Perkinsus marinus susceptibility and defense-related activities in eastern oysters Crassostrea virginica. temperature effects

Abstract

Susceptibility of Crassostrea virginica to Perkinsus marinus was compared with diploid and triploid (2N and 3N) C. gigas at 10, 15, and 25 degree C in the first experiment and at 3 salinities, 3, 10, and 20 ppt, in the second experiment. In both experiments, oysters were challenged twice with P. marinus trophozoites. The temperature effect experiment was terminated 68 days after 1st challenge and 27 days after 2nd challenge by P. marinus. The salinity effect experiment was terminated 50 days after 1st challenge and 34 days after 2nd challenge by P. marinus. Results revealed that at 15 and 20 degree C, infection prevalence was higher in challenged C. virginica than in challenged 2N and 3N C. gigas. But at 10 degree C, challenged 3N C. gigas had a prevalence higher than challenged 2N C. gigas and C. virginica. In all salinity treatments, prevalence was higher in challenged C. virginica than challenged 2N and 3N C. gigas. Weighted prevalence increased with temperature and salinity and was highest in C. virginica groups. Since, in both experiments, much higher infection prevalence and intensity were found in non-challenged C. virginica than in non-challenged 2N and 3N C. gigas, part of the recorded prevalence and intensity in C. virginica may be attributed to the hidden infection from the field. High mortality occurred in both 2N and 3N C. gigas during temperature and salinity acclimation and at the 25 degree C and 3 ppt treatments.