Salinity stress responses in Slipper cupped oyster Crassostrea iredalei from Setiu Wetlands, Terengganu, Malaysia

Abstract

Aim: The present study investigated some important functional responses to salinity stress in Slipper cupped oyster Crassostrea iredalei from Setiu Wetlands, Terengganu, Malaysia. Methodology: Slipper cupped oysters were subjected to different salinities of 7,14, 28 and 35 ppt for 2 weeks. Total haemocyte count (THC), phagocytic activity, ionic absorption, total protein concentration (TPC), superoxide dismutase activity (SOD) and histological changes of the oyster tissues were determined after 2 weeks of experiment. Results: THC significantly decreased at 7 ppt but increased at 35 ppt (p<0.05). The phagocytic activities affected. The SOD activities were significantly higher (p<0.05) at 7 and 14 ppt compared with 28 and 35 ppt. Higher TPC were also observed at 28 and 35 ppt. Potassium ion concentration (mmol l-1) increased gradually with the increasing salinities. Salinity stress was also associated with histological changes in the gills and digestive gland tubules of the oysters. Interpretation: The present study has revealed the functional I responses of C. iredalei to salinity changes, and the negative impact of low salinities on the oyster immune system.