• Development and Reproduction
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• v.2 no.1
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• pp.75-80
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• 1998

메기 정자는 그 길이가 약 62.5 \mu m이며 구형의 핵, 짧은 중편 및 꼬리를 ㄱ진 일반적인 메기류 정자의 미세구조적 특징을 나타내었다. 정자는 대부분의 경골어류의 정자에서와 같이 첨체를 가지고 있지 않았으며 염색질은 완전치 농축되어 있었다. 핵와(nuclear fossa)는 약 0.6 \mu m 함입되어 있었고 그 속에 기부 중심립과 말단 중심립의 일부가 포함되어 있었다. 두 중심립은 140 \circ C의 각도로 배열되어 있었으며 말단 중심립에서 9개의 부수체가 언형질막을 향하여 배열되어 있었다. 미토콘드리아는 중편 세포질에서 2층 또는 3층으로 배열되어 있었으며 핵의 후반부와 꼬리의 기부를 둘러싸고 있었다. 꼬리는 축사만으로 구성되어 있었으며 lateral fins는 관찰되지 않았다. 메기 정자의 가장 큰 구조적 특징은 중편 세포질에 구성되어 있는 관구조(tubular structure)이었다. 대부분의 경골어류의 정자는 중편 세포질에 미토콘드리아만을 포함하고 있으나, 메기 정자에서는 중편 세포질의 전반부에 미토콘드리아가 포함되어 있고, 후반부에는 소관이 모여 망상구조를 형성하는 관구조가 잘 발달되어 있었다. 이와 같은 관구조는 현재까지 Characiformes의 정자 이외의 다른 경골어류에서는 보고된 바 없으며 이러한 구조는Characiformes과 메기류의 계통학적 관계를 연구하는데 매우 중요한 형질로 여겨진다. ^u The spermatozoa of Silurus asotus are appoximately 62.5 \mu m in length and relatively simple cells composed of spherical head, a short midpiece and a tail as in most Siluriformes. The ultrastructure of the spermatozoa of S. asotus is characterized by the following features. The nucleus measuring about 1.5 \mu m in length is depressed with a deep nuclear fossa of about 0.6 \mu m in length, two fifth of the nuclear diameter. The fossa contains the proximal centriole and the half of the distal centriole. Two centrioles form an angle of approximately 140 \circ to each other. the nine satellite rays radiate from the outer surface of the distal centriole. the mitochondrea surround the basal nucleus and the axoneme, and are arranged in two or three layers in the postnuclear cytoplasm. The lateral fins are lost in the sperm tail. The most significant feature is manifested in the midpiece. The midpece comprises two parts, the mitochondria and the tubular structure unlike other teleost fishes containing only the mitochondria. The tubular structure was reported only in the spermatozoa of Citharinus belonging to the characiformes of teleost fishes. Thus it is considered to be a good characteristics for the study of phylogenetic link between Siluriformes and Characiformes.

• Korean Journal of Ecology and Environment
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• v.33 no.3 s.91
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• pp.274-281
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• 2000

The dynamic of fish community was investigated in the Wonju stream from March 1998 to February 1999. The collected species during the surveyed period were 24 species belonging to eight families. Eight species (33%) of them were endemic species of Korea. According to relative abundance in the studied areas, Moroco oxycephalus (30.7%), Zacco platypus (29.6%), Carassius auratus (10%), Pseudogobio esocinus (9.4%) and Rhinogobius brunneus (3.6%) dominated. Hemibarbus longirostris, Pungtungia herzi, Squalidus japonicus coreanus, Zacco temmincki, Cobitis rotundicaudata, Silurus asotus, Silurus microdorsalis and Micropterus salmoides were rare to the areas, which occupied less than 0.1% in relative abundance. Dominant species was M. oxycephalus (Kumda-ri, Kwanseol-dong, Hanggu-dong, heongyang-ri), Z. platypus (Gaeun-dong) and C. auratus (Jusan-ri). It was revealed by the analysis of community that St. 3 was the most diverse among all study stations. Coreoleuciscus splendidus and Coreopera herzi have been assumed vanished in the Wonju stream. The species occurring in suddenly decreasing trend were Microphysogobio yaluensis, Liobagrus andersoni, Cottus poecilopus and R. brunneus. The species occurring in representative increasing trend were Cyprinus carpio, C. auratus, P. esocinus, M. oxycephalus, and Z. platypus.

• Ecology and Resilient Infrastructure
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• v.5 no.2
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• pp.105-109
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• 2018

The main objective of this investigation was to examine oxygen consumption and ammonia excretion within cultured catfish, Silurus asotus ($22.9{\pm}0.9cm$, $100.7{\pm}11.7g$ n = 30) by noise and vibration stress in aquaculture farm. The vibration of 48, 58 and 68 dB (V) and noise of $77.6{\pm}1.8dB$ (A) from an electric vibrator was turned on for 15 minutes during each hour each day(0800-1800) for 11 days experimental period. The oxygen consumption (OC) of S. asotus the beginning of the experiment (0 day) in 58 dB group after 1, 5, 9 and 11 days was decreased 21.8, 30.2, 36.0 and 53.2%, respectively. In 68 group after 1, 7 and 11 days was decreased 22.7, 35.1 and 57.7%, respectively. The OC decreased exponentially and the relationship between them was expressed as OC = 0.374D + 90.762 ($r^2=0.048$) at 48 dB, OC = -3.581D + 89.520 ($r^2=0.831$) at 58 dB and OC = -4.109D + 90.907 ($r^2=0.884$) at 68 dB. Ammonia excretion (AE) of the beginning of the experiment in 48, 58 and 68 groups after 1 day was increased by 34.8, 51.8 and 63.2%, respectively, but it was decreased significantly from 3 to 11 days. The AE increased exponentially and the relationship between them was expressed as AE = -1.646D + 115.915 ($r^2=0.265$) at 48 dB, AE = -8.230D + 122.132 ($r^2=0.750$) at 58 dB and AE = -7.086D + 123.690 ($r^2=0.614$) at 68 dB.

• Development and Reproduction
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• v.22 no.2
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• pp.165-174
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• 2018

The aim of study is to contribute to this knowledge-base by investigating the respiratory function, the metabolic rate and the difference of physiological responses un-der low water temperature ($20^{\circ}C{\rightarrow}15^{\circ}C$) stress be-tween diploid and triploid far eastern catfish, Silurus asotus. During the 48 hrs of water temperature stress exposure time, the respiratory frequencies, $CO_2$ and ${NH_4}^+$ concentrations of diploid had higher values than those of triploid (p<0.05). However, pH of triploid was higher than those of diploid (p<0.05), and oxygen consumption rate was not different between diploid and triploid (p>0.05). The level of plasma cortisol and plasma glucose of triploid was lower than those of the diploid (p<0.05). However, in case of lactic acid, there were not significant between triploid and diploid (p>0.05). These results suggest that diploid was more sensitive for low water temperature stress response than triploid in this species.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.5
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• pp.445-450
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• 2010

This study investigated the effects of dietary lipid sources on growth performance and body composition of juvenile far eastern catfish, Silurus asotus. Three replicate groups of fish (average weight 3.6 g) were fed with one of the following experimental diets containing 10% beef tallow (BT), 5% BT plus 5% corn oil (CO), 5% BT plus 5% linseed oil (LO), or 5% BT plus 5% squid liver oil (SO) as the lipid source for 5 weeks. No significant difference was observed in the survival among groups. The weight gain of fish fed the LO (high in 18:3n-3) and SO (high in n-3 highly unsaturated fatty acid) diets was significantly higher than that of the fish fed the CO (high in 18:2n-6) and BT diets (P<0.05). The feed efficiency of fish fed LO and SO diets was significantly higher than that of the fish fed the BT diet (P<0.05), but not significantly different from that of the fish fed the CO diet. The protein efficiency ratio of fish fed the SO diet was significantly higher than that of fish fed the CO and BT diets (P<0.05), but not significantly different from that of fish fed the LO diet. The 18:1n-9 of whole-body polar lipid fraction in fish fed the BT diet increased compared to that of fish fed the other diets. Fish fed the CO and LO diets had significantly higher contents of 18:2n-6 and 20:4n-6, and 18:3n-3, than the fish fed the other diets in polar and non-polar lipid fractions, respectively (P<0.05). Significantly higher contents of 20:5n-3 and 22:6n-3 were observed in the whole-body polar lipid fraction of fish fed the SO diet compared with fish fed the other diets (P<0.05). The study results indicate that linseed oil and squid liver oil containing n-3 fatty acids are good dietary lipid sources for the growth of far eastern catfish.

• Journal of Aquaculture
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• v.9 no.3
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• pp.205-213
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• 1996

Experiments were carried out to investigate the effect of GnRH-analogue (GnRH-a) on the induction of ovulation in catfish, S. asotus. Fully matured female catfish ($250\~600\;g$) received a single intraperitoneal injection of GnRH-a ($50\~200\;{\mu}g/kg{\cdot}body$ weight) showed the successful induction of ovulation. More than $86\%$ of treated females were ovulated after injection of GnRH-a ($90\;{\mu}g/kg$) at $25{\pm}1^{\circ}C$. The majority of spawning took place within 22 to 25 hours after the injection. The gonadosomatic index (GSI) and pseudo-GSI in the group treated with $120\;{\mu}g/kg$ GnRH-a were $23-30\%$ and $18-21\%$, respectively. Average fertilization and hatching rates were $94\%\;and\;81\%$, respectively. Electron microscopically, gonadotrophs of maturing female catfish were characterized by the presence of numerous small, electron-dense granules of approximately $150\~300$ nm in diameter and a few larger, less electron-dense granules of approximately $800\~1000$ nm in size in their cytoplasm. Gonadotrophs of GnRH-a treated catfish showed that their was a distinct decrease in number of small and large granules. The rough endoplasmic reticulum was composed of numerous cisternae conspicuosly dilated to various degrees.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.8
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• pp.1141-1149
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• 2014

The present study was conducted to investigate a supplemental effect of magnesium hydrogen phosphate (MHP, $MgHPO_4$) as an alternative phosphorus (P) source on growth and feed utilization of juvenile far eastern catfish (Silurus asotus) in comparison with three conventional P additives (monocalcium phosphate (MCP), dicalcium phosphate (DCP) and tricalcium phosphate [TCP]) as positive controls. A basal diet as a negative control was prepared without P supplementation and four supplemental P sources were added at the level of 2%. Five groups of 450 fish having mean body weight of 11.3 g following 24 h fasting after three week adaptation period were randomly distributed into each of 15 tanks (30 fish/tank). Fish were hand-fed to apparent satiety twice a day for 8 weeks. Fish fed MHP had weight gain (WG), protein efficiency ratio and specific growth rate comparable to those fed MCP. Fish fed MHP and MCP had feed efficiency (FE) significantly higher (p<0.05) than those fed DCP. Fish groups fed control and TCP showed the lower FE than the other groups which was significantly different (p<0.05) from those of fish fed the other diets. Survival rate was not significantly different (p>0.05) among treatments. Fish fed control had the lowest hematocrit, which was significantly different (p<0.05) from that of fish fed MHP. Fish fed MCP and MHP had plasma P higher (p<0.05) than fish fed the other diets. Relative efficiencies of MCP, DCP and TCP to MHP were found to be 100.5 and 101.3%, 92.0 and 91.6%, and 79.1 and 80.9% for WG and FE, respectively. P availability was determined to be 88.1%, 75.2%, 8.7%, and 90.9% for MCP, DCP, TCP, and MHP, respectively. Consequently, MHP recovered from wastewater stream showed that as an alternative P source its performance was comparative with MCP on growth and feed utilization of juvenile far eastern catfish.

• Journal of Life Science
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• v.26 no.3
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• pp.296-301
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• 2016

An antibacterial peptide from skin extract of the catfish Silurus asotus was purified and characterized. The acidified skin extract was put through a Sep-Pak C18 solid phase extraction cartridge using a stepwise gradient and divided into flow-through (F.T.), 10% methanol-elute (RM10), 60% methanolelute (RM60), and 100% methanol-elute (RM100) fractions. RM10, RM60, and RM 100 showed antimicrobial activity against Escherichia coli D31. On the other hand, the F.T. fraction did not show antimicrobial activity. Among the various fractions, RM 60 had the highest activity. RM 60 was partially purified on a cation exchange column (CM52) by a stepwise gradient. The ammonium acetate (pH 5.15) 0.02 M – 0.8 M fraction showed antimicrobial activity. Then an antimicrobial peptide was purified using a 0.6M fraction with strong antibacterial activity through a series of five C18 reversed-phase HPLC columns. For the characterization of the purified peptide, the molecular weight and amino acid sequence were analyzed by MALDI-TOF MS and Edman degradation. The molecular weight of this peptide was about 4182.1 [M+H]⁺. The amino acid sequence of this peptide was partially determined as follows: PALXXKARREAKVKF. These findings suggest that this peptide plays a significant role in the innate defense system of catfish skin.

• Development and Reproduction
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• v.21 no.2
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• pp.193-204
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• 2017

The influence of triploidization on histological characteristics of retina, trunk kidney, liver and midgut tissue, and cell cycle of tail fin and gill tissue in far eastern catfish, Silurus asotus were analyzed. In the infertile triploid fish, the nucleus and/or cell size of secondary proximal tubule cells of trunk kidney, hepatocyte and midgut epithelium are much larger than those of the corresponding cells in the diploid fish (P<0.05). However, triploid tissue showed fewer number of outer nuclear layer in retina and nuclei in secondary proximal tubule of trunk kidney than those for diploid tissue. The mean percentages of the $G_l-$, the S- and the $G_2+M-phase$ fractions were 92.5%, 3.2% and 4.3% in tail fin tissue of diploid, and 93.4%, 2.6% and 4.0% in those of triploid, respectively. There were no significant differences in the percentages of each cell cycle fraction between diploid and triploid. The mean percentages of each phase fractions were 75.1%, 11.1% and 13.8% in gill tissue of diploid and 85.2%, 8.9% and 5.9% in those of triploid, respectively. The differences of cell cycle between tail fin tissue and gill tissue were statistically significant in diploid and triploid (P<0.05). Also, the differences between diploid and triploid were statistically significant in tail fin tissue and gill tissue (P<0.05). Cyclin D1 and cyclin E expressions were not significantly difference between gill tissue and tail fin tissue, and protein expressions of induced triploid were higher than those of diploid. Results from this study suggest that some characteristics in the triploid exhibiting larger cell and nucleus size with fewer number of cell than diploid can be used as an indicator in the identification of triploidization and ploidy level in far eastern catfish.

• Asian-Australasian Journal of Animal Sciences
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• v.28 no.1
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• pp.111-119
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• 2015

A growth trial was conducted to determine the optimal incorporation level of dietary magnesium hydrogen phosphate (MHP, $MgHPO_4$), which was manufactured from swine manure and phosphorus (P), required by juvenile far eastern catfish (Silurus asotus). Graded MHP of 0.5%, 1.0%, 1.5%, and 2.0%, and 2.0% monocalcium phosphate (MCP) each was added to the basal diet (control) in lieu of cellulose to become the range of available P (AP) from 0.4% to 0.8% of which diets were designated as control, MHP0.5, MHP1.0, MHP1.5, MHP2.0, and MCP, respectively. Control diet contained fish meal (20%), soybean meal (40%), wheat flour (27%), corn gluten meal (5%), fish oil (2%) and soy oil (2%) as main ingredients. Following a 24 h fasting, 540 fish with a mean body weight of 11.8 g were randomly allotted to 6 groups in triplicate, whereby 18 tanks ($0.4{\times}0.6{\times}0.36cm$, water volume of 66 L) were prepared. The feeding experiment lasted for 8 weeks. Fish group fed the control diet showed the lowest weight gain (WG) and feed efficiency (FE) among treatments. The WG was, however, not significantly different (p>0.05) from that of fish group fed MHP0.5. Fish group fed MHP2.0 showed the highest WG and FE of which values were not significantly different from those of fish groups fed diets MHP1.0 and MHP1.5 as well as MCP (p>0.05) except fish groups fed control and MHP0.5. Aspartate aminotransferase was significantly decreased with an increase in available P, while alanine aminotransferase did not show a significant difference among treatment. The highest inorganic P in plasma was observed in fish fed MHP2.0. From the present results, a second-order regression analysis revealed that the optimal dietary MHP level and the AP requirement were found to be 1.62% and 0.7%, respectively.