апр 10, 2017

Octopus and squid evolution officially even weirder than we thought

When Inky the octopus escaped from his tank at New Zealand's National Aquarium in April 2016, he squirmed through a six-inch-wide drainpipe and stole away into the Pacific. He stole more than a few human hearts along the way, too. Inky fans celebrated the animal who outwitted the aquarium: "Please watch out – he is heavily armed," one commentator quipped.


The intelligence of octopuses goes far beyond escape artistry. They can unscrew glass jars from the inside and solve other complex mechanical problems. They play. Some are capable of body-contorting mimicry. All of this is to say that cephalopods – the spineless, many-legged creatures including octopuses and cuttlefish – stand out among their fellow mollusks. Pity in comparison the oyster, a mollusk that, sadly, doesn't even have a proper brain.

Cephalopods are unusual not only because they solve puzzles and clams cannot. Squids, cuttlefish and octopuses do not follow the normal rules of genetic information, according to research published Thursday in the journal Cell. Their RNA is extensively rewritten, particularly the codes for proteins found in the animals' neurons.

Put simply, that's very weird. According to the central dogma of molecular biology, cells convert DNA sequences to RNA, which then creates proteins.

Imagine a library full of cookbooks, where you're not allowed to check anything out. But you are allowed to copy recipes as you need them. The copies must almost always be verbatim, as though done by a faithful scribe. RNA plays the role of scribe.

Widespread RNA editing comes at a cost. If a mutation occurs at an editing site, the animals' cells can no longer tweak it. "You can't mess around with that underlying structure," Rosenthal said. It turns out that these squids and octopuses have much lower rates of DNA mutation – which Rosenthal called the "currency of evolution" – than other organisms. In other words, while most animals adapt and evolve through changes in DNA, they seemed to prioritize RNA recoding.

To further investigate how the animals curb their DNA mutation rate in favor of RNA recoding, Rosenthal plans to manipulating cephalopod genetics using the CRISPR-Cas9 gene editing technique. He'll just have to keep the octopus tank lids shut tightly each night.

The Washington Post

by Ben Guarino