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Today Jonathan investigates the amazing world of suckers!
今天乔纳森将考察令人惊奇的吸盘类动物的世界！
Cephalopods!
头足类动物！
Welcome to Jonathan Bird's Blue World!
欢迎来到乔纳森·伯德的蓝色世界！
An octopus is on the prowl, looking for an unsuspecting fish to pounce upon.
一只章鱼在四处游荡，寻找毫无戒心的鱼捕食。
A cuttlefish is hunting with mesmerizing colors to distract its prey.
一只乌贼正在利用其迷人的色彩捕猎，以分散猎物的注意力。
A school of reef squid hover in the water column.
一群礁石鱿鱼在水柱中盘旋。
What do these magnificent animals have in common?
这些漂亮的动物有什么共同之处吗？
They are all cephalopods.
它们都是头足类动物。
Cephalopod means "head-foot" because this animal's head (the part with the eyes) is connected to its feet.
头足类动物的意思是“头足”，因为这种动物的头（带眼睛的部分）与足部相连。
The part out in front that looks like a head is actually the body.
前面看起来像头的部分，实际是身体。
And in fact biologists don't call those things feet, they are called arms.
事实上，生物学家不把它们叫做脚，而是叫做手臂。
So cephalopod is actually a terrible name, but it's what we have got.
所以，头足类动物实际上是一个可怕的名字，但我们就这么叫。
Squid, octopods, cuttlefish and nautiluses are all members of the class cephalopoda,
鱿鱼、章鱼、乌贼和鹦鹉螺都属于头足类动物。
but the really weird thing is that cephalopods are mollusks.
但真正奇怪的是，头足类动物是软体动物。
So they are related to animals like snails and clams, which seems a little crazy.
所以，它们和蜗牛、蛤蜊等动物相关，这看起来有点疯狂。
This is based mostly on their internal construction, not their outward appearance.
这主要是基于它们的内部构造，而不是外观。
Perhaps the most obvious difference between most cephalopods and other mollusks is the apparent lack of a shell.
也许大多数头足类动物和其他软体动物之间最明显的区别，是缺少外壳。
The octopuses do not have shells at all.
章鱼根本没有壳。
The squid have a small internal shell.
鱿鱼有一个很小的内壳。
Nautiluses are the only cephalopods with an external shell.
鹦鹉螺是唯一有外壳的头足类动物。
Nautiluses are found in the South Pacific and Indian oceans, typically in deep water.
鹦鹉螺分布在南太平洋和印度洋，通常生活在深海区。
Cephalopods have well-developed nervous systems, much more sophisticated than other mollusks.
头足类动物有发达的神经系统，比其他软体动物复杂得多。
And they can be quite inquisitive.
它们可能会很好奇。
The cephalopod eye is one of the most notable examples of convergent evolution in all of the animal world,
头足类动物的眼睛，是动物世界中趋同进化最显著的例子之一。
because this eye evolved from completely different ancestors than the eyes of mammals,
因为这种眼睛是从与哺乳动物的眼睛完全不同的祖先那里进化而来的，
yet it turned out to function in almost the exact same way.
但功能却几乎完全相同。
Cephalopods, therefore, have extremely good eyesight.
因此，头足类动物的视力非常好。
Of course the most well-known of the cephalopods are the octopuses, named for their eight arms.
当然，最著名的头足类动物是章鱼，以它们的八条手臂而得名。
They are masters of disguise, able to change colors and skin patterns instantly.
它们是伪装大师，能立即改变颜色和皮肤图案。
With no shell, or bones the octopus can fit through tiny holes.
章鱼没有壳，也没有骨头，能穿过很小的孔。
They make terrible pets because they can escape from virtually any aquarium!
它们是可怕的宠物，因为它们几乎可以逃离任何水族馆！
The octopus has a mouth with a beak used to bite prey.
章鱼嘴上有一个用来咬食猎物的嘴喙。
A hunting octopus often balloons over a rock to trap a fish.
捕猎的章鱼经常在岩石上涨大后捕食鱼类。
Then it will use venomous saliva to kill the prey when it bites.
当它咬食猎物时，会用含有毒素的唾液杀死猎物。
But the Blue-Ringed octopus of the South Pacific has venom so powerful
但是，南太平洋的蓝环章鱼毒液很强，
that the bite of this octopus is lethal to a human.
其咬食对人类来说都是致命的。
The mimic octopus is said to mimic other animals in order to hunt or evade predators.
据说，这种会模仿的章鱼为了猎杀或躲避捕食者，可以模仿其他动物。
This one has a convincing flounder imitation going on,
这只正在模仿比目鱼，很令人信服，
but it's unclear how looking like a flounder is advantageous.
但并不太清楚看起来像比目鱼有利是怎么回事。
It might just be the most efficient way to swim and stay camouflaged—convergent camouflage if you will.
如果愿意的话，这可能是游泳和保持伪装的最有效的方法。
A coconut octopus in Indonesia carries a shell so that when the need arises, she can hop inside and hide.
印度尼西亚的一只椰子章鱼有壳，需要的时候，它可以跳到壳里藏起来。
This clever behavior makes the octopus a tool user,
这种聪明的行为使章鱼能够使用工具，
putting her in a category of animals considered more sophisticated and intelligent, like monkeys and dolphins.
人们因此把它归入像猴子和海豚一样，被认为是更复杂和更聪明的动物类别。
