Sublethal cellular effects of short-term raphidophyte and brevetoxin exposures on the eastern oyster Crassostrea virginica

The susceptibility of shellfish to raphidophyte toxicity is not well resolved. This study examined the sublethal cellular responses of eastern oysters Crassostrea virginica exposed to 2 raphidophyte blooms (Chattonella subsalsa or Fibrocapsa japonica). Also, based on the hypothesis that raphidophyte toxicity is related to brevetoxin production, we determined the cellular responses of oysters to purified brevetoxin (PbTx-3) exposure in a separate experiment. We evaluated 3 cellular biomarkers, constituting both cellular damage and detoxification responses: lysosomal destabilization, lipid peroxidation and glutathione concentration. Exposing oysters to water collected from both blooms significantly increased lysosomal destabilization rates in oyster digestive gland when compared to controls, as did exposure to 1 and 10 nM PbTx-3. Glutathione and lipid peroxidation levels were not significantly affected in any treatment. The physiological stress response (i.e. increased lysosomal destabilization rates) in oysters exposed to brevetoxin, C. subsalsa bloom water, or F. japonica bloom water is consistent with that found in oysters exposed to Heterosigma akashiwo (Raphidophyceae) blooms and cultures. The results indicate that oysters are susceptible to raphidophyte and brevetoxin toxicity, and are not solely a vector for neurotoxic shellfish poisoning. The common physiological response to raphidophyte and brevetoxin exposure is consistent with the hypothesized production of brevetoxin by this group, but alternatively may reflect a more general stress response in oysters.