VOA标准英语2010年-US Scientists Unlock Clues to Mystery

Researchers find circadian clock in Monarch¹'s antenna² plays a major role in navigation

Shelley Schlender | Michoacán, Mexico 22 March 2010

Scientists believe antennas³ are critical to the navigation of the Monarch butterfly.

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Monarch Watch
Reppert Lab

Deep in the forests of Michoacán, several hours drive north of Mexico City, tourists watch millions of Monarch butterflies as they cling to fir trees, gather on bushes, or take off in flight.

The striking black and orange insects winter in these mountains every year, traveling up to 4,800 kilometers to get here, from as far away as Canada. They stay through the winter, then, in the spring, the females leave these fir tree forests and head as far north as Kansas, to lay their eggs on milkweed plants.

It's an odyssey⁴ that inspires Chip Taylor, director of the Monarch Watch program in Lawrence, Kansas, over 2,000 kilometers north of the butterflies' winter habitat.

Chip Taylor is director of the Monarch Watch program in Lawrence, Kansas.

"We see them usually between the 14th and 21st of April if they get this far north," he says, adding that many of them can barely fly after their journey. "A lot of those butterflies are so tattered⁵ and broken, that they're crawling from milkweed and milkweed to lay the eggs."

A journey guided by the senses

Just as remarkable⁶ as the distance they fly is how the butterflies navigate⁷. After all, they don't have guides, or maps, or GPS equipment. Instead, they use sight, smell, touch and other senses to find their way. To study that, butterfly scientists track the insects' normal flight paths, then they confuse them and track their path again.

Taylor says his research teams used this method to discover that butterflies need accurate information about the earth's magnetic fields. "Ten seconds of exposure to the strong magnetic field was enough to totally disorient the butterflies. They could not maintain a course," he reports.

Sunlight matters, too, and by manipulating artificial sunlight, scientists can fool butterflies into traveling in the wrong direction.

At the University of Massachusetts, neuroscientist Steven Reppert studies the Monarch butterfly's migration⁸ with a sophisticated apparatus⁹. It's a kind of flight simulator; essentially¹⁰ a large barrel. His research team connects a butterfly to a thin wire tether to track its normal flight path and then to track how that path changes once they've confused it.

Based on flight simulation studies, Reppert says that Monarchs¹¹ use visual cues about the daylight sky to set their internal compass, as well as their brain's circadian clock, which regulates hormones¹² and behavior. Reppert says researchers thought they had this control system mostly figured out. But then they took a closer look at the insects' antenna.

These Monarch butterflies are wintering in the mountains several hours drive north of Mexico City, some traveling from as far away as Canada.

A multipurpose organ for navigation

"The antenna are really remarkable organs," Reppert says. "They're odor sensors¹³. But they do a lot more than that. They can sense vibrations¹⁵, they can act as ears, they can sense changes in barometric¹⁶ pressure, so there's a number of things that the antennae¹⁷ can do."

To study these abilities, Reppert's team decided¹⁸ to confuse the butterflies, at least a little, by removing their antenna. But this did more than eliminate their sense of smell and vibration¹⁴. It totally befuddled¹⁹ their navigation.

Reppert says, "This finding was actually quite heretical to us. We did not know quite what to do with it at the time." So, they devised another experiment.

Removing the Monarchs' antenna not only eliminated their sense of smell and vibration, it also befuddled their navigation.

On the chance that smell mattered more than they had realized, the researchers painted butterflies' antenna to block their odor receptors. And just in case sunlight played a role, Reppert's team used clear paint on some butterflies' antenna and black paint on others. The clear paint allowed in daylight, and those butterflies navigated²⁰ normally. The ones painted black could not.

Antenna data leads the way

This meant that the Monarch's antenna can detect light. But an even bigger surprise was up ahead. Scientists knew that the circadian clock in the insect's brain responds to light signals from the eyes. They had assumed that that system provided all the daylight data that the butterfly's navigation system needed.

But it turns out that the circadian clock signals produced in the butterfly's antenna are at least as crucial as the clock in its brain. The butterfly's bug-sized GPS needs that antenna data, so when winds and other surprises hit, the Monarch still flies in the right direction.

As for how all these pieces work together, Reppert says, the clues are tantalizing²¹. "The antenna are talking to the brain and controlling the behavior in a very specific way. And we need to understand that."

Reppert's lab plans more experiments. He predicts they'll find that the ability of the Monarch's antenna to sense odors and magnetic waves may also help them set the course for the day. And he says the lessons learned will help us understand the role of circadian clocks in other animals, including people.
 

1 monarch   

n.帝王，君主，最高统治者

参考例句：

• The monarch's role is purely ceremonial.君主纯粹是个礼仪职位。
• I think myself happier now than the greatest monarch upon earth.我觉得这个时候比世界上什么帝王都快乐。

2 antenna   

n.触角，触须；天线

参考例句：

• The workman fixed the antenna to the roof of the house.工人把天线固定在房顶上。
• In our village, there is an antenna on every roof for receiving TV signals.在我们村里，每家房顶上都有天线接收电视信号。

3 antennas   

[生] 触角，触须（antenna的复数形式）

参考例句：

• Marconi tied several antennas to kites. 马可尼在风筝上系了几根天线。 来自超越目标英语 第3册
• Radio astronomy today is armed with the largest antennas in the world. 射电天文学拥有世界上最大的天线。

4 odyssey   

n.长途冒险旅行；一连串的冒险

参考例句：

• The march to Travnik was the final stretch of a 16-hour odyssey.去特拉夫尼克的这段路是长达16小时艰险旅行的最后一程。
• His odyssey of passion, friendship,love,and revenge was now finished.他的热情、友谊、爱情和复仇的漫长历程，到此结束了。

5 tattered   

adj.破旧的，衣衫破的

参考例句：

• Her tattered clothes in no way detracted from her beauty.她的破衣烂衫丝毫没有影响她的美貌。
• Their tattered clothing and broken furniture indicated their poverty.他们褴褛的衣服和破烂的家具显出他们的贫穷。

6 remarkable   

adj.显著的，异常的，非凡的，值得注意的

参考例句：

• She has made remarkable headway in her writing skills.她在写作技巧方面有了长足进步。
• These cars are remarkable for the quietness of their engines.这些汽车因发动机没有噪音而不同凡响。

7 navigate   

v.航行，飞行；导航，领航

参考例句：

• He was the first man to navigate the Atlantic by air.他是第一个飞越大西洋的人。
• Such boats can navigate on the Nile.这种船可以在尼罗河上航行。

8 migration   

n.迁移，移居，（鸟类等的）迁徙

参考例句：

• Swallows begin their migration south in autumn.燕子在秋季开始向南方迁移。
• He described the vernal migration of birds in detail.他详细地描述了鸟的春季移居。

9 apparatus   

n.装置，器械；器具，设备

参考例句：

• The school's audio apparatus includes films and records.学校的视听设备包括放映机和录音机。
• They had a very refined apparatus.他们有一套非常精良的设备。

10 essentially   

adv.本质上，实质上，基本上

参考例句：

• Really great men are essentially modest.真正的伟人大都很谦虚。
• She is an essentially selfish person.她本质上是个自私自利的人。

11 monarchs   

君主，帝王( monarch的名词复数 )

参考例句：

• Monarchs ruled England for centuries. 世袭君主统治英格兰有许多世纪。
• Serving six monarchs of his native Great Britain, he has served all men's freedom and dignity. 他在大不列颠本国为六位君王服务，也为全人类的自由和尊严服务。 来自演讲部分

12 hormones   

n. 荷尔蒙，激素 名词hormone的复数形式

参考例句：

• This hormone interacts closely with other hormones in the body. 这种荷尔蒙与体內其他荷尔蒙紧密地相互作用。
• The adrenals produce a large per cent of a man's sex hormones. 肾上腺分泌人体的大部分性激素。

13 sensors   

n.传感器，灵敏元件( sensor的名词复数 )

参考例句：

• There were more than 2000 sensors here. 这里装有两千多个灵敏元件。 来自《简明英汉词典》
• Significant changes have been noted where sensors were exposed to trichloride. 当传感器暴露在三氯化物中时，有很大变化。 来自辞典例句

14 vibration   

n.颤动，振动；摆动

参考例句：

• There is so much vibration on a ship that one cannot write.船上的震动大得使人无法书写。
• The vibration of the window woke me up.窗子的震动把我惊醒了。

15 vibrations   

n.摆动( vibration的名词复数 )；震动；感受；（偏离平衡位置的）一次性往复振动

参考例句：

• We could feel the vibrations from the trucks passing outside. 我们可以感到外面卡车经过时的颤动。
• I am drawn to that girl; I get good vibrations from her. 我被那女孩吸引住了，她使我产生良好的感觉。 来自《简明英汉词典》

16 barometric   

大气压力

参考例句：

• Electricity compensates for barometric pressure as well as system pressure variations. 用电补偿大气压和系统压力的变化。
• A barometric altimeter indicates height above sea level or some other selected elevation. 气压高度表用以指示海平面或另外某个被选定高度以上的高度。

17 antennae   

n.天线；触角

参考例句：

• Sometimes a creature uses a pair of antennae to swim.有时某些动物使用其一对触须来游泳。
• Cuba's government said that Cubans found watching American television on clandestine antennae would face three years in jail.古巴政府说那些用秘密天线收看美国电视的古巴人将面临三年监禁。

18 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

19 befuddled   

adj.迷糊的，糊涂的v.使烂醉( befuddle的过去式和过去分词 )；使迷惑不解

参考例句：

• He was befuddled by drink. 他喝得迷迷糊糊的。
• John is very amusing when he is completely befuddled. 当约翰喝得完全糊涂了的时候，他非常有趣儿。 来自《现代英汉综合大词典》

20 navigated   

v.给（船舶、飞机等）引航，导航( navigate的过去式和过去分词 )；（从海上、空中等）横越；横渡；飞跃

参考例句：

• He navigated the plane through the clouds. 他驾驶飞机穿越云层。 来自《简明英汉词典》
• The ship was navigated by the North Star. 那只船靠北极星来导航。 来自《简明英汉词典》

21 tantalizing   

adj.逗人的；惹弄人的；撩人的；煽情的v.逗弄，引诱，折磨( tantalize的现在分词 )

参考例句：

• This was my first tantalizing glimpse of the islands. 这是我第一眼看见的这些岛屿的动人美景。 来自《简明英汉词典》
• We have only vague and tantalizing glimpses of his power. 我们只能隐隐约约地领略他的威力，的确有一种可望不可及的感觉。 来自英汉非文学 - 历史