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INFLUENCE OF SEASONAL FACTORS ON OYSTER HEMOCYTE KILLING OF VIBRIO PARAHEMOLYTICUS
Volety, A. K., J T. Winstead, AND W S. Fisher. INFLUENCE OF SEASONAL FACTORS ON OYSTER HEMOCYTE KILLING OF VIBRIO PARAHEMOLYTICUS. Presented at 91st Annual Meeting of the National Shellfisheries Association Annual Meeting, Halifax, Nova Scotia, 18-22 April 1999.
Seasonal variation of cellular defenses of oyster Crassostrea virginica against Vibrio parahaemolyticus were examined from June 1997 to December 1998 using a recently developed bactericidal assay that utilizes a tetrazolium dye. Mean hemocyte numbers, plasma lysozyme, and P. marinus infection in oysters were also examined. Hemolymph was sampled from oysters collected at Bayou Texar, Pensacola, Florida once every month. To determine if gametogenic cycle and/or energy reserves affect hemocyte activity, gonadal stage, tissue total lipids and lipid classes in digestive diverticulum tissue were also determined. Hemocyte bactericidal activity and mean hemocyte numbers in oyster hemolymph was higher in warmer months (40-80%) compared to winter months (0-30%). In contrast, total lipid and triglyceride concentration in digestive diverticulum tissue was higher in winter months and decreased with spawning in summer months. Lysozyme activity was also higher in winter than in summer months. The role of temperature and salinity on hemocyte killing capacity and plasma lysozyme in oysters is being investigated with the recognition that a varity of influences, including seasonal reproductive changes and potential environmental stimulation, are possible.