• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.1
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• pp.45-51
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• 2014

Scuticociliates are regarded as serious pathogens in marine aquaculture worldwide. In Korea, they cause mass-mortalities in fish such as the commercially important olive flounder Paralichthys olivaceus. In particular, mixed infections of scuticociliates with pathogenic bacteria have been commonly reported. During efforts to identify natural marine-algae derived products that possess anti-bacterial and anti-scuticociliate properties, we found that an 80% methanolic extract of the red alga Polysiphonia morrowii Harvey exhibits both anti-scuticociliate activity against Miamiensis avidus, which is a major causative agent of scuticociliatosis, and anti-bacterial activities against fish pathogenic bacteria. Activity-guided fractionation and isolation of the 80% methanolic extract of P. morrowii yielded three bromophenols, which were identified as 3-bromo-4,5-dihydroxybenzyl methyl ether (1), 3-bromo-4,5-dihydroxybenzaldehyde (2) and urceolatol (3) based on spectroscopic analyses. 3-bromo-4,5-dihydroxybenzyl methyl ether (1) showed the highest anti-bacterial and anti-scuticociliate activities, with a minimal inhibitory concentration (MIC) of $62.5{\mu}g/mL$ (against Vibrio anguillarum) and minimal lethal concentration (MLC) of 62.5 ppm (in seawater). Investigations of the anti-bacterial and anti-scuticociliate activities of seventeen bromophenol derivatives, including the three isolated natural bromophenols, showed that the existence of an electron donating group or atom with a non-covalent electron pair at $C_4$ of the 2-bromophenol structure may be important in anti-scuticociliate activity. These findings suggest that the extract and bromophenol derivatives of P. morrowii may provide useful alternatives in aquaculture anti-scuticociliate therapies.

• Journal of fish pathology
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• v.15 no.2
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• pp.77-82
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• 2002

Effects of stress-induced suppression of humoral immunity on scuticociliate killing activity of olive flounder plasma were investigated. Changes in glucose level. alternative complement activity and Iysozyme activity of plasma by handling stress were analysed in relation to in vitri parasiticidal activity of plasma. The plasma glucose level was about two times higher in fish after a handling stress than in control fish. Plasma lysozyme activity and natural haemolytic activity were decreased in suessed fish.The scuticociliate killing activity of plasma was significantly lower in stressed fish than in non-stressed control fish. The present results indicated that stress-induced immunodepression could be a cause of scuticociliatosis occurrence in olive flounder.

• Journal of fish pathology
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• v.34 no.1
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• pp.47-53
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• 2021

Scuticociliates are one of the serious parasitic threats faced by the marine aquaculturists worldwide. To date, Uronema nigricans, Philasterides dicentrarchi, Miamiensis avidus, Uronema marinum, and Pseudocohnilembus persalinus have been reported as the important culprit species causing scuticociliatosis in fish. The present paper reports the finding of an additional scuticociliate isolate from the gill of diseased olive flounder Paralichthys olivaceus in Korea. Based on the morphological characteristics, a scuticociliate in this study was identified as Paranophrys marina. Phylogenetic analysis placed P. marina as a sister lineage to three species of Pseudocohnilembus and Mesanophrys carcini within the order Philasterida.

• Journal of fish pathology
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• v.33 no.2
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• pp.177-184
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• 2020

In an attempt to find a feed additive showing an anti-scuticociliate effect, extracts from Citrus unshiu Peel were tested against virulent scuticociliate infection. The most effective anti-scuticociliate killing activity in vitro was observed in the extract squeezed from homogenizing water-soaked dried tangerine peel (DTP). In addition, we have investigated the effect of DTP as a feed additive on growth rate and anti-parasitic activity of olivaceus flounder. DTP extract added diets (0.1, 0.5, 1, and 5%/feed weight) were fed to flounder for 7 days for checking a growth rate and 14 days for a challenging test. As a result, the feed conversion rate was significantly improved only in 1% DPT extract group compared to the control and 0.5% DTP extract fed group showed 100% of survival rate in the challenge test, all of which indicating that DTP extract would be a potential feed additive against scuticociliatosis.

• Journal of Aquaculture
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• v.20 no.2
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• pp.106-113
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• 2007

Biological characteristics of Philasteridies dicentrarchi (Ciliophora:Scuticociliate) isolated from the cultured olive flounder Paralichthys olivaceus was determined out by culture, growth conditions, and in vitro relief effect of chemical compounds. The scuticociliate has an active propagation ability by utilizing organic matters obtained from cell strain, bacteria, assorted feed, brain tissue and rotifer tissue. The ciliate achieved population growth activity under the conditions of $5{\sim}45\;ppt$ in salinity and pH 6-9. The ciliate had survived and propagated under the water temperature ranging $10{\sim}30^{\circ}C$, but active growth was observed in the temperature ranges of $10{\sim}25^{\circ}C$. Therapeutic trials were performed with formalin and hydrogen peroxide. The extermination time of the parasites with formalin was in 30 minutes both at 300 and 400 ppm, 60 minutes at 200 ppm, 90 minutes at 100 ppm, and 120 minutes at 50 ppm, respectively. In hydrogen peroxide treatments extermination time was 60 minutes in 300 ppm, 90 minutes in 200 ppm, and 150 minutes at 150 ppm and 100 ppm concentrations.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.5
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• pp.652-659
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• 2021

Microorganism-derived compounds, such as peptidoglycan, lipoteichoic acid, and β-glucan were supplemented in the scuticociliate Miamiensis avidus (M. avidus) vaccine to verify the specify component contribution to the adjuvant effect. Vaccine was formulated with the inactivated M. avidus antigen (YS2, 4.44×10⁵ cells/fish) in combination with either peptidoglycan (10 ㎍ and 100 ㎍/fish), lipoteichoic acid (5 ㎍ and 50 ㎍/fish), or β-glucan (10 ㎍ and 100 ㎍/fish). Olive flounder injected with peptidoglycan supplemented vaccine (10 ㎍ and 100 ㎍/fish) exhibited significant protection, and the relative percent survival (RPS) was 55% and 65% at 4 weeks post vaccination (wpv), respectively, at the corresponding doses. The vaccine groups with added lipoteichoic acid (5 ㎍ and 50 ㎍/fish) exhibited RPS of 40% and 5%, respectively. Additionally, the group with added β-glucan (100 ㎍/fish) exhibited RPS of 35%, but no effect was observed in the group with added 10 ㎍/fish β-glucan. At 8 wpv, olive flounder injected with peptidoglycan and lipoteichoic acid supplemented vaccines exhibited protection with RPS range of 11/11% and 5/21%, respectively, at the respective doses. M. avidus vaccine containing 10 ㎍ and 100 ㎍/fish of β-glucan exhibited the RPS of 32% and 37%, respectively. Conclusively, peptidoglycan contributed in high protection of the M. avidus vaccine, and thus, it can be used as an effective adjuvant in the M. avidus vaccine.

• Journal of fish pathology
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• v.26 no.2
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• pp.65-75
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• 2013

Population growth equation of scuticociliate Miamiensis avidus was obtained from the experimental results of in vitro culture condition to estimate the growth rate and carrying capacity from the growth equation. In addition, intraperitoneal infections into olive flounder Paralichthys olivaceus were carried out into 2 different conditions: different concentrations of M. avidus in same water temperature and same concentration of M. avidus in different water temperatures. Olive flounder mortality was threshold dependent with both the temperature and M. avidus density parameters. In this paper, we propose a mathematical model to study M. avidus growth in olive flounder based upon the interactions between parasite and host. The mathematical model was logistic growth differential equation (1.2). The parameters were found with Matlab program through the Levenberge-Marquardt method. In theorem, equilibrium values between the infected fish population and dead population could found. Our equilibrium points were a stable equilibrium and an unstable equilibrium. From the equation (1.6), it was possible to predict the amount of cumulative mortality of olive flounder along with the time after M. avidus infection.

• Journal of fish pathology
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• v.30 no.2
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• pp.107-114
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• 2017

We evaluated the anti-parasitic efficacy of hydrogen peroxide against a scuticociliate Miamiensis avidus in olive flounder Paralichthys olivaceus. In vitro tests showed that hydrogen peroxide above 50 mg/l is effective for killing M. avidus. In vivo effects were assessed in olive flounder after immersion infection with $2.8{\times}10^3M.\;avidus/ml$ for 2 days, and in naturally infected fish obtained from Jeju area farms. Bathing treatment with 100 and 200 mg/l hydrogen peroxide showed markedly higher survival rates of olive flounder than control groups (p<0.05). The number of live M. avidus in fish tissues were reduced for 3 days in naturally-infected fish after a single bath. In conclusion, hydrogen peroxide can be a good therapeutant particularly in the early stage of M. avidus infection.

• Journal of fish pathology
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• v.23 no.3
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• pp.303-311
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• 2010

Our previous finding summarizing that larval sieving process is inevitable but triggers the outbreak of scutica-like ciliates (SLCs) in the seed production of Patinopecten yessoensis urged further study to determine best suggestable sieving interval in an agreeable range of water quality. In the mass seed production of the scallop, SLC outbreak was closely related to the larval sieving in which larvae were drained on the basis of every 3-day (5T), 5-day (3T), 7-day (2T), or 9-day (1T) from culture tanks onto a mesh screen and placed back into new water in cleaned tanks. The larval performance of growth and survival was clearly dependent on the sieving intervals. It was in order of 3T, 5T, 2T, and 1T for both of growth and survival and in reverse order for SLC infection frequency, confirming that larval sieving is necessary but damageable if it overwhelms the larval resistance. Interestingly, the larval damages by the sieving persisted to their ensuing spat life in terms of nursery growth, survival, and abnormality.

• Journal of fish pathology
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• v.21 no.1
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• pp.1-11
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• 2008

We report the existence of new type of phosphatidylcholine-hydrolyzing phospholipase D (PLD), which has been characterized and partially purified in the scuticociliate, Uronema marinum. The enzyme from partial purification showed that it was existed in membrane fraction and was a neutral PLD, which catalyzed both transphosphatidylation and hydrolysis reaction. The activity of partially purified membrane-bound PLD was also found to be optimal at pH 7.0-7.5 for 2 hours at 37℃ and depended strictly on the presence of Ca2+ (2.5 mM) and Mg2+ (1.6 mM). Immunoblot analysis indicated that the enzyme was distinct from hPLD1 (human PLD1) and hPLD2 (human PLD2) because it was not recognized by a polyclonal antibody raised to the 12 terminal amino acid of these enzymes. We also found that the membrane-bound PLD is a PIP2-dependent PLD and that GTP-binding proteins are not implicated in the regulation of this enzyme: This enzyme activity is markedly stimulated by phosphatidylinositol 4,5-bisphosphate (PIP2) but not by the small G-protein Arf and GTPrS. In addition, this enzyme was capable of hydrolyzing phosphatidylcholine (PC) but not phosphatidylethanolamine (PE), implying that PC was a preferred substrate.