Three morphological types of the genus Metagonimus encysted in the dace, Tribolodon taczanowskii, caught from the Sumjin River

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Abstract
Three morphological types of the genus Metagonimus were found encysted in the dace, Tribolodon taczanowskii, caught from the Sumjin River, Korea. They include Metagonimus Yokogawa type (M. yokogawai), Miyata type, and Koga type according to Saito's classification. The metacercariae were experimentally fed to rats and hamsters and a total of 1,624 Metagonimus worms were recovered from their small intestine. The number of each type was 820 for Yokogawa type, 688 for Miyata type, 46 for Koga type, and 70 undetermined. The major differential keys between Yokogawa and Miyata types were in the position of two testes, distribution of uterine tubules, and size of the eggs, and the keys between Miyata and Koga types were in the position of two testes, distribution of vitelline follicles, and size of the eggs. The validity of Miyata type as a specific level should be retained until more convincing evidences are obtained. Koga type is regarded as a synonym of M. takahashii. The present results reveal that there are 3 morphological types of Metagonimus whose larvae are encysted in the dace, T. taczanowskii, from the Sumjin River.