自我编辑者

第六天早晨，Chiara为她们俩煮了咖啡，然后坐在水箱旁的椅子上。Pasta倒挂在玻璃角落，身体的钟形轻轻地脉动着。她的触手像缓慢绽放的花朵般在周围漂浮。

On the sixth morning, Chiara made coffee for both of them and sat down in the chair beside the tank. Pasta was hanging upside down from a corner of the glass, the bell of her body pulsing gently. Her arms drifted around her like a slow flower.

“还有一件事我想告诉你，”Chiara说，“我想慢慢地说，因为这是我所知关于章鱼最奇怪的事情。”

"There is one more thing I want to tell you," Chiara said, "and I want to tell it slowly, because it is the strangest thing about octopuses I know."

Polly坐在水箱边缘。

Polly perched on the rim.

“章鱼可以实时编辑自己的RNA，”Chiara说，“这是它们不断在做的事情。没有其他动物能像章鱼和一些相关的头足类动物那样频繁地进行这种操作。”

"Octopuses can edit their own RNA in real time," Chiara said. "It is something they do constantly. No other animal does this at the rate that an octopus and a few related cephalopods do."

她停顿了一下。她知道接下来的部分需要小心。

She paused. She knew the next part required care.

DNA是动物的长期蓝图。它变化不大。RNA是工作副本。当细胞需要构建蛋白质时，它会从DNA中制造RNA。在大多数动物中，RNA几乎与DNA完全匹配。

DNA is the long-term blueprint of an animal. It does not change much. RNA is the working copy. The cell makes RNA from DNA when it needs to build a protein. In most animals, the RNA matches the DNA almost exactly.

在章鱼中，RNA并不匹配。当RNA被制造时，细胞会重写其中的部分。这些编辑大多发生在构建神经系统的基因组部分。特别是章鱼的神经系统，通过这些编辑不断被构建和重建。

In octopuses, the RNA does not match. As the RNA is being made, the cell rewrites parts of it. Most of these edits happen in the parts of the genome that build the nervous system. The nervous system of an octopus, in particular, is built and rebuilt constantly with these edits.

“为什么？”Chiara在Polly问之前说道，“我们有一个理论。RNA编辑是可逆的，而DNA突变不是。章鱼可以根据水温或食物的化学成分调整其神经系统。它可以即时调节自己的大脑。代价是基因组本身，长期蓝图，无法进化太多。这个物种在数千万年间，或多或少地停滞在相同的DNA上。它们用短期的灵活性换取了长期的停滞。”

"Why?" Chiara said, before Polly could ask. "We have a theory. RNA editing is reversible. DNA mutation is not. An octopus can adjust its nervous system in response to the temperature of the water or the chemistry of the food it eats. It can tune its own brain on the fly. The cost is that the genome itself, the long-term blueprint, has not been able to evolve much. The species is stuck with the same DNA, more or less, for tens of millions of years. They paid for short-term flexibility with long-term stagnation."

Polly看着Pasta漂浮。章鱼的身体缓慢地脉动。眼睛附近的皮肤闪烁着柔和的粉色和浅棕色。

Polly watched Pasta drift. The octopus's body pulsed slowly. The skin near the eyes flickered through a soft pulse of pinks and pale browns.

“每只章鱼，”Chiara说，“都是与其他章鱼略有不同的动物，而你我和其他鹦鹉则不是这样。相同的DNA。但工作机制是每个生命为那片水和那种食物新建的。它们是地球上也许没有其他动物能比拟的独立大脑。”

"Each individual octopus," Chiara said, "is a slightly different animal from each other one, in a way that you and I and other parrots are not. The same DNA. But the working machinery is built fresh, every life, for that water and that food. They are individual brains in a way that perhaps no other animal on Earth is."

她喝了口咖啡。

She drank her coffee.

“这也是为什么，”她说，“两只章鱼在面对同一个迷宫时，可以用完全不同的方式解决。Pasta用两只触手合作解决了迷宫。去年我们有另一只章鱼用了三只触手。还有一只等了一个小时，然后用身体直接进去。它们不是用相同的大脑解决相同的问题。它们各自用自己为自己构建的大脑解决。”

"It is also why," she said, "two octopuses given the same maze can solve it in completely different ways. Pasta solved the maze with two arms cooperating. We had another octopus last year who used three. We had another who waited an hour and then went straight in with the body. They are not solving the same problem with the same brain. They are each solving it with the brain they have made for themselves."

Pasta的眼睛开合着。触手漂浮着。

Pasta's eye opened and closed. The arms drifted.

Polly想到了自己的大脑。它没有被实时编辑。它像大多数大脑一样被构建了一次，现在就是她的了。她并不羡慕Pasta的灵活性。但她非常喜欢知道像Pasta这样的动物存在。

Polly thought about her own brain. It had not been edited in real time. It had been built once, the way most brains are built, and was now simply hers. She did not envy Pasta the flexibility. But she liked very much knowing that animals like Pasta existed.

Chiara站起来。“我得去写一份资助申请，”她说。“如果你愿意，可以和她待一上午。”

Chiara stood up. "I have to go write a grant," she said. "You stay with her for the morning, if you want."

Polly留下了。

Polly stayed.