VOA慢速英语--科学家:蜘蛛利用电场在空气中移动

Scientists: Spiders Use Electric Fields to Move through Air

Scientists have long wondered how spiders can use the webbing they make to fly.

The 19th century English naturalist¹ Charles Darwin commented on their behavior when very small spiders landed on his ship, the HMS Beagle. He noted² that they were following lines of smooth silk. He thought the creatures might have been using warm air to take to the sky. However, new research shows a totally different cause may be involved.

Erica Morley and Daniel Robert are with the University of Bristol in Britain. They were interested in exploring another explanation for the spiders’ ability. They thought spiders might sense and use electrostatic fields in the air.

Morley told VOA: “There have been several studies looking at how air movement and wind can get spiders airborne, but the electrostatic hypothesis was never tested.”

But some observers suggested electrostatic fields might be the reason the many draglines some spiders use to float never get tangled⁴.

Kimberley Sheldon is a biologist with the University of Tennessee, Knoxville, in the United States. She said that although “these spiders will have 5 or 6 draglines, those strands⁵ of silk do not get entangled⁶. So, we've known for a while that electrostatics probably [are] at least interacting with the spider, with the silk lines themselves to keep them from getting tangled.”

Sheldon was not involved in the latest study.

Morley and Robert created a box with a grounded metal plate on the bottom and a plate on the top. It was designed so they could send an electrical current through the box. They placed spiders inside the box and turned on the electricity, then watched as the spiders reacted to the electric field.

When the electric field was on, the spiders lifted their abdomens⁸ into the air and started raising up on the very ends of their legs. Morley told VOA that spiders only move this way before they release silk draglines to fly away, in a process called ballooning.

When the spiders did balloon and rise into the air, turning off the electric current caused them to drop.

Sheldon compares this to someone taking a balloon and rubbing it against their clothing. "If you hold the balloon [near your head], your hair stands on end. That's kind of what's happening with the spider silk.”

Clearly the spiders were able to sense the local electrostatic field and react by releasing silk, but Morley and Robert wanted to know how.

Morley noted that as a sensory⁹ biologist, she was interested in understanding what sensory system spiders might use to sense electric fields.

“We know that they have very sensitive hairs that are displaced by air movements or even sound. So, I thought that it’s possible that they might be using these same hairs to detect electric fields,” she said.

This was exactly what she observed. The small hairs along the spiders’ legs react not only to physical experiences like air movement, but also to the electric field. In nature, it makes sense for spiders to sense both the electrostatic field around them as well as wind conditions. Spiders probably use both when taking off and moving through the sky.

Mathematician¹⁰ Longhua Zhao is with Case Western Reserve University in Cleveland, Ohio. She has made computer models of how spiders balloon. She told VOA that both the electrical field and the air flow are important.

“They definitely play very important roles; however, we don’t know at this point, which is the dominant¹¹ factor,” she added.

Lead researcher Morley pointed¹² out that spiders are not the only creatures to balloon. “Caterpillars and spider mites¹³, which are arachnids but not spiders, balloon as well,” she noted.

Arachnids have eight legs and a body made of two parts.

Invertebrates¹⁴ have no back bone.

Morley hopes other researchers will follow up her study to see if these other creatures react in much the same way as spiders.

I’m Pete Musto.

Words in This Story

abdomen⁷ - n. the part of the body below the chest that contains the stomach and other organs?

dragline - n. a rope used for dragging or hauling something.

electrostatic - adj. relating to stationary¹⁵ electric charges or fields as opposed to electric currents.?

factor - n. something that helps produce or influence a result?

hypothesis - n. an idea or theory that is not proven but that leads to further study or discussion?

plate - n. a thin, flat piece of metal?

role - n. a part that someone or something has in a particular activity or situation

silk - n. a smooth, soft, and shiny cloth that is made from thread produced by silkworms?

tangle³ - v. to become or cause (something) to become twisted together?

webbing - n.

1 naturalist   

n.博物学家(尤指直接观察动植物者)

参考例句：

• He was a printer by trade and naturalist by avocation.他从事印刷业，同时是个博物学爱好者。
• The naturalist told us many stories about birds.博物学家给我们讲述了许多有关鸟儿的故事。

2 noted   

adj.著名的，知名的

参考例句：

• The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
• Jim is noted for arriving late for work.吉姆上班迟到出了名。

3 tangle   

n.纠缠；缠结；混乱；v.(使)缠绕；变乱

参考例句：

• I shouldn't tangle with Peter.He is bigger than me.我不应该与彼特吵架。他的块头比我大。
• If I were you, I wouldn't tangle with them.我要是你，我就不跟他们争吵。

4 tangled   

adj. 纠缠的，紊乱的 动词tangle的过去式和过去分词

参考例句：

• Your hair's so tangled that I can't comb it. 你的头发太乱了，我梳不动。
• A movement caught his eye in the tangled undergrowth. 乱灌木丛里的晃动引起了他的注意。

5 strands   

n.（线、绳、金属线、毛发等的）股( strand的名词复数 )；缕；海洋、湖或河的)岸；（观点、计划、故事等的）部份v.使滞留，使搁浅( strand的第三人称单数 )

参考例句：

• Twist a length of rope from strands of hemp. 用几股麻搓成了一段绳子。 来自《简明英汉词典》
• She laced strands into a braid. 她把几股线编织成一根穗带。 来自《简明英汉词典》

6 entangled   

adj.卷入的；陷入的；被缠住的；缠在一起的v.使某人（某物/自己）缠绕，纠缠于（某物中），使某人（自己）陷入（困难或复杂的环境中）( entangle的过去式和过去分词 )

参考例句：

• The bird had become entangled in the wire netting. 那只小鸟被铁丝网缠住了。
• Some military observers fear the US could get entangled in another war. 一些军事观察家担心美国会卷入另一场战争。 来自《简明英汉词典》

7 abdomen   

n.腹，下腹(胸部到腿部的部分)

参考例句：

• How to know to there is ascarid inside abdomen?怎样知道肚子里面有蛔虫？
• He was anxious about an off-and-on pain the abdomen.他因时隐时现的腹痛而焦虑。

8 abdomens   

n.腹（部）( abdomen的名词复数 )

参考例句：

• The women especially disliked their stomachs or abdomens, hips, thighs and legs. 这些妇女特别不喜欢自己的胃部，腹部，臀部，大腿，腿部。 来自互联网
• They danced not with their legs or arms, but with their entire bodies, undulating their abdomens. 他们跳舞不是用腿和臂，而是用整个身子，腹部一起一伏地扭动着。 来自互联网

9 sensory   

adj.知觉的，感觉的，知觉器官的

参考例句：

• Human powers of sensory discrimination are limited.人类感官分辨能力有限。
• The sensory system may undergo long-term adaptation in alien environments.感觉系统对陌生的环境可能经过长时期才能适应。

10 mathematician   

n.数学家

参考例句：

• The man with his back to the camera is a mathematician.背对着照相机的人是位数学家。
• The mathematician analyzed his figures again.这位数学家再次分析研究了他的这些数字。

11 dominant   

adj.支配的，统治的；占优势的；显性的；n.主因，要素，主要的人(或物)；显性基因

参考例句：

• The British were formerly dominant in India.英国人从前统治印度。
• She was a dominant figure in the French film industry.她在法国电影界是个举足轻重的人物。

12 pointed   

adj.尖的，直截了当的

参考例句：

• He gave me a very sharp pointed pencil.他给我一支削得非常尖的铅笔。
• She wished to show Mrs.John Dashwood by this pointed invitation to her brother.她想通过对达茨伍德夫人提出直截了当的邀请向她的哥哥表示出来。

13 mites   

n.（尤指令人怜悯的）小孩( mite的名词复数 )；一点点；一文钱；螨

参考例句：

• The only discovered animals are water bears, mites, microscopic rotifers. 能够发现的动物只有海蜘蛛、螨和微小的轮虫。 来自辞典例句
• Mites are frequently found on eggs. 螨会经常出现在蛋上。 来自辞典例句

14 invertebrates   

n.无脊椎动物( invertebrate的名词复数 )

参考例句：

• Insects and worms are all invertebrates. 昆虫和蠕虫都是无脊椎动物。 来自辞典例句
• In the earthworm and many other invertebrates, these excretory structures are called nephridia. 在蚯蚓和许多其它无脊椎动物中，这些排泄结构称为肾管。 来自辞典例句

15 stationary   

adj.固定的，静止不动的

参考例句：

• A stationary object is easy to be aimed at.一个静止不动的物体是容易瞄准的。
• Wait until the bus is stationary before you get off.你要等公共汽车停稳了再下车。