THE CHARACTERISTICS OF REDIAL GENERATIONS IN LYMNAEA-TRUNCATULA EXPOSED TO FASCIOLA-HEPATICA MIRACIDIA AFTER POISONING BY SUBLETHAL DOSES OF CUPRIC CHLORIDE

Adult Lymnaea truncatula were placed in a sublethal dose of copper chl oride (0.1 mg/l) for 1 h, and then in normal water before being expose d to a single Fasciola hepatica miracidium on the 2nd or 9th day of th e experiment. Infection rates were higher in untreated snails and in s nails infected 9 d after treatment (73.5 and 71.4%) than in snails inf ected 2 d after copper contact (48.1%). Histological examination of su rviving snail on the 30th day after miracidial exposure revealed that the total number of rediae was 25 and 31 per snail in snail groups inf ected 2 and 9 d respectively after copper contact, and 44 in untreated controls. There was a drop in the number of live, free rediae in infe cted snails after treatment contact. This decrease was more marked in the first redial generation than in the first cohort of the second gen eration. These results reveal that the infection rate in snails and th e redial burden of F hepatica were reduced by the copper treatment of snails before miracidial exposure but placement of survivors in water for 8 d after treatment limited the consequences of chemical toxicity.