Octopus Genome Reveals Secret of Intelligence

Octopuses (not octopi) are incredible; they're definitely the animal I would most like to be melded with in a nuclear meltdown scenario. We all know they have eight legs but did you know they have three hearts? Their blood is blue because they use a copper and cyanide based oxygen transport molecule instead of haemoglobin. They are highly intelligent, capable of finding and remembering a route through a maze. They are exceptionally good at changing not just their colour but also their texture to mimic their surroundings (see video below) and some species have even been observed using tools.

A recent open access article from Nature reports details of the first sequencing of an octopus genome. Contained within the genetic code they think they may have found a couple of clues as to the remarkable intelligence of these curious creatures. Analysis showed that there were two families of genes that had many more members then would normally be found in molluscs (octopuses are molluscs); namely, protocadherins and the C2H2 family of genes.

Before the first draft of the human genome was published in 2000 there was the naive assumption (although reasonable at the time) that the more complex an organism the more genes it must have. Sensible guesses for the number of genes in the human genome were in the range of 50,000-100,000. When it was revealed that we only had about 22,000 it surprised everyone. It turns out, though, that it isn't how many genes you have but what you do with them that counts. One gene can be expressed in many different ways resulting in production of different proteins with slightly different functions; this is how you can get complexity from a small number of genes. To achieve this, though, you need a set of genes capable of manipulating the other genes in such a way; one such group are the C2H2 family. 

Protocadherins are involved with developing neurons, the basic component of any nervous system. Mammals are known to produce a large number of these proteins but generally other families of animals do not. Oysters and other molluscs tend to have about 20 different protocadherins, we now know octopuses have 168. This would allow them to develop a much more complex nervous system than they otherwise might; indeed, octopuses have the largest nervous system of any invertebrate.

Finally the researchers, a joint team from Chicago and Okinawa, revealed that they discovered many hundreds of genes that are unique to octopuses. Some of these are known to be involved in the animal's remarkable mimicking ability but the majority remain a mystery. A rich seam for future research, no doubt.

So there you have it, it would seem that several of the amazing abilities of the octopus could be down to genetic factors. Spare them a thought the next time you chow down on some calamari.