The thiamethoxam-based insecticide Cruiser 350 Fs induced histopathological and oxidative stress in the stingless bee Partamona helleri (Hymenoptera: Apidae: Meliponini)

The stingless bee Partamona helleri plays a crucial role in pollinating both native and cultivated plants. However, the intensive use of pesticides in agriculture are contributing to the decline of its population. Thiamethoxam, a systemic neonicotinoid insecticide, acts on the nervous system, however, it can also affect other non-target insect organs. This study evaluated the sublethal effects of chronic oral exposure to a thiamethoxam formulation on the fat body and Malpighian tubules in P. helleri workers. Bees were exposed orally for seven days to sublethal concentration of thiamethoxam (0.09 ng g⁻¹). The results revealed histopathological alterations in the fat body and Malpighian tubules, including changes in protein and carbohydrate reserves, nuclear pyknosis, cytoplasmic vacuolization, and affect lipid peroxidation in P. helleri. These findings indicate that chronic exposure of P. helleri workers to the residual concentration of thiamethoxam found in the field elicits a detoxification response in the fat body and Malpighian tubules; however, the previously reported high mortality rate suggests that these physiological responses are insufficient to mitigate the toxic effects of thiamethoxam on this pollinator.