Department of General and Applied Biology, Institute of Biosciences, São Paulo State University (UNESP), Rio Claro, SP, Brazil.
Department of Entomology and Acarology, Luiz de Queiroz College of Agriculture (ESALQ), Piracicaba, SP, 13418-900, Brazil.
Chemosphere. 2022 Feb;288(Pt 1):132461. doi: 10.1016/j.chemosphere.2021.132461. Epub 2021 Oct 5.
In recent years, the importance of bee's biodiversity in the Neotropical region has been evidencing the relevance of including native bees in risk assessments. Therefore, the sublethal effects of the insecticide thiamethoxam on the survival and morphological parameters of the stingless bee Melipona scutellaris were investigated in the present study. Cells from both non-target organs (Malpighian tubules and midgut) and target organs (brain) were analyzed for morphological alterations using light microscopy and transmission electron microscopy. The findings showed that when M. scutellaris foragers were exposed to a sublethal concentration of thiamethoxam (LC = 0.000543 ng a. i./μL), longevity was not reduced but brain function was affected, even with the non-target organs attempting to detoxify. The cellular damage in all the organs was mostly reflected in irregular nuclei shape and condensed chromatin, indicating cell death. The most frequent impairments in the Malpighian tubules were loss of microvilli, disorganization of the basal labyrinth, and cytoplasmic loss. These characteristics are related to an attempt by the cells to increase the excretion process, probably because of the high number of toxic molecules that reach the Malpighian tubules and need to be secreted. In general, damages that compromise the absorption of nutrients, excretion, memory, and learning processes, which are essential for the survival of M. scutellaris, were found. The present results also fill in gaps on how these bees respond to thiamethoxam exposure and will be useful in future risk assessments for the conservation of bee biodiversity.
近年来，在新热带地区蜜蜂生物多样性的重要性证明了在风险评估中纳入本地蜜蜂的相关性。因此，本研究调查了杀虫剂噻虫嗪对无刺蜜蜂 Melipona scutellaris 生存和形态参数的亚致死效应。使用光镜和透射电镜分析了非靶标器官（马氏管和中肠）和靶标器官（脑）的细胞形态变化。结果表明，当采集蜂 M. scutellaris 暴露于亚致死浓度的噻虫嗪（LC = 0.000543 ng a. i./μL）时，寿命没有缩短，但大脑功能受到影响，即使非靶标器官试图解毒也是如此。所有器官的细胞损伤主要表现为核形状不规则和染色质浓缩，表明细胞死亡。马氏管最常见的损伤是微绒毛丧失、基底迷路紊乱和细胞质丧失。这些特征与细胞试图增加排泄过程有关，可能是因为大量有毒分子到达马氏管并需要分泌。一般来说，发现了会损害吸收营养、排泄、记忆和学习过程的损伤，这些过程对 M. scutellaris 的生存至关重要。本研究结果还填补了关于这些蜜蜂对噻虫嗪暴露反应的空白，将有助于未来保护蜜蜂生物多样性的风险评估。
