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CHEMICAL EFFECTS ON OYSTER (CRASSOSTREA VIRGINICA) HEMOCYTE MICROBICIDAL ACTIVITY
Citation:
Oliver, L M., A. K. Volety, AND W S. Fisher. CHEMICAL EFFECTS ON OYSTER (CRASSOSTREA VIRGINICA) HEMOCYTE MICROBICIDAL ACTIVITY. Presented at 91st Annual Meeting of the National Shellfisheries Association, Halifax, Nova Scotia, April 18-22, 1999.
Description:
Oyster (Crassostrea virginica) hemocytes, or blood cells, perform important internal defense functions such as phagocytosis and intracellular destruction of pathogens and bacteria. Using techniques such as phagocytosis and chemiluminescence assays, potential impairment of hemocyte immunocompetance resulting from in vitro and in vivo exposure to anthropogenic chemicals has been demonstrated. A new microbicidal assay recently optimized for oyster hemocytes shows promise for this type of investigation, and may better measure the integrative cidal function of hemocytes compared to measuring discrete portions of the phagocytic process. Hemocytes were exposed in vitro for 3-18 h to various chemicals including metals, organics, and biotoxins. Tributyltin (TBT), previously shown to exacerbate Perkinsus marinus infections when administered to oysters in vivo, inhibited killing of Vibrio parahaemolyticus and cultured P. marinus, at in vitro concentrations exceeding 32 ppb. The lowest TBT concentration caused a slight elevation, or hormesis, of hemocyte killing activity. Although in vitro results suggest immunosuppression by chemical exposure, previous assessment of defense activities of indigenous oysters collected from Tampa Bay suggested that these activities were elevated in oysters with high tissue burdens of certain metals. In a separate study, oysters were deployed at different sites in Pensacola Bay, Florida, to test the effect of exposure to chemical mixtures on hemocyte microbicidal activity. Oysters deployed at contaminated habitats tended to have higher hemocyte bactericidal activity (21%) compared to oysters from relatively clean areas (0%).