并非只有脊椎動(dòng)物才知道應(yīng)該何時(shí)吞下那粒小藥丸。生物學(xué)家日前首次發(fā)現(xiàn)，一種無(wú)脊椎動(dòng)物——燈蛾毛蟲(chóng)(Grammia incorrupta)——在患病的時(shí)候竟然也知道“自行服藥”,。這一發(fā)現(xiàn)意味著,，與人們的認(rèn)識(shí)相比,，這種行為可能更加廣泛地存在于動(dòng)物世界中,。
美國(guó)康涅狄格州米德?tīng)栴D市衛(wèi)斯理大學(xué)的進(jìn)化生態(tài)學(xué)家Michael Singer和他的同事之所以取得這一發(fā)現(xiàn)，是因?yàn)樗麄冏⒁獾綗舳昝x(chóng)非常愛(ài)吃亞利桑那爆玉米花(Plagiobothrys arizonicus)和其他一些帶毒的含有吡咯里西啶類(lèi)生物堿的食物,。燈蛾毛蟲(chóng)經(jīng)常會(huì)被寄生蠅的幼蟲(chóng)所寄生,。由于上述毒素能夠增加燈蛾毛蟲(chóng)的存活幾率——盡管它們同時(shí)也會(huì)抑制其生長(zhǎng)，因此研究人員懷疑,，生物堿是否起到了某種藥物的作用,。
在實(shí)驗(yàn)室中，研究人員向被寄生蠅幼蟲(chóng)寄生以及未被寄生的燈蛾毛蟲(chóng)提供了吡咯里西啶類(lèi)生物堿或糖,。研究人員發(fā)現(xiàn),，與未被寄生的同伴們相比，攜帶了寄生蠅幼蟲(chóng)的燈蛾毛蟲(chóng)所 食用的生物堿是前者的兩倍,，而這些生物堿則使燈蛾毛蟲(chóng)的存活率增加了20%,。研究人員在最近的《科學(xué)公共圖書(shū)館—綜合》（PLoS ONE）上公布了這一研究成果。Singer認(rèn)為,，這意味著當(dāng)生活在野外的燈蛾毛蟲(chóng)以爆玉米花和其他有毒的植物為食時(shí),，它們實(shí)際上正在自我治療。
美國(guó)加利福尼亞大學(xué)戴維斯分校的生態(tài)學(xué)家Richard Karban指出,，人類(lèi)生病了會(huì)去藥房買(mǎi)藥,，而被蠕蟲(chóng)折磨的黑猩猩則知道通過(guò)食用一些粗糙且生有刺毛的葉子來(lái)刮掉腸胃中的寄 生蟲(chóng)。但是這項(xiàng)新的研究表明,，即便是“那些缺乏高級(jí)的中樞神經(jīng)系統(tǒng)的動(dòng)物仍然具有完成這樣一種復(fù)雜行為的能力”,。
Singer表示，生態(tài)學(xué)家在研究野生動(dòng)物的行為時(shí),，需要考慮到這種自我治療。Singer強(qiáng)調(diào),，更好地了解瀕臨滅絕的物種如何從它們所處的環(huán)境中獲得治療被證明是保護(hù)這些物種的關(guān)鍵,。（生物谷Bioon.com）
生物谷推薦原始出處：
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.
