Sex-specific differences in cadmium accumulation and responses in the freshwater snail Cipangopaludina cathayensis

Cadmium (Cd) is a non-essential element with strong toxicity to aquatic mollusks. Although sex-specific Cd accumulation has been reported, the distinct impacts on males and females and their adaptive strategies remain unclear. We exposed freshwater snails (Cipangopaludina cathayensis) to 0.5 mg/L Cd for 14 days and analyzed Cd accumulation, histology, biochemical indicators, gonadal transcriptomics, and hepatopancreatic metabolomics. Cd levels in ovaries were significantly higher than in testes, while hepatopancreatic levels showed no sex difference. Cd disrupted gonadal antioxidant defenses and induced oxidative stress: testes maintained persistently elevated total superoxide dismutase (T-SOD) and glutathione (GSH), whereas ovarian levels initially rose then declined. Structural damage (seminiferous tubule rupture, follicular wall disruption) and reduced sex steroid hormones (testosterone (T) and estradiol (E2)) further impaired gonadal function. Transcriptomic analysis revealed that testes upregulated protein metabolism pathways (e.g., Protein digestion and absorption, Protein processing in endoplasmic reticulum with HSP70/HSP90) to maintain homeostasis under Cd stress. Hepatopancreatic metabolomics showed disrupted lipid metabolism, with females displaying greater lipid droplet accumulation. Under Cd stress, males retained stronger exogenous nutrient transport and repair capacity, whereas females relied on energy-intensive endogenous synthesis. Overall, Cd effects were more severe in females, highlighting clear sex-specific differences in response and tolerance.