Effects of chronic low-salinity stress on gill histology, osmoregulation and metabolomics of Palaemon carinicauda

Abstract Salinity represents a major environmental factor that affects shrimp growth, survival, development and reproduction. The ridgetail white prawn Palaemon carinicauda exhibits strong adaptability to low-salinity environments, making it an excellent model for investigating salinity adaptation mechanisms in crustaceans. The current study comprehensively assessed the impact of chronic low-salinity on P. carinicauda by analysing histological changes, osmoregulatory functions and non-targeted metabolomics. Overall, compared with the control (salinity 25), shrimps cultured at low salinity (salinity 3) exhibited lower survival rates as well as pronounced gill damage which included oedematous swelling of gill filaments. Furthermore, the relative expression of osmoregulation-related genes was significantly enhanced ( ), except for AQP which was downregulated. The activities of Na + /K + -ATPase and Ca 2+ -ATPase were also significantly higher ( ) after 7, 14 and 21 days of exposure to low salinity. Finally, metabolomic analysis identified 423 differential metabolites in the gills of P. carinicauda after exposure to low salinity conditions, with most of these being enriched in pathways such as glycine, serine and threonine metabolism, alanine, aspartate and glutamate metabolism, sulphur metabolism, pyruvate metabolism, oxidative phosphorylation and the citrate cycle. These fundings enhance current understanding of the adaptive mechanisms of P. carinicauda under low-salinity stress and offer a theoretical basis for developing shrimp aquaculture with the efficient use of low-salinity water.