Physiological and behavioral effects of titanium dioxide nanoparticle exposure on stingless bee foragers

Bee population decline is associated with various stressors, including exposure to pollutants. Among these, titanium dioxide (TiO₂), an emerging nanoparticle (NP) pollutant, potentially affects living organisms, including bees. This study evaluates the impact of TiO₂ NPs ingestion (1.35 or 13.5 µg/mL) on the behavior and physiology of the stingless bee Partamona helleri. X-ray spectroscopy confirmed the presence of Ti in the bees' gut, and 3D X-ray microscopy revealed a reduction in body volume. Although survival, food consumption, flight, and respiration were unaffected. In addition, bees exposed to 13.5 µg/mL of TiO₂ NPs exhibited reduced walking distances. TiO₂ NPs exposure decreased the total hemocyte count, with notable changes in the proportions of specific hemocyte types: decreased the proportions of plasmatocytes in bees exposed to 13.5 µg/mL, and decreased the granulocytes, and increased the prohemocytes in both concentrations. Furthermore, enzymatic activity was affected with increased levels of catalase (CAT), superoxide dismutase (SOD), and ferric-reducing antioxidant power (FRAP), alongside a decrease in glutathione S-transferase (GST) activity. These findings suggest that TiO₂ NPs may pose a risk to bee health, highlighting the need for further research to fully understand the implications of nanoparticles exposure on pollinators.