低剂量杀虫剂对星豹蛛捕食效应的影响及其机理

探讨低剂量杀虫剂对蜘蛛捕食效应的影响及其生化机理。采用药膜法,测定了低剂量吡虫啉作用下,星豹蛛和甘蓝蚜敏感性、捕食效应以及成蛛体内乙酰胆碱酯酶(AChE)、谷胱甘肽S-转移酶(GSTs)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和中肠蛋白消化酶的活力变化。低剂量农药作用下,星豹蛛对甘蓝蚜的功能反应类型为HollingⅡ型,与对照组相比,随着猎物密度的增大星豹蛛的捕食量增加,寻找效应降低,对猎物的处理时间Th缩短,从而增强了对猎物的捕食作用;低剂量农药处理后,星豹蛛体内AChE和GSTs活性均显著低于对照组(P0.05),说明酶活性受到抑制,且抑制作用随吡虫啉浓度的增大而加强,随作用时间的延长而减弱;SOD,CAT和中肠蛋白消化酶活性显著增强,与对照组相比存在显著或极显著差异(P0.05),且随吡虫啉浓度增大和作用时间的延长而逐渐降低,最后接近对照组。低剂量杀虫剂作用下,蜘蛛体内AChE活性受到抑制,AChE敏感性降低,对神经递质乙酰胆碱的分解作用下降,使蜘蛛的兴奋性增加;GSTs、SOD、CAT等代谢酶活性发生变化,使蜘蛛的新陈代谢加速,从而刺激捕食;中肠蛋白消化酶的活性增强,提高了对猎物的消化吸收功能。总之,在低剂量杀虫剂作用下,星豹蛛通过外在的捕食行为和体内一系列酶系生理生化反应的综合作用促进蜘蛛对害虫的控制作用。

The effect of low-dose of pesticide on predation of spider and its preliminary mechanisms

Spiders are among the most abundant predators of insects and other invertebrates in agro- and forest ecosystems, playing an important ecological role by regulating invertebrate populations. Biological control using spiders may represent a sustainable method of controlling agricultural pest species and reducing the amount of pest damage on crops. However, pesticide application on agricultural crops may directly or indirectly impact spider foraging in the crop. In particular, pesticides may have mutagenic effects on spiders, negatively affecting the spider population abundance and transferring these effects to the next generation. Recent studies have reported that low-dose pesticides kill pests, but promote the predation of natural enemies. Therefore, revealing the mechanism behind low-dose pesticides on natural enemies is critical to improving predator ability, exploring the potential control of insect predators and coordinating bio- and chemical control.Our aim was to investigate the effect of low-dose pesticides on spider predation behavior and reveal the underlying mechanisms. Pardosa astrigera was treated with a low-dose of imidacloprid using the drug-film method. We determined the sensitivity of P. astrigera, the predation effect of P. astrigera on B. brassicae and the activity of acetylcholinesterase (AChE), glutathione S-transferase (GSTs), superoxide dismutase (SOD), catalase (CAT) and midgut proteinase. The results showed that under different concentrations of imidacloprid, the predacious functional response of spiders on aphids belonged to the Holling type. Compared with the control, the theoretical maximal consumption increased, searching efficiency decreased and the prey handling time declined with increasing aphid density. Therefore, low-dose pesticide levels resulted in enhanced predation by spiders. When P. astrigera was treated with a low-dose of pesticide, this species showed a reduction in AChE and GSTs activity compared with the control (P < 0.05), suggesting spider activity was inhibited. The inhibition was enhanced with increasing pesticide concentration and weakened with prolonged treatment. SOD, CAT and midgut proteinase activity were induced significantly at the low-dose of 1, 3 and 5mg/L(P < 0.050, but decreased gradually with increased concentration and extended treatment, with activity close to the control. After low-dose pesticide treatment, P. astrigera showed inhibited AChE activity, leading to reduced AChE sensitivity, less decomposition of AChE in nerve transfer and increased spider activity. Increased GSTs, SOD and CAT activity induced by low-dose pesticide, accelerated the spiders' metabolism, stimulating predatory behavior. Enhanced midgut proteinase activity may benefit food digestion and nutrient absorption. The low-dose pesticide regime may enhance the predatory behavior of P. Astrigera via three main pathways. First, it enhances the instant attack rate, shortens prey handling time and increases the amount of prey per day. Second, it affects physiological enzyme activity, inhibits to a degree the metabolic detoxification enzyme subject of: low doses of imidacloprid causing a reduction in AChE sensitivity of the neurotransmitter acetylcholine decomposition, resulting in higher spider excitability; increased protection enzyme, such as GSTs, SOD, CAT, function oxidases (MFOs) and esterase, resulting in the acceleration of spider metabolism, stimulating predator behavior. Third, on the physiological activity of digestive enzymes, low doses of pesticides activate protein midgut digestive enzymes, improving the digestion and absorption function of prey. In summary, certain concentrations of pesticide promote the predation function of P. astrigera against prey, changing spider behavior through a series of physiological and biochemical reactions.