What Makes Octopuses So Smart? Their Ability To Rewrite Their RNA May Have Something To Do With It

In April of 2016, Inky the octopus escaped from his tank at New Zealand’s National Aquarium, and down a pipe to freedom. Inky’s story was covered by several news outlets, and people all over the world cheered him on. Inky is not the only octopus to exhibit intelligent behavior. Octopuses have been known to open jars, mimic other creatures, and many other interesting things. Cuttlefish are masters of disguise, and squid can communicate by flashing the colors of their skin.

What is it that makes these animals so smart? A study released on Thursday by the journal Cell reports that coleoid cephalopods, a classification of mollusks that includes octopuses, squid, and cuttlefish, have the amazing ability to rewrite their RNA.

DNA, which stands for deoxyribonucleic acid, is made up of four different nucleotide bases: adenine, thymine, guanine, and cytosine. The order in which these bases are arranged with other bases dictates the genetic makeup of an organism. DNA is what holds the information, and RNA, ribonucleic acid, copies that information and carries it to the cells.

Think of DNA like the instruction manual for how to build an organism, and the cells are the workers. There is only one manual, and millions of workers. If all the workers tried to read the manual at once, then the manual could be destroyed or broken, which would result in the death of the organism. Enter RNA. RNA is like the foreman who copies down the manual and passes out a copy to each of the workers.

Cuttlefish in reef
Cuttlefish in reef [Image by WhitcombeRD/iStock]

What does this mean for octopuses and other coleoids? Well, with their ability to rewrite their RNA, they actually create proteins that were not in their genetic makeup at all. The RNA foremen are not simply copying the instruction manual, but are making changes to their copies. This is not a common occurrence, either. Eli Eisenburg, a biophysicist at Tel Aviv University in Israel, and co-author of the study had this to say about the RNA editing.

“Basically, this is a mechanism to make proteins that are not encoded in the DNA. They are not present in the genomic sequence. With these cephalopods, this is not the exception. This is the rule. The rule is that most of the proteins are being edited.”

Researchers believe that Octopuses and coleoids use this RNA editing in order to adapt to the rapidly changing temperatures of the waters in which they live, and perhaps even to help them change colors to hide from enemies.

It is important to note that this same process of RNA editing is not as prevalent in other mollusks, such as sea slugs or nautiluses. It existed, but it was there in much lower levels than those in octopuses and other coleoids.

Another thing that researchers looked at was how many RNA recoding sites existed in the animals. They found that octopuses and cuttlefish shared tens of thousands of RNA recoding sites while other species, such as humans and mice only shared around 40.

Common octopus

This ability does not come without a price for the octopus, however. Other animal species adapt to their surroundings through mutations in their DNA. If a DNA mutation occurred at an RNA recoding site, then the octopus would lose the ability to change the RNA at that site, which would be detrimental. It appears as though octopuses have given up the ability to have DNA mutations occur in favor of adaptation through RNA editing.

The study did not definitively prove that this ability to rewrite RNA is what makes octopuses so smart, but it did hint at the possibility. With continued research and studies, who knows what scientists will discover next?

[Featured Image by Ian Waldie/Getty Images]