Ovarian development and proteomic profiling of female Litopenaeus vannamei exposed to low salinity stress

Salinity is a key environmental factor affecting gonadal development in euryhaline crustaceans, yet the underlying molecular mechanisms remain unclear. Although Litopenaeus vannamei can survive across a wide salinity range, its ovarian development requires optimal salinity. To investigate the mechanisms by which salinity affects ovarian maturation, shrimp were cultured at different salinities (3%, 2.5%, 2%, and 1.5%). Ovarian maturation was observed, and TMT-labeled quantitative proteomic analyses were performed on ovarian, eyestalk, hepatopancreas, and gill tissues. Results showed that low salinity significantly reduced the ovarian maturation rate, with progressively lower rates at decreasing salinities. Proteomic analysis identified 3240 differentially expressed proteins (DEPs). GO and KEGG enrichment analyses revealed that under low salinity stress, up-regulated DEPs were primarily involved in energy metabolism, oxidative stress response, and nutrient transport, while down-regulated DEPs were associated with pathways related to immunity, stress response, and apoptosis. Notably, two proteins critical for ovarian development—vitellogenin and chorion peroxidase—exhibited significantly reduced expression abundance in the eyestalk, hepatopancreas, and gills of low salinity groups (particularly at 1.5% and 2%). qRT-PCR validation experiments yielded largely consistent results at the transcriptional level, confirming that low salinity stress inhibited the expression of these key reproductive genes in peripheral tissues. In summary, this study shows from a proteomic perspective that a low salinity environment may force shrimp to allocate more energy to basic physiological activities like osmoregulation, and suppressing the expression of crucial reproductive proteins like vitellogenin and chorion peroxidase, ultimately impairing ovarian development in L. vannamei . These findings offer an important basis for understanding of the molecular mechanisms by which salinity regulates reproduction in crustaceans.