[Reactive oxygen species and defense mechanisms in marine bivalves]

The main results published on the production of reactive oxygen intermediates by hemocytes and digestive glands of marine bivalves such as mussels, oysters or clams have been reviewed and discussed. Mussel and oyster hemocytes respond to appropriate stimuli with a burst of respiratory activity and the generation of reactive oxygen intermediates in a manner resembling the respiratory burst of mammalian phagocytes. However, interspecies differences in hemocytes-mediated antimicrobial defense mechanisms occur since clam hemocytes do not show any increase of reactive oxygen intermediate production upon similar stimulations. Hepatopancreatic gland of bivalves, as mammalian and fish liver produce reactive oxygen species during the one-electron reduction of xenobiotics, and mechanistic differences appear between bivalves and mammals. Thus, it appears that, in spite of some interspecies differences, the generation of cytotoxic reactive oxygen species is a general protective mechanism of most, if not all, animal species.