• Journal of Environmental Health Sciences
• /
• v.28 no.5
• /
• pp.102-105
• /
• 2002

The gills of seven black rockfish, Sebastes melanops collected from Hatfield Marine Science Center Aquarium during September 19-October 3,2001 were examined for parasites attached to the gills. The species of Sebastes melanops were Microcotyle sebastis baled on the number of clamps and testes. The prevalence of 42.9％ was recorded for host and fourteen worms of three black rockfish were recovered. Mean intensity of infection of Microcotyle sebastis individuals per infected host for black rockfish was 2.0(range 1-11). Monogenea helminth sites were mainly consist of second and third gill arch's filaments of black rockfish. The results revealed that surface area of the 2nd and 3rd pair of gills might affect the distribution of Microcotyle sebastis.

• Journal of Aquaculture
• /
• v.10 no.4
• /
• pp.387-394
• /
• 1997

A total of 353 farmed rockfish, Sebastes schlegli Hilgendorf, 1880 were sampled from 3 localities on Korean coastline over a 12 month period. Full parasitological examination revealed the polypisthocotylean monogenean Micorcotyle sebastis Goto, 1894 to be abundant with infections consistently reaching over 90~100% prevalence throughout the year. A seasonal pattern in parasite abundance on the gills is evident, with the population peaking twice, the largest in winter and again in summer. While the parasitic load on the left and right gills was not dissimilar, parasites within the gill sets were found to favour settlement of the II and III gill arches. A comparison of parasite abundance with host length, revealed that the smaller length fish classes (<17cm standard body length) had significantly heavier infections than those of larger fish (>17 cm standard body length). This report represents the fist record of Microcotyle sebastis on farmed rockfish in Korean coastal waters.

• Journal of Environmental Health Sciences
• /
• v.29 no.1
• /
• pp.16-18
• /
• 2003

Seven specimens of Sebastes melanops, black rockfish and three of S. maliger, quillback rockfish, were collected from Oregon Coast Aquarium during the period of September 19 to November 5, 2001 and examined for parasites. One monogenean helminth species and parasitic copepod species were recorded from black and quillback rockfishes, respectively. A total of 26 parasites were collected: 16 Microcotyle sebastis from the gill filaments of black and quillback rockfishes and 10 Clavella adunca were found in the fins of black rockfish. The prevalence of Microcotyle sebastis was 40.0%, and intensity of infection was 2.0(1-11). With regard to Clavella adunca, the prevalence and intensity were 20.0% and 1.4(2-8), respectively.

• Fisheries and Aquatic Sciences
• /
• v.4 no.4
• /
• pp.197-200
• /
• 2001

To investigate the re-treatment time of Microcotyle sebastis by oral administration of praziquantel, the residue levels of praziquantel in plasma of rockfish Sebastes schlegeli administered orally at a dose of 200 mg/kg B.W. were analyzed by reversed-phase HPLC, and the concentrations of praziquantel in the plasma were correlated with the extermination of M. sebastis. The absorption and depletion of praziquantel in the blood of rockfish were fast and the residual concentrations of praziquantel declined below $4\mu g/mL$ within 24 hr post treatment. Most of worms were exterminated within 3 hr after oral administration of praziquantel, however, a small number of M. sebastis were not killed by the treatment until end of the experiment. Considering fast drop of praziquantel in blood and extermination pattern of M. sebastis in the present results, retreatment at an interval of 9-12 hr would be effective for eradication of M. sebastis.

• Journal of Environmental Health Sciences
• /
• v.29 no.4
• /
• pp.55-57
• /
• 2003

Nine (34.6%) of the 26 rockfishes taken from Newport fish market, Oregon in July 2003 had a total of 135 monogenetic trematodes attached the gills. Microcotyle sebastis, Megalocotyle trituba and Trochopus australis were encountered, occurring in rockfishes examined. In the monogenetic trematodes in Sebastes spp, the prevalence were found to be between 30.8 and 40.0%. Prevalence of M. sebastis was 37.5%, 40.0% on M. trituba and 30.8% on T. australis. Nine of Sebastes spp. were infected with one or two species of monogenetic trematodes. Intensities of infection for M. sebastis, M. trituba and T. australis were recorded as 2.0 (2-12), 22.0 (48-62) and 1.0 (1-3), respectively. It may be that the intensities of infection for M. trituba should be high, and M. sebastis and T. australis little low.

• Fisheries and Aquatic Sciences
• /
• v.1 no.1
• /
• pp.79-81
• /
• 1998

To investigate the influence of originated host and water temperature on the infectivity and growth of Microcotyle sebastis, juveniles of Schlegel's black rockfish (Sebastes schlegeli) were exposed to the eggs of M. sebastis originated from. Schlegel's black rockfish and black rockfish (Sebastes inermis) at $10^{\circ}C$ and $10^{\circ}C$. There were significant differences between the two isolates in the infectivity of eggs, and the growth of worms. The growth of M. sebastis was significantly affected by water temperature, and worms grew faster in $20^{\circ}C$ than in $10^{\circ}C$.

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

• Parasites, Hosts and Diseases
• /
• v.59 no.1
• /
• pp.89-95
• /
• 2021

Microcotyle sebastis is a gill monogenean ectoparasite that causes serious problems in the mariculture of the Korean rockfish, Sebastes schlegelii. In this study, we isolated the parasite from fish farms along the coasts of Tongyeong, South Korea in 2016, and characterized its infection, morphology and molecular phylogeny. The prevalence of M. sebastis infection during the study period ranged from 46.7% to 96.7%, and the mean intensity was 2.3 to 31.4 ind./fish, indicating that the fish was constantly exposed to parasitic infections throughout the year. Morphological observations under light and scanning electron microscopes of the M. sebastis isolates in this study showed the typical characteristics of the anterior prohaptor and posterior opisthaptor of monogenean parasites. In phylogenetic trees reconstructed using the nuclear 28S ribosomal RNA gene and the mitochondrial cytochrome c oxidase I gene (cox1), they consistently clustered together with their congeneric species, and showed the closest phylogenetic relationships to M. caudata and M. kasago in the cox1 tree.

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

• Parasites, Hosts and Diseases
• /
• v.61 no.3
• /
• pp.332-337
• /
• 2023

Infestations of parasites, particularly those caused by copepods and monogeneans, are a major hindrance to aquaculture and have a big negative economic impact. Sebastes schlegelii, a farmed Korean rockfish, is particularly prone to copepods and monogeneans. This study comprehended how parasitic copepods and rockfish from a farm in Tongyeong-si, Gyeongsangnam-do, Korea, are related to the monogenean trematode Microcotyle sebastis. Our research revealed that monogeneans predominated, with a rate of 98.4% and an average infection intensity of 7 per infected fish. With an average infection intensity of 4 per sick fish, the infection rate for parasitic copepods was equally considerable, coming in at 91.7%. The high co-infection rate of both parasite families, at 90.8%, is noteworthy. Furthermore, Lepeophtheirus elegans and Peniculus truncatus, 2 parasitic copepod species, were discovered to have M. sebastis eggs attached to their bodies. This demonstrates a connection between parasitic copepod infestations in farmed Korean rockfish and the monogenean trematode M. sebastis. These discoveries highlight the necessity for creating more potent parasite control methods for the aquaculture sector and shed light on the intricate relationships between various parasite species.