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

Abstract

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.