Interactive effects of temperature and salinity on the survival, oxidative stress, and Na+/K+-ATPase activity of newly hatched obscure puffer (Takifugu obscurus) larvae

Obscure puffer (Takifugu obscurus) is an anadromous fish widely distributed around the coastal and inland rivers in East Asia. T. obscurus often encounters fluctuations in temperature and salinity. This study aimed to investigate the effect of the interactions of temperature and salinity on survival and oxidative stress response of newly hatched T. obscurus larvae. A combination of three temperatures (19, 25, and 31 degrees C) and three salinities (0, 10, and 20ppt) was applied for 96h under laboratory conditions. The newly hatched larvae could not tolerate 31 degrees C for 96h. No death was recorded at other temperatures during this experiment. Malondialdehyde concentrations increased significantly after 6h of exposure to high salinity (10 and 20ppt) and then decreased until the end of the experiment at each temperature. The highest superoxide dismutase activity was observed under the exposure to 20ppt for 24h at 31 degrees C. Na+/K+-ATPase activity significantly increased as salinity increased, especially at low temperatures. With the prolong of exposure time, the integrated biomarker response (IBR) values showed an increase until 48h and then declined at 96h in most treatments. The largest IBR value appeared when larvae were exposed to the highest temperature and salinity for 24h. Our study indicated that high temperature with high salinity may negatively affect the early development of T. obscurus and their combined effects should be considered in the larvae culture.