Institute of Bee Health, Vetsuisse Faculty, University of Bern, Bern, Switzerland.
Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, USA.
Sci Total Environ. 2021 Sep 1;785:146955. doi: 10.1016/j.scitotenv.2021.146955. Epub 2021 Apr 10.
Insecticides are contributing to global insect declines, thereby creating demand to understand the mechanisms underlying reduced fitness. In the eusocial Hymenoptera, inclusive fitness depends on successful mating of male sexuals (drones) and efficient collaborative brood care by female workers. Therefore, sublethal insecticide effects on sperm and glands used in larval feeding (hypopharyngeal glands (HPG)) would provide key mechanisms for population declines in eusocial insects. However, while negative impacts for bumblebee colony fitness have been documented, the effects of insecticide exposure on individual physiology are less well understood. Here, we show that field-realistic concentrations (4.5-40 ng ml) of the neonicotinoid insecticide thiamethoxam significantly impair Bombus terrestris sperm and HPGs, thereby providing plausible mechanisms underlying bumblebee population decline. In the laboratory, drones and workers were exposed to five thiamethoxam concentrations (4.5 to 1000 ng ml). Then, survival, food consumption, body mass, HPG development, sperm quantity and viability were assessed. At all concentrations, drones were more exposed than workers due to higher food consumption. Increased body mass was observed in drones starting at 20 ng ml and in workers at 100 ng ml. Furthermore, environmentally realistic concentrations (4.5-40 ng ml) did not significantly affect survival or consumption for either sex. However, thiamethoxam exposure significantly negatively affected both sperm viability and HPG development at all tested concentrations. Therefore, the results indicate a trade-off between survival and fitness components, possibly due to costly detoxification. Since sperm and HPG are corner stones of colony fitness, the data offer plausible mechanisms for bumblebee population declines. To adequately mitigate ongoing biodiversity declines for the eusocial insects, this study suggests it is essential to evaluate the impact of insecticides on fitness parameters of both sexuals and workers.
杀虫剂正在导致全球昆虫数量减少，因此人们越来越需要了解导致昆虫适应能力下降的机制。在真社会性膜翅目昆虫中，合子适合度取决于雄性（雄蜂）的成功交配和雌性工蜂的有效合作育雏。因此，亚致死浓度的杀虫剂对精子和用于幼虫喂养的腺体（下咽腺 (HPG)）的影响将为真社会性昆虫种群减少提供关键机制。然而，尽管已经记录了对熊蜂群体适应能力的负面影响，但杀虫剂暴露对个体生理的影响还不太清楚。在这里，我们表明，田间实际浓度（4.5-40ngml）的新烟碱类杀虫剂噻虫嗪显着损害了熊蜂的精子和 HPG，从而为熊蜂种群减少提供了合理的机制。在实验室中，雄蜂和工蜂暴露于五种噻虫嗪浓度（4.5 至 1000ngml）下。然后，评估了存活率、食物消耗、体重、HPG 发育、精子数量和活力。在所有浓度下，由于食物消耗较高，雄蜂比工蜂暴露更多。从 20ngml 开始，雄蜂的体重增加，从 100ngml 开始，工蜂的体重增加。此外，在环境实际浓度（4.5-40ngml）下，无论性别，都不会显着影响存活率或食物消耗。然而，噻虫嗪暴露显着降低了所有测试浓度下的精子活力和 HPG 发育。因此，结果表明生存和适应能力成分之间存在权衡，可能是由于代价高昂的解毒作用。由于精子和 HPG 是群体适应能力的基石，因此该数据为熊蜂种群减少提供了合理的机制。为了充分减轻真社会性昆虫的生物多样性减少，本研究表明，评估杀虫剂对雄性和雌性的适应能力参数的影响至关重要。
