INVESTIGATIONS INTO THE TRANSMISSION OF PARASITES OF THE BAY SCALLOP,ARGOPECTEN-IRRADIANS (LAMARCK, 1819), DURING QUARANTINE INTRODUCTION TO CANADIAN WATERS

The potential impact of bay scallop Argopecten irradians (Lamarck) par asites on commercially important bivalve species in Canadian Atlantic waters was assessed using two transmission experiments. The first was a parallel flow-through system passing water from the bay scallops ove r-five species of native bivalves. The second was a synchronous spawni ng of infected bay scallops and uninfected blue mussels Mytilus edulis , to determine if larval bivalves are more susceptible to parasite tra nsmission than adults. Zoospores of Perkinsus karlssoni were observed adhering to D-stage larvae of bay scallops approximately 48 hours post -spawning, suggesting this to be the method of transmission. Surface s terilization of fertilized bay scallop ova with 1% iodophor for 15 min utes failed to destroy the zoospores. No evidence of transmission of b ay scallop parasites to adults of other species was found during the t en month experimental period. Results of the second experiment are inc onclusive. No P. karlssoni zoospores were seen among the larvae, and n o tissue-stages have been detected subsequently in the exposed mussels .