Toxicological evaluation of different pesticides in Tetragonisca angustula Latreille (Hymenoptera, Apidae)

ABSTRACT. The stingless bee Tetragonisca angustula is an important pollinator of different agricultural and native crops. This study evaluated changes in the relative activity of esterases and critical electrolyte concentration in brain cells after exposure to pesticides malathion and thiamethoxam. Lethal concentration 50% showed greater toxicity of thiamethoxam in relation to malathion. Esterases EST-3 and EST-4 (carboxylesterase) were partially inhibited after contamination by contact and ingestion of malathion and contamination by contact with thiamethoxam, suggesting participation of these esterases in the metabolization of these compounds. The lowest critical electrolyte concentration (CEC) was found after contamination by malathion ingestion (0.15 M), indicating changes in gene expression. The alterations observed in the intensity of EST-3 and EST-4 and the chromatin structure indicate that pesticides can act in gene expression and be used as biomarkers of contaminant residues. Furthermore, knowing the susceptibility of T. angustula bees to pesticides, it would be possible to use this species for biomonitoring environmental quality in preserved areas and agroecosystems.

摘要。无刺蜂（Tetragonisca angustula）是多种农业作物与本土原生作物的重要传粉者。本研究探究了暴露于杀虫剂马拉硫磷（malathion）与噻虫嗪（thiamethoxam）后，该蜂脑细胞内酯酶（esterases）相对活性及临界电解质浓度（critical electrolyte concentration, CEC）的变化。半数致死浓度（LC₅₀）结果显示，相较于马拉硫磷，噻虫嗪的毒性更强。经接触与经口暴露于马拉硫磷，以及接触噻虫嗪后，酯酶EST-3与EST-4（羧酸酯酶，carboxylesterase）均受到部分抑制，表明此类酯酶参与了上述两类杀虫剂的代谢过程。经口暴露于马拉硫磷的样本临界电解质浓度（CEC）最低（0.15 M），提示基因表达发生了改变。EST-3、EST-4的酶活强度与染色质结构所出现的改变表明，此类杀虫剂可调控基因表达，且可作为污染物残留的生物标志物。此外，在明确无刺蜂（T. angustula）对杀虫剂的敏感性后，即可利用该物种开展保护区与农业生态系统的环境质量生物监测工作。