Silver nanoparticles and silver ions indistinguishably decrease sperm motility in Pacific oysters (Magallana gigas) after short-term direct exposure

The present study aimed to evaluate the reprotoxicity of environmental (0.25μg.L^-1) and supra-environmental (25μg.L^-1 and 250μg.L^-1) levels of silver nanoparticles (Ag NP) on the Pacific oyster (Magallana gigas), by determining sperm quality. For that, we evaluated sperm motility, mitochondrial function and oxidative stress. To determine whether the Ag toxicity was related to the NP or its dissociation into Ag ions (Ag⁺), we tested the same concentrations of Ag⁺. We observed no dose-dependent responses for Ag NP and Ag⁺, and both impaired sperm motility indistinctly without affecting mitochondrial function or inducing membrane damage. We hypothesize that the toxicity of Ag NP is mainly due to adhesion to the sperm membrane. Blockade of membrane ion channels may also be a mechanism by which Ag NP and Ag⁺ induce toxicity. The presence of Ag in the marine ecosystem is of environmental concern as it may affect reproduction in oysters.