Toxin profile change in vegetative cells and pellicle cysts of Alexandrium fundyense after gut passage in the eastern oyster Crassostrea virginica

摘要

Vegetative cells and pellicle cysts of the toxic dinoflagellate Alexandrium fundyense Balech were fed to the eastern oyster Crassostrea virginica Gmelin under controlled conditions. Paralytic shellfish toxins (PSTs) were measured in vegetative cells and pellicle cysts prior to feeding and directly after passage through the oyster alimentary canal and defecation as intact cells. Oysters fed with vegetative cells and those fed with pellicle cysts accumulated toxins. One experimental treatment tested for direct uptake of toxins from the water (oysters and A. fundyense cells were separated by a screen); PSTs were not accumulated from the water by the oysters. There were no significant changes in total, per-cell toxicity after passage through the oysteralimentary canal, suggesting limited transfer of toxins from intact cells to the oysters. However, there were statistically significant changes in the toxin composition of cells following gut passage. Vegetative cells and pellicle cysts from feces had increased amounts of saxitoxin (STX) and decreased amounts of gonyautoxin 4 (GTX4) per cell, compared to amounts prior to gut passage. Following gut passage, pellicle cysts showed better survival in the feces than vegetative cells, which is consistent withthe view of pellicle-cyst formation as a successful survival strategy against adverse conditions.