Pyrethroid pesticides like deltamethrin and cypermethrin are widely used in aquaculture, yet their food safety implications remain understudied. This research investigated their acute toxicity, tissue-specific bioaccumulation, and elimination patterns in crucian carp (Carassius auratus). Acute toxicity tests determined 96 h LC50 values of 9.68~11.22 ng·mL⁻¹ (deltamethrin) and 3.12~5.01 ng·mL⁻¹ (cypermethrin) with 95% confidence intervals. During 8-day exposures to sublethal concentrations (1/10 and 1/100 of LC50), deltamethrin accumulated predominantly in the liver (peak: 21.98 ng·g⁻¹ at 1.04 ng·mL⁻¹, standard deviation is 0.064 ng·mL⁻¹), whereas cypermethrin concentrated in muscle (peak: 9.76 ng·g⁻¹ at 0.40 ng·mL⁻¹, standard deviation is 0.138 ng·mL⁻¹). A 7-day elimination phase revealed faster clearance of low-concentration residues, with >50% removal within 24 h in all tissues. Bioconcentration factors were highest in the liver (36.62 for deltamethrin) and muscle (45.17 for cypermethrin). These results highlight tissue-specific accumulation risks and rapid initial elimination, providing critical data to optimize pesticide-dosing protocols, mitigate ecotoxicological threats, and enhance food safety in aquaculture systems.

Nanoplastics are ubiquitous in aquatic environments, and elucidating their bioaccumulation behavior is essential for assessing toxicity and trophic transfer risks. While most studies focus on nanoplastics properties (e.g., type, size, surface charge), the influence of organismal growth stage remains unclear. Through bioaccumulation kinetic experiments with 10 mg/L polystyrene nanoplastics (PSNPs), this study found that Tetrahymena thermophila (T. thermophila) in the lag phase (cell density 4 × 10⁴ cells/mL) exhibited the highest uptake rate of nanoplastics, 1.2–5.8 times that of the exponential phase (1–5 × 10⁵ cells/mL) and 7.7 times that of the stationary phase (>5 × 10⁵ cells/mL). Lag phase cells also had a larger specific surface area (0.319 vs. 0.271/0.269 μm⁻¹), supporting their heightened uptake capacity. Under PSNP exposure, exponential and stationary phase cells showed significantly elevated reactive oxygen species (ROS) levels, accompanied by downregulated superoxide dismutase (SOD) and stable catalase (CAT) activity, indicating impaired antioxidant defense and potential redirection of energy toward stress mitigation. Consistent with efficient internalization, confocal imaging revealed clear PSNP colocalization within food vacuoles of lag period cells. Proteomic and transcriptomic analysis further confirmed the upregulation of carrier proteins, FAD/FMN oxidoreductases, and pathways associated with cellular components (membrane and organelle membrane) and molecular functions (transporter activity and transmembrane transporter activity) in lag-phase T. thermophila. Collectively, these findings provide a molecular-level understanding of the multi-phase-dependent bioaccumulation of PSNPs, offering critical insights for assessing the environmental risks of polystyrene nanoplastics in dynamic aquatic ecosystems.