Infection of Enteromyxum leei in cultured starry flounder Platichthys stellatus
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Abstract:
Enteromyxum leei has been identified as the causative agent of emaciation disease in a wide range of marine fish hosts. In this study, we aimed to determine the effect of the parasitic infection of Enteromyxum species on starry flounder that were cultured in aquaculture farms of Jeju island in Korea. As the mortality of cultured olive flounder Paralichthys olivaceus because of E. leei infection increased, some fish farms on Jeju island attempted to culture the starry flounder Platichthys stellatus, as an alternative. Myxosporeans with a developmental stage similar to E. leei were found in the intestines of cultured starry flounders. The partial 18S rDNA of myxosporeans showed 100% similarity with E. leei. To reveal the effect of E. leei infection on starry flounder, the intensity of E. leei infection measured using quantitative polymerase chain reaction, and the condition factor (CF) of fish were measured and analyzed statistically. The results showed that high-intensity E. leei infection significantly decreased the CF of the starry flounder. However, the pathogenicity of E. leei to starry flounder is low, considering its mortality and clinical signs.Keywords:
Platichthys
Paralichthys
Olive flounder
Myxozoa
Two bacteria strains were isolated from emaciated olive flounder (Paralichthys olivaceus) in aquafarm and were identificated as Vibrio harveyi (JV1) and Edwardsiella tarda (JE1), respectively. In the challenge experiments, we found 100% cumulative mortalities in all of olive flounder injected with JV1, JE1 or JV1+JE1 within eleven days after the injection. Two bacteria strains were reisolated from dead fish and were analyzed using the PCR method. In the physilogical analysis, the hematocrit, AST, ALT and cholesterol levels in experimental groups were increased significantly compared to those in control group, but the glucose, total protein and triglyceride levels were significantly decreased. Additionally, the lysozyme activity in the blood serum was decreased. The histopathological observations of the intestine showed that all groups had detachment and destruction of epithelial tissues except for the control group.
Paralichthys
Olive flounder
Edwardsiella tarda
Vibrio harveyi
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Streptococcus parauberis (stain SNUFPC-050803), isolated from diseased olive flounder Paralichthys olivaceus in Jeju Island, Korea, was evaluated for its pathogenicity to healthy juvenile flounder (29.3 g in average body weight). When challenged with the isolate by intraperitoneal injection with tenfold serial dilutions of 4.5 × 10-106 CFU/fish, the cumulative mortality ranged from 10% to 80% within 14 days except for 4.5 × 10 CFU/fish and control with no mortality. Disease signs were hemorrhage around the mouth, eyes and pectoral fins, pale and friable liver with hepatomegaly and ascitic fluid in the peritoneal cavity. These signs were similar to those of naturally affected fish. S. parauberis was reisolated and identified by PCR method, which confirmed the pathogenicity of the bacterium to olive flounder.
Olive flounder
Paralichthys
Streptococcus iniae
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Paralichthys
Olive flounder
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Experiments were carried out to investigate the effects of lead exposure on survival, growth and oxygen consumption of juvenile oliver flounder, Paralichthys olivaceus. Survival rate of the oliver flounder was significantly affected above 150㎍/L. Growth of the olive flounder exposed to ≥ 150 ㎍/L of lead concentration was significantly lower than that of fish reared in normal condition. Metabolic rate of fish exposed to lead ≥ 80 ㎍/L concentration was significantly reduced with increasing lead concentration than that in normal condition. This study revealed that high lead concentration (≥ 80 ㎍/L) reduced growth and metabolic rates of juvenile olive flounder suggesting potential influence of lead on the natural mortality of olive flounder in the coastal areas.
Paralichthys
Olive flounder
Juvenile fish
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Freezing of adult flounder Platichthys flesus and turbot Psetta maxima for 24 h resulted in mean decrease of total length ( L T ) of 2·1 and 1·3% and a reduced body mass ( M ) of 3·1 and 1·3%, respectively. Increasing the freezing time to 25 days increased the shrinkage in turbot but not in flounder. The L T and M T conversion equations for the different species and time spent frozen are given. The differences between species could be explained by the higher volume to surface area relationship in turbot compared with flounder.
Platichthys
Maxima
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Enteromyxum leei has been reported to cause emaciation disease in various fish species. To determine the effect of parasite intensity on cultured olive flounder Paralichthys olivaceus, we investigated the relationship between the relative condition factor (rCF = CF/standard CF × 100) and parasite load with quantitative polymerase chain reaction (qPCR) and the challenge test. A total of 57 cultured olive flounders were obtained from 11 fish farms and divided into five groups based on their rCF. We investigated the parasite intensity in the posterior intestine of the fish. The parasite load was closely matched to severe loss of body weight. In addition, olive flounders were inoculated either orally or anally with intestinal scrapings of infected fish or phosphate-buffered saline. The fish were reared at natural water temperature and transferred to different tanks, and the water temperature was adjusted to 20°C after 6 weeks of inoculation. When the water temperature was increased to 20°C, the rCF decreased in the experimentally infected group. The results demonstrated that qPCR can be utilized to determine the relative abundance of E. leei in olive flounders and water temperature is an important factor to track the progress of the emaciation disease.
Paralichthys
Olive flounder
Myxozoa
Myxosporea
Emaciation
Parasite load
Trichodina
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This study is to find out the effects of various iron concentrations on growth, feeding and feed efficiency of olive flounder, Paralichthys olivaceus, The growth rate, feeding rate and feed efficiency of olive flounder in each experiments were represented by the relative value. The relative growth rate and relative feed efficiency of olive flounder were kept almost constant below the iron concentration of 1.0 mg/, but were significantly decreased above the 5,0 mg/ iron concentration. The growth rate, feeding rate and feed efficiency of olive flounder exposed to 10.0mg/ iron concentration were significantly decreased than that exposed to normal condition. From these results, it could be concluded that the high level of 5.0 mg/ iron concentration in the bottom water would curtail production of olive flounder in coastal area.
Paralichthys
Olive flounder
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Garlic (Allium sativum) is known to have antimicrobial effects but there are few data on its effects against fish pathogenic bacteria. This study was conducted for possible development of natural food antimicrobials from garlic extracts, particularly allicin. The filter sterilized, aqueous extract of garlic was tested for its ability to inhibit the growth of 7 fish pathogenic bacteria (E. tarda, V. ichthyoenteri, V. harveyi, P. damselae, S. iniae, S. parauberis, L. garviae) using the disc diffusion test, minimum inhibitory concentration test, and minimum bacteriocidal concentration test. The garlic extract inhibited growth and killed most of the organisms tested. The disc diffusion test was performed using garlic extracts (100%, 50%, 25%, 10%, each 20㎍), and MIC test was also performed using a diluted concentration of garlic extracts (488 - 250,000 ㎍/㎖). According to the results, garlic extracts exhibited antimicrobial activity against all of seven bacteria, and these results suggest that this garlic extract can be used as an antimicrobial substance against fish bacterial diseases in the fish industry.
Paralichthys
Olive flounder
Pathogenic bacteria
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Paralichthys
Olive flounder
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Streptococcal diseases are known as serious problems in fresh water and marine fish culture industry worldwide. Recently, the importance of the infection of Streptococcus parauberis has been increased among the streptococcicosis since severe outbreaks in cultured olive flounder (Paralichthys olivaceus) were recorded in Korea. The aims of the present study were to investigate immunomodulatory differences between S. parauberis and S. iniae. In this study, S. parauberis isolated from diseased olive flounder was investigated on the characteristics of morphological and immune responses. Immune response of the fish to the pathogen was characterized by bactericidal activity in the serum, phagocytic activity and reactive oxy- gen intermediaters (ROIs) production of olive flounder. The capsules of both bacteria, S. parauberis and S. iniae seem to be associated with the ability to resist killing activity of normal sera. Also, capsulated strains could survive in the phagocytes and induce to lower ROIs production.
Olive flounder
Paralichthys
Streptococcus iniae
Isolation
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