Physiological Function Disturbances and Adaptive Responses in Nile Tilapia (Oreochromis niloticus) Under Different Salinity Stresses

The physiological functions of aquatic organisms are closely linked to changes in environmental salinity. High-salinity environments can disrupt energy metabolism, induce inflammation, and negatively impact normal growth and development. However, aquatic organisms possess self-regulatory mechanisms that can mitigate these impacts to some extent. This study aimed to investigate the adaptive regulatory processes in Nile tilapia (Oreochromis niloticus, Linnaeus, 1758) exposed to high-salinity environments by evaluating metabolic enzyme activities and levels of inflammatory markers. The increased levels of IL-1 beta and elevated ACP activity suggested that high-salinity conditions (15 and 30 ppt) induced intestinal inflammation. Concurrently, the elevated activities of SOD and GSH, along with decreased SDH activity, pointed to heightened oxidative stress in the brain and a reduced mitochondrial energy supply. Additionally, the adaptive features of intestinal energy metabolism under high-salinity conditions were evident, with adjustments in HK and PK activities mitigating the effects of suppressed PFK activity. Moreover, elevated lipase (LPS) activity in muscle tissue under salinity stress indicated that fat is mobilized to supply energy for muscle activity without affecting muscle protein. In conclusion, salinity stress triggered inflammatory and oxidative stress responses in Nile tilapia, yet the fish exhibited self-regulatory processes in energy metabolism. This study provides a theoretical basis for understanding the adaptive mechanisms of aquatic organisms in stressful environments.