Surface ultrastructure of newly excysted metacercariae of Paragonimus heterotremus.

The newly excysted metacercariae of P. heterotremus were examined by scanning electron microscopy (SEM). Large dome-shaped papillae, small ones with a pit, and small ones with a smooth surface were observed around the suckers. The number of the small dome-shaped papillae with a pit was about 30 around the oral sucker and that of the small ones with a smooth surface varied from 9 to 13 around the ventral sucker. The present report is the first record of excysted metacercariae of P. heterotremus examined by SEM.

Experimental infection of Oncomelania quadrasi with Paragonimus ohirai.

Two hundred Oncomelania quadrasi collected from Leyte, Philippines were exposed to infection with Paragonimus ohirai, a rodent type lung fluke. In a group, each snail was exposed individually to 10 miracidia hatched from eggs which were brought from Japan to the Philippines. In another group, 100 snails were placed in a Petri dish and P. ohirai miracidia were added to provide 10 per snail. The observations were made each successive week after exposure. All the snails examined were positive for the larvae of P. ohirai. Nine-ten weeks after exposure, many cercariae were recognized. It was proved that O. quadrasi is highly susceptible to P. ohirai.