Cercariae of Clonorchis sinensis were attempted to penetrate into various fry of fresh water fishes in order to examine the conditions of infection and the further development in the fish. The following conclusions were made. Cercariae of C. sinensis penetrated into the muscle of the fry of Pseudorasbora parva were found to be able to develop. Cercariae penetrated into the fry of Pseudorasbora parva migrated into the organs of the fry to kill their host. From each dead individual of P. parva, more than 10 larvae of C. sinensis could be discovered. Cercariae attached on the Cyprinus carpio, Carassius and gold fish were almost killed before penetration into the body and even one or two cercariae penetrated were also killed as time passed. Cercariae of C. sinensis infected on the fry of Cyprinus Carpio, Carassius auratus and gold fish could not survive more than 60 days. Cercariae penetrated into Cyprinus carpio and Carassius auratus could not develop into complete metacercariae even after 3O days. Cercariae of Clonorchis sinensis penetrated into the fry of Aplocheilus latipes were killed within 10 hours and the cercariae attached on the caudal fin were destroyed in 2 hours. It was found that no cercariae of Clonorchis sinensis could penetrate into the body of the fry of Misgurnus anguillicaudatus.
parasitology-helminth-trematoda-Clonorchis sinensis ; cercariae ; Pseudorasbora parva ; Cyprinus carpio ; Carassius auratus ; gold fish ; Aplocheilus latipes ; Misgurnus anguillicaudatus ; mucous substance

The author reported in the previous pager on his observation of sudden death of Clonorchis sinensis cercaria before penetration into the body of fry such as Cyprinus carpio and Carassius auratus. And in these studies, the reason behind the fact was investigated and it was found that the mucous substances on the surface of a certain fishes have a strong wormicidal effect to the larva of C. sinensis. When cercariae of C. sinensis were immersed into the mucous substance of gold fish for three minutes 36 seconds to 4 minutes 20 seconds, into that of Aplocheilus latipes for 4 minutes 30 seconds to 5 minutes 20 seconds, into that of Cyprinus carpio for 5 minutes 15 seconds to 6 minutes l6 seconds, and into that of Carassius auratus for 5 minutes 20 seconds to 7 minutes 30 seconds, it was observed that they were all killed. No wormicidal effect against C. sinensis could be observed with the mucous substance obtained from Pseudorasbora parva, Misgurnus anguillicaudatus and Ophicephalus argus. No wormicidal effect against Metagonimus sp. cercaria is observed with the mucous substance obtained from Cyprinus carpio, Carassius auratus. The wormicidal effect of the mucous substances obtained from gold fish was destroyed when heated over 60 C. The movements of metacercaria of C. sinensis stopped after 10 minutes application of the mucous substance obtained from Cyprinus carpio and they were killed within 30 minutes. When the adult worms collected from the bile duct of experimentally infected rabbits for 20 to 60 days, were immersed into mucous substance from Cyprinus carpio, they were killed between 25 minutes and 35 minutes. No wormicidal effect could be observed with the mucous substance obtained from dead Cyprinus carpio, Carassius auratus, gold fish, when applied to the adult worms and larvae of C. sinensis.
parasitology-helmith-trematoda-Clonorchis sinensis, Metagonimus sp. ; Cyprinus carpio ; Carassius auratus ; Aplocheilus latipes ; Pseudorasbora parva ; Misgurnus anguillicaudatus ; Ophicephalus argus ; gold fish ; mucous substance