Transcriptome analysis and effects of low salinity stress on ovarian development in Litopenaeus vannamei

Litopenaeus vannamei is an economically important shrimp species that can survive in a variety of environments; however, low salinity compromises its reproduction. To investigate whether salinity affects ovarian development in L. vannamei, we reared female shrimp under optimal (30‰) and low (25‰, 20‰, 15‰) salinity conditions. On day 26 post-induction, the ovarian maturation rates were 67.7%, 58.3%, 56.7%, and 31.7% for the 30‰, 25‰, 20‰, and 15‰ salinity groups, indicating that low-salinity compromises ovarian maturation. To provide mechanistic insight, we performed comparative transcriptomic analysis of hepatopancreas, eyestalk, gill, and ovary tissues five days post-maturation induction. GO and KEGG enrichment analyses revealed that upregulated differentially expressed genes (DEGs) under low-salinity conditions (n = 2359 total) were primarily associated with immune response, apoptosis regulation, polysaccharide metabolism, and antioxidation pathways, reflecting stress adaptation to maintain cellular homeostasis. Downregulated DEGs (n = 2008 total) were significantly enriched in pathways related to energy metabolism, lipid metabolism, and estrogen signaling, indicating the inhibition of metabolic and reproductive pathways. Trend analysis identified the ovarian development-related gene, vitelline membrane outer layer protein 1 (VMO1), whose expression was verified to decrease significantly with declining salinity. These results provide practical guidance for L. vannamei breeding and a new perspective for understanding salinity-mediated reproductive regulation.