并非只有脊椎动物才知道应该何时吞下那粒小药丸。生物学家日前首次发现，一种无脊椎动物——灯蛾毛虫(Grammia incorrupta)——在患病的时候竟然也知道“自行服药”。这一发现意味着，与人们的认识相比，这种行为可能更加广泛地存在于动物世界中。
美国康涅狄格州米德尔顿市卫斯理大学的进化生态学家Michael Singer和他的同事之所以取得这一发现，是因为他们注意到灯蛾毛虫非常爱吃亚利桑那爆玉米花(Plagiobothrys arizonicus)和其他一些带毒的含有吡咯里西啶类生物碱的食物。灯蛾毛虫经常会被寄生蝇的幼虫所寄生。由于上述毒素能够增加灯蛾毛虫的存活几率——尽管它们同时也会抑制其生长，因此研究人员怀疑，生物碱是否起到了某种药物的作用。
在实验室中，研究人员向被寄生蝇幼虫寄生以及未被寄生的灯蛾毛虫提供了吡咯里西啶类生物碱或糖。研究人员发现，与未被寄生的同伴们相比，携带了寄生蝇幼虫的灯蛾毛虫所 食用的生物碱是前者的两倍，而这些生物碱则使灯蛾毛虫的存活率增加了20%。研究人员在最近的《科学公共图书馆—综合》（PLoS ONE）上公布了这一研究成果。Singer认为，这意味着当生活在野外的灯蛾毛虫以爆玉米花和其他有毒的植物为食时，它们实际上正在自我治疗。
美国加利福尼亚大学戴维斯分校的生态学家Richard Karban指出，人类生病了会去药房买药，而被蠕虫折磨的黑猩猩则知道通过食用一些粗糙且生有刺毛的叶子来刮掉肠胃中的寄 生虫。但是这项新的研究表明，即便是“那些缺乏高级的中枢神经系统的动物仍然具有完成这样一种复杂行为的能力”。
Singer表示，生态学家在研究野生动物的行为时，需要考虑到这种自我治疗。Singer强调，更好地了解濒临灭绝的物种如何从它们所处的环境中获得治疗被证明是保护这些物种的关键。（生物谷Bioon.com）
生物谷推荐原始出处：
PLoS ONE 4(3): e4796. doi:10.1371/journal.pone.0004796
Self-Medication as Adaptive Plasticity: Increased Ingestion of Plant Toxins by Parasitized Caterpillars
Michael S. Singer1*, Kevi C. Mace1, Elizabeth A. Bernays2
1 Department of Biology, Wesleyan University, Middletown, Connecticut, United States of America, 2 Department of Entomology, University of Arizona, Tucson, Arizona, United States of America
Self-medication is a specific therapeutic behavioral change in response to disease or parasitism. The empirical literature on self-medication has so far focused entirely on identifying cases of self-medication in which particular behaviors are linked to therapeutic outcomes. In this study, we frame self-medication in the broader realm of adaptive plasticity, which provides several testable predictions for verifying self-medication and advancing its conceptual significance. First, self-medication behavior should improve the fitness of animals infected by parasites or pathogens. Second, self-medication behavior in the absence of infection should decrease fitness. Third, infection should induce self-medication behavior. The few rigorous studies of self-medication in non-human animals have not used this theoretical framework and thus have not tested fitness costs of self-medication in the absence of disease or parasitism. Here we use manipulative experiments to test these predictions with the foraging behavior of woolly bear caterpillars (Grammia incorrupta; Lepidoptera: Arctiidae) in response to their lethal endoparasites (tachinid flies). Our experiments show that the ingestion of plant toxins called pyrrolizidine alkaloids improves the survival of parasitized caterpillars by conferring resistance against tachinid flies. Consistent with theoretical prediction, excessive ingestion of these toxins reduces the survival of unparasitized caterpillars. Parasitized caterpillars are more likely than unparasitized caterpillars to specifically ingest large amounts of pyrrolizidine alkaloids. This case challenges the conventional view that self-medication behavior is restricted to animals with advanced cognitive abilities, such as primates, and empowers the science of self-medication by placing it in the domain of adaptive plasticity theory.
