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题目材料：
Insects have been shown to self-medicate.Caterpillars of the tiger moths Grammia incorrupta and Esrigmene acraea defend themselves against insect parasitoids by sequestering pyrrolizidine alkaloids (PA) from their food plants.These caterpillars have specialist taste receptor cells that detect PA even at extremely low levels and stimulate feeding.Bernays and Singer(2005) showed that the PA receptors on the mouthparts of parasitized caterpillars responded more vigorously than receptors of unparasitized controls. Based on previous work demonstrating that increased responsiveness of the taste receptors to PA stimulates feeding. Bernays and Singer concluded that these caterpillars have a mechanism for increasing the intake of protective chemicals as a response to parasitization. Singer and colleagues(2009) extended this work for Grammia incorrupta,and set it in the context of a framework for rigorously detecting cases of therapeutic self- medication.They made the important argument that three criteria should be satisfied to verify cases of therapeutic self-medication: (1)the behavior should improve the fitness of animals infected parasites or pathogens; (2) it should decrease fitness in uninfected animals; and(3)the behavior should be triggered by infection.They found that all three criteria were satisfied for the ingestion of PA by Grammia incorrupta.
以上解析由 考满分老师提供。
