Variations of enzyme activities in the haemocytes of scallop Chlamys farreri after infection with the acute virus necrobiotic virus (AVNV)

Acute virus necrobiotic virus (AVNV) is one of the main pathogens for large scale mortality of Chinese scallop Chlamys farreri. In this paper, C. farreri were infected by different dilutions of AVNV supernatant (50, 5−1, 5−2, 5−3, 5−4, 5−5, 5−6, 5−7, respectively), and dead individuals were counted every day for 15 days. Samples from groups of 5−3 and 5−5 were taken every day till 15 days and the activities of acid phosphatase (ACP), alkaline phosphatase (ALP), superoxide dismutase (SOD), myeloperoxidase (MPO), phenoloxidase (PO), peroxidase (POD) and catalase (CAT) in haemocytes were measured. The results of virus challenge showed that survival rates of scallops in groups of 50 and 5−1 decreased sharply after the first day and died out completely on the 5th and 4th day, respectively. In other groups (5−2, 5−3, 5−4, 5−5, 5−6 and 5−7), survival rates decreased gradually till 6 or 7 days, then kept steady till 15 days, and they were dose-dependent, increasing from 12% to 80% as the dose decreased from 5−2 to 5−7 viral supernatant. In the control group, survival rate was 88%. Enzyme activities for groups of 5−3 and 5−5 illustrated that activities of ACP, SOD, MPO, PO in groups of 5−3 and 5−5 were significantly higher than the control group in the first 9 or 10 days, and went back to the control group levels gradually after 10 days. Moreover, their activities in group of 5−3 varied more than that in the group of 5−5, especially activities of MPO, PO. Differently, the activities of POD and CAT were reduced or induced by virus infection and showed no regular trends in the experiments. The activity of ALP was not detected.