Effects of Low-Salinity Stress on Histology and Metabolomics in the Intestine of Fenneropenaeus chinensis

Simple Summary: Acute low-salinity stress can affect intestinal microbiota composition and differentially expressed genes in Fenneropenaeus chinensis. However, the effects of acute low-salinity stress on the metabolic profile of F. chinensis remain unclear. In this study, intestinal histological examination and untargeted metabonomic analysis of F. chinensis were conducted after exposure to low-salinity stress at different time points. Our results demonstrated that the intestinal morphological structure of F. chinensis and many differential intestinal metabolites were present in a low-salinity environment. Fourteen key metabolites were screened to predict their metabolism under stressful conditions. Furthermore, some related pathways, such as phenylalanine, tyrosine, and tryptophan biosynthesis; fatty acid and retinol metabolism; and ABC transporters, were significantly enriched, which played an important role in the low-salinity environment. This study contributes to our understanding of the molecular response mechanisms to low-salinity stress in shrimp. Metabolomics has been used extensively to identify crucial molecules and biochemical effects induced by environmental factors. To understand the effects of acute low-salinity stress on Fenneropenaeus chinensis, intestinal histological examination and untargeted metabonomic analysis of F. chinensis were performed after exposure to a salinity of 15 ppt for 3, 7, and 14 d. The histological examination revealed that acute stress resulted in most epithelial cells rupturing, leading to the dispersion of nuclei in the intestinal lumen after 14 days. Metabolomics analysis identified numerous differentially expressed metabolites (DEMs) at different time points after exposure to low-salinity stress, in which some DEMs were steadily downregulated at the early stage of stress and then gradually upregulated. We further screened 14 overlapping DEMs, in which other DEMs decreased significantly during low-salinity stress, apart from L-palmitoylcarnitine and vitamin A, with enrichments in phenylalanine, tyrosine and tryptophan biosynthesis, fatty acid and retinol metabolism, and ABC transporters. ABC transporters exhibit significant abnormalities and play a vital role in low-salinity stress. This study provides valuable insights into the molecular mechanisms underlying the responses of F. chinensis to acute salinity stress.