Tomé Hudson Vv, Pascini Tales V, Dângelo Rômulo Ac, Guedes Raul Nc, Martins Gustavo F
Departamento de Biologia Geral, Universidade Federal de Viçosa, Viçosa, MG 36570-900, Brazil.
Parasit Vectors. 2014 Apr 24;7:195. doi: 10.1186/1756-3305-7-195.
The yellow fever mosquito Aedes aegypti is essentially a container-inhabiting species that is closely associated with urban areas. This species is a vector of human pathogens, including dengue and yellow fever viruses, and its control is of paramount importance for disease prevention. Insecticide use against mosquito juvenile stages (i.e. larvae and pupae) is growing in importance, particularly due to the ever-growing problems of resistance to adult-targeted insecticides and human safety concerns regarding such use in human dwellings. However, insecticide effects on insects in general and mosquitoes in particular primarily focus on their lethal effects. Thus, sublethal effects of such compounds in mosquito juveniles may have important effects on their environmental prevalence. In this study, we assessed the survival and swimming behavior of A. aegypti 4th instar larvae (L4) and pupae exposed to increasing concentrations of insecticides. We also assessed cell death in the neuromuscular system of juveniles.
Third instar larvae of A. aegypti were exposed to different concentrations of azadirachtin, deltamethrin, imidacloprid and spinosad. Insect survival was assessed for 10 days. The distance swam, the resting time and the time spent in slow swimming were assessed in 4th instar larvae (L4) and pupae. Muscular and nervous cells of L4 and pupae exposed to insecticides were marked with the TUNEL reaction. The results from the survival bioassays were subjected to survival analysis while the swimming behavioral data were subjected to analyses of covariance, complemented with a regression analysis.
All insecticides exhibited concentration-dependent effects on survival of larvae and pupae of the yellow fever mosquito. The pyrethroid deltamethrin was the most toxic insecticide followed by spinosad, imidacloprid, and azadirachtin, which exhibited low potency against the juveniles. All insecticides except azadirachtin reduced L4 swimming speed and wriggling movements. A similar trend was also observed for swimming pupa, except for imidacloprid, which increased the swimming activity of pupa. Curiously, the insecticides did not affect cell damage in the neuromuscular system of larvae and pupae.
Deltamethrin and spinosad were the main compounds to exhibit lethal effects, which allowed the control of A. aegypti larvae and pupae, and impair their swimming potentially compromising foraging and predation likelihood.
黄热病媒介埃及伊蚊本质上是一种栖息于容器的物种，与城市地区密切相关。该物种是包括登革热病毒和黄热病病毒在内的人类病原体的传播媒介，其控制对于疾病预防至关重要。针对蚊虫幼虫阶段（即幼虫和蛹）使用杀虫剂的重要性日益增加，特别是由于针对成虫的杀虫剂抗性问题不断加剧以及在人类住所使用此类杀虫剂对人类安全的担忧。然而，杀虫剂对昆虫尤其是蚊子的影响主要集中在其致死作用上。因此，此类化合物对蚊虫幼虫的亚致死效应可能对其在环境中的生存有重要影响。在本研究中，我们评估了暴露于浓度不断增加的杀虫剂的埃及伊蚊四龄幼虫（L4）和蛹的存活及游泳行为。我们还评估了幼虫神经肌肉系统中的细胞死亡情况。
将埃及伊蚊三龄幼虫暴露于不同浓度的印楝素、溴氰菊酯、吡虫啉和多杀菌素中。评估10天内的昆虫存活率。对四龄幼虫（L4）和蛹的游动距离、静止时间以及慢速游动时间进行评估。用TUNEL反应标记暴露于杀虫剂的L4和蛹的肌肉和神经细胞。存活生物测定的结果进行生存分析，而游泳行为数据进行协方差分析，并辅以回归分析。
所有杀虫剂对黄热病媒介蚊虫的幼虫和蛹的存活均表现出浓度依赖性影响。拟除虫菊酯类溴氰菊酯是毒性最强的杀虫剂，其次是多杀菌素、吡虫啉和印楝素，印楝素对幼虫的毒性较低。除印楝素外，所有杀虫剂均降低了L4的游泳速度和扭动动作。对于蛹的游泳也观察到类似趋势，但吡虫啉除外，它增加了蛹的游泳活动。奇怪的是，杀虫剂并未影响幼虫和蛹神经肌肉系统中的细胞损伤。
溴氰菊酯和多杀菌素是表现出致死作用的主要化合物，这使得可以控制埃及伊蚊幼虫和蛹，并损害其游泳能力，可能会影响觅食和被捕食的可能性。
