Characterization of glutaredoxin (Grx) gene expression in Pacific white shrimp (Litopenaeus vannamei) under low-salinity conditions

This study investigated the effects of salinity on physiological stress in Pacific white shrimp (Litopenaeus vannamei) through field surveys and laboratory experiments. Field observations from 23 farms in Gyeonggi Province showed that shrimp reared under low salinity (<6 psu) tended to have lower condition factors than those in moderate salinity (6–17 psu), although the differences were not statistically significant (p>0.05). In laboratory trials, shrimp were exposed to various salinity (5, 15, and 30 psu), and the expression of glutaredoxin 3 (Grx3) was analyzed as an indicator of oxidative stress. Grx3 expression significantly increased at 5 psu (3 and 9 h) and 15 psu (9 h), but not at 30 psu. The transient increase followed by a decline suggests an acute stress response and subsequent adaptation. Bacterial disease monitoring detected infections in some individuals, but no clear salinity-related pattern was observed, indicating that low salinity may act as a stressor rather than a direct cause of disease. Overall, extremely low salinity (≤5 psu) may induce physiological stress, whereas 15 psu appears to provide relatively stable conditions.