Recovery of cercariae

Live oysters for experimental purposes were obtained from Foveaux Strait between June and October, 1963, and March and July, 1964. Each oyster, right valve uppermost, was kept alive in a 7in diameter finger bowl two-thirds filled with sea-water. Daily examinations of the water were made for liberated cercariae. The greatest concentration of cercariae was usually found on the bottom of the finger bowl opposite the exhalent chamber of the oyster.

Oysters showing infection were transferred to new bowls and those showing no infection had their water changed daily. If the oysters did not liberate cercariae page 5 within a week they were opened and a superficial examination was made of their visceral mass for the presence of sporocysts. If sporocysts were absent, the oysters were dissected or sectioned for any deep-seated infection.