Infection of the Giant Scallop Placopecten Magellanicus from Newfoundland with an Endozoic Alga

Some aspects of the relationship between a unicellular alga and the giant scallop, Placopecten magellanicus, are presented. The relationship is confined to the shallow water populations of the pectinid species (Port au Port Bay, St. Mary's Bay, Bonavista Bay, Newfoundland). Scallops from deeper water, including Georges Bank, are particularly free of the alga. It is believed that the alga's requirements for light prevents its establishment beyond a certain depth.