Effect of copper nanoparticles and ions on spermatozoa motility of sea trout (Salmo trutta m. Trutta L.)

Highlights: • Cu ion effect on the sea trout spermatozoa motility was more harmful then that of the copper nanoparticles. • Various copper products used affected certain parameters differently. • Low copper concentration in water environment notably caused a reduction in male gamete velocity that may impair reproduction. • Various copper products had different influance on LIN, ALH and time of motility duration. -- Abstract: Nanoproducts are being increasingly used in various industrial products, leading to a greater risk of water pollution through their discharge into environment as production byproducts. Increased levels of environmental pollution with nanoproducts pose a threat to all living organisms. Nanopollutants may have toxic effects on gametes and fertilization process in species with external fertilization, thereby reducing effectiveness of reproduction or greatly impairing it. The objective of the present study was to determine the effect of copper nanoparticles (Cu and CuO) and copper ions (CuSO₄·5H₂O) on the spermatozoa motility of sea trout and compare their harmful effects. Copper nanoparticles (NPs) of primary particle size <100 nm and CuO NPs of particle size <50 nm as well as a solution of CuSO₄·5H₂O were used for the study. Concentration of the products tested (CuNPs, CuONPs, and CuSO₄·5H₂O) was expressed as mg Cu L⁻¹ in the media regardless of dissolution and aggregation. A suspension with concentration up to 500 mg L⁻¹ in an aquatic environment was tested. Spermatozoa motility under direct contact with copper at 10 s post activation was evaluated using an automated system (CASA). Copper products in an aqueous environment primarily cause a reduction of spermatozoa velocity (VCL). A significant reduction of velocity in CuSO₄·5H₂O salt solution occurred at concentration starting from 8 mg L⁻¹, whereas in solutions containing CuNPs and CuONPs this process is observed from 50 mg L⁻¹. Reduction of percentage of motile spermatozoa occurred in CuNPs from a concentration of 125 mg L⁻¹, while in CuONPs and CuSO₄·5H₂O, the effect began at concentration from 250 mg L⁻¹. In a solution of CuSO₄·5H₂O at a concentration of 500 mg L⁻¹, strong agglutination of sperm cells occurred and movement ceased (immobilization IC100). Exposure to CuONPs decreased the motility rate to below IC50, while for CuNPs, the motility rate reached 80%. Changes in linearity (LIN) and amplitude of head displacement (ALH) differed according to Cu products. Cu as CuSO₄·5H₂O and CuONPs impaired the LIN, while CuNPs lowered ALH. Duration of motility increased at low CuSO₄·5H₂O concentration. The effect of Cu ion on sea trout spermatozoa motility was more harmful than that of copper nanoparticles. The various copper products used affected motility parameters differently. Contamination of aqueous environment with copper primarily caused reduction in male gamete velocity, which may impair reproduction. Various copper products had different effects on LIN, ALH, and motility duration, which can also affect fertilization.