경북(慶北) 형산강(兄山江)에서 채집(採集)된 담수어(淡水魚)에 있어서 흡충류(吸蟲類) 피리유충(被裏幼蟲) 기생상(寄生狀)의 변화(變化)

Abstract

In order to determine infection patterns with digenetics larval trematodes in freshwater fish were studied in the three localities of the river Hyungsan during the period from September, 1995 to August, 1996, and compared with the data reported previously in the same river. Of 15 species of fish examined, the encysted larvae of Cyathocotyle orientalis and Exorchis oviformis were found most frequently from 13 species of fresh-water fish. The metacercariae of Metacercaria hasegawai were found from 12 species, those of Echinochasmus species from 10 species, Methorchis orientalis from 4 species, Clonorchis sinensis from 3 species and Metagonimus species from 2 species of fish. The infection rates of 2 species of fish with Clonorchis sinensis cysts were lower than those reported in 1984, whereas the rate was higher in one species, Pungtungia herzi. The intensity of Clonorchis infection in Pungtungia herzi appeared rather higher than those reported in 1984, whereas their intensity of infection were found lower in 2 species of fish, Gnathopogon atromculatus and Pseudorasbora parva. The infection rates of fish with Metagonimus metacercariae were lower than the results in 1984, whereas their intensity of infection was found increased in 2 species of fish such as Carassius carassius and Moroco oxycephalus. The encysted larvae of Cyathocotyle orientalis, Echinochasmus species, Exouchis oviforms, Metacercaria hasegawai and Metorchis orientalis showed variations in infection rates of fish in 1984 and in the present study, and intensities in the 5 kinds of the encysted compared with those in 1984. However, it was impossible to compare the infection rates for the encysted larvae on the scales, fins and tail as they varied so considerably in both 1984 and 1996 surveys. The infection rates of several species of fish with Metagonimus species in the present study decreased compared with those in 1984. This study indicate that the rate of infection with digenetic larval trematodes in fresh-water fish is still relatively high in the river Hyungsan. And the metacercarial burden in the fish varies greatly by different fish in 1984.