Smart Cephalopods

Octopus intelligence may come from a molecule also found in human brains

We have more in common with these sea creatures than it may seem.

Nir Friedman

Octopuses are some of the most fascinating animals on Earth

The cephalopods have so many unique traits they’ve regularly been compared to aliens.

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“They say if you want to meet an alien, go diving and make friends with an octopus.”

Prof. Nikolaus Rajewsky, Scientific Director, Berlin Institute for Medical Systems Biology, Max Delbrück Center

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Nir Friedman

On top of their multi-armed motor skills and color-changing abilities, octopuses are known to be incredibly smart, able to solve puzzles for food, and even use tools.

Octopus brains are just as interesting as what octopuses do with them.

Octopuses have a mini-brain in each arm in addition to their central brain — making the solitary brains in our skulls look pretty pathetic by comparison.

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The question until now has been, how did cephalopods develop nervous systems so much more complex than their fellow invertebrates?

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New research led by the Max Delbrück Center for Molecular Medicine shows that development was driven by molecules that control gene expression in cephalopod brains, much like they do in humans and other vertebrates.

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Molecules called microRNAs turn gene expression on and off. Octopus evolution has given rise to a huge amount of microRNA concentrated in their brains.

In a study published in Science Advances, the researchers identify 138 microRNA families in the octopus. Of those, 42 were shared between octopuses and squids, and 35 appeared only in octopuses.

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That’s the largest evolutionary expansion in microRNA found in any invertebrate, which could explain why octopuses display intelligence normally seen only in vertebrates.

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The researchers suggest microRNA’s ability to turn specialized brain functions on could make them a necessary step in animals developing complex brains.

Grygoriy Zolotarov

Nir Friedman

Of course, microRNA alone doesn’t give rise to intelligence. But a paper published in BMC Biology earlier this year shows another similarity between the octopus and human brains.

That research found a high number of transposons — also known as “jumping genes,” which copy themselves around the genome — in octopus brains’ learning center.

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In human brains, these transposons are thought to influence the development of neurons and thus our cognitive abilities.

However, we don’t need to worry about competition from octopuses just yet.

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Humans have more than 10 times the microRNAs of octopuses. But compared to other mollusks that have only gained five microRNA families since splitting from their last shared ancestor, octopuses are a major outlier.

Study author Prof. Nikolaus Rajewsky plans to collaborate with other octopus researchers to understand cephalopod brains better and discover the full effects of their microRNA.

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