Unravelling the role of environmentally realistic concentrations of titanium dioxide nanoparticles in altering gametogenesis and gonadal health of female Pacific oysters (Magallana gigas): a histopathological approach

Titanium dioxide nanoparticles (TiO₂ NPs) raise environmental concerns due to their potential adverse effects on marine bivalves. However, research on females, particularly their gonad quality and reproduction, remains limited. Despite the availability of numerous health status biomarkers, histopathological analysis remains crucial for assessing toxicological effects. This study aimed to shed light on the potential reprotoxicity of environmentally realistic concentrations of TiO₂ NPs during gametogenesis in female Magallana gigas. Oysters were exposed to waterborne 10 and 100 μg/L of TiO₂ NPs for 3 and 7 days. Thereafter, females were identified, and the gonadal health status was assessed through qualitative and quantitative histology alongside titanium bioaccumulation evaluation. Partial indices for interlobular and intralobular alterations were applied for the first time to the gonad, improving the understanding of histopathological alterations caused by TiO₂ NPs. Our results indicated that the severity of histopathological alterations was concentration and time-dependent, even though no bioaccumulation was detected. We observed an acceleration of gametogenic stage development and disturbances in sex determination. This study provides tools to assess TiO2 NPs’ impacts on bivalve populations and ecosystem balance, especially in highly touristic marine areas.