The Editor of Itself

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

"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 perched on the rim.

"Octopuses can edit their own RNA in real time," Chiara said. "No other animal does this at the rate they do."

DNA is the long-term blueprint of an animal. It does not change much in a lifetime. 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 exactly.

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 that build the nervous system.

"Why?" Chiara said. "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 its food. It tunes its own brain. The cost is that the species itself has not been able to evolve much. They paid for short-term flexibility with long-term stability."

Pasta drifted. Her skin near the eyes flickered through soft pinks and pale browns.

"Each individual octopus," Chiara said, "is a slightly different animal from every 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."

Polly thought about her own brain. 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.