Is This the Secret That Makes Cephalopods so Smart?

octopus

Story at-a-glance -

  • Octopuses, squid and cuttlefish use RNA editing much more extensively than other animals (both marine- and land-based)
  • Cephalopods edit RNA frequently and then may use the tweaked RNA to create new proteins that affect their biology
  • Cephalopods most often edit RNA that’s related to nervous system functions; at least one previous study showed that octopuses are able to use RNA editing to adapt to different water temperatures

By Dr. Becker

Octopuses, squid and cuttlefish, which are coleoid cephalopods, are considered to be the most intelligent invertebrates. Octopuses are the most studied out of the bunch, and as such are often considered to be the smartest, but the extent of their (and other cephalopods') intellectual abilities remain largely unknown. In one of the latest studies to date, researchers revealed that octopuses, squid and cuttlefish have at least one "genetic oddity" that may explain, in part, their seemingly unusual intelligence.1

The animals use RNA editing much more extensively than other animals (both marine- and land-based). This is significant, because RNA, the messenger that passes instructions from DNA in order for proteins to be created, is typically not rewritten to the extent that new proteins are created. This is precisely what occurs in cephalopods, however, which can edit RNA and then may be using the tweaked RNA to create new proteins.

"Rather than one gene producing one protein, this type of RNA editing, called recoding, could allow a single octopus gene to produce many different types of proteins from the same DNA," The Washington Post reported.2 "These RNA changes can have a dramatic impact on squid or octopus biology."

Is RNA Recoding Responsible for Making Cephalopods so Smart?

When the researchers looked into RNA editing in less intelligent mollusks, including a nautilus and a sea slug, it was found to occur much less often. Even more intriguing, the cephalopods most often edit RNA that's related to nervous system functions.3 At least one previous study showed that octopuses are able to use RNA editing to adapt to different water temperatures.4

This nervous system manipulation may come at a price evolutionarily speaking, as DNA mutations were sparse near the recoding sites, presumably to preserve them.

Since evolution typically occurs as a result of DNA mutations, this means cephalopods may not evolve very quickly, but the trade-off seems to be worth it. Even as the world's oceans are changing and posing survival challenges to many marine species, numbers of cephalopods have increased significantly in the last 60 years, with researchers noting in the journal Current Biology:5

"Cephalopods (squid, cuttlefish and octopuses) have a unique set of biological traits, including rapid growth, short lifespans and strong life-history plasticity, allowing them to adapt quickly to changing environmental conditions … This study presents the first evidence that cephalopod populations have increased globally, indicating that these ecologically and commercially important invertebrates may have benefited from a changing ocean environment."

Fascinating Cephalopods: Do They Have a Sense of Self?

The discovery only adds to cephalopods' aura of fascination and mystery. Although they're separated from humans by more than 700 million years, evolutionary wise, and couldn't appear to be more different, we share some similarities, including our eyes. Cephalopods also have large brains. Octopuses have about half a billion neurons, similar to a dog, but most of them are in their arms, which they use to smell and taste.

Octopuses are known for their incredible dexterity. They possess the ability to unscrew a jar lid from the inside and have outwitted more than one researcher. The Guardian highlighted a book by Australian philosopher Peter Godfrey-Smith, titled "Other Minds: The Octopus, The Sea and the Deep Origins of Consciousness." Godfrey-Smith poses the question that cephalopods may have a sense of self — a revelation he came to after a close encounter with a cuttlefish while snorkeling. According to The Guardian:6

"The cuttlefish hadn't been afraid — it had seemed as curious about him as he was about it … That it was possible to observe some kind of subjective experience, a sense of self, in cephalopods fascinated Godfrey-Smith … he recounts an octopus taking his collaborator by hand on a 10-minute tour to its den, 'as if he were being led across the sea floor by a very small eight-legged child.'

… Most aquariums that have attempted to keep octopuses have tales to tell of their great escapes – even their overnight raids of neighboring tanks for food … Godfrey-Smith writes of animals [in aquariums] learning to turn off lights by directing jets of water at them, short-circuiting the power supply. Elsewhere octopuses have plugged their tanks' outflow valves, causing them to overflow."

In 2016, in a scene that seems like it came out of the movie "Finding Dory," an aquarium in New Zealand reported that one of its octopuses had escaped from its tank when the lid was left ajar. But he didn't only escape from his tank — he found his way back to the ocean. The octopus, named Inky, entered a small drainpipe leading to the ocean, freeing himself.7 Since cephalopods have no bones, they can fit through extremely small spaces.

These creatures are also known for having unique personalities and playful behaviors. In the wild, they're also known to use tools and have the amazing ability to change color, shape and even texture to mimic other creatures and blend in with their environments.

Should Cephalopods Be Eaten?

Cephaolopods' intelligence and skills has led some to ponder the moral and ethical dilemma of whether cephalopods should be eaten. The New Yorker quipped:8

"Jaron Lanier, the computer scientist and early pioneer of virtual reality, long ago stopped eating cephalopods … Cephalopods are on their own from the moment they're born, he points out: with no concept of parenting, they pass on nothing to future generations. 'If cephalopods had childhood,' he goes so far as to suggest, 'surely they would be running the Earth.'"

It's a question with no easy answer, especially as other intelligent animals are also considered food, but just one more quandary for this already enigmatic species. Aside from the recent RNA editing discovery, one other intriguing finding occurred in 2015, when researchers decoded the entire genome of the octopus, revealing it has 10,000 more genes than humans.

Clifton Ragsdale, Ph.D., of the University of Chicago, one of the study's authors, told The Independent, "The last British zoologist Martin Wells [grandson of H.G. Wells and renowned cephalopod expert] said the octopus is an alien. In this sense, then, our study describes the first sequenced genome from an alien."9

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