评论
打印
After stalking an unsuspecting cuttlefish across the seafloor, this moray eel is finally ready to pounce.
在海底跟踪了一条毫不知觉的墨鱼一段时间后，这条海鳗终于准备进攻了。
As the eel snags the mollusk in its long teeth, its prey struggles to escape.
当海鳗长长的牙齿咬住这个软体动物后，它的猎物拼命地试图挣脱。
But before it can wriggle away, a second set of teeth lunge from the eel's throat, making short work of the captive cuttlefish.
但在它能成功逃脱前，海鳗喉咙里的第二套牙齿咬了上来，让猎物无法逃脱。
This adaptation is called a pharyngeal jaw.
这个进化被称为咽颚。
And while it might seem more fitting for an alien parasite than a fish, it's actually one of the most common adaptations under the sea.
虽然它更像来自外星的寄生虫，而不是一条鱼，而事实上它是海底最常见的进化之一。
At some point millions of years ago, early fish evolved a jointed oral jaw from one of the bony arches that supported their frontal gills.
在数百万年前的某个时间点，早期鱼类从一个嘴弓进化出了一个连接在一起的口腔颌骨，它可以支撑它们前面的鱼鳃。
This exterior, oral jaw was perfect for capturing or chewing prey, but these early fish had a problem.
这个外部的口腔颌骨非常适合抓捕或咀嚼猎物，但这些早期鱼类有一个难题。
They had no limbs to manipulate food while eating, making it easy for their mobile prey to escape before they took the first bite.
它们没有肢体来操弄食物，在它们咬第一口之前，它们灵活的食物会很容易逃脱。
Essentially, it was impossible for fish to capture and chew their prey at the same time with just one set of jaws.
简而言之，要鱼用一套牙齿在同一时间既抓捕又咀嚼是不太可能的。
So to hold their food and eat it too, an even deeper gill arch evolved into a secondary set of jaws.
所以为了既抓住又食用它们的食物，一个更深的鳃弓就进化成了第二套牙齿。
Unlike oral jaws connected by a bone joint, these pharyngeal jaws were suspended in muscle, offering them a wide range of motion to turn, tug, and tear on food.
和由骨关节连接的口腔牙齿不同，这些咽颚长在肌肉上，使得它们能够对食物进行扭转、拖拉和撕扯等一系列的动作。
Some pharyngeal jaws actively chew, while others retract to pull chunks of food down the throat. Of course, the teeth a jaw has also factor in here.
有的咽颚可以咀嚼食物，而同时其它咽颚可以收缩把食物块拖下喉咙。当然，颚上所长的牙齿也是一个重要因素。
For example, an oral jaw with fangs is exceptional for catching and holding on to fast-moving prey.
例如，长着尖牙的口腔颌骨非常容易捕获并抓牢快速游动的食物。
But depending on what that prey is, a fish might want sharp pharyngeal teeth to tear through tissue,
但由于食物的不同，有的鱼可能需要锋利的咽齿以便撕扯软组织，
flat pharyngeal molars to grind plant matter, or a powerful pharyngeal bite to crush shelled prey.
需要平的咽磨牙以便研磨植物食物，或一个有力的咽牙来咬碎带壳的猎物。
Fortunately some fishes can change their secondary teeth to match a new diet over several years.
幸运的是，有些鱼能够花几年时间更换它们的第二套牙齿，以适应不同的食物。
This flexibility allows fish to adapt and find food in a huge variety of aquatic environments.
这种灵活性使得它们能够适应非常广泛的海洋环境并获取食物。
Some pharyngeal jaws have formed to eat food too hard for most fishes.
有的咽颚演化到可以吃对大部分鱼都太硬的食物。
California Sheephead use pointed teeth from their oral jaws to pry urchins off rocks
加州羊头鱼使用嘴巴上的尖牙将海胆从岩石上撬开，
before crushing their spiny exteriors in strong pharyngeal jaws that have fused with the bones of their skulls.
用强壮的已经和头骨融合的咽颚把海胆长满刺的身体压碎。
Other fish prioritize eating huge quantities of food.
有的鱼则偏重吃大量的食物。
The pharyngeal jaws of grass carp have two bone components that move in unison to pull plant life into their stomachs, consuming over 18 kilograms of seaweed a day.
草鱼的咽颚有两个骨骼组件，它们一致行动以便把植物拖进它们的胃，这样它们可以一天吃掉超过18公斤的海藻。
Other pharyngeal jaws are adapted to suit incredibly specific circumstances.
其它咽颚演化到能适应令人难以置信的特定环境。
Consider this species of pearlfish that lives inside sea cucumbers and feeds on their guts.
比如这种珍珠鱼，它们生活在海参身体里面并以它们的内脏为食。
Fish are the most diverse group of vertebrates with over 30,000 unique species,
鱼类是最多样化的脊椎动物群体，它们拥有超过30000种独特的物种，
and much of that diversity is due to the hundreds of unique jaws separating otherwise identical species.
而大部分的多样性是由于数百个独特的颌骨，使得它们和其它相同的物种不一样。
Perhaps the best example of this dental diversity can be seen in cichlids.
也许慈鲷是多样性牙齿的最好例子。
This family of fish is primarily found in select African and South American lakes.
该鱼科主要分布于非洲和南美的某些湖泊。
Typically, large lakes like these would be occupied by a handful of distantly related species, each adapted to consume one of the lake's limited food sources.
通常像这样的大湖会被少数远亲物种占用，而每种物种演化成食用湖泊有限的食物中的一种。
But here, almost every corner of the ecosystem is occupied by a different species of cichlid.
但在这里，几乎生态系统的每个角落都被不同的慈鲷物种占据。
There are over 1,700 cichlid species, many almost identical save for their uniquely adapted jaws
在超过1700种的慈鲷当中，许多都有独特的几乎完全相同的下颚，
which have evolved to eat crustaceans, mollusks, worms, algae, plankton, and even the scales of other fish.
这些演化使得它们可以吃甲壳类动物、软体动物、蠕虫、藻类、浮游生物，甚至其他鱼的鳞片。
These oral adaptations are so essential for survival,
这些嘴的进化对它们的繁衍至关重要，
that different species use their pharyngeal jaws to make unique mating sounds that allow female cichlids to identify males of their own species.
使得不同的物种可以使用咽颚来发出独特的交配声音，这样雌性慈鲷得以识别属于自己物种的雄性。
This technique limits interspecies breeding, and ensures the parent fish will pass on their specialized jaws.
这个技能限制了不同种类间的交配，从而确保父母能遗传它们独特的嘴巴。
Scientists are still discovering all the ways this incredible skeletal mechanism functions.
科学家们仍在不断发现这种令人难以置信的骨骼机制的所有职能。
But given what we know already, it's fair to say that for most fish, two jaws are better than one.
但鉴于我们已经知道的，可以公平地说，对于大多数鱼来说，两个嘴巴比一个好。
