Changes in metabolism and immunity in response to acute salinity stress in Chinese razor clams from different regions

Salinity change is a vital abiotic stress that dramatically affects the growth and survival of marine bivalves. Three groups of Chinese razor clams (Sinonovacula constricta) were collected from high (Lianyungang City, China, LYGSC) and low (Ninghai County, China, NHSC, and Shenzhe No. 1, SZSC) salinity regions. The survival rate (SR), metabolism (oxygen consumption rate, OCR; ammonia excretion rate, AER), Na+/K+-ATPase (NKA), and immune-related enzymes (superoxide dismutase, catalase, and alkaline phosphatase) were measured at different times under acute salinity stress. The results showed that death occurred only in NHSC and SZSC in salinities of 30 and 35 ppt at 72 h. All above mentioned parameters increased at first and then decreased over time. The maximum value appeared at 12 or 24 h and increased with a rise in salinity. The OCR and AER of LYGSC were the highest and SZSC was higher than NHSC after stress. The NKA activity of LYGSC was higher than that of SZSC and NHSC in general. The activities of immune enzymes of LYGSC were significantly low in salinities of 30 and 35 ppt (P < 0.05). These results indicated that the SR and metabolic capacity of LYGSC were higher than those of SZSC and NHSC. Short-term salinity stress may not lead to significant differences between SZSC and NHSC. Our results demonstrated that Chinese razor clams living in a high-salt environment have stronger salt tolerance than those of living in a low-salt environment. The study provides a reference for exploring the physiological mechanism of salt tolerance in bivalves and the selective breeding of new stress-resistant varieties.