• Journal of fish pathology
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• v.23 no.1
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• pp.119-122
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• 2010

Mortality and gill lesions in snakehead, Channa argus (body length range, 20.3-22.2 cm) reared in a aqua-farm in Busan, Korea, were associated with a dense bloom of Apiosoma-like ciliate, Order Petrichida. The size of parasite was $48.83{\pm}7.75{\mu}m{\times}14.29{\pm}2.66{\mu}m$. Histological examination revealed that a severe edema and collapse of the gill tissue were observed in a number of samples of snakehead. The mechanism of gill damage was likely due to physical irritation by the parasite. It is believed that this is the first report of Apiosoma-like ciliate in cultured fish in Korea.

• Journal of fish pathology
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• v.23 no.1
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• pp.113-118
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• 2010

The present work describes myxozoan parasite found in the skin of cultured snakehead, Channa argus fingerings (total length, 5.5~7.2 cm) from Busan, Korea. Nature spores and plasmodia were found in the skin mucus of infected fishes. In fresh state, the total length of the spore was $27.96{\pm}2.50{\mu}m$. The size of spore body was $14.16{\pm}1.78{\mu}m{\times}4.88{\pm}0.61{\mu}m$. The polar capsules were pyriform and the size was $5.57{\pm}0.66{\mu}m{\times}1.36{\pm}0.33{\mu}m$. This is the first report of Henneguya sp. from cultured fish species in Korea, and further studies are necessary for definitive identification.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.2
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• pp.114-121
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• 2012

A novel neuropeptide was isolated from the skin of the snakehead Channa argus using the dorsal retractor muscle (DRM) of a starfish Asterina pectinifera as a bioassay system. The amino acid sequence of the purified peptide was analyzed using automated sequencing and MALDI-TOF mass spectrophotometry. The primary structure of the purified peptide was determined to be Pro-Ala-Leu-Ala-Leu. To investigate the complete primary structure of this peptide, Pro- Ala-Leu-Ala-Leu-OH and Pro-Ala-Leu-Ala-Leu-NH2 were synthesized. The chemical and pharmacological properties of the synthetic peptides were compared with those of the native peptide. Both the native peptide and synthetic Pro-Ala- Leu-Ala-Leu-OH had identical behaviors on the reverse-phase and cation-exchange HPLC chromatograms. Synthetic Pro-Ala-Leu-Ala-Leu-OH showed contractile activity on the DRM, and the threshold concentration of this peptide was approximately $10^{-8}$ M. The maximal contractile effect ($E_{max}$) of this peptide was $294{\pm}45.4$% at $10^{-5}$ M.

• Korean Journal of Microbiology
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• v.31 no.2
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• pp.113-122
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• 1993

Aeromonas veronii was isolated from the haemorrhagic ulcer of the snakehead that had been infected in natural condition, This bacterium was injected hypodermically into the healthy snakeheads and the effect was compared to the naturally infected fish. Both groups showed severe necrosis, falling off of epidermal tissue and hypodermal muscle. In both groups, severe histophathological changes were observed in gill, digestive tract and kidney just before death. Artificially injected fish showed necrosis of tissue in skin, gill and digestive tract from 2 days after injection. Then it showed necrosis or cell atrophy of tissue in kidney from 5 days after injection, and in liver and spleen just before death. Snakehead infected with haemorrhagic ulcer died within 9 days after infection, showing the symptom of skin damage and metabolic inhibition in respiration" digestion, excretion, etc. It was concluded that Aeromonas veronii (CA26) that was isolated from the naturally infected fish is the main bacterium causing haemorragic ulcer in the snakehead.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.3
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• pp.653-660
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• 2016

Snakehead, Channa argus were intraperitoneally infected with Nocardia seriolae. at the concentrations of $1.5{\times}10^7cfu/m{\ell}$ or $1.5{\times}10^8cfu/m{\ell}$. The infected fish were kept in aquaria at $25^{\circ}C$ and $30^{\circ}C$ for 3 weeks. Clinical signs and mortality were monitored daily to evaluate the virulence. All artificially infected fish showed the same clinical sign found in naturally infected fish. All the fish infected with $1.5{\times}10^8cfu/m{\ell}$ of N. seriolae died within 24days. N. seriolae showed higher virulence to snakehead at the temperature $30^{\circ}C$. Internal lesions such as whitish nodules in the infected internal organs were not correlated with mortality but some degenerative changes were observed in all the infected organs within a week. Whitish nodules in the infected organs which are the typical character in nocardial infection was initially found at two weeks after the artificial infection in snakehead.

• Korean Journal of Microbiology
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• v.30 no.3
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• pp.164-170
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• 1992

Haemorrhagic ulcer in cultured snakehead(Chann0 argus) is widespread in Korea during the summer season. Round haemorrhagic ulcers as the main symptom of this epizootic disease can be found on the skin of the head. body, as well as fins of this fish. This study was conducted to investigate the pathology of this disease. First. Aeromonas veronii. the dominant species. was isolated from diseased snakeheads. Then this bacterium was injected into healthy snakeheads hypodermically. Such injection was found to induce haemorrhagic ulcers very similar to those observed in naturally infected fish. One or two days afier the injection, a red spot developed around the injection site. and grew bigger to from a red area. This enlarged area then developed into haemorrhagic ulcer, accompanied by substantial skin loss. Within five days. muscle necrosis proceeded to the extent that a perforation was made between the injection site and the opposite side. The fifty per cent lethal dosage was found to be $1\times10^{5}$CFU/0.25 ml by intraperitoneal injection. The results of this experiment lead us to conclude that Arromonas veronii is a major bacterium which causes haemorragic ulcer in cultured snakcheads.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.5
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• pp.353-360
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• 1990

The bacterium Edwardsiella tarda was injected into healthy snakeheads (Channa argus) in order to prove the causative agent of ascite. The bacterium dominantly isolated from 2 cultured ascite snakeheads was injected into fish by the dose of $5\times10^6$ CFU/ 0.25ml, but the same dose of $0.65\%$ physiological saline was injected into the each control. The injected fish was divided into 4 groups such as intraperitoneal, intramuscle, control intra-peritoneal and control intramuscle according to their injection points. Each was composed of 10 healthy snakeheads respectively. Ascites and haemorrhagic ulcers became distinct 5 days after injection, but controls did not show any abnormal symptoms during the experimental period. Edwardsiella tarda was reisalated out of the injected fish's ascite, liver, kidney, spleen and haemorrhagic ulcer on the skin. Regardless of the injecting methods, liver was necrotized more severely than any other internal organ, but both the glomeruli of kidney and spleen were considerably damaged. Necrosis of muscle and a number of leucocytes were observed at the ulcerous region of the intramuscular injected fish. It is concluded that judging from the above results the Edwardsiella tarda is a causative agent to cause ascite in snakehead.

• Korean Journal of Veterinary Research
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• v.36 no.2
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• pp.297-303
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• 1996

The regional distribution and relative frequency of endocrine cells in the GIT of the snakehead, Channa(Oph icephalus) argus were studied immunohistochemically. Five kinds of endocrine cells and one kind of nerve cell were identified in this study. A few numbers of secretin-immunoreactive cells were restricted to the cardia and fundus of the stomach. Moti-lin- and GRP-immunoreactive cells were rare in the epithelium of the distal and proximal intestines. PYY-immunoreactive cells were found in a few number in the pyloric caeca and were rare in the distal intestine. Substance P-immunoreactive cells were distributed relatively numerous from the fundus to the distal intetsine. Also, their nerve cells were detected in occurrence in the lamina propria in the distal intestine. No neurotensin-, met-Enk- and GIP-immunoreactive cells were found in the GIT of the snakehead.

• The Korean Journal of Mycology
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• v.27 no.1 s.88
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• pp.32-38
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• 1999

A Saprolegnia sp. was isolated from cultured snakehead, Channa argus, and its physiological characteristics were investigated. The optimum temperature, pH and NaCl concentration for mycelial growth of Saprolegnia sp. were $25^{\circ}C$, 6.0 and 0%, respectively. The mycelial growth was increased with the addition of 10 mM phosphate and 10mg/L casamino acid. The essential oils extracted from three plants, Artemisia princeps var. orientalis, Thuja orientalis and Chamaecyparis obtusa have been tested to know whether they inhibit the growth of Saprolegnia sp. at six different oil concentrations(10, 100, 500, 1,000, 1,500 and 2,000 ppm). Essential oil from A. princeps var. orientalis began to inhibite the mycelial growth of Saprolegnia sp. at the concentration more than 10ppm. Using other essential oils from T. orientalis and C. obtusa, those initially inhibited the mycelial growth of Saprolegnia sp. at the concentration over 10 ppm and complate inhibition of mycelial growth was observed at over 500 ppm. The histopathological features of Snakehead infected by Saprolegnia sp. were studied. A club shape of gill lamella epithelial cells was observed in the gill. The mycelial cells were penetrated into muscular tissue, and the accumulation of the ceroid was observed in the liver, spleen and kideny tissue in common. The necrosis of tubular epithelial cells was seen in the liver tissue, parenchymal tissue in the spleen and tubular epithelial cells in the kidney.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.4
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• pp.492-502
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• 1995

This paper describes the relationship between the behavior of the snakehead ( Channa arps) of 44cm long and the environmental noise levels due to the piling work. The experiment is conducted in the aquafarm located near Asan lake, Pyongtaek in 1993. The fish trajectory is obtained by a biotelemetry system in which a pulsed ultrasonic pinger attached onto the dorsal is tracked three dimensionally, and the noise and the vibration levels both in air and in water are measured. The results of this study are as follows: 1) The noise levels in water and in air and the vibration level measured at a distance of 90m from the noise source, increased by 36.5dB $(re\;l{\mu}Pa)$, 2308$(re\;0.0002{\mu}bar)$ and $5.9{\mu}m$ repectively compared to the levers before piling. 2) The highest variation of the swimming speed was observed right after the piling works and the width of variation decreased with the elapsed time. The average speeds of the fish before and during the works were measured as 0.8 times and 1.1 times of the body length, respectively. 3) It is found that the fish escapes into the mud of the aquafarm when a heavy shock wave occurred. Consequently, the heavy shock by the piling works could produce a considerably unfavorable effect to the fish.