Seasonal features of Heterophyopsis continua metacercariae in perches, Lateolabrax japonicus, and infectivity to the final host.

As the second intermediate host, the perch Lateolabrax japonicus provides metacercariae of Heterophyopsis continua to man. Fry of the perch arrive at and grow to mid-sized fish in the brackish water of Jinju Bay, South Korea. The H. continua metacercariae occur in perch as small and mid-sized forms in July and grow to the large form by August. The size distribution of metacercariae shifts dominantly to the large form in September and then remains as it was. Adult H. continua recovery was high from experimental chicks infected with the medium and large metacercariae collected in September and reduced to half from the chicks infected with those of October. Collectively, the H. continua metacercariae grew to the large form in about 20 days and achieved infectivity to chicks after 2 months in the perches.