Physiological, Transcriptomic, and Metabolomic Insights into Ammonia-Nitrogen Stress in the Hepatopancreas of Litopenaeus vannamei Acclimated to Low Salinity
Simple Summary Low-salinity farming is popular for Litopenaeus vannamei cultivation but easily causes ammonia accumulation that endangers shrimp survival. Most previous studies focus on single stress or normal salinity, while the shrimp response to ammonia stress after low-salinity adaptation remains unclear. Here, we acclimated shrimp to 5‰ salinity and exposed them to high ammonia for 96 h. Ammonia stress caused hepatopancreatic oxidative damage and disturbed hemolymph nitrogen metabolism. Multi-omics analysis revealed 112 differentially expressed genes (DEGs) and altered lipid and amino acid metabolism. Three core secretion, metabolism and immune pathways, together with key gene-metabolite pairs, were identified. This study clarifies the physiological and molecular mechanisms underlying shrimp tolerance to combined low-salinity and ammonia stress, supporting the healthy development of low-salinity aquaculture.