How an octopus’s cleverness may have evolved

Octopuses and mammals may come by their smarts in a similar way.

The California two-spot octopus (Octopus bimaculoides) has similar nervous system development genes as those found in intelligent vertebrates like humans, researchers report in the Aug. 13 Nature. The first complete analysis of the octopus’s genome reveals genetic reorganizations that separate the brainy, complex octopus from its simpler relatives.

Octopuses wow scientists with their ability to learn and solve problems. Researchers knew that the animal had a larger genome than “dumber” mollusks, like snails or shellfish, says study author Daniel Rokhsar, an evolutionary biologist at the University of California, Berkeley and the Okinawa Institute of Science and Technology in Japan. The octopus’s genome largely contains the same basic material as other mollusks, Rokhsar and colleagues found, but specific groups of octopus genes have been duplicated and rearranged.

One highly copied group of genes contain instructions for making protocadherin proteins. Having a greater variety of these proteins, which play a role in nervous system development, enables the construction of more complex neural networks, Rokhsar says. While limpets and oysters have around 20 protocadherin genes, the researchers found that the octopus has 168. Mammals also produce a large variety of protocadherins, but use fewer genes to do so. Octopuses and vertebrates may have evolved completely different mechanisms to achieve diversity in these proteins, says Jan Strugnell, an evolutionary biologist at La Trobe University in Melbourne, Australia.

The study also revealed thousands of genes found only in octopuses, squid and other cephalopods. Some of these genes are involved with the octopus’s color-changing abilities, but it’s unclear what many others do, Rokhsar says.

The new study provides crucial information needed to understand octopus evolution, Strugnell says. Rokhsar says the researchers now want to analyze the genomes of other species of octopus and squid.