Cephalopod Intelligence Tied to Genetic Anomaly

cuttlefish

Cuttlefish (shown here), squid, and octopuses can edit their own RNA. (Photo credit: David Litman/Shutterstock)

Cephalopods, such as the squid and octopus, have long been known for their wily intelligence. Their complex behaviors include unlocking and escaping from aquarium tanks, opening jars, and communicating with one another using a system similar to Morse code. These underwater creatures, along with cuttlefishes, are all coleoids, which is a subclass of cephalopods. New research highlights another unique ability of these underwater creatures: they can edit their own RNA.

RNA sends messages. These messages instruct what proteins should be made. Cephalopods such as cuttlefish, squid, and octopus, have the ability to edit their own RNA, which means they can change the message that gets read. For example, changing just one portion of the code could change how–or even if–a protein works. In most cases, when RNA editing occurs, it can have disastrous results. Somehow this does not appear to be the case in cephalopods. In fact, researchers think this ability to edit their own RNA may explain these animals’ unusual intelligence.

Joshua J.C. Rosenthal of the Marine Biological Lab in Woods Hole, Massachusetts, along with Eli Eisenberg and Noa Liscovitch-Brauer of Tel Aviv University in Israel outlined their findings in an article published this past April in the journal Cell. In previously published research, they had found that more than 60 percent of RNA transcripts in the squid brain are recoded by editing. In contrast, in humans, only a fraction of 1 percent of RNA show a recoding event.

In this new research, the scientists report that squid, octopus, and cuttlefish have tens of thousands of RNA editing sites in their genes. The majority of the edited proteins are found in brain tissue, leading the researchers to hypothesize that RNA editing aided in complex brain development in these animals. The scientists did not find similar evidence in RNA editing in more primitive forms of mollusks such as nautiluses.

“This shows that high levels of RNA editing is not generally a molluscan thing; it’s an invention of the coleoid cephalopods,” Joshua J.C. Rosenthal said in a press release about the research. “There is something fundamentally different going on in these cephalopods where many of the editing events are highly conserved and show clear signs of selection.”

In general, RNA editing is not evolutionarily beneficial. However, it appears that natural selection has favored this ability in coleoids, although it negatively impacts, and in fact slows down, DNA-based evolution in these animals.

“The conclusion here is that in order to maintain this flexibility to edit RNA, the coleoids have had to give up the ability to evolve in the surrounding regions–a lot,” Rosenthal said. “Mutation is usually thought of as the currency of natural selection, and these animals are suppressing that to maintain recoding flexibility at the RNA level.”

More to Explore
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Science Reveals Yet Another Reason Octopuses and Squids Are So Weird
Octopuses, Squid, and Cuttlefish: RNA Editing Instead of Genome Evolution?
High-level RNA editing in cephalopods

 

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