Physiological changes in Pacific oyster Crassostrea gigas exposed to the herpesvirus OsHV-1μVar

Since 2008, mass mortality events of Crassostrea gigas have been occurring along the French coast when seawater temperature exceeds 16 degrees C. These mortality events are related to a particular genotype of the ostreid herpesvirus named OsHV-1 War. The present study aimed to detail various physiological aspects underlying the onset of the disease. In the laboratory, both exposed (infected) and na ve (healthy) oysters were maintained at 13.0 degrees C and 20.6 degrees C. These temperatures were respectively lower and higher than the threshold values of 16 degrees C at which the disease generally occurs. At 20.6 degrees C, exposed oysters were characterized by a reduction in energetic reserves (carbohydrates and triglycerides) together with a decrease in protein content. Sterol levels were lower in exposed oysters than in na ve individuals, irrespective of temperature. Finally, activities of some key enzymes related to energetics were similar in exposed and na ve oysters and did not change with temperature. This result suggests that although energetic reserves were being diminished in infected oysters, their metabolic activities remained similar to that of healthy animals. (C) 2014 Elsevier B.V. All rights reserved