Acute stress response in hepatopancreas of Pacific white shrimp Litopenaeus vannamei to high alkalinity

The crustacean hepatopancreas is a complex organ, with multiple functions that are essential for coping with adverse environments. Excessive alkalinity in water seriously threatens the survival of crustaceans, however, studies on its mechanism of alkalinity stress and adaption are still limited. In this study, we aimed to investigate the mechanism of acute alkalinity stress in hepatopancreas of Pacific white shrimp Litopenaeus vannamei (initial weight: 0.22±0.13 g) by integrating physiological, histological, transcriptome, and metabolome analyses. Groups performed acute alkalinity stress for 24 h, including control (alkalinity: 45 mg/L) and treatment (alkalinity: 350 mg/L). The physiological parameters related to energy metabolism, ammonia detoxification, and oxidative stress were significantly changed under acute alkalinity stress, including glycogen, glucose, fatty acid synthesis, glucose dehydrogenase, glutamine synthase, urea, superoxide dismutase, catalase, glutathione peroxidase, and malondialdehyde. The expression levels of genes and metabolites were significantly changed, which related to glycolysis/gluconeogenesis, fatty acid metabolism, glycerophospholipid metabolism, amino acid metabolism, ammonia metabolism, and antioxidation. In addition, the local structure of the hepatopancreas was damaged and accompanied by cell apoptosis. The above results indicate that the glycogen catabolism in hepatopancreas was significantly enhanced under acute alkalinity stress, while the lipid anabolism was inhibited. Additionally, the ornithine-urea cycle mechanism was further mobilized to alleviate the ammonia excretion and accumulation in the internal environment. The antioxidant capacity and glycerophospholipid metabolism were disturbed in hepatopancreas. In addition, acute alkalinity stress would induce apoptosis in hepatopancreas. The current study will provide important clues for understanding the stress response mechanism of Pacific white shrimp under acute alkalinity stress and lay a theoretical basis for the optimization of related saline-alkaline aquaculture.