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In the ocean's depths, two titans wage battle: the sperm whale and the colossal squid.
在海洋深处，两位狠角色正在龙争虎斗--一只抹香鲸和大王鱿。
Sperm whales use echolocation to hunt these squid for food, but even against this gigantic animal, squid can put up an impressive fight.
抹香鲸会用回声定位来捕食大王鱿，但就算是面对如此强劲的对手，大王鱿也不甘示弱。
Scientists know this because on the bodies of washed-up whales,
科学家得出此结论，是因为在搁浅的鲸鱼身上
they frequently find huge, round suction scars, emblazoned there by large, grasping tentacles.
他们经常能发现由强吸力造成的巨大的圆形伤疤，那是被巨大的触角吸附后留下的印记。
Ranging in size from this giant's impressive 14 meters to the 2.5 centimeters of the southern pygmy squid,
大小可以从令人惊叹的14米长的大王鱿，到2.5厘米长的南太平洋侏儒鱿鱼，
these creatures fall into the group of animals known as cephalopods.
这些生物在动物中属头足类的无脊椎动物。
There are about 500 squid species worldwide, and they live in all the world's oceans,
全球大概有500余种鱿鱼，生存区域遍布全球海域，
making them a reliable food source for whales, dolphins, sharks, seabirds, fish, and even other squid.
这让它们成为鲸鱼、海豚、鲨鱼、海鸟、鱼，甚至是其他鱿鱼的完美食物来源。
Indeed, squid themselves are fearsome ocean predators.
鱿鱼是海中的可怕的掠食者。
But their most extraordinary adaptations are those that have evolved to help them thwart their predators.
但它们在进化史上最令人惊叹的，是它们已经进化得可以对抗它们的捕食者。
Squid, which can be found mainly in estuarine, deep-sea, and open-water habitats, often swim together in shoals.
鱿鱼，通常成群的出没在浅滩、河口、深海以及开放性水域。
Being out in the open without anywhere to hide makes them vulnerable, so as a first line of defense, they rely on large, well-developed eyes.
但没有躲避的地方，暴露在外让它们非常脆弱，所以它们把进化完全的大眼睛作为它们的首要防范机制。
In the colossal squid, these are the size of dinner plates, the largest known eyes in the animal kingdom.
它们的眼睛可以达到主餐盘大小，大王鱿拥有动物中最大的眼睛。
When it's dark or the water is murky, however, squid rely on a secondary sensory system,
但是当光线不足或是水域浑浊时，大王鱿会依靠它的第二传感系统，
made from thousands of tiny hair cells that are only about twelve microns long and run along their heads and arms.
数以千记的微小毛细胞，长度仅12微米，长在它们头和触角上。
Each of these hair cells is attached to axons in the nervous system.
每一根毛细胞都附着在神经系统的轴突上。
Swimming animals create a wake, so when the hairs on the squid's body detect this motion,
动物游过时会造成一层层波动，因此当鱿鱼身上的毛细胞感受到波动时，
they send a signal to the brain, which helps it determine the direction of the water's flow.
会向大脑发送信号，信号会帮助大脑判断水纹波动的方向。
This way, a squid can sense an oncoming predator in even the dimmest waters.
这样，即使是在光线非常微弱的环境下，鱿鱼们还是可以预测到掠食者的方向。
Aware of the threat, a squid can then mask itself from a predator.
在预知到危险的情况下，鱿鱼可以伪装自己不被捕食者发现。
Squid skin contains thousands of tiny organs called chromatophores, each made of black, brown, red or yellow pigments and ringed in muscle.
鱿鱼的皮肤包含上千个环绕着肌肉的色素细胞，每个细胞都呈黑、棕、红或黄色。
Reflecting cells beneath the chromatophores mirror the squid's surroundings, enabling it to blend in.
长在色素细胞下的反射细胞会映射鱿鱼周围的环境，以便它们伪装自己。
So, when the muscles contract, the color of the pigment is exposed, whereas when the muscles relax the colors are hidden.
所以，当肌肉收缩时，颜色显露出来，当肌肉松弛放松时，颜色就会消失。
Each of these chromatophores is under the individual control of the squid's nervous system, so while some expand, others remain contracted.
每一个色素细胞都是受鱿鱼的神经细胞单独控制的，所以这些细胞可以部分收缩，部分放松。
That enables countershading, where the underside of the squid is lighter than the top,
这让鱿鱼可以进行“反荫蔽”，鱿鱼的肚子颜色会比背部颜色浅，
to eliminate a silhouette that a predator might spy from below.
这样就不会造成剪影，以防捕食者从下方偷袭。
Some predators, however, like the whales and dolphins, get around this ruse by using sound waves to detect a squid's camouflaged form.
但是有些捕食者，比如鲸鱼和海豚，会利用声波来检测鱿鱼的伪装。
Not to be outfoxed, the squid still has two more tricks up its sleeve.
为了不被以智取胜，鱿鱼还是留了两招。
The first involves ink, produced inside its mantle.
第一就是它的身体可以分泌出墨汁。
Squid ink is made mostly of mucus and melanin, which produces its dark coloring.
鱿鱼的墨汁大部分是由粘液和生成黑色的黑色素构成。
When squid eject the ink, they either use it to make a large smokescreen that completely blocks the predator's view
当鱿鱼喷出墨汁时，亦是会喷出大片的黑色墨汁来完全阻挡住捕食者的视线，
or a blob that roughly mimics the size and shape of the squid.
亦或是吐出和鱿鱼体型形状大致一样的墨团。
This creates a phantom form, called a pseudomorph, that tricks the predator into thinking it's the real squid.
墨团会行成一个叫做“伪形”的假鱿鱼来迷惑捕食者，让他们以为“伪形”是真的鱿鱼。
As a final touch, squid rely on jet propulsion to rapidly shoot away from their hunters,
最后，鱿鱼会依靠使劲喷射让自己快速地逃离捕食者所在地点，
reaching speeds of up to 25 miles per hour and moving meters away in mere seconds.
它们的喷射速度可以达到每小时25英里，在短短几秒钟的时间内就移动数秒。
This makes them Earth's fastest invertebrates.
鱿鱼是地球上最快的无脊椎动物。
Some squid species have also developed unique adaptive behaviors.
一些品种的鱿鱼还进化出了适应性行为。
The deep-sea vampire squid, when startled, uses its webbed arms to make a cape it hides behind.
深海的吸血鬼鱿鱼在受到惊吓后，会用带蹼的触手支出一个屏障让自己躲在后面。
The tiny bobtail, on the other hand, tosses sand over its body as it burrows away from prying eyes.
微小的尾巴同时把沙子扔在自己的身体上，就像挖洞一样远离窥视的双眼。
The Pacific flying squid uses jet propulsion for another purpose: to launch itself right out of the water.
太平洋褶柔鱼把喷射推进用在其他用途：把自己发射到水面之外。
Squids' inventive adaptations have allowed them to proliferate for over 500 million years.
鱿鱼那如同发明创造般的进化让他们在超过50亿年的时间里繁衍生息。
Even now, we're still uncovering new species.
甚至现在，还有很多种类的鱿鱼是我们没有发现的。
And as we do, we're bound to discover even more about how these stealthy cephalopods have mastered survival in the deep and unforgiving sea.
就像我们做的那样，我们必然会发现更多有关这些隐秘的头足类动物是如何如大师般生活在无情深海中。
