The glycoprotein hormone family consists of follicle-stimulating hormone (FSH; GTH1), luteinizing hormone (LH; GTH2), and thyroid-stimulating hormone (TSH), which are secreted by the pituitary gland in all mammalian species, and chorionic gonadotropin, which is secreted by placental trophoblast cells in primates and equids. These hormones consist of non-covalently associated α-, β- subunits. Within a species, the amino acid sequence of α-subunit is identical across all glycoprotein hormones and is encoded by a single gene. The αβ dimer is the active form of the hormone, and biological specificity is conferred by the β-subunit. Both of α and β subunit of eel FSH has two N-glycosylation sites (α-subunit: Asn56 and Asn79; β -subunit: Asn5 and Asn22, respectively). In the present study, we constructed deglycosylated mutants at single and double sites in each subunits of eel FSH for identification of Asn linked oligosaccharides' biological role. Mutant cDANs were cloned into pcDNA3 expression vector and transiently transfected into CHO suspension cells. The quantity of rec-eelFSHs were quantified by sandwich ELISA system, using monoclonal antibodies produced in our lab. The wild type rec-FSH protein was detected at the predicted molecular weight of 34 kDa by western blot. The molecular weight of deglycosylated mutants at single site decreased with about 4 kDa and of mutants at double sites decreased with 8 kDa. After PNGase treatment in the rec-eel FSH proteins, molecular weight also decreased to 7-8 kDa. We generated stably parental cell lines, engineered to express a β-arrestin 2EA fusion protein, expressing eel FSHR and C-terminal deleted mutant. 2 out of 5 receptor cells each were selected by G-418 and we tested these cell lines in a receptor functionality using PathHunter β arrestin assay (DiscoverX). Follicle stimulating hormone acts through binding to its specific receptor. Binding of ligand to the receptor activates the adenosine 3',5'-cyclic monophosphate (cAMP) pathway (McFarland et al., 1989; Ji and Ji, 1991a; Rose, 1998) and the inositol 1phosphate (IP1) the second messenger systems. After stimulation of eelFSH receptor stably transfected Parental CHO cells with FSH wild type and mutant hormones as a ligand, production of cAMP and IP-1 were evaluated (Cisbio). cAMP IC-50 values by eelFSHwt; αΔ56; αΔ79; αΔ56_79; and βΔ5 were 33.1; 1154.7; 22; 410 and 311.9 ng/ml, respectively. IP-1 IC-50 values by eelFSHwt; αΔ56; αΔ79; αΔ56_79 and βΔ5 were 6.8; 7.1; 4.4; 3.8 and 10.2 ng/ml, respectively too. The cAMP activation was greatly decreased in the αΔ56αmutant. Thus, the site of α56 oligosaccharide in the eel plays an pivotal role for the cAMP stimulation using eel FSH receptor cell lines. In the IP-one assay, the activity in the αΔ56 and βΔ5 mutants was a little decreased than the wt. The biological roles of N-linked oligosaccharides in GPCR internalization are going to be estimated by measuring β arrestin recruitment system.

The glycoprotein hormone family consists of luteinizing hormone (LH), follicle stimulating hormone (FSH) and thyroid stimulating hormone, which are secreted by the pituitary gland in all mammalian species, and choriogonadotropin (CG), which is secreted by the placenta in primates and equids. The hormones are composed of a common α subunit and a hormone specific β subunit which are non-covalently associated. Recent advances in biotechnology, particularly in the production of recombinant proteins, have provided opportunities to produce sufficient quantities of recombinant fish GTHs using various expression hosts. Japanese eel Anguilla japonica is one of the most important fish species being aquacultured in Japan but is hampered from the fact that this species does not reproduce in captivity. Artificial induction of gonadal maturation has been successful by administration of pituitary extracts or human chorionic gonadotropin, but the understanding the regulatory mechanism of gonadal development moderated by follicle stimulating hormone (FSH) and luteinizing hormone (LH) remains elusive due to lack of suitable amounts of eel gonadotropins (GTHs). In the present study, we produced tethered rec-eel LH and deglycosylated mutants (56, 79 and 56-79 of α subunit; 10 of β-subunit) of Asn-linked oligosaccharides in CHO suspension cells. Luteinizing hormone acts through binding to its specific receptor. Binding of ligand to the receptor activates the adenosine 3',5'-cyclic monophosphate (cAMP) pathway (McFarland et al., 1989; Ji and Ji, 1991a; Rose, 1998) and the inositol 1 phosphate (IP1) secondary messenger systems. After stimulation of eelLH/CG receptor transfected CHO cells with rec-LH wild type (wt) and mutant hormones as a ligand, production of cAMP and IP-1 were evaluated (Cisbio). cAMP IC-50 values by rec-eelLH wt; αΔ56; αΔ79; αΔ56_79 and βΔ10 were 606.2; 374.9; 100.3; 14.2 and 210.9 ng/ml, respectively. IP-1 IC-50 values by rec-eelLH wt; αΔ56; αΔ79; αΔ56.79 and βΔ10 were 28.3; 16.04; 4.3; 2.1 and 3.6ng/ml, respectively too. As seen in both of the second messenger production, general stimulatory pattern is analogous. cAMP and IP-1 stimulation by wild type and αΔ56, as well as αΔ79 and βΔ10 were approximate, but the stimulating effect of double mutant (αΔ56_ 79) was drastically higher. According to the data, deglycosylated eelLH may bind to the receptor with high affinity and cAMP production is gradually increased. Furthermore, receptor activation by tethered rec-eel mutant ligands (FreeStyle CHO-MAX Expression System) will be evaluated with β arrestin recruitment and GPCR internalization for N-linked oligosaccharides’ biological role in activation of eelLH/CGR.

This study was conducted to analyze fishing capacity and bycatch by mesh size and entrance size of spring net pot conductedby water tank and field experiment. The water tank experiments were conducted by using traps with mesh size of 22 mm and entrance size of 120 mm and 140 mm, respectively in the water tank of NIFS. The field experiment was conducted using 5 kinds of spring net pot with mesh sizes of 20 mm, 22 mm, 35 mm and entrance size of 120 mm, 130 mm, 140 mm, 360 mm by coastal trap fishery vessel operating around the area of Geoje island. In the result of water tank experiments, the catch of conger eel was 1.5 times higher when using trap with entrance size of 140 mm than that of 120 mm. In the field experiment, when using same mesh size, the larger the entrance size, the higher amount of conger eel catch, bycatch and number of bycatch species. When using the same entrance size, the larger the mesh size, the lower amount of conger eel catch and number of bycatch species, whereas the amount of bycatch showed increasing trend.

Shortfin eel (Anguilla bicolor pacifica) is a species of commercial importance and its production is greatly affected due to the infection by Heterosporis anguillarum. In this study, we evaluated the effect of H. anguillarum infection on the growth of Shortfin eel. A disease that trunk muscle of cultured shortfin eel, Anguilla bicolor pacifica, were irregular and resulted in death, breakout of the commercial eel culture farm. We observed that the trunk muscle of infected eels were irregular and represented white or yellowish externally. Histopathologically, a great numbers of large or small spores and sporophorocysts were also observed in degenerated muscle layer. The cloning of specific gene of H. anguillarum, encoding small subunit ribosomal RNA (SSU-rRNA) was amplified by the polymerase chain reaction(PCR) from the muscle lesion of diseased eel. The size of clone gene is well matched with the size of small subunit ribosomal RNA of H. anguillarum and thus confirming the infection by H. anguillarum.

The purpose of the study is to estimate the Green-House-Gas (GHG) emissions from domestic eel farm in the water recirculation system or still-water system by the assessment of energy consumptions and GHG emissions for establishing to reduce standards of GHG from a sustainable perspective. GHG emission components as seeds, feed, fuel, electricity, fixed capital, fish respiration, and others were analysed at the different culture type between water recirculation system and still-water system by 3 stage farm size of small, medium, large scale. The result showed that the mean GHG emission of the eel farm was 18.7kg·CO2 in the stage of production per fish 1kg at different culture type and farm size. Therefore it could be useful for policy, planning, and regulation of aquaculture development with establishing GHG reduction standards.

In order to obtain the fundamental data about the behavior of conger by underwater audible sound, this experiment was carried out to investigate the hearing ability of Conger eel Conger myriaster which was in the coast of Jeju Island by heartbeat conditioning method using pure tones coupled with a delayed electric shock. The audible range of conger eel extended from 50Hz to 300Hz with a peak sensitivity at 80Hz including less sensitivity over 200Hz. The mean auditory thresholds of conger eel at the frequencies of 50Hz, 80Hz, 100Hz, 200Hz and 300Hz were 105dB, 92dB, 96dB, 128dB and 140dB, respectively. The positive response of conger eel was not evident after the sound projection of over 200Hz. At the results, the sensitive frequency range of conger eel is narrow in spite of swim bladder. Auditory masking was determined for Conger eel by using masking stimuli with the spectrum level range of about 60~70dB (0dB re 1μPa/Hz). According to white noise level, the auditory thresholds increased as compared with thresholds in a quiet background noise including critical ratio at 68dB of white noise from minimum 26dB to maximum 30dB at test frequencies of 80Hz and 100Hz. The noise spectrum level at the start of masking was distributed at the range of about 68dB within 80~100Hz.

Reproductive ecology of the sharp toothed eel, Muraenesox cinereus was investigated based on the samples captured in southern Korean waters from January 2010 to December 2011. Gonadosomatic index began to increase in April, and reached maximum between July to August. After spawning it began to decrease from October. Reproductive season was estimated to April-September, with peak in July. Fecundity was proportional to the size of the female, with the clutch size varying from 56,000 eggs in the smallest female (anal length, 27.0cm) to 1,400,000 eggs in the largest (anal length, 49.5cm). Size at 50% sexual maturity (AL50), determined from mature females, were 21.9cm. Annual reproductive cycles of this species could be divided into four successive stages; immature stage (October-February), maturing stage (March-May), mature stage (June-August) and spent stage (August-October).

소음 스트레스로 인한 뱀장어(Anguilla japonica)의 영향을 파악하기 위하여 스트레스 지표로 사용되는 코티졸, 포도당, 알부민 및 glucocorticoid receptor(GCR) 유전자의 발현 양을 측정, 분석하여 노출되지 않은 대조구와 비교하였다. 그 결과, 알부민은 노출 1시간 후에 낮은 값을 보인 반면 코티졸과 포도당은 대조구에 비해 매우 큰 차이를 보이며 높게 나타났다. GCR 유전자의 조직 발현 결과 간, 아가미, 근육 및 소장에서 많이 발현하였다. 소음 노출에 따른 시간의 변화에서 간과 아가미 근육과 소장에서 발현이 감소하는 양상을 나타내었다. 실험결과 뱀장어의 glucocorticoid receptor 유전자의 발현변화가 소음 스트레스로 인한 영향을 파악하는데 유용한 지표가 될 수 있음을 확인하였다.

Recently, Fishermen have required to expand the circumference of trap entrance for conger eel because it was difficult to take the catch out as well as to put the baits into. A series of fishing experiments was carried out in coastal areas of Tongyoung, Korea in 2008 and 2009 using the traps to describe the effect of the entrance size on the catch. The experimental traps (five types) were used in filed experiments with four types circumference size traps (140, 180, 220 and 260mm) with mesh size 22mm and another type was used the same one usually using in filed with mesh size 35mm (750mm circumference). The experiment results were, the conger eels of total length 35mm more or so were caught 85, 93, 142 and 176 individual by the experiment traps with mesh size 22mm as increase circumference size from 140mm to 260mm, respectively. And the small conger eels of the total length below 35mm to be prohibited to catch by law were caught 145, 160, 288 and 304 individual according to increase the circumference size of trap, respectively. In addition, in case of the trap with mesh size 22mm, bycatches were 230 - 260 individuals and much more than bycatches of the trap with mesh size 35mm. In conclusion, when we expand the circumference size of trap according to fishermen's requirement, we should review not only economic of fishery but also increasement the bycatch of non-target fishes and small size fishes.

Present study was conducted to improve the spring frame net trap for conger eel, Conger myriaster which prevents by-catch and protects immature fish. A series of comparative fishing experiment was carried out in water off the south-east coast of Korea from Nov. 2004 to Jul. 2005. And analyzed the amount of catch, by-catch rate, and CPUE, etc. of experimental traps which were the spring frame net traps, sorted four types of flappers. And the compared gear was a plastic conger eel pot. The conclusions were as follows. By-catch rates of spring frame net trap with the compressed flapper bound by nylon mono-filament was about 0-3%. CPUE of spring frame net trap with the compressed flapper was about 50-60% lower than that of traditional and plastic pot. And in case of conger eel that the total length is over 350mm, CPUE was little different on each type of flapper of every mesh size.