• Journal of fish pathology
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• v.33 no.1
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• pp.7-14
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• 2020

A disease that manifested severe anemia of the gills occurred in the olive flounder (Paralichthys olivaceus), which was cultured for 5-6 months with a recirculation water system in the laboratory. Microscopic observations showed immature parasite in the gills and mature adults in the oral cavity. The matured parasite was 5.60-9.32 (7.42) mm in total length, with 4 pairs of clamps on the pedunculated haptor, which was separated from the body proper by a long isthmus. From the morphological observations of the larvae, it was identified as Neoheterobothirum hirame belonging to the monogenea. The average hematocrite of infected fish was 10.3 ± 2.8%, significantly lower than that of normal flounder 31.4 ± 4.2%. Histopathologically, fish infected with N. hirame exhibited reduced numbers of erythrocytes in blood vessels of the gill filament and lamellae, reduced red pulp area of the spleen, and hepatocyte atrophy. From the above results, the cause of severe anemia in olive flounder was identified as N. hirame infection. This study shows an example where the growth of pathogens can be a problem in the recirculation system due to low water exchange rate.

• Fisheries and Aquatic Sciences
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• v.5 no.2
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• pp.141-143
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• 2002

The treatment efficacy of oral administration of praziquantel against the blood-sucking monogenean Microcotyle sebastis under the commercial rockfish-culture conditions was evaluated. The quantity of praziquantel added to the food was calculated so that the amount of praziquantel ingested daily by fish was 200mg or 400mg/kg body weight (bw). The fish were fed a moist-pelleted fish meal supplemented with praziquantel at an rate of 0 (control), 200 or 400 mg of praziquantel per kg bw, respectively, for 3 times at an interval of 24 h. On 1 day to 8 days after the treatment, 10 fish were taken randomly from each net-pen daily (80 fish in each group in total), and the efficacy of each treatment was confirmed. Abundance of worms were significantly reduced in groups fed praziquantel-supplemented diets. The results clearly demonstrated that feeding the praziquantel-supplemented diet was effective for controlling M. sebastis infestation in practical commercial rockfish-culture systems without imposing any handling stress.

• Journal of fish pathology
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• v.10 no.2
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• pp.137-142
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• 1997

A monogenean gill parasite, Prosomicrocotyla gotoi, and a digenean intestinal fluke. Opecoelus sphaericus, were found from greenilngs (Hexagrammos otakii) captured at the Korean southern sea. P. gotoi was characterized by having two separated frills of opisthaptor and distinguished from P. chirii in testis and clamp numbers. O. sphaericus had three pairs of finger-like marginal appendages on the ventral sucker and the parasite was distinguished from O. nipponicus in the location pattern of testes. These two helminth species were the first recording species in Korea.

• Korean Journal of Ichthyology
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• v.11 no.2
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• pp.134-138
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• 1999

This study investigated the relationship between attachment site preference of the skin parasite, Entobdella hippoglossi and mucous cell density, moucus cell size and epidermis thickness on the surface of the Atlantic halibut Hippoglossus hippoglossus. Parasites occupying the ventral surface of their host were significantly longer and wider than those found on the other zones of the fish (P<0.05). The mean size of the mucous cells on the front region was significantly greater than the other regions on the dorsal and ventral surface (P<0.05). The average numbers of mucous cells and the epidermal thickness in the skin of the halibut were shown that the front region had significantly higher numbers of mucous cells and thicker layer than the rear region on the dorsal and ventral surface of the halibut, respectively (P<0.05).

• Journal of fish pathology
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• v.11 no.1
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• pp.29-33
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• 1998

Distribution of a monogenean helminth Microcotyle sebastis on the gills of cultured Korean rockfish (Sebastes schlegeli) was investigated with regard to gill arches, sides of gill hemibranches (anterior or posterior), and their sections (dorsal, medial and ventral). M. sebastis has a significant preference for the second and third pair of gills, and shows marked affinity for anterior hemibranches of each gill branch, and medial sections of each gill hemibranch. The results suggest that the larger volume of water flows and surface area of the second and third pair of gills might affect the distribution of M. sebastis, and the concentrated distribution of M. sebastis on the anterior medial section of gills would be related with the increasing chances of mating by niche restriction.

• 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.

• Journal of fish pathology
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• v.11 no.2
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• pp.113-117
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• 1998

The influence of temperature on the rate of egg production and embryonic development of Microcotyle sebastis was investigated to determine the precise time of a second treatment. The survival time of the adults of M. sebastis was inversely proportional to temperature. The number of laid eggs per each replicate during the first 24 h was $39.3{\pm}4.0$ at $10^{\circ}C$, $62.7{\pm}14.2$ at $15^{\circ}C$, $101.0{\pm}5.6$ at $20^{\circ}C$ and $89.0{\pm}11.0$ at $25^{\circ}C$. The time required for egg hatching of M. sebastis was $31.30{\pm}4.88$, $17.52{\pm}3.24$, $11.59{\pm}3.02$ and $10.76{\pm}3.10$ days at 10, 15, 20 and $25^{\circ}C$, respectively. The regression models of the time required for the beginning and 50% point of hatching according to the different temperatures were as follows; Beginning of hatch: D=58.2000-$4.2067{\times}Temp+0.0867{\times}(Temp)^2$ ($P\leq0.01$), 50% of hatch: D=91.3833-$7.5767{\times}Temp+0.1767{\times}(Temp)^2$ ($P\leq0.01$).