Effect of salinity on growth performance and resistance of the clam Cyclina sinensis against Vibrio parahaemolyticus infection

Abstract

We examined the growth performance, immune parameters and the susceptibility to Vibrio parahaemolyticus in the clam Cyclina sinensis, which had been reared at different salinity levels of 10‰, 20‰ and 30‰ for 60 days. At the end of the feeding experiment, the biggest shell length and body weight was found in 20‰, followed by 30‰ and 10‰. No significant differences in superoxide dismutase (SOD) activity were observed among the clams held in 10‰, 20‰ and 30‰. Na+/K+ -ATPase (NKA) activity of the clams held in 20‰ and 30‰ were significantly lower than that in group 10‰. The lowest activities of lysozyme (LZM) and glutamic-pyruvic transaminase (GPT) were found in group 10‰. The Integrated Biomarker Response index (IBR) values of the clams had an inverse relationship with salinity: 11.28, 3.40 and 2.85 in 10‰, 20‰ and 30‰, respectively. At the end of the feeding experiment, the clams were infected with V. parahaemolyticus. As time after infection goes on, the survival rate of clams reared in 20‰ was not significantly different with the other two treatments from 24 to 48h after infection. However, from 72 to 120h after infection, it was significantly lower than those reared in 10‰, while it was significantly higher than those reared in 30‰. It is concluded that the clam C. sinensis reared in 10‰ seawater may reduce growth performance and immune ability, whereas increase resistance against V. parahaemolyticus infection.