听力文摘：神奇的蟹

Amazing Crabs²

神奇的蟹

What's the difference between a hard-shelled blue crab¹ and a soft-shelled blue crab?

你知道软壳青蟹和硬壳青蟹有什么区别吗？

Is this a trick question?

这个问题很难吗？

I'll give you a hent. It has to do with the crab’s skeletal system.

我来给你个提示。这与螃蟹的骨骼系统是紧密相关的。

Skeletal system? You got me there, I know that like other crustaceans³, periodicallymolt. That is, the crab sheds its hard shell and forms a new one. But I don't have a clue as to what that means about the skeletal system?

骨骼系统？哦，我大概懂了。就像是其它的甲壳类动物一样，螃蟹会定期的褪壳。也就是说，螃蟹褪掉原有的硬壳再重新长出新壳。但问题是，我想不明白这怎么就和骨骼系统扯上了关系。

Well, I'll tell you. When a blue crab sheds its hard shell, its exoskeleton, it has to wait about a week for the new shell to harden. Before that happens, this outer layer of tissue is too soft and flexible to transmit muscle contractions⁵ as it did, and will do again when the crab’s new shell hardens. And yet these creatures are somehow still able to move about, even immediately after molting⁶.

那就由我来告诉你吧。当一只青蟹褪掉了它的硬壳（也就是它的外骨骼）之后，新长出的壳要等上大概一个星期才能变硬。在壳变硬之前，外面的那层“壳”太软太韧了，以致于无法进行正常的肌肉收缩。在新壳变硬之时还要再进行一次。而且，不知为何，青蟹在这种情况下还是能到处爬来爬去的，即使是刚刚褪壳的时候也是如此。

How is that possible?

这怎么可能呢？

It's possible using a hydrostatic skeleton. Many animals, such as worms, rely on hydrostatic skeletons all their lives. What this means is that muscle contractions are transmitted through an incompressible fluid. Immediately after molting, the hydrostatic pressure inside crabs jumps significantly higher, allowing the crabs to use this pressure to move their muscles. While a hydrostatic skeleton isn’t so remarkable⁷ in itself, what is remarkable is that the crab alternates between using the two kinds of skeletons. Scientists suspect that crabs probably aren’t alone in this feat⁸ and plan to investigate the skeletal systems of other creatures that molt⁴.

使用铃静力骨架就可以了！许多种动物，比如说蠕虫，它们一生都是靠铃静力骨架支撑下来的。这也就是说，肌肉的收缩通过不可压缩铃被传送到了身体各部分。青蟹刚刚褪壳的时候，体内的铃静压力陡然飚到很高，这使得青蟹可以利用压力来使肌肉活动。青蟹的铃静力骨架并不是特别出众，真正出众的是青蟹在外骨骼和铃静力骨架之间出众的交替使用能力。科学家们猜测，蟹并不是唯一一种此类动物，接下来，科学家们将会研究更多褪壳生物的骨骼系统。

1 crab   

n.螃蟹，偏航，脾气乖戾的人，酸苹果；vi.捕蟹，偏航，发牢骚；vt.使偏航，发脾气

参考例句：

• I can't remember when I last had crab.我不记得上次吃蟹是什么时候了。
• The skin on my face felt as hard as a crab's back.我脸上的皮仿佛僵硬了，就象螃蟹的壳似的。

2 crabs   

n.蟹( crab的名词复数 )；阴虱寄生病；蟹肉v.捕蟹( crab的第三人称单数 )

参考例句：

• As we walked along the seashore we saw lots of tiny crabs. 我们在海岸上散步时看到很多小蟹。 来自《简明英汉词典》
• The fish and crabs scavenge for decaying tissue. 鱼和蟹搜寻腐烂的组织为食。 来自《简明英汉词典》

3 crustaceans   

n.甲壳纲动物（如蟹、龙虾）( crustacean的名词复数 )

参考例句：

• These crustaceans provide a valuable food source for some fish. 这些甲壳纲动物是某些鱼类重要的食物来源。 来自《简明英汉词典》
• When the tide ebbs it's a rock pool inhabited by crustaceans. 退潮时，它便成为甲壳动物居住的岩石区潮水潭。 来自辞典例句

4 molt   

n.换毛，脱皮，换毛期

参考例句：

• The fourth time they molt,they change into pupae.换第四次皮时，它们蜕变成蛹。
• This veterinary product is very effective in preventing animal molt.这种兽药对于防治兽类掉毛很有效。

5 contractions   

n.收缩( contraction的名词复数 )；缩减；缩略词；（分娩时）子宫收缩

参考例句：

• Contractions are much more common in speech than in writing. 缩略词在口语里比在书写中常见得多。 来自《简明英汉词典》
• Muscle contractions are powered by the chemical adenosine triphosphate(ATP ). 肌肉收缩是由化学物质三磷酸腺苷(ATP)提供动力的。 来自辞典例句

6 molting   

n.蜕皮v.换羽，脱毛( molt的现在分词 )

参考例句：

• The old cuticle is digested by molting fluid. 旧表皮被蜕皮液消化。 来自辞典例句
• Molting in insects is triggered by rising levels of a hormone called ecdysone. 昆虫的脱皮是由于称为脱皮素激素的含量升高而引起的。 来自辞典例句

7 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。

8 feat   

n.功绩；武艺，技艺；adj.灵巧的，漂亮的，合适的

参考例句：

• Man's first landing on the moon was a feat of great daring.人类首次登月是一个勇敢的壮举。
• He received a medal for his heroic feat.他因其英雄业绩而获得一枚勋章。