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Research Papers
Introduction
Hormesis is the stimulatory effect induced in organisms exposed to low doses of potentially toxic agents. It has been reported in numerous biological, toxicological and pharmacological studies. It should be considered as an adaptive response of insects and characterized by a biphasic (i.e., U- or inverted U-shape pattern) quantitative dose-response (Southam & Ehrlich, 1943; Calabrese & Baldwin, 1999, 2001, 2002; Calabrese, 2010). Considerable mechanistic evidence indicates that the hormetic effects represent the overcorrection of growth in response to stimulation by low level of inhibitors (Stebbing, 1982), or the overcompensation in response to disruption in homeostasis (Calabrese & Baldwin, 2002). Usually, organisms were left in contact with the toxin at low-doses for a long time, and the responses in the biological characteristics could be described by using a hormetic dose-response model (Calabrese & Baldwin, 2003). Because the biphasic dose response represents a general pattern of biological responsiveness, it is expected to become increasingly significant within the toxicological evaluation and risk assessment practices as well as for biomedical applications (Calabrese, 2008). Hormesis is now generally accepted as a stress response phenomenon (Cutler, 2013; Guedes & Cutler, 2014).
Frequent or improper insecticide use can result in ecological backlashes: insecticide resistance and pest resurgence or outbreaks, both of which have threatened the sustainability of agriculture (Guedes & Cutler, 2014). In field crops, lowering of insecticide concentration usually occurs after its initial application (Desneux et al., 2005). Therefore, under field conditions, in addition to direct mortality by typical acute toxicity (lethal effect), insecticides may also affect various key biological traits of the exposed insects through physiological and behavioral sublethal effects. Identifying and characterizing such effects could be crucial for understanding the global effects of insecticides on pests, and therefore, for optimizing the management of their applications on crops (Haynes, 1988; Desneux et al., 2007; Tan et al., 2012; Guo et al., 2013). Traditionally, measurement of the acute toxicity of pesticides to arthropods has relied largely on the determination of an acute median lethal dose or concentration. In addition to the direct mortality induced by pesticides, their sublethal effects on biology, physiology and behavior in arthropods had been also studied for a complete analysis...