Infections virales chez les huîtres Crassostrea angulata Lmk. et Crassostrea gigas Th.

Two viral infections associated to some epizooties have been observed in Crassostrea angulata Lmk. The first one concerns the Gill disease in which the viral damages go hand in hand with a cellular hypertrophy, while, in the second one, the contaminated cells are associated with a deterioration of the connective tissue. These branchial necrosis associated to a virus have been observed again recently in some Portuguese oysters from the natural deposits of the Cadix (Spain) area. Moreover, the study of the summer mortalities (July 1977) in the oyster Crassostrea gigas Th. demonstrated the presence in this species of a virus of the same type as the one associated to the massive mortalities of the Portuguese oyster. In both cases, the viral morphogenesis takes place from a cytoplasmic plaque, producing some icosahedral virions of a size of 350 nm. Some of these viruses' characteristics drove us to link them to the Iridovirus group.