• Parasites, Hosts and Diseases
• /
• v.24 no.2
• /
• pp.194-200
• /
• 1986

A study on the population density of crayfish intermediate hosts and infestation status of crayfish with encysted larvae of Paragonimus westermani in Ulchin county, Kyungpook Province, Korea was conducted from May to October in 1986. The population density of the crayfish ranged from 1 to 13, with an average of 4 per man-hour. Among the six habitats, Ducheon had a somewhat higher density than that of the others. Of eight hundred and seventeen crayfish examined, 127 or 15.5 per cent harboured the metacercarial larvae of Paragonimus westermani. The majority of the larvae were found in three parts of the body: most frequently in the cephalothorax, next in the gills, and then in the liver. The average number of metacercarial larvae per infected crayfish ranged from 1.0 to 1.9, with an average of 1.7. Summarizing the results, this study indicates that the population density of crayfish intermediate host and infestation rates for the crayfish with encysted larvae of Paragonimus westermani in Ulchin county of Kyungpook Province is relatively high.

• Journal of fish pathology
• /
• v.26 no.1
• /
• pp.1-9
• /
• 2013

The acute toxicity and sublethal effects of nitrite on the dark-banded rockfish, Sebastes inermis (mean body weight: $83.3{\pm}7.2$ g), were studied under static conditions for a period of 96 h. The acute toxicity of nitrite was at the 50% lethal concentration ($LC_{50}$) of 700 mg/L. The sublethal effects on selected hematological parameters of the dark-banded rockfish, such as its osmolality, hematocrit, cortisol, alanine aminotransferase (ALT), and aspartate aminotransferase (AST), were measured after 0, 6, 12, 24, 48, 72, and 96 h of exposure to 0, 50, 100, 200, 400, or 700 mg/L nitrite. Sublethal nitrite caused a progressive reduction in the hematocrit of the fish, depending on the nitrite concentration and the exposure period. Exposure to 100-700 mg/L nitrite for 96 h caused a reduction in the hematocrit and an increase in cortisol, ALT, and AST compared with the control levels. Abnormal ultrastructural changes in the gills and liver tissues were observed in fish exposed to 700 mg/L nitrite for up to 96 h compared with the control tissues. Ultrastructural changes included atrophic gill mitochondria and hepatocytes that developed smooth endoplasmic reticulum and atrophic mitochondria. Although no rockfish mortality occurred at 500 mg/L nitrite, all the hematological parameters examined responded adversely to a nitrite dose of 200 mg/L for 96 h. These results show that although the acute toxic concentration of nitrite for the dark-banded rockfish is > 700 mg/L, sublethal concentrations of nitrite also negatively affect its hematological parameters.

• Asian-Australasian Journal of Animal Sciences
• /
• v.23 no.12
• /
• pp.1557-1565
• /
• 2010

Methyl paraben (MP), which is used as a preservative in pharmaceutical and cosmetic (shampoo) products, foods and beverages, enters into the aquatic environment and can pose a potential fish health hazard. In this experiment, effects of MP were evaluated in adult male common carp (Cyprinus carpio) by exposing them to fractions (1/$143^{rd}$ to 1/29th) of the $LC_{50}$ dose with every change of water for 28 days. Vitellogenin induction, metabolic enzymes, somatic indices and bioaccumulation were studied at weekly intervals. The $96^{th}$ h $LC_{50}$ of MP in fingerlings was 120 mg/L. Compared to the control, except for increases (p<0.01) in alkaline phosphatase (EC 3.1.3.1), alanine aminotransferase (EC 2.6.1.2) and liver size, there were decreases (p<0.01) in activity of acid phosphatase (EC 3.1.3.2), aspartate aminotransferase (EC 2.6.1.1), and testiculosomatic index following exposure to any dose of MP. Vitellogenin induction was significantly higher (p<0.01) in exposed than unexposed (control) fish. The bioaccumulation of MP in testis, liver, brain, gills and muscle tissues of fish increased significantly (p<0.01) with increase of dose from 0.84 ppm to 1.68 ppm. Dose and duration of exposure (p<0.01) indicated that an exposure period of 1 to 2 weeks was sufficient to cause changes in the quantifiable parameters studied. Fish exposed to 4.2 ppm MP became lethargic after the $26^{th}$ d. Histologically, degeneration, vacuolization and focal necrotic changes in liver and fibrosis-like changes in testicular tissue were noted.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.50 no.1
• /
• pp.15-24
• /
• 2017

This study examined the effects of dietary supplementation with citrus by-product (CBP) on the growth, feed utilization, innate immunity, and histology of the gills and intestine of juvenile olive flounder Paralichthys olivaceus during low water temperature season. A vitamin C-free basal diet was regarded as a control and five other diets were formulated that contained 30 and 300 mg of L-ascorbyl-2-polyphosphate (LAPP) or CBP as vitamin C equivalents/kg diet, or the antibiotic oxytetracycline (OTC) (designated as control, LAPP30, LAPP300, CBP30, CBP300, and OTC, respectively). Olive flounder (initial body weight $44.6{\pm}0.32g$) were fed the six experimental diets to apparent satiation for 9 weeks. Growth and feed utilization were significantly higher in CBP30 than in the control and LAPP groups. The lysozyme activity was significantly higher in CBP30 than in LAPP300. Enterocyte height was significantly higher in CBP30 than in the control. The number of goblet cells was increased significantly with LAPP30, LAPP300, and CBP30. These results demonstrate that CBP can reduce or replace vitamin C and antibiotic in the diet of olive flounder during the low-water-temperature season. The optimal CBP supplementation level seems to be approximately 1%, which is equivalent to 30 ppm vitamin C/kg in the fish diet.

• Fisheries and Aquatic Sciences
• /
• v.17 no.3
• /
• pp.377-380
• /
• 2014

RNA interference (RNAi)-mediated transcriptional knock-down of Crassostrea gigas big defensin 1 and 2 genes (Cg-BigDef1 and Cg-BigDef2) was investigated. The cDNA sequences of Cg-BigDef1 and Cg-BigDef2 were identical, excluding an additional fragment of 20 nucleotides in Cg-BigDef1; thus, a long double-stranded RNA (dsRNA) targeting the mRNA of Cg-BigDef2 effectively downregulated both Cg-BigDef2 and Cg-BigDef1. In addition, long dsRNA targeting green fluorescent protein (GFP) did not affect transcription of the two big defensin genes. These results suggest that the transcriptional downregulation of Cg-BigDef1 and Cg-BigDef2 was mediated by sequence-specific RNA interference (RNAi). Despite injection of long dsRNA targeting Cg-BigDef2 into only the adductor muscle, knock-down of Cg-BigDef1 and Cg-BigDef2 was observed in the adductor muscle, hemocytes, mantle, and gills, suggestive of systemic spread of RNAi in C. gigas. Furthermore, the inhibitory effect of dsRNA persisted until 72 h post-injection, indicative of a long-lasting RNAi-mediated knock-down of target genes.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.51 no.1
• /
• pp.15-22
• /
• 2018

Alpha-pinene is an organic compound that possesses antibiotic and anti-parasitic activities. In this study, we developed a layered nanocomposite to combat against Miamiensis avidus which causes scuticociliatosis in the olive flounder Paralichthys olivaceus. We used a solid-solid reaction to develop the layered nanocomposite, incorporating-pinene ($C_{10}H_{16}$) into organically modified montmorillonite. We used cetyltrimethylammonium cations as the interlayered modifier for the adsorption of hydrophobic pinene molecules. The X-ray diffraction patterns of the nanocomposite structure showed that the basal spacing increased from $9.6{\AA}$ to $30.4{\AA}$. Interestingly, the fraction of ${\alpha}$-pinene released remained constant for a long period of time (228 h) due to the layered nature of the nanocomposite. Additionally, optical microscopic images of the treated scuticociliatids revealed that their cells were lysed, and this effect increased with the increasing concertration of ${\alpha}$-pinene. Histopathological assessment of ${\alpha}$-pinene nanocomposite-treated olive flounder gills revealed no significant morphological changes, even at the highest concentration of the ${\alpha}$-pinene. The nanocomposite has several advantages, including easy handling, high solubility, low toxicity, and the easy formulation of granules or powder, which improve the pesticidal activity of ${\alpha}$-pinene. Collectively, our results suggest that ${\alpha}$-pinene nanocomposite may be a useful treatment against scuticociliatosis.

• Korean Journal of Veterinary Research
• /
• v.50 no.1
• /
• pp.29-35
• /
• 2010

Yersinia (Y.) ruckeri has been recognized as a serious bacterial pathogen to several kinds of fish, including rainbow trout. However, there are no reports about the characteristics and pathogenicity of Y. ruckeri isolated from farm-cultured eels. In this study, we isolated and characterized Y. ruckeri from the farm-cultured eel Anguilla japonica in Korea. We investigated the phenotypic and genotypic characteristics of Y. ruckeri and tested the virulence of Y. ruckeri isolates on experimentally infected eels. Examination of the flagellar morphology of Y. ruckeri by electron microscopy showed peritrichous flagella in its cell body. Biochemical reaction studies showed overall identical profiles between the isolates and the reference strain of Y. ruckeri in API 20E and API ZYM tests. We sequenced the 16S rRNA of the Y. ruckeri (1,505 bp) for the genotypic characterization (National Center for Biotechnology Information accession number EU401667). Comparison of the 16S rRNA sequences with previously reported Y. ruckeri strains revealed similar phylogenetic relationships. In the virulence assay of the Y. ruckeri on eels, the eels exhibited listlessness, but Y. ruckeri was reisolated from those of the gills and kidneys.

• Korean Journal of Ecology and Environment
• /
• v.44 no.4
• /
• pp.364-372
• /
• 2011

The pale chub (Zacco platypus) is generally found in Asian countries, such as Korea, Japan, and China. Nevertheless, very little information exists about the genes involved in the metabolism of xenobiotics in this species. This species is useful in monitoring the environmental impact on various pollutants in freshwater as a sentinel fish species. We cloned the full-length cDNA sequence of xenobiotic metabolizing cytochrome P450 1A (CYP1A) gene from Z. platypus and characterized it. Tissue distribution and timedependent induction of CYP1A were studied by real-time RT-PCR. Induction pattern of CYP1A was studied by exposing the fish to an arylhydrocarbon receptor agonist, ${\beta}$-naphthoflavone (BNF). The liver showed the highest level of expression in basal state as well as BNF- treated fish. However, appreciable levels of expression were also recorded in Gill and kidney and the least level of expression was observed in the eye. The results of the time-course study revealed an induction in the liver, brain, and gills after 6 h and 12 h in most of the tissues. This study provides an insight into the xenobiotics metabolizing system of Z. platypus and offers baseline information for further research related to biomarker, stress, and adaptive response of this ecologically important fish species in the freshwater environment.

• Development and Reproduction
• /
• v.18 no.4
• /
• pp.233-240
• /
• 2014

The early growth response protein 1 (Egr-1) is a widely reported zinc finger protein and a well known transcription factor encoded by the Egr-1 gene, which plays key roles in many aspects of vertebrate embryogenesis and in adult vertebrates. The Egr-1 expression is important in the formation of the gill vascular system in flounders, which develops during the post-hatching phase and is essential for survival during the juvenile period. However, the complete details of Egr-1 expression during embryo development in olive flounder are not available. We assessed the expression patterns of Egr-1 during the early development of olive flounders by using reverse transcription polymerase chain reaction (RT-PCR) analysis. Microscopic observations showed that gill filament formation corresponded with the Egr-1 expression. Thus, we showed that Egr-1 plays a vital role in angiogenesis in the gill filaments during embryogenesis. Further, Egr-1 expression was found to be strong at 5 days after hatching (DAH), in the development of the gill vascular system, and this strong expression level was maintained throughout all the development stages. Our findings have important implications with respect to the biological role of Egr-1 and evolution of the first respiratory blood vessels in the gills of olive flounder. Further studies are required to elucidate the Egr-1-mediated stress response and to decipher the functional role of Egr-1 in developmental stages.

• Proceedings of the Korean Society of Fisheries Technology Conference
• /
• 2000.05a
• /
• pp.505-505
• /
• 2000

Perkinsus sp. has been identified as responsible organism for the decrease in Manil clam production along the west and south coast of Korea. Monthly investigation on infection intensity and pathology of Perkinsus infected Manila clam population was carried out in Komsoe Bay located in the west coast during February and December 1999. About one hundred clams were collected each month for the analysis. Infected clams were incubated in fluid thioglycollate media over a week, stained with iodine solution, digested with 2M NaOH and the number of Perkinsus present in an individual recorded. Histological slides were also prepared from infected clams and their pathologic symptoms were examined using a microscope. Trophozoites of Perkinsus sp. were dominantly distributed on gills and epithelia of digestive glands however a few numbers could be detected at siphons and foot tissues. Heavily infected clams often exhibited white spots on mantle and foot tissues due to the inflammatory reaction of the hemocytes, forming nodules. Trophozoites were also found along the connective tissues of follicles during spawning season indicating that Perkinsus sp. may disturb reproduction of the clam. Total number of Perkinsus sp. in an individual clam varied from none to 9, 550, 000 with a monthly mean of 279, 663 to 2, 198, 558 during the course of study. The number of Perkinsus sp. in the clam was found to lowest durin July and August when unusually low salinity was recorded in this area due to the heavy rain. Highest monthly infection intensity in terms of total number of Perkinsus sp. i clam was observed in February, when water temperature recorded as lowest during the study. Small size of clams with shell length of ten mm or less were not infected with Perkinsus sp. It was concluded that Perkinsus infection in Manila clam is in pa controlled by changes in salinity and clam growth; low salinity environment minimize infection intensity while tile clams get more Perkinsus as they grow.