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In 1864, French zoologist August Duméril was baffled while investigating the axolotl.
1864年，法国动物学家奥古斯特·杜梅里尔在研究蝾螈时感到困惑不解。
Unlike many other amphibians, which transform into terrestrial adults, axolotls retain their juvenile characteristics and never leave the water.
与成年后变成陆地生活的其它两栖类动物不同，美西螈一直保持青少年特征，而且从不离开水。
In an attempt to induce metamorphosis, Duméril spent months removing their gills.
为了诱导它们变形，杜梅里尔花了几个月的时间切除它们的鳃。
But in most instances, the axolotls simply... grew them back.
但多数情况下，美西螈很快又长出了鳃。
Indeed, axolotls are masters of regeneration: they can flawlessly regenerate body parts ranging from amputated limbs and crushed spines to parts of their eyes and brains.
的确，美西螈是再生大师：它们能完美地长出身体部位，从断肢、脊椎到部分眼睛和大脑。
So how do they do it? And what other secrets are they keeping? This extraordinary salamander is native to the wetlands in Mexico City.
那它们如何做到的呢？它们还有哪些秘密呢？这种奇特的蝾螈的栖息地是墨西哥城的湿地。
Ancient Aztec people considered it the incarnation of a God named Xolotl -- hence the axolotl's name, roughly meaning "water monster."
古代阿兹特克人认为它是名为Xolotl的神的化身--名称美西螈由此而来，意思大致是“水怪”。
Axolotls reach sexual maturity with gills and a tadpole-like dorsal fin.
长出鳃和蝌蚪状的背鳍后，美西螈达到性成熟。
Scientists think their forever-young condition, called "neoteny," evolved because of their stable habitat.
科学家们认为，这种“幼态化”的永远年轻状态，是因为栖息地稳定的进化结果。
For salamanders that develop in waters that dry up, efficiently transitioning to land is essential.
对生活在会干涸水域的蝾螈来说，有效转移到陆地生活至关重要。
But the lakes axolotls evolved in were unchanging year-round and didn't host many aquatic predators.
但美西螈演化所处的湖泊终年不变，而且湖里没有太多的水生捕食者。
So, scientists think it was advantageous for axolotls to forgo the demands of metamorphosis.
因此，科学家们认为放弃变形的需求有利于美西螈。
However, they haven't completely lost this ability. If exposed to certain substances, axolotls will turn into adults.
然而，它们并非完全丧失变形能力。如果暴露在某些物质中，美西螈会变为成年。
But they'll often experience shorter lifespans and lose some of their self-healing abilities.
但经常寿命较短，也丧失一些自我修复能力。
These regenerative talents may seem like crazy superpowers to begin with, but axolotls have good use for them.
这些再生才能可能一开始看起来像超棒的超能力，但美西螈善用了它们。
As babies, they're in direct competition. So, they snack on each other.
在婴儿期，它们就处于直接竞争中，所以，它们会吃对方。
This is usually not a huge problem thanks to how quickly they can regenerate body parts.
这通常不是一个大问题，因为它们的身体器官再生速度非常快。
When an axolotl loses a limb, tissues stimulate growth in the area. Skin cells divide and cover the wound.
当美西螈失去肢体时，组织会刺激该区域的生长。皮肤细胞分裂并覆盖住伤口。
Then, progenitor cells, which can develop into various bodily tissues, form a mass at the site of injury and nearby nerves secrete growth-promoting proteins.
接着，祖细胞在受伤部位形成团块，能发展成各种身体组织，且附近神经分泌出促生长蛋白质。
Over the next few weeks, a new limb emerges as cells proliferate and differentiate in coordination.
接下来的几周里，随着细胞的增殖和分化，一个新的肢体出现了。
This process could potentially lead to uncontrolled growth and tumor formation.
这一过程可能导致不可控生长和肿瘤的形成。
But axolotls are remarkably resistant to cancer. They have a system in place that tightly controls cellular proliferation.
但美西螈对癌症有很强抵抗力，它们有一个严格控制细胞增殖的系统。
To better understand the axolotl's baffling biology, scientists sequenced its genome.
为更了解美西螈令人困惑的生物学特性，科学家们对其基因组进行了测序。
They found it to be more than ten times longer than a human's. Mutations can change the length of any animal's genome.
他们发现比人类的长十倍以上。突变可改变任何动物基因组的长度。
For whatever reason, salamanders have much more DNA than other vertebrates because they lose parts of it less frequently.
不管什么原因，蝾螈比其他脊椎动物拥有更多DNA，因为它们不那么频繁地失去一部分。
Investigating the axolotl's genome, scientists saw many repeated sequences, most of which don't code for proteins and have no known function.
研究美西螈的基因组时，科学家发现了许多重复序列，其中大多数不编码蛋白质，也不知其功能是什么。
They also found genes that are key in regeneration.
他们还发现了再生的关键基因。
However, the biggest factor that sets axolotl regeneration apart may not be a set of unique genes, but how they regulate their genes.
但美西螈与众不同的再生最大因素可能不是一组独特的基因，而是它们如何调节自己的基因。
It's no wonder that axolotls are one of science's most studied animals. But their population in the wild has plummeted.
难怪美西螈是科学界研究最多的动物之一。但它们在野外的数量急剧下降。
Hundreds of years ago, axolotls thrived under the Aztec capital.
几百年前，美西螈在阿兹特克首府繁荣起来。
Within the surrounding lakes, Aztec people built islands called chinampas for growing crops.
在周围的湖泊中，阿兹特克人建造了奇南帕浮田岛来种植庄稼。
This highly productive form of agriculture created a vast system of canals, expanding the lake system's shallow, sheltered habitat -- the axolotls' ideal environment.
这种高产农业形式创造了巨大的运河系统，拓展了有庇护的湖泊浅水区栖息地--美西螈的理想栖息环境。
But when Spanish invaders arrived, they began draining the lakes. And even more water has been diverted in recent years.
但西班牙入侵者到达后，他们开始抽干湖水；近年来，更多的水被引走。
Today, the entire population of wild axolotls is found in just one place, Lake Xochimilco, where it's threatened by pollution and invasive fishes.
今天，只发现一个地方有野生美西螈--索奇米尔科湖，在那里，它们受到污染和入侵鱼类的威胁。
People are working to regenerate the ecosystem and strengthen the 2,000 year old chinampa farming tradition.
人们正努力恢复那里的生态系统，还强化有2000年历史的奇南帕浮田岛农业传统。
If interest grows, farmers could recover abandoned chinampas and support the local community -- along with the axolotl.
如果收益增加，农民可以恢复被遗弃的奇南帕浮田岛，支持美西螈的同时，也支持了当地社区。
Eventually, the benefits of saving this salamander might be even greater.
最终，拯救美西螈的益处可能更大。
Scientists hope that one day we'll be able to apply the axolotl's masterful tumor suppression and regenerative abilities to the human body.
科学家们希望，有一天我们能将美西螈高超的肿瘤抑制和再生能力应用到人体上。
Perhaps its secrets are the real reason for the slimy god monster's smile.
也许，其秘密正是这个黏糊糊神怪微笑的真正原因。
