VOA慢速英语2019--蜻蜓透明牙齿之谜

Solved: Dragonfish Transparent¹ Teeth Mystery

Dragonfish live deep down in the dark ocean, and are frightening-looking creatures.

Their sharp, transparent teeth help them survive in the hostile environment. The cause of their see-through teeth has long been a mystery. But scientists say they have an answer.

In the near-black deep water, a substance covering the teeth prevents any light from reflecting off the teeth surface. This helps a dragonfish hide their big teeth from creatures it wants to eat.

“The mouth is invisible and the prey² is caught more easily,” said scientist Marc Andre Meyers of the University of California, San Diego. He led the research, which was published this month in the journal Matter.

Dragonfish have teeth similar to humans and other animals. They are made up of an outer layer of enamel³, and an inner layer of hard, dense⁴, bony tissue called dentin. But in dragonfish, the material has been reorganized.

In the fish teeth enamel are extremely small crystals. And in the dentin, scientists found extremely small pieces of a protein called collagen. If such structures were larger, they would make light scatter⁵. But because they are so small, light passes with ease. The teeth are also very thin.

Together, these differences prevent any light that may be in the deep water from reflecting off the tooth surface. This makes it easier for the dragonfish to hunt in the waters.

Meyers explained that, before, scientists believed dragonfish teeth were made of another, unknown material.

“However, we discovered that they are made of the same materials as our human teeth...”

And that surprised them, he said. “Same building blocks, different scales and hierarchies⁶. Nature is amazing in its ingeniosity.”

The researchers found the fish in depths of up to 1,000 meters in the Pacific Ocean, off the coast of California.

Dragonfish are small, long, and black. They grow to be about 25 centimeters long. In the deep water, dragonfish attract smaller fish to their big, open mouths with beard-like attachments⁷ that have a light on the end.

The dragonfish is not the only creature with transparent teeth. Others, like the anglerfish and hatchetfish, have them, as well. While they have not been investigated yet, Meyers said, “I suspect they have a similar structure.”

I’m Anne Ball.

Words in This Story

transparent – adj. able to be seen through

reflecting – v. to move in one direction, hit a surface, and then quickly move in a different and usually opposite direction — usually + off

invisible – adj. impossible to see

enamel – n. the very hard outer layer of a tooth

hierarchy⁸ – n. a system in which people or things are placed in a series of levels with different importance or status

ingeniosity – adj. very smart or clever : having or showing ingenuity⁹

attract – v. to cause (someone) to choose to do or be involved in something

beard – n. the long hair that grows on the chin of some animals

1 transparent   

adj.明显的，无疑的；透明的

参考例句：

• The water is so transparent that we can see the fishes swimming.水清澈透明，可以看到鱼儿游来游去。
• The window glass is transparent.窗玻璃是透明的。

2 prey   

n.被掠食者，牺牲者，掠食；v.捕食，掠夺，折磨

参考例句：

• Stronger animals prey on weaker ones.弱肉强食。
• The lion was hunting for its prey.狮子在寻找猎物。

3 enamel   

n.珐琅，搪瓷，瓷釉；(牙齿的)珐琅质

参考例句：

• I chipped the enamel on my front tooth when I fell over.我跌倒时门牙的珐琅质碰碎了。
• He collected coloured enamel bowls from Yugoslavia.他藏有来自南斯拉夫的彩色搪瓷碗。

4 dense   

a.密集的，稠密的，浓密的；密度大的

参考例句：

• The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。

5 scatter   

vt.撒，驱散，散开；散布/播；vi.分散，消散

参考例句：

• You pile everything up and scatter things around.你把东西乱堆乱放。
• Small villages scatter at the foot of the mountain.村庄零零落落地散布在山脚下。

6 hierarchies   

等级制度( hierarchy的名词复数 )； 统治集团； 领导层； 层次体系

参考例句：

• That's a trip of two hierarchies. 那是两个领导层之间的互访。
• Hierarchies of authority, spans of control, long-range plans, and budgets. 等级森严的权力机构，控制范围，长期计划，预算。 来自英汉文学 - 廊桥遗梦

7 attachments   

n.（用电子邮件发送的）附件( attachment的名词复数 )；附着；连接；附属物

参考例句：

• The vacuum cleaner has four different attachments. 吸尘器有四个不同的附件。
• It's an electric drill with a range of different attachments. 这是一个带有各种配件的电钻。

8 hierarchy   

n.等级制度；统治集团，领导层

参考例句：

• There is a rigid hierarchy of power in that country.那个国家有一套严密的权力等级制度。
• She's high up in the management hierarchy.她在管理阶层中地位很高。

9 ingenuity   

n.别出心裁；善于发明创造

参考例句：

• The boy showed ingenuity in making toys.那个小男孩做玩具很有创造力。
• I admire your ingenuity and perseverance.我钦佩你的别出心裁和毅力。