• Parasites, Hosts and Diseases
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• v.59 no.1
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• pp.83-88
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• 2021

Life cycle stages, including daughter sporocysts, cercariae, and metacercariae, of Parvatrema duboisi (Dollfus, 1923) Bartoli, 1974 (Digenea: Gymnophallidae) have been found in the Manila clam Ruditapes philippinarum from Aphae-do (Island), Shinan-gun, Jeollanam-do, Korea. The daughter sporocysts were elongated sac-like and 307-570 (av. 395) ㎛ long and 101-213 (av. 157) ㎛ wide. Most of the daughter sporocysts contained 15-20 furcocercous cercariae each. The cercariae measured 112-146 (av. 134) ㎛ in total length and 35-46 (av. 40) ㎛ in width, with 69-92 (av. 85) ㎛ long body and 39-54 (av. 49) ㎛ long tail. The metacercariae were 210-250 (av. 231) ㎛ in length and 170-195 (av. 185) ㎛ in width, and characterized by having a large oral sucker, genital pore some distance anterior to the ventral sucker, no ventral pit, and 1 compact or slightly lobed vitellarium, strongly suggesting P. duboisi. The metacercariae were experimentally infected to ICR mice, and adults were recovered at day 7 post-infection. The adult flukes were morphologically similar to the metacercariae except in the presence of up to 20 eggs in the uterus. The daughter sporocysts and metacercariae were molecularly (ITS1-5.8S rDNA-ITS2) analyzed to confirm the species, and the results showed 99.8-99.9% identity with P. duboisi reported from Kyushu, Japan and Gochang, Korea. These results confirmed the presence of various life cycle stages of P. duboisi in the Manila clam, R. philippinarum, playing the role of the first as well as the second intermediate host, on Aphae-do (Island), Shinan-gun, Korea.

• Journal of Marine Life Science
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• v.3 no.2
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• pp.96-100
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• 2018

Clonorchis sinensis is a main parasite that infects humans by making freshwater fish as an intermediate host in South Korea. There are so many reports about the infestation status of Clonorchis sinensis metacercariae (CsMc) in freshwater fish living in the river, but there are a few studies of fish in the lake. In this study, we examined CsMc in Cyprinid fish sampled from Soyang Lake, Namyang Lake, Andong Lake and Chunchun Lake from 2016 to 2017. Metacercaria of trematodes were found from Hemiculter eigenmanni and Carassius auratus in Namyang Lake, and Zacco platypus and Opsarichthys uncirostris in Soyang Lake. As a result of PCR using Clonorchis sinensis specific primer sets, it was confirmed that the metacercariae from Hemiculter eigenmanni in Namyang Lake was CsMc. This study provides information on CsMc infestation status of Cyprinid fish in four lakes and it is the first report of CsMc infestation in Namyang Lake.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.1
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• pp.61-67
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• 1984

The life history of a trematod fluck, Himasthla kusasigi was studied on the morphological characters of metacercariae, its infection rate in the clam and the contamination experiment to the herring gull, Larus crassiostris. The size of the metacercariae was $210{\sim}230{\times}220{\mu}m$, excysted metacercariae was $420{\times}160{\mu}m$ and it had 31 collar spines. The ventral sucker($112{\times}100{\mu}m$) was located just below the central part of the body. Esophagus was narrow and long, the intestine was branched in the upper part of the ventral sucker and extended to the hind part of the body. Excretory bladder without the infected part was located in the hind part of the body. The branched excretory tube was filled with the small granules and extended to the pharynx area. The infection rate of the metacercariae varied from place to place. In Naecho do and Puan the rates were $98.4\%$ and $95.9\%$ respectively. The infected number of Himasthla kusasigi per clam was positively proportional to the size of the clam. The adult fluckes developed from the metacercariae were obtained from the experimented herring gull. The metacercariae emerge from their cysts in the stomach of the herring gull, then they migrate it the intestine and 25 days after, most of them were found in the intestine. The size of the adult was $4.8{\sim}7.5{\times}0.22{\sim}0.24mm$, oral sucker; $68{\sim}120{\times}70{\sim}120{\mu}m$, pharynx: $80{\times}50{\mu}m$, ventral sucker: $630{\sim}680{\times}610{\sim}680{\mu}m$. The head collar $48{\sim}75{\times}10{\mu}m$ had 31 collar spines. The isolated trematod fluck from the samples was classified as a Himasthla kusasigi by the morphological characteristics of the adult flock and its metacercariae. We oberved that the second intermediate host of Himasthla kusasigi was hard clam, Meretrix lusoria, while its final host was herring gull, Larus crassiostris and Tringa ochropus.

• Parasites, Hosts and Diseases
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• v.24 no.2
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• pp.109-114
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• 1986

In order to observe the growth and development of Fibricola seoulensis metacercariae, the tadpoles of Rana nigromaculata were experimentally infected with the cercariae. The meta cercariae of various developmental stages were recovered from the tadpoles after 2 to 65 days of infection. They were prepared for morphological observation, and were given orally to mice to observe their infectivity. The following results were obtained. 1. All of the tadpoles exposed to the cercariae were observed to harbour the larvae in their abdominal cavity. 2. The young metacercariae of 2 days after infection were $121.1{\mu}m$ long and $63.3{\mu}m$ wide. They grew linearly for the first 14 days to be $262.0{\mu}m$ long and $166.4{\mu}m$ wide. Thereafter, no more growth recognized until 65 days. 3. The larvae of 2 days old were similar with cercarial body and had 2 suckers, a pharynx, 2 ceca and a primordium of germ cells but no tribocytic organ. On the 8th day, they had tribocytic organ, and their morphology resembled that of mature metacercariae. 4. The metacercariae younger than 10 days could not infect the mice. Only the metacercariae older than 14 days had infectivity. The recovery rates increased by the age of metacercariae from 19.0% in 14 days old to 70.0% in 40 days old. Above findings indicate that the tadpole is indispensable for metacercarial development and it needs at least 2 weeks for maturation. The tadpole is a pivotal host in the life cycle of F. seoulensis for connection between the snail and the frog.

• Korean Journal of Environmental Biology
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• v.17 no.2
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• pp.169-173
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• 1999

The present study was undertaken to survey the infection status of Metagonimus sp. metacercariae in freshwater fishes from Tong river located in Kangwon Province, a total of 178 freshwater fishes of 11 species were collected by a fish net and traps from the end of September to early October 1998. They were brought to the laboratory and examined under a stereomicroscope after artificial digestion with pepsin-HCI solution for one hour. Ten out of eleven species of freshwater fishes examined were found to contain metacercariae of Metagonimus sp. The most frequently infected fish was Liobagrus andersoni Regan 91.7% (11 of 12 fishes), followed by Gobiobotia breviburba Mori 75.0% (6 of 8 fishes), Zacco temmincki 66.2% (49 of 74 fishes), Cobitis koreensis Kim 50.0% (1 of 2 fishes), Microphysogobio longidorsails Mori 42.9% (9 of 21 fishes), Cobitis rotundicudata Wakiya et Mori 33.3% (2 of 6 fishes), Hemibarbus longirostris 33.3% (1 of 3 fishes), Pungtungia tenuicorpus 30.0% (3 of 10 fishes), Coreoleuciscus splenddus Mori 28.6% (4 of 14 fishes), Coreoperca herri Herzeanstein 11.1％ (1 of 9 fishes) respectively Metagonimus metacercariae was not found from Moroco kumgangensis Uchida of freshwater fish. The total number of Metagonimus sp. metacercariae was 81, 17, 216, 1, 14, 2, 1, 4, 10, 1, respectively. Infection rates of Metagonimus sp. in the five districts was shown as follows : Chongson-up Kyulam-ri 50.0% (12 of 24 fishes), Chongson-up Kasu-ri 34.0% (17 of 50 fishes), Shindong-up Unchi-ri 56.0% (14 of 25 fishes), Shingdong-up Kosong-ri 57.1％ (20 of 35 fishes), Shingdong-up Duckchon-ri 54.5% (24 of 44 fishes) respectively. Infection rate of freshwater fish was 48.9% (87 of 178 fishes) and from the results obtained in this survey, it was confirmed that freshwater fishes from Tong river was infected with metacercariae of Metagonimus sp.

• Parasites, Hosts and Diseases
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• v.34 no.4
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• pp.283-285
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• 1996

Six metacercariae were found from the gill filaments of Conger myriaster purchased at Mokpo-shi in korean on September, 1996. Based on the morphology of the excysted specimen. we identified them as metacercariae of Heterophyosis continua, C. myriaster is a new intermediate host H. continua in the literature.

• Parasites, Hosts and Diseases
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• v.41 no.1
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• pp.41-45
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• 2003

Effects of gamma irradiation on the worm survival and chromosomal aberration of Clonorchis sinensis were studied. The metacercariae irradiated with various amounts of gamma radiation (ranging from 5 Gy to 50 Gy) were fed to rats, and the effects were compared with those of non-irradiated controls. Recovery rates of adult worms in irradiated groups were reduced gradually as increasing of the irradiation doses. No worm was recovered from rats which were fed with 50 Gy irradiated metacercariae. The chromosome number was 2n = 56 in all worms from all experimental groups. However, the groups irradiated with 20 Gy, 25 Gy or 30 Gy showed variations in the chromosome number, depending on different cells in the same individual. Radiation doses used in this study did not appear to induce chromosome aberrations, however, irradiation with 30 Gy showed slightly reduced chromosome size.

• Parasites, Hosts and Diseases
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• v.41 no.2
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• pp.101-105
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• 2003

The metacercariae of Acanthotrema felis Sohn et at., 2003 (Digenea: Heterophyidae) were discovered in a species of the brackish water fish, Acanthogobius flavimanus, in the Republic of Korea. They were experimentally fed to kittens, and adult flukes were harvested 7 days later. The adults were morphologically characterized by the presence of a bipartite seminal vesicle, the ventral sucker associated with a ventrogenital sac enclosing 3 sclerites (2 long and pointed, and 1 short and thumb-like), and an unarmed gonotyl. The adult flukes were identified as A. felis Sohn et al., 2003, and the brackish water fish A. flavimanus has been verified as one of its second intermediate hosts.

• Parasites, Hosts and Diseases
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• v.39 no.3
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• pp.247-253
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• 2001

Three freshwater snail species of the family Lymnaeidae have been reported from Korea, Radix auricularia coreana, Austropeplea ollula and Fossaria truncatula. Out of 3 lymnaeid snail species, A. ollula was naturally infected with the Echinostoma cinetorchis cercariae (infection rate : 0.7%). In the experiments with the laboratory-bred snails, F. truncatula as well as A. ollula was also susceptible to the E. cinetorchis miracidia with infection rates of 25% and 40%, respectively. All of three lymnaeid snail species exposed to the E. cinetorchis cercariae were infected with the E. cinetorchis metacercariae. It is evident that A. ollula acts as the first molluscan intermediate host of E. cinetorchis in Korea, and F. truncatula may be a possible candidate for the first intermediate host of this intestinal fluke. Also, three lymnaeid snail species targeted were experimentally infected with E. cinetorchis metacercariae.

• Parasites, Hosts and Diseases
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• v.21 no.2
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• pp.157-166
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• 1983

In an attempt to clarify the epidemiological feature of C. sinensis in Mangyeong riverside area, the prevalence of clonorchiasis, infestation rate of the cercariae in Parafossarulus manchouricus, and detection rate of the metacercariae in fresh-water fishes were investigated from March 1 to September 30, 1983 at the upper, middle and lower reaches of the river. The results obtained were summarized as follows : 1. Detection rate of C. sinensis egg among inhabitants was 8.2% out of a total of 1,266 personsr, but the differences in detection rates were not statistically significant among upper, middle and lower reaches. According to sect, the detection rates were 10.3% in male and 6.1% in female (p<0.05), but by age groups, increases of the rates were observed as increase in age (p<0.05). 2. Out of a total of 380 fresh-water fishes of 32 different species, 93 fishes (25%) of 12 species were found positive with Clonorchis metacercariae, and there were differences in infection rates of the metacercariae among the fishes in 3 parts of the river; 11% in upper, 35% in middle, and 34% in lower reaches respectively. The metacercarial detection rates from various fishes were 97% in Pseudorasbora larva, Cultriculus eigenmanni (85%) , Gnathepogon strigatus (67%), Microphysogobio yaluensis (50%), Gnathopogon coreanus (47%), Pungtungia hergi (44%), Abbotting riwularis (40%), Moroco oxycephalus (33%), Coreoleuciscus splendidus (32%), Gnathepogon majimap (26%), Rhodeus ocellatus (7%), and Aphyocypris chinensis (3%) respectively. 3. Although very few p. manchouricus were collected at upper reach, 12 snails (0.7%) among a total of 1,713 were found infected with Clonorchis cercariae. Also the cercariae of Echinochasmup iapenicus (7.99%), Lexogenes liberum (0.99%), Cyathocotyle orientalis (0.75%), Esorchis oviformis (0.23%) and Asymphylodora japonica (0.05%) were detected from the snails.