抄録
Hundreds of thousands of six-month-old carp which might harbour Bothriocephalus opsariichthyd s YAMAGUTI at the rate of about 20 per cent were cultured in a big swamp in Sanami district, Gunma prefecture. Hundreds of fish were drawn randomly from there and were kept in a net cage of 1.5 m3set in the other pond of 1.2 m deep in same district during the period from November, 1975 to May, 1976. Fifty eight fish of them were sacrificed for examination for the cestode once a month.
The rate of fish which had the cestode fell suddenly from 17.3 per cent in November to 5.2 per cent in December, but the latter rate was maintained as it was until next May. Every living worm which stayed in host's intestine laid eggs again in April. It seems that the life cycle of this cestode may be turned only by the wintered adult worm.
