The visual system of the octopus has been mapped and it is impressive  

So similar and yet so different from ours

Humans and octopuses descended from a common ancestor 500 million years ago, yet the visual system evolved very differently to serve the same purpose. We both have a pupil and a lens that guides light to the retina.

Cephalopods have the largest brains of any invertebrate, with nearly 2/3 of the information-processing tissue involved in vision alone. As you can see, these sea creatures have really good vision, even in the dark.

Now, research from the University of Oregon is the first to successfully map the visual system of octopuses, which required an analysis of 26,000 cells.

The analysis found four different types of cells, each releasing different chemical signals. Neurotransmitters, like in us, occur in octopuses, but in them there are several smaller nuclei of neurons. The scientists identified several genetic factors and signaling molecules that are unique to octopuses and likely help shape their neurological development.

The atlas presented here offers a map for such studies and more generally offers a way to understand the functional, developmental and evolutionary logic of the cephalopod visual system.

Like vertebrates, the visual system in octopuses is layered, but not like ours. The variety of cell types and the way they are organized in the cephalopod brain is very different.

On an obvious level, neurons don’t fire on each other – they use different neurotransmitters. But they might be doing the same kind of calculations, just in a different way.

One of the biggest questions is how the visual system of cephalopods develops. Octopuses spend years developing their enormous brains, but how does information from the retina aid development?

In vertebrates, photoreceptors in the retina deliver the message to neurons. But in cephalopods, the retina is not connected directly to the brain and instead, the photoreceptors are connected directly to the optic lobe of the brain.

Future studies will investigate whether these direct messages affect the development of immature neurons and how many of them eventually join the mature visual system. Scientists are continuing the study to map the remaining 1/3 of octopus brains.

The research was published in Current Biology .