• Korean Journal of Ichthyology
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• v.27 no.4
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• pp.306-309
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• 2015

In 2014, high mortality was observed in olive flounder (Paralichthys olivaceus) during experimental infection. Diseased fish did not show any outward clinical signs, but numerous fungal hyphae were detected in the gills. No parasites or bacteria were isolated from the diseased fish. A high mortality rate (100%) resulted when cohabitation with fungi-infected fish were applied to healthy fish. The affected fish exhibited sever fungi infection in the gills. Histopathological examination revealed numerous fungal hyphae and mycelium around gill filament, lamellar and racker. These results suggest that the fungi may be related with the mortality of olive flounder.

• The Korean Journal of Zoology
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• v.21 no.3
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• pp.87-102
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• 1978

Electron microscopic studies were made to investigate changes in the fine structure of the liver, kidney and gills of Carassius carassius L. following exposure to 1 and 2.5 ppm of $HgCl_2$. The following results were obtained: 1. In the mercury-treated liver cells, an increase in the number of lysosomes were noticed. These lysosomes appeared to be of two types; round ones containing some crystalline structures and others with phagocytosed glycogen granules and mitochondria. Also observed were mitochondrial swelling where the matrix appeared less electrondense, and segregation of the nucleoli in the nucleus. 2. In the kidney, mercury treatment resulted in thickening of the basement membrane of the glomerulus, and appearance of vacuoles and cytoplasmic bodies in the proximal convoluted tubule. The vacuoles seemed to be formed from mitochondria. Nuclear shrinkage was also noticed at 2.5 ppm of $HgCl_2$. 3. Many large and small lysosomes appeared in response to mercury in the epithelial cells of the gill lamella. Also the lamellar membrane became fuzzy in appearance. 4. It can be concluded from these results that mercury-induced changes in the fine structure are associated with activation of detoxication processes and impairment of energy metabolism.

• Development and Reproduction
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• v.24 no.3
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• pp.187-196
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• 2020

The caspase10 encodes an initiating caspase that plays an important role in the maintaining the cellular homeostasis by regulating the steps involved in the immune response and cell death. We investigated the expression of caspase10 during the different developmental stages and in olive flounder tissues. Caspase10 increased in the late stage of the formation of immune tissue, and high expression was observed in the gills, kidney, skin, and spleen. The current study analyzed the expressional changes of caspase10 in olive flounder infected with viral hemorrhagic septicemia virus (VHSV). One of the major causes of mass mortality, VHSV infection in olive flounder attributes to significant expression of caspase10 in the gills, spleen, skin, and kidneys. The results indicate a close association of caspase10 expression with the immune response to VHSV infection in olive flounder. The observations could form the basis data for exploration of other fish immune system.

• Development and Reproduction
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• v.22 no.4
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• pp.341-350
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• 2018

Chemokines is a small protein that plays a major role in inflammatory reactions and viral infections as a chemotactic factor of cytokines involved in innate immunity. Most of the chemokines belong to the chemokine groups CC and CXC. To investigate the immune system of the olive flounder (Paralichthys olivaceus), an expression pattern specifically induced in the early developmental stages of analysis is examined using qRT-PCR. We also examined tissue-specific expression of both CC and CXC chemokine in healthy olive flounder samples. CC and CXC chemokine shows increased expression after immune-related organs are formed compared to expression during early development. CC chemokine was more highly expressed in the fin, but CXC chemokine showed higher expression in the gills, spleen, intestines, and stomach. Spatial and temporal expression analysis of CC and CXC chemokine were performed following viral hemorrhagic septicemia virus (VHSV) infection. CC chemokine showed high expression in the gills, which are respiratory organs, whereas CXC chemokine was more highly expressed in the kidneys, an immune-related organ. These results suggest that CC and CXC chemokine play an important role in the immune response of the olive flounder, and may be used as basic data for the immunological activity and gene analysis of it as well as other fish.

• Ocean and Polar Research
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• v.43 no.4
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• pp.365-370
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• 2021

Manila clam Ruditapes philippinarum is present at high rates of density in tidal flats in Cheonsu Bay on the west coast of Korea, where clams often exhibit mass mortalities in late summer. We monitored the pathologic condition of clams at Hwangdo tidal flat (HD) to understand the parasitic impacts on clam fitness. Manila clams were fully ripe in July and spawned during August and September, as the histology indicated. The histology revealed that clams in HD tidal flats were heavily infected by the protozoa parasite Perkinsus olseni, as the monthly prevalence ranged from 53% (September) to 93% (August). In addition, Manila clams were co-infected by the metazoan parasite Cercaria tapetis and Parvatrema duboisi with the prevalence of 0-33% and 0-14%, respectively. Massive hemocyte infiltration and subsequent inflammation were commonly observed from the gills of P. olseni infected clams. Clusters of P. olseni trophozoites and heavy hemocyte infiltration were also observed from the female gonad, suggesting that P. olseni interferes with host gonad maturation. The larval trematode occupied almost the entire host gonad, resulting in gonad castration. In addition, Metacercaria of P. duboisi were observed from the subsurface of the mantle. Ray's fluid thioglycollate medium assay (RFTM) indicated that clams collected in August and September contained approximately 4.0×106 P. olseni cells/g gills. Condition Index (CI) declined gradually from spring to early summer, and the decline in CI was interpreted as a consequence of the heavy parasitism, as the parasites drain the host's net energy to be used in somatic growth and gamete production.

• Toxicological Research
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• v.35 no.3
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• pp.249-255
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• 2019

Cadmium is a strong toxic heavy metal which presents in paints and liquid wastes and causes oxidative stress in fish. On the other hand, lead is widely used for different purposes, e.g. lead pipes, it targets vital organs such as liver and kidney causing biochemical alterations. The present study evaluates the effects of 60 days exposure to Cd and Pb either single or combined together in African catfish. Sixty-four fishes were divided into 3 groups and exposed to $CdCl_2$ (7.02 mg/L) or $PbCl_2$ (69.3 mg/L) or a combination of them along with control group. Activities of acid phosphatase (ACP), lactate dehydrogenase (LDH) and glucose-6-phosphate dehydrogenase (G-6-PDH) were estimated. Moreover, gill, liver and kidney were assayed for activities of superoxide dismutase (SOD), catalase (CAT) and levels of glutathione (GSH) and malondialdehyde (MDA). Individual exposure showed that both Cd and Pb significantly decreased LDH activity and SOD activity in the kidney. Pb significantly increased G-6-PDH activity and decreased GSH level in the gill. CAT activity in liver and kidney elevated significantly on Cd exposure while lead caused a significant depletion in the liver and significant elevation in the kidney. Both Cd and Pb significantly increased MDA levels in liver and kidney while Pb increased its level in gills. The combined exposure resulted in normalization of LDH, G-6-PDH activity, and CAT activity in liver and kidney as well as GSH level in both tissues and MDA in gill and kidney. The combination increased SOD activity and MDA level in liver and decreased SOD activity in kidney and GSH level in gills. In conclusion, the antioxidant system of African catfish was adversely affected by prolonged exposure to Cd and Pb. The combined exposure caused less damage than individual exposure and returned most parameters to those of controls.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.5
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• pp.668-675
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• 2021

The infection status of domestic farmed eels Anguilla japonica, Anguilla bicolor and Anguilla marmorata with Japanese eel endothelial cell-infecting virus (JEECV) and anguillid herpesvirus 1 (AnHV) was examined at the major eel farming areas in Korea. These viruses were detected in all areas examined, regardless of the eel species or age. Any farm with a history of viral infection in adult fish confirmed the infection to be transmitted to stocked fry within 3 to 5 months. It is proposed that both viruses are horizontally transmitted within a given farm. The primary symptoms and histopathological lesions produced by the two viral infections are similar, making it difficult to distinguish the two diseases through clinical symptoms. Both viruses displayed 100% detection in the gills, suggesting that the gills are an optimal tissue for JEECV and AnHV monitoring. This study concluded that JEECV and AnHV were prevalent on eel farms across the country and caused very high mortality when the two viruses co-infected fry. Additional studies, including experimental infections, are needed to clearly understand the pathogenicity of each virus and the risk of co-infection.

• Journal of fish pathology
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• v.34 no.1
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• pp.55-61
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• 2021

One of the major problems in fish production is that parasite-induced episodes of disease can result in significant impacts to the health of stock, mortalities and, economical losses. Seabreams are economically important fish in both the capture fishery and aquaculture sectors in Oman and represent potential species for aquaculture. The current study set out to investigate infection of polyopisthocotylean monogeneans on the gills of wild goldlined seabream, Rhabdosargus sarba, caught from Musairah region in Oman. The prevalence, mean intensity and abundance of polyopisthocotyleans on 145 fish was found to be 52.41%, 5.65 and 3.04, respectively. Three species of microcotylid parasite were isolated, one being Atrispinum acarne while the remaining two species require further study to identify them. There was no significant difference in the infection rate between host sex, however, parasite burdens were higher on larger sized fish (p<0.05) and were found to favour the first gill arch (p< 0.05). The study found that the sample of Rhabdosargus sarba landed in the waters around Musairah are heavily infected, with a predominantly immature population of microcotylids. Further work is required to better understand the potential risk each species poses to the health of its host before a decision is made on the suitability of new candidate fish species for commercial aquaculture.

• Fisheries and Aquatic Sciences
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• v.24 no.2
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• pp.89-98
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• 2021

The accumulation of ammonia, a consequence of intensive aquaculture activity, can damage cultured animals. We analyzed the survival rates, growth, antioxidant responses, and immune responses of abalones, Haliotis discus hannai (mean shell length 70.2 ± 4.9 mm; mean body weight 36.9 ± 3.6 g), biweekly for four weeks, to determine the accumulated concentrations of ammonia (0, 0.1, 0.2, 0.4, 0.8, and 1.6 mg/L). In our biweekly measurements, a survival rate of ≥ 95% was observed for all concentrations of ammonia. The specific growth rate (SGR) decreased at ≥ 0.8 mg/L (p < 0.05), but the daily increment in shell length (DISL) showed no significant change (p < 0.05). Regarding antioxidant responses, the superoxide dismutase (SOD) activity of the hepatopancreas was increased at ammonia concentrations over 0.8 and 0.2 mg/L (p < 0.05) at two and four weeks, respectively, and the SOD activity of the gills increased at concentrations over 0.4 and 1.6 mg/L (p < 0.05) at four weeks. The catalase (CAT) activity of the hepatopancreas and gills increased at ammonia concentrations > 0.8 mg/L (p < 0.05). Phenoloxidase (PO) activity increased at ammonia concentrations over 0.8 mg/L (p < 0.05), and Lysozyme (LZM) increased at concentrations over 0.8 and 0.4 mg/L (p < 0.05). Overall, our findings indicated that ammonia concentrations over 0.8 mg/L in seawater might damage the SGR, antioxidant responses, and immune responses in H. discus hannai. Our findings suggest the necessity of improvement or reinstallation for abalone aquaculture systems and can be used to assess the toxic effects of ammonia on H. hannai.

• Fisheries and Aquatic Sciences
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• v.26 no.2
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• pp.97-104
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• 2023

CD96 is a membrane-bound receptor discovered in humans in 1992 that is mainly present in natural killer cells and T cells derived from haematopoietic cells and performs immune functions. Based on the sequence of CD96 obtained from red seabream (Pagrus major), phylogenetic analysis with other species, infections of normal fish, Streptococcus iniae and red sea bream iridovirus (RSIV), and expression analysis was conducted using real-time polymerase chain reaction. Phylogenetic analysis showed the highest homology with Sparus aurata, and multiple sequence analysis confirmed the conservation of major domains between different fish species. Normal fish high expression results were confirmed in the head kidney, and spleen, which are the haematopoietic organs of the fish. High expression levels were confirmed in the gills, liver, spleen, and kidney on day three after RSIV infection. After S. iniae infection, high expression was confirmed in the gills and liver on day one, and high expression was confirmed in the spleen from 12 hours. These results show that PmCD96 functions as an immune gene in P. major and is considered a basic research case for CD96 in fish's hematopoietic organ immune system.