Protective role of medium-concentration selenium nanoparticles against high salinity-induced oxidative stress in Crassostrea hongkongensis gills and hepatopancreas

This study investigated the effects of selenium nanoparticles (Se NPs) on the physiological responses of Crassostrea hongkongensis during high salinity exposure, which threatens this commercially important species. Oysters were pretreated with Se NPs (0, 0.4, 4, and 40 μg/L) for 14 days, followed by high salinity (30 psu) exposure for 7 days. Antioxidant, metabolic, and immune parameters were analyzed in gill and hepatopancreas tissues. Results revealed tissue-specific responses to Se NPs under salinity stress, with medium concentrations (4 μg/L) showing significant protective effects. In gills, medium Se NPs enhanced selenium-dependent antioxidant systems (glutathione peroxidase, GSH-PX and glutathione S-transferase, GST) and regulated metabolic enzymes (acid phosphatase, ACP; alanine aminotransferase, ALT; aspartate aminotransferase, AST). The hepatopancreas demonstrated increased antioxidant capacity (decreased malondialdehyde, MDA; increased superoxide dismutase, SOD) and metabolic adaptations (increased ALT). High Se NPs concentrations (40 μg/L) exacerbated physiological stress. These findings advance our understanding of nanomaterial-environment interactions with aquaculture implications.