Science2014-07-01 3:17 PM

在对抗性气味中寻找花朵会变得更难 Flower discrimination by pollinators in a dynamic chemical environment

论文摘要 

昆虫会循着花的气味来寻找它们下一个采蜜的地方,但一项新的研究报告,对抗性气味,其中包括人造的气味会通过改变这些昆虫脑中的对靶气味的气味感知而让这一作业变得较为困难。在此之前,科学家们一直对昆虫是如何在空气中的各种自然及人造气味中辨别出某些花的气味所知不多。Jeffrey Riffell等人在此对烟草天蛾的飞蛾进行了行为学及神经生物学测试。这些飞蛾所采食的是怀特曼陀罗花的花蜜,而这些花常常相隔几百码。这些花常常生长在杂酚油灌木中,后者会发出闻上去像是曼陀罗发出的气味,从而挑战那些寻找曼陀罗花蜜的昆虫的嗅觉情状导航。为了确定曼陀罗花气味化合物的不断变化的频率是如何影响该飞蛾找到这种植物的能力,研究人员将飞蛾放入风洞内并测试它们在1-20赫兹(Hz)的频率范围内对曼陀罗混合物的反应。飞蛾会对在1-2Hz之间的花的气味脉动做出最强的反应。在更高的频率时,它们会毫无反应。研究人员还测试了飞蛾对在不同气味背景——其中包括那些组成杂酚油灌木气味及来自人造污染物气味的气味背景——中的花混合物的反应。他们发现,改变背景气味可阻止飞蛾对曼陀罗的探究。他们说,这是因为不同的气味背景会影响脑中处理气味的神经元。Riffell等人的工作揭示,靶气味频率及气味背景内容都会支配某个昆虫探究某靶气味的能力。自然气味背景的改变——可能通过人造气味而改变——会让传粉昆虫更难找到标靶花朵。一篇《观点栏目》文章提出了更多的见解。

Abstract 

Pollinators use their sense of smell to locate flowers from long distances, but little is known about how they are able to discriminate their target odor from a mélange of other natural and anthropogenic odors. Here, we measured the plume from Datura wrightii flowers, a nectar resource for Manduca sexta moths, and show that the scent was dynamic and rapidly embedded among background odors. The moth’s ability to track the odor was dependent on the background and odor frequency. By influencing the balance of excitation and inhibition in the antennal lobe, background odors altered the neuronal representation of the target odor and the ability of the moth to track the plume. These results show that the mix of odors present in the environment influences the pollinator’s olfactory ability.

Editor's Summary

How hawkmoths sniff out a flower

Pollinators such as butterflies and bees are the true targets of the flower odors we love so much. Though we might imagine insects “following their noses,” the wealth of odors in the real world can drown out the smell of a flower, making it hard to find. Riffel et al. found that hawkmoths find angel's trumpets by creating a neuronal picture within their antennal lobe, the part of the moth brain that receives olfactory signals from the antennae (see the Perspective by Szyszka). The picture represents both the flower and the background odors. Finding a flower involves a complex reading of both background and target odors, and changes in the background odors—including human pollutants—can hinder the process.

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