Departamento de Biologia Geral, Universidade Federal de Viçosa, Viçosa, Minas Gerais 36570-900, Brazil.
Departamento de Ciências Naturais, Matemática e Educação, Universidade Federal de São Carlos, Campus Araras, Araras, São Paulo 13.600-970, Brazil.
Ecotoxicol Environ Saf. 2024 Sep 1;282:116677. doi: 10.1016/j.ecoenv.2024.116677. Epub 2024 Jul 5.
Stingless bees (Hymenoptera: Meliponini) are pollinators of both cultivated and wild crop plants in the Neotropical region. However, they are susceptible to pesticide exposure during foraging activities. The fungicide fluazinam is commonly applied in bean and sunflower cultivation during the flowering period, posing a potential risk to the stingless bee Partamona helleri, which serves as a pollinator for these crops. In this study, we investigated the impact of acute oral exposure (24 h) fluazinam on the survival, morphology and cell death signaling pathways in the midgut, oxidative stress and behavior of P. helleri worker bees. Worker bees were exposed for 24 h to fluazinam (field concentrations 0.5, 1.5 and 2.5 mg a.i. mL), diluted in 50 % honey aqueous solution. After oral exposure, fluazinam did not harm the survival of worker bees. However, sublethal effects were revealed using the highest concentration of fluazinam (2.5 mg a.i. mL), particularly a reduction in food consumption, damage in the midgut epithelium, characterized by degeneration of the brush border, an increase in the number and size of cytoplasm vacuoles, condensation of nuclear chromatin, and an increase in the release of cell fragments into the gut lumen. Bees exposed to fluazinam exhibited an increase in cells undergoing autophagy and apoptosis, indicating cell death in the midgut epithelium. Furthermore, the fungicide induced oxidative stress as evidenced by an increase in total antioxidant and catalase enzyme activities, along with a decrease in glutathione S-transferase activity. And finally, fluazinam altered the walking behavior of bees, which could potentially impede their foraging activities. In conclusion, our findings indicate that fluazinam at field concentrations is not lethal for workers P. helleri. Nevertheless, it has side effects on midgut integrity, oxidative stress and worker bee behavior, pointing to potential risks for this pollinator.
无刺蜂（膜翅目：木蜂科）是新热带地区栽培作物和野生作物的传粉者。然而，它们在觅食活动中容易接触到农药。杀菌剂氟唑菌酰胺在豆类和向日葵的花期常被使用，这对作为这些作物传粉者的无刺蜂 Partamona helleri 构成了潜在风险。在这项研究中，我们研究了急性口服暴露（24 小时）氟唑菌酰胺对无刺蜂 Partamona helleri 工蜂的生存、形态和细胞死亡信号通路、氧化应激和行为的影响。工蜂暴露于氟唑菌酰胺（田间浓度 0.5、1.5 和 2.5mg a.i. mL）中 24 小时，用 50%蜂蜜水溶液稀释。口服暴露后，氟唑菌酰胺对工蜂的生存没有危害。然而，使用最高浓度的氟唑菌酰胺（2.5mg a.i. mL）显示出亚致死效应，特别是食物消耗减少，中肠上皮损伤，特征为刷状缘退化，细胞质空泡数量和大小增加，核染色质浓缩，以及更多的细胞碎片释放到肠腔中。接触氟唑菌酰胺的蜜蜂表现出自噬和细胞凋亡增加，表明中肠上皮细胞死亡。此外，该杀菌剂诱导了氧化应激，表现为总抗氧化和过氧化氢酶酶活性增加，谷胱甘肽 S-转移酶活性降低。最后，氟唑菌酰胺改变了蜜蜂的行走行为，这可能会妨碍它们的觅食活动。总之，我们的研究结果表明，田间浓度的氟唑菌酰胺对无刺蜂 Partamona helleri 工蜂没有致死作用。然而，它对中肠完整性、氧化应激和工蜂行为有副作用，这表明这种传粉者存在潜在风险。
