.6-6.2 min) in both the wild-type eel LHR and activating mutants. However, cell surface receptor loss in the cells expressing inactivating mutants D417N and Y558F was slightly observed in the cells expressing inactivating mutants D417N and Y558F, despite treatment with a high concentration of agonist. These results provide important information on LHR function in fish and the regulation of mutations of highly conserved amino acids in glycoprotein hormone receptors.

• 생명과학회지
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• 제23권10호
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• pp.1288-1294
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• 2013

뱀장어 자어의 형태변화에 관한 연구는 자어의 인공사육을 위해 알아야 할 중요한 부분이다. 본 연구에서는 두부의 형태학적 관찰과 함께, 부화 이후 변태 직후까지의 단계별 안구의 조직학적인 변화를 관찰하였다. 이들 결과로 부화 후 100일과 변태를 기점으로 상악과 하악의 발달에 큰 차이를 관찰할 수 있었으며, 치아는 실뱀장어로 변태하면서 퇴화한다는 것을 알 수 있었다. 안구 망막에서의 조직학적인 주요 변화는 부화 100일 이후의 OPL (outer plexiform layer)과 ONL (outer nuclear layer)의 형성과 변태 이후 간상세포층의 변화이며, 안구의 각막은 부화 10일째 자어에서 관찰되지 않았지만 이후 모든 단계에서 관찰되었다. 실뱀장어의 양산을 위해 초기 자어의 발달에 관한 더 많은 정보가 필요하며, 본 결과가 자어의 인공사육시스템 안정화에 도움이 될 것으로 기대한다.

• 한국수산과학회지
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• 제47권5호
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• pp.597-602
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• 2014

We determined the effects of starvation, water temperature, and water flow on the onset of metamorphosis in leptocephali of the Japanese eel Anguilla japonica. Leptocephali larger than 50 mm (ca. 200 days old) were reared in 10-L tanks under different feeding, water temperature, and water flow regimes. Fasted leptocephali metamorphosed earlier and faster than did the fed ones. Metamorphosis was faster in the high water flow tank (1.2 L/min) than in the tank with flow at 0.6 L/min. The duration of metamorphosis was slightly shorter at $26^{\circ}C$ than at $23^{\circ}C$. To conclude, starvation induced the metamorphosis of artificially produced leptocephali larger than 50 mm TL. Increased water flow and water temperature both appear to induce and shorten metamorphosis.

• 수산해양교육연구
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• 제20권1호
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• pp.90-94
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• 2008

Growth and water quality in Japanese eel, Anguilla japonica ($6.0{\pm}0.9g$) fed extruded and paste type diets were compared for 8 weeks. Fish in the duplicate tanks were fed with one of three experimental diets: two different extruded pellet diets and one paste type diet. Six FRP tanks were used with stocking density of 3.6 kg per tank (3 m3). Restricted feeds (ca. 2% of body weight) were served twice daily. Weight gains were checked at the end of every two-week interval, and water qualities in terms of NH4-N and NO2-N were determined daily one hour after feeding in the morning. Water temperature, dissolved oxygen, and pH were constantly kept within the optimum range, while fifty percent of total water volume was changed daily. Eels fed the extruded pellet diets showed significantly better (P<0.05) growth performance than did eels fed the paste type diet. The amount of feed waste from the paste type diet was significantly greater than those from the extruded pellet diets (P<0.05). Ammonia (NH4-N) waste was significantly higher from the paste diet than from the extruded pellet diets (P<0.05). These results show that extruded pellet diets are better than the paste type diet for growth and water quality management in eel culture.

• 한국환경과학회지
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• 제20권8호
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• pp.943-951
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• 2011

We investigated the effects of temperature changes on the oxygen consumption rhythm in Japanese eels, Anguilla japonica, using an automatic intermittent flow respirometer (AIFR). The endogenous rhythm of the oxygen consumption rate (OCR) in the eels (n = 18; 44-74 cm, 145-690 g), freshly collected by bag net from estuaries, was nearly synchronous with the tidal pattern of the estuarine collection site. The magnitude of mean OCR (mOCR) of eels showed variable range of 82.2 - 116.5 ml $O_2\;kg^{-1}ww \;h^{-1}$ under constant conditions. In case of increasing temperature from 25 to $38^{\circ}C$, the OCR of eels exhibited a gradually increasing trend with a rhythmic pattern until $36^{\circ}C$. Above $36^{\circ}C$ the rhythms of the OCR dampened and the OCR decreased rapidly at around $36-37^{\circ}C$. The OCR of the eels exhibited the maximum value at $38^{\circ}C$, and then it sharply decreased. The results suggested that the critical thermal maximum (CTM) regarding the endogenous rhythms of the eels was at around $36-37^{\circ}C$ when water temperature increased at $0.5^{\circ}C$/14 h following the acclimation at $25^{\circ}C$. In case of decreasing temperature ($0.5^{\circ}C$/14 h) from 25 to $0^{\circ}C$, the OCR of the eels displayed a abrupt decrease up to $23^{\circ}C$, and between at 23 and $20^{\circ}C$, there was an agitation which showed a slight increase in the OCR with a duration of 1-2 days. Below $9^{\circ}C$, the OCR rhythm of the eels showed a constant state regardless of temperature decreasing. These results suggest that the Japanese eel has an upper incipient lethal temperature at $36^{\circ}C$, with a lower thermal limit at $9^{\circ}C$. The biochemical aspects of the eels influenced by water temperature need to be further studied.