鱼儿看似没有耳朵，但是他们可以听见声音吗？


Hints:
otoliths
calcium carbonate
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选材／校对／翻译：hqj5715
When you look at a live fish, you can't see its ears because they're entirely internal, located inside the head just behind each eye. Each ear is a small, hollow chamber, lined with nerve hairs and containing three otoliths — or ear stones — that rest lightly on the nerve hairs. Here's how otoliths help fish detect sound. Sound is conducted through water as a series of pressure waves, which cause the whole body of the fish to vibrate. The ear stones are much more dense than the rest of the fish, so as the chambers of the ear vibrate, the stones lag behind, bumping and stimulating the nerve hairs. The nerve hairs then send a message to the brain that there’s a ruckus going on. In small fish, the ear stones may be just the size of a tiny grain of sand. Large fish have ear stones as big as marbles. And the ear stones actually grow along with the fish — every day fish produce small amounts of calcium carbonate to be layered onto their ear stones. In fact, examining ear stones is one of the ways biologists determine the age of fish. And biologists aren’t the only ones interested in ear stones — Native Americans around the Great Lakes once collected and valued the otoliths of large fish.
当你注视一条活鱼，你不能看到它的耳朵因为他们是完全在内部的，位于头的内部且正好在每个眼睛的后面。鱼的耳朵是小的腔室，有神经纤毛附着并含有3个耳石--耳石附着于神经纤毛上。 这里我们所要讨论的是耳石怎样帮助鱼发现声音。声音以一系列的具有压力的波通过水来传播，这些波浪使鱼的整个身体振动。 耳石的密度比鱼其他部分密度要大的多，因此，当耳房振动时，耳石处于滞后位置，撞击并刺激神经纤毛。然后神经纤毛便向大脑传送有声音在产生的信息。 在小的鱼中，耳石也许只有一个细小沙晶的大小。而大的鱼的耳石可以和石弹大小相似。耳石实际上是伴随鱼的生长而生长--鱼每天都会产生少量的碳酸钙附着于耳石的表面。 实际上，监测耳石是生物学家决定鱼年龄的一种方式。对耳石感兴趣的并不只是生物学家--五大湖周边的原著美国人曾经收集并珍视大鱼的耳石。