Impact of short-term hyposalinity stress on akoya pearl oyster, pinctada fucata (Gould 1850)

Abstract

The increase precipitation linked to climate change is well documented. In coastal waters, there is a frequent lowering of salinity during periods of rainfall and runoff from rivers and estuaries. This study assessed the effects of short-term hyposalinity stress on Akoya pearl oyster, Pinctada fucata (Gould 1850), focusing on the immunological parameters consisting of lysozyme and phenoloxidase (PO) activities. Akoya pearl oysters were exposed to short periods of 3 h daily for 30 days of hyposaline stress at 14 and 24 psu, followed by a recovery period that mimics the conditions typical for culture site at bays or estuaries experiencing heavy freshwater input, with a quick return to initial salinity of 34 psu. Lysozyme activity of oysters exposed to temporary salinity of 14 psu was 0.085 ± 0.028 mg mL-1. This value was lower (P < 0.5) than lysozyme activity of oysters kept in temporary salinity of 24 psu (0.153 ± 0.030 mg mL-1) and control (0.160 ± 0.031 mg mL-1). Phenoloxidase activity of oysters exposed to temporary salinity of 14 and 24 psu was 0.013 ± 0.002 and 0.013 ± 0.001, respectively which was significantly lower than the control (0.016 ± 0.001). The results indicate that under short-term hyposalinity stress, Akoya pearl oysters might be susceptible to the threat of disease due to low lysozyme and PO activities.