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The Effects of Temperature, Salinity and Pesticides on Oyster Hemocyte Activities


<OL> <LI> To determine by flow cytometry if different temperatures(4, 25 or 37 C), salinities (1, 15 or 32 o/oo),and pesticide mixture would affect the mortality of oyster hemocytes or the hemocyte phagocytic activity against E. coli and V. vulnificus. <LI> To determine if the serum (non-cellular) component of the oysters' hemolymph is required to prevent hemocyte mortality and for normal phagocytosis of E. coli and V. vulnificus. <LI> To determine if the in vitro exposure of pesticides will affect oyster hemocyte mortality and normal phagocytosis of E. coli and V. vulnificus.</ol> Probable outputs include data regarding how changes in temperature, salinity, and pesticides affect the ability of the oysters to phagocytosize bacteria by the oyster's immune cells, hemocytes.

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Non-Technical Summary: Oyster deaths have an enormous negative impact on the livelihood of oyster farmers. The causes of sudden oyster deaths are unknown and are thought to be linked to a number of possible causes including increased water temperature, changes in salinity in the oyster's estauraries, and contamination with pesticides. The ability of the oyster to defend itself from environmental exposures is largely due to the immune cells called hemocytes which are cells that engulf foreign bacteria to protect the oyster. It has been proposed that the ability of the oyster to take up bacteria may be affected by changes in the temperature,salinity, and pesticides that may contaminate the water in the estauraries where the oyster's grow. This research is designed to identify which of these factors have a major impact of the oyster's ability to defend itself. This knowledge will help the oyster industry determine how to modify environmental conditions to enhance the chances of survival of the oyster. <P> Approach: The Eastern oyster, Crassostrea virginica will be collected from approved shellfish harvesting waters from Apalachicola Bay, Apalachicola, Florida. Flow cytometry will be used to evaluate the effects of different temperatures, salinities, and hemolymph serum on hemocyte mortality and phagocytosis of common pathogenic bacteria (E. coli and V. vulnificus) at timed intervals in acclimatized oysters. The specific salinity treatments (1, 15, 32 o/oo) are selected because they are representative of the average salinity (15 o/oo), and the hypo and hyper-salinities (1 and 32 o/oo, respectively) represent the range of salinities that may result from fluctuations in tides and rainfall in the normal aquatic environment of the C. virginica species. The three seasonal water temperatures that the C. virginica species will be exposed to are on average 4, 25 and 37 C. The three pesticides will be chosen (imidacloprid, permethrin and fipronil), since they have been used in the area of Apalachicola Bay, Florida. The time periods are selected because the time required for the oyster to acclimate to different temperatures and salinities had been estimated to be up to 3-5 days.

Rodrick, Gary
University of Florida
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